Researcher Database

Gen Sazaki
Institute of Low Temperature Science Frontier Ice and Snow Science
Professor

Researcher Profile and Settings

Affiliation

  • Institute of Low Temperature Science Frontier Ice and Snow Science

Job Title

  • Professor

Degree

  • Doctor of Engineering(Osaka City University)
  • Master of Engineering(Osaka City University)
  • Bachelor of Engineering(Osaka City University)

URL

Research funding number

  • 60261509

J-Global ID

Research Interests

  • crystal growth, ice, protein, development of advanced optical microscopy   Crystal Growth   

Research Areas

  • Natural sciences / Bio-, chemical, and soft-matter physics
  • Nanotechnology/Materials / Thin-film surfaces and interfaces
  • Nanotechnology/Materials / Crystal engineering
  • Nanotechnology/Materials / Applied materials

Academic & Professional Experience

  • 2014/07 - 2014/09 Chinese Academy of Science National Microgravity Laboratory, Institute of Mechanics Visiting Professor
  • 2007/08 - 2014/03 - Specially Appointed Professor,Dept. Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University
  • 2007 - 2014/03 - 大阪大学大学院工学研究科電気電子情報工学専攻 特任教授
  • 2008 - 2012 科学技術振興機構さきがけ研究者 さきがけ研究者
  • 2008 - 2012 Hokkaido University Institute of Low Temperature Science
  • 2008 - 2012 Researcher on Precursory Research for Embryonic Science and Technology (PRESTO),Japan Science and Technology Agency
  • 2012 - 北海道大学低温科学研究所 教授
  • 2012 - Professor,Institute of Low Temperature Science, Hokkaido University
  • 2007 - 2008 スペイン科学研究高等評議会,アンダルシア地球科学研究所,結晶学研究室 契約研究者
  • 2007 - 2008 Investigado Contrato,Laboratorio de Estudios Cristalograficos, Instituto Andaluz de Ciencias de la Tierra, Consejo Superior de Investigaciones Cientificas
  • 2001 - 2007 Tohoku University Institute for Materials Research
  • 2001 - 2007 Lecturer,Institute for Materials Research, Tohoku University
  • 2004 - 2006 Tohoku University Center for Interdisciplinary Research
  • 2004 - 2006 Project Leader,Center for Interdisciplinary Research, Tohoku University
  • 2001 - 2004 Tohoku University Center for Interdisciplinary Research
  • 2001 - 2004 Program Leader,Center for Interdisciplinary Research, Tohoku University
  • 1994 - 2001 Tohoku University Institute for Materials Research
  • 1994 - 2001 Research Associate,Institute for Materials Research, Tohoku University

Education

  •        - 1994  Osaka City University
  •        - 1994  Osaka City University  Graduate School, Division of Engineering  Department of Applied Chemistry
  •        - 1991  Osaka City University
  •        - 1991  Osaka City University  Graduate School, Division of Engineering
  •        - 1989  Osaka City University  Faculty of Engineering
  •        - 1989  Osaka City University  Faculty of Engineering  Department of Applied Chemistry

Association Memberships

  • 応用物理学会   日本マイクログラビティ応用学会   日本物理学会   日本結晶成長学会   The Japan Society of Applied Physics   The Japan Society of Microgravity Application   The Physical Society of Japan   Japanese Association of Crystal Growth   

Research Activities

Published Papers

  • Quasi-liquid layers can exist on polycrystalline ice thin films at a temperature significantly lower than on ice single crystals
    J. Chen, K. Nagashima, K. Murata, G. Sazaki
    Crystal Growth & Design 19 (1) 116 - 124 2019/01 [Refereed][Not invited]
  • Murata Ken-ichiro, Nagashima Ken, Sazaki Gen
    PHYSICAL REVIEW MATERIALS 2 (9) 2475-9953 2018/09/10 [Refereed][Not invited]
  • Bayer-Giraldi Maddalena, Sazaki Gen, Nagashima Ken, Kipfstuhl Sepp, Vorontsov Dmitry A, Furukawa Yoshinori
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 115 (29) 7479 - 7484 0027-8424 2018/07/17 [Refereed][Not invited]
  • Nagashima Ken, Sazaki Gen, Hama Tetsuya, Murata Ken-ichiro, Furukawa Yoshinori
    CRYSTAL GROWTH & DESIGN 18 (7) 4117 - 4122 1528-7483 2018/07 [Refereed][Not invited]
  • Dmitry A. Vorontsov, Gen Sazaki, Evgeniia K. Titaeva, Ekaterina L. Kim, Maddalena Bayer-Giraldi, Yoshinori Furukawa
    Crystal Growth and Design 18 (4) 2563 - 2571 1528-7505 2018/04/04 [Refereed][Not invited]
     
    The morphology and growth kinetics of ice single crystals in aqueous solutions of type III antifreeze protein (AFP-III) have been studied in detail over a range of AFP-III concentrations and supercoolings. In pure water, the shape of ice crystals changes from the circular disklike to planar dendritic with increasing supercooling. In AFP-III solutions, ice crystals in the form of faceted plates, irregular dendrites with polygonized tips, and needles appear with increasing supercooling and AFP-III concentration. The growth rate of ice crystals in the crystallographic a direction is 2 orders of magnitude higher than that in the c direction. AFP-III molecules cause the stoppage of the growth of the prismatic and basal faces at low supercoolings. When supercooling exceeds the critical value, AFP-III favors the acceleration of the growth in both a and c directions. The observed behavior of AFP-III is explained in terms of the Cabrera-Vermilyea pinning model and the specificity of the dissipation of latent heat from the growing crystals with different shapes.
  • Masahiro Inomata, Ken-ichiro Murata, Harutoshi Asakawa, Ken Nagashima, Shunichi Nakatsubo, Yoshinori Furukawa, Gen Sazaki
    CRYSTAL GROWTH & DESIGN 18 (2) 786 - 793 1528-7483 2018/02 [Refereed][Not invited]
     
    We measured the velocity V-step of isolated elementary spiral steps and the distance L-eq between adjacent equivalent spiral steps on ice basal faces by advanced optical microscopy. We determined the step kinetic coefficient beta from V-step measured under various supersaturations. We performed similar experiments under various temperatures T, and determined the temperature dependence of beta of ice basal faces, for the first time, in the temperature range of -26.0 to 2.7 degrees C. When -6.2 <= T <= 2.7 degrees C, the value of beta decreased significantly with decreasing T. In contrast, when -15.0 <= T <= -6.2 degrees C, the value of beta increased with decreasing T, and had the maximum at T approximate to -15 degrees C. When -26.0 <= T <= 15.0 degrees C, the value of beta decreased monotonically with decreasing T. Such complicated temperature dependence of beta strongly implies the existence of unknown phenomena in the temperature range examined. To obtain a clue to the complicated behavior of beta, we also measured dependence of L-eq on surface supersaturation Aptsurf. When 13.0 <= T <= 3.2 degrees C, plots of L-eq vs 1/Delta mu(surf) satisfactorily follow the spiral growth model. However, when 26.0 <= T <= 15.0 C, the Leq vs 1/Delta mu(surf) plots do not follow any model: this temperature range agrees with the temperature range in which beta decreased monotonically with decreasing T.
  • Shingo Mizue, Shunsuke Ibaraki, Ryuta Ise, Gen Sazaki, Yuya Oaki, Hiroaki Imai
    CRYSTAL GROWTH & DESIGN 17 (7) 3694 - 3699 1528-7483 2017/07 [Refereed][Not invited]
     
    Self-organized formation of parallel-banded structures was demonstrated through the twisted growth of K2Cr2O7 in a thin layer of a viscous solution containing poly(acrylic acid) on a glass substrate. Dense branching of the twisted crystals was induced by increasing their growth rate under a controlled flow of nitrogen gas. Periodically banded structures were then obtained by the synchronization of the twist in the parallel branches. Specific structural colors originating from the parallel-banded structures as a diffraction grating were observed on the self-organized patterns of the twisted crystals.
  • Yoshinori Furukawa, Ken Nagashima, Shun-ichi Nakatsubo, Izumi Yoshizaki, Haruka Tamaru, Taro Shimaoka, Takehiko Sone, Etsuro Yokoyama, Salvador Zepeda, Takanori Terasawa, Harutoshi Asakawa, Ken-ichiro Murata, Gen Sazaki
    SCIENTIFIC REPORTS 7 2045-2322 2017/03 [Refereed][Not invited]
     
    The free growth of ice crystals in supercooled bulk water containing an impurity of glycoprotein, a bio-macromolecule that functions as 'antifreeze' in living organisms in a subzero environment, was observed under microgravity conditions on the International Space Station. We observed the acceleration and oscillation of the normal growth rates as a result of the interfacial adsorption of these protein molecules, which is a newly discovered impurity effect for crystal growth. As the convection caused by gravity may mitigate or modify this effect, secure observations of this effect were first made possible by continuous measurements of normal growth rates under long-term microgravity condition realized only in the spacecraft. Our findings will lead to a better understanding of a novel kinetic process for growth oscillation in relation to growth promotion due to the adsorption of protein molecules and will shed light on the role that crystal growth kinetics has in the onset of the mysterious antifreeze effect in living organisms, namely, how this protein may prevent fish freezing.
  • Ken-ichiro Murata, Harutoshi Asakawa, Ken Nagashima, Yoshinori Furukawa, Gen Sazaki
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 113 (44) E6741 - E6748 0027-8424 2016/11 [Refereed][Not invited]
     
    Since the pioneering prediction of surface melting by Michael Faraday, it has been widely accepted that thin water layers, called quasi-liquid layers (QLLs), homogeneously and completely wet ice surfaces. Contrary to this conventional wisdom, here we both theoretically and experimentally demonstrate that QLLs have more than two wetting states and that there is a first-order wetting transition between them. Furthermore, we find that QLLs are born not only under supersaturated conditions, as recently reported, but also at undersaturation, but QLLs are absent at equilibrium. This means that QLLs are a metastable transient state formed through vapor growth and sublimation of ice, casting a serious doubt on the conventional understanding presupposing the spontaneous formation of QLLs in ice-vapor equilibrium. We propose a simple but general physical model that consistently explains these aspects of surface melting and QLLs. Our model shows that a unique interfacial potential solely controls both the wetting and thermodynamic behavior of QLLs.
  • Gen Sazaki, Ken Nagashima, Ken-ichiro Murata, Yoshinori Furukawa
    PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS 62 (2) 408 - 412 0960-8974 2016/06 [Refereed][Not invited]
     
    In this experimental course, attendees will learn how to obtain useful information about growth processes of crystals using ordinary optical microscopes, which are usually available in laboratories. We will demonstrate how thicknesses of crystals can be estimated from interference colors. We will also show in-situ observations of spiral steps and strain distributions by differential interference contrast microscopy and polarizing microscopy, respectively. (C) 2016 Elsevier Ltd. All rights reserved.
  • G. Sazaki, H. Nada, S. Naritsuka
    PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS 62 (2) 41 - 42 0960-8974 2016/06 [Refereed][Not invited]
  • Ken Nagashima, Gen Sazaki, Tetsuya Hama, Harutoshi Asakawa, Ken-ichiro Murata, Yoshinori Furukawa
    CRYSTAL GROWTH & DESIGN 16 (4) 2225 - 2230 1528-7483 2016/04 [Refereed][Not invited]
     
    Surface melting of ice crystals forms quasi liquid layers (QLLs) on ice surfaces, and affects a wide variety of natural phenomena. Since QLLs enhance various chemical reactions in ice clouds, the formation of QLLs by atmospheric gases has been studied intensively. However, such studies were performed using spectroscopy techniques, which have low spatial resolution. Here we show the first direct-visualization of QLLs on ice basal faces in the presence of hydrogen chloride (HCl) gas (model atmospheric gas) by advanced optical microscopy, which can visualize individual 0.37 nm-thick elementary steps on ice crystal surfaces. We found that the HCl gas induced the appearances of QLLs with a droplet shape in the temperature range from -15.0 to -1.5 degrees C, where no QLL appears in the absence of HCl gas. This result indicates that HCl gas adsorbed on ice crystal surfaces probably changed the surface structure of ice crystals and then induced the subsequent melting of ice surfaces. We also observed the movement, shape change, and splitting of the droplet QLLs when water vapor was undersaturated. The long-term (1 h) existence of the droplet QLLs under the undersaturated conditions strongly suggests that the droplet QLLs were thermodynamically stable HCl solutions.
  • Harutoshi Asakawa, Gen Sazaki, Ken Nagashima, Shunichi Nakatsubo, Yoshinori Furukawa
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 113 (7) 1749 - 1753 0027-8424 2016/02 [Refereed][Not invited]
     
    Surfaces of ice are covered with thin liquid water layers, called quasi-liquid layers (QLLs), even below their melting point (0 degrees C), which govern a wide variety of phenomena in nature. We recently found that two types of QLL phases appear that exhibit different morphologies (droplets and thin layers) [Sazaki G. et al. (2012) Proc Natl Acad Sci USA 109(4):1052-1055]. However, revealing the thermodynamic stabilities of QLLs remains a longstanding elusive problem. Here we show that both types of QLLs are metastable phases that appear only if the water vapor pressure is higher than a certain critical supersaturation. We directly visualized the QLLs on ice crystal surfaces by advanced optical microscopy, which can detect 0.37-nm-thick elementary steps on ice crystal surfaces. At a certain fixed temperature, as the water vapor pressure decreased, thin-layer QLLs first disappeared, and then droplet QLLs vanished next, although elementary steps of ice crystals were still growing. These results clearly demonstrate that both types of QLLs are kinetically formed, not by the melting of ice surfaces, but by the deposition of supersaturated water vapor on ice surfaces. To our knowledge, this is the first experimental evidence that supersaturation of water vapor plays a crucially important role in the formation of QLLs.
  • Ken-Ichiro Murata, Harutoshi Asakawa, Ken Nagashima, Yoshinori Furukawa, Gen Sazaki
    Physical Review Letters 115 (25) 1079-7114 2015/12/17 [Refereed][Not invited]
     
    We have experimentally determined the surface tension-to-shear viscosity ratio (the so-called characteristic velocity) of quasiliquid layers (QLLs) on ice crystal surfaces from their wetting dynamics. Using an advanced optical microscope, whose resolution reaches the molecular level in the height direction, we directly observed the coalescent process of QLLs and followed the relaxation modes of their contact lines. The relaxation dynamics is known to be governed by the characteristic velocity, which allows us to access the physical properties of QLLs in a noninvasive way. Here we quantitatively demonstrate that QLLs, when completely wetting ices, have a thickness of 9±3 nm and an approximately 200 times lower characteristic velocity than bulk water, whereas QLLs, when partially wetting ices, have a velocity that is 20 times lower than the bulk. This indicates that ice crystal surfaces significantly affect the physical properties of QLLs localized near the surfaces at a nanometer scale.
  • Harutoshi Asakawa, Gen Sazaki, Ken Nagashima, Shunichi Nakatsubo, Yoshinori Furukawa
    CRYSTAL GROWTH & DESIGN 15 (7) 3339 - 3344 1528-7483 2015/07 [Refereed][Not invited]
     
    Surface melting of ice significantly governs a wide variety of phenomena in nature. We recently succeeded in directly observing the surface melting on ice basal faces (Proc. Natl. Acad. Sci. U.S.A. 2012, 109, 1052-1055) by our advanced optical microscopy, which can detect 0.37-nm-thick elementary steps on basal faces. However, the direct observation of surface melting on the other prism and high-index faces remains an experimental challenge. To fully obtain a comprehensive understanding, we need to examine the surface melting on these faces. Here we show the appearance of two types of quasi-liquid layers (QLLs) on prism and high-index faces just below the melting point. We quickly raised the temperature of ice crystals and then observed prism and high-index faces during a roughening process. We found that with increasing temperature, round liquid-like droplets (alpha-QLLs) first appeared at temperatures higher than -1.4 to -0.5 degrees C, and then thin liquid-like layers (beta-QLLs) also appeared at temperatures higher than -0.8 to -0.3 degrees C, as in the case of basal faces. This result demonstrates that the presence of two types of QLL phases with different morphologies plays an intrinsically important role in the surface melting of ice crystals, irrespective of face indexes. We also revealed that the roughening process was caused thermally.
  • Gen Sazaki, Guoliang Dai
    Theoretical and Applied Mechanics Letters 5 (4) 173 - 176 2095-0349 2015/07/01 [Refereed][Not invited]
     
    Bunching of elementary steps by solution flow is still not yet clarified for protein crystals. Hence, in this study, we observed elementary steps on crystal surfaces of model protein hen egg-white lysozyme (HEWL) under forced flow conditions, by our advanced optical microscopy. We found that in the case of a HEWL solution of 99.99% purity, forced flow changed bunched steps into elementary ones (debunching) on tetragonal HEWL crystals. In contrast, in the case of a HEWL solution of 98.5% purity, forced flow significantly induced bunching of elementary steps. These results indicate that in the case of HEWL crystals, the mass transfer of impurities is more significantly enhanced by forced solution flow than that of solute HEWL molecules. We also showed that forced flow induced the incorporation of microcrystals into a mother crystal and the subsequent formation of screw dislocations and spiral growth hillocks.
  • Shunsuke Ibaraki, Ryuta Ise, Koichiro Ishimori, Yuya Oaki, Gen Sazaki, Etsuro Yokoyama, Katsuo Tsukamoto, Hiroaki Imai
    CHEMICAL COMMUNICATIONS 51 (40) 8516 - 8519 1359-7345 2015 [Refereed][Not invited]
     
    We demonstrate the oscillatory phenomenon for the twisting growth of a triclinic crystal through in situ observation of the concentration field around the growing tip of a needle by high-resolution phase-shift interferometry.
  • Guoliang Dai, Lei Zheng, Gen Sazaki, Yoshinori Furukawa
    CRYSTAL GROWTH & DESIGN 14 (10) 5303 - 5309 1528-7483 2014/10 [Refereed][Not invited]
     
    On a {10 (1) over bar} face of a monoclinic crystal of hen egg-white lysozyme (HEWL), we visualized the attachment and detachment processes of individual fluorescent-labeled HEWL (F-HEWL) molecules by a fluorescent single-molecule visualization technique. We measured the changes in number density of F-HEWL molecules, whose positions were not changed for longer than a certain residence time, as a function of an adsorption time. We first confirmed that under an equilibrium condition, there was an induction period (similar to 120 min) of the attachment/detachment processes, during which period the number density remained constant. After the induction period, the number density increased linearly with the adsorption time, as it was recently found on a tetragonal HEWL crystal [Dai, G. L. Cryst. Growth Des 2011, 11 (1), 88-92]. In addition, we performed similar measurements under a supersaturated condition. Then we found that supersaturation significantly enhanced the attachment process after the induction time. The attachment/detachment processes finally reached a steady state, in which the attachment rate was higher than the detachment one. Moreover, we also found that in a rare case, an F-HEWL molecule adsorbed on a step laterally moved following the advancement of a growing step.
  • Dmitry A. Vorontsov, Gen Sazaki, Suong-Hyu Hyon, Kazuaki Matsumura, Yoshinori Furukawa
    JOURNAL OF PHYSICAL CHEMISTRY B 118 (34) 10240 - 10249 1520-6106 2014/08 [Refereed][Not invited]
     
    Some biological substances control the nucleation and growth of inorganic crystals. Antifreeze proteins, which prohibit ice crystal growth in living organisms, promise are also important as biological antifreezes for medical applications and in the frozen food industries. In this work, we investigated the crystallization of ice in the presence of a new cryoprotector, carboxylated epsilon-poly-L-lysine (COOH-PLL). In order to reveal the characteristics and the mechanism of its antifreeze effect, free-growth experiments of ice crystals were carried out in solutions with various COOH-PLL concentrations and degrees of supercooling, and the depression of the freezing point and growth rates of the tips of ice dendrites were obtained using optical microscopy. Hysteresis of growth rates and depression of the freezing point was revealed in the presence of COOH-PLL. The growth-inhibition effect of COOH-PLL molecules could be explained on the basis of the Gibbs-Thomson law and the use of Langmuir's adsorption isotherm. Theoretical kinetic curves for hysteresis calculated on the basis of Punin-Artamonova's model were in good agreement with experimental data. We conclude that adsorption of large biological molecules in the case of ice crystallization has a non-steady-state character and occurs more slowly than the process of embedding of crystal growth units.
  • Harutoshi Asakawa, Gen Sazaki, Etsuro Yokoyama, Ken Nagashima, Shunichi Nakatsubo, Yoshinori Furukawa
    CRYSTAL GROWTH & DESIGN 14 (7) 3210 - 3220 1528-7483 2014/07 [Refereed][Not invited]
     
    We measured velocities V-step of lateral displacement of individual elementary steps on an ice basal face, for the first time, by advanced optical microscopy, under various bulk water vapor pressure p(H2O)(infinity). Distances L between adjacent spiral steps exhibited considerable variation under constant p(H2O)(infinity). Hence, we analyzed V-step as functions of L and p(H2O)(infinity). Then we found that (1) under a constant p(H2O)(infinity), V-step decreased with decreasing distances L when L <= 15 mu m and that V-step remained constant when L >= 15 mu m. We named V-step of L >= 15 mu m (isolated steps) V-step(int) and analyzed dependencies of V-step(int) on p(H2O)(infinity). Then we found that (2) the slope of the V-step(int) vs p(H2O)(infinity) plot gradually decreased with increasing p(H2O)(infinity). We proposed a model that took into account both the volume diffusion of water vapor molecules and the surface diffusion of water admolecules on a terrace. Our model could explain result (1) mainly by the competition of adjacent spiral steps for water admolecules diffusing on a terrace but could not explain the result (2) satisfactorily.
  • Gen Sazaki, Harutoshi Asakawa, Ken Nagashima, Shunichi Nakatsubo, Yoshinori Furukawa
    CRYSTAL GROWTH & DESIGN 14 (5) 2133 - 2137 1528-7483 2014/05 [Refereed][Not invited]
     
    During the growth of ice crystals, spiral growth is one of the important growth mechanisms that dominate their growth. However, the structure of spiral steps on ice crystal surfaces at temperatures near the melting point has not been identified. Here we show a possible model structure of spiral steps on basal and prism faces of I-h ice crystals grown from water vapor just below 0 degrees C. We observed in situ the coalescences of spiral steps and steps of two-dimensional (2D) islands by our advanced optical microscopy, which can visualize individual elementary steps (single-bilayer height) of 2D islands on ice basal faces. We found that both spiral steps and 2D island steps on basal and prism faces show single-bilayer heights, though Burgers' vectors of screw dislocations on both faces need to have double-bilayer heights because of a crystallographic requirement. These results suggest that at the center of a spiral growth hillock, steps of two adjacent single bilayers coincide and then form a double-bilayer step and that the steps of two single bilayers gradually detach themselves with increasing radii of their spiral steps. We observed the appearance of double spiral steps, which strongly supports our model structure, at -15.0 degrees C (the lowest temperature of our setup).
  • Takahisa Matsuzaki, Gen Sazaki, Masami Suganuma, Tatsuro Watanabe, Takashi Yamazaki, Motomu Tanaka, Seiichiro Nakabayashi, Hiroshi Y. Yoshikawa
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 5 (1) 253 - 257 1948-7185 2014/01 [Refereed][Not invited]
     
    Hydrogels with tunable elasticity has been widely used as micromechanical environment models for cells. However, the imaging of physical contacts between cells and hydrogels with a nanometer resolution along the optical axis remain challenging because of low reflectivity at hydrogel-liquid interface. In this work, we have developed an advanced interferometric optical microscopy for the high contrast visualization of cell-hydrogel contact. Here, reflection interference contrast microscopy (RICM) was modified with a confocal unit, high throughput optics and coherent monochromatic light sources to enhance interferometric signals from cell-hydrogel contact zones. The advanced interferomety clearly visualized physical contacts between cells and hydrogels, and thus enabled the quantitative evaluation of the area of cell-hydrogel adhesion.
  • Yoshihisa Suzuki, Gen Sazaki, Kaori Hashimoto, Takahisa Fujiwara, Yoshinori Furukawa
    JOURNAL OF CRYSTAL GROWTH 383 67 - 71 0022-0248 2013/11 [Refereed][Not invited]
     
    We show the possibility of unidirectional freezing of colloidal random suspensions as a novel method for growing colloidal crystals. First we confirmed the rejection of polystyrene particles from unidirectionally growing ice water interfaces by observing color gradations of colloidal crystals formed in front of the interfaces. The rejection of particles from the growing interfaces increased particle concentration in the colloidal crystals. Then we succeeded in achieving colloidal crystallization in front of ice water interfaces during the unidirectional freezing of water suspensions of polystyrene particles. The colloidal crystals thus brained exhibited a columnar shape that is typically observed in the unidirectional colloidal crysrallizarion using centrifugation. (C) 2013 Elsevier B.V. All rights reserved.
  • Shigeru Sugiyama, Noriko Shimizu, Gen Sazaki, Mika Hirose, Yoshinori Takahashi, Mihoko Maruyama, Hiroyoshi Matsumura, Hiroaki Adachi, Kazufumi Takano, Satoshi Murakami, Tsuyoshi Inoue, Yusuke Mori
    CRYSTAL GROWTH & DESIGN 13 (5) 1899 - 1904 1528-7483 2013/05 [Refereed][Not invited]
     
    Agarose has been utilized in protein crystallization to control nucleation of protein crystals. It reduces convection, prevents crystal sedimentation, and increases tolerance to environmental perturbations, resulting in high-quality protein crystals. However, crystallographers have seldom used agarose hydrogel because it requires preincubating the crystallization solution at high temperatures where a high-temperature-sensitive protein may be inactivated or aggregated. To overcome this disadvantage, we used a thermoreversible gel polymer (TGP) made from synthetic polymer. TGP turns into hydrogel upon warming and liquefies upon cooling. This novel approach enabled us to prepare the crystallization solutions at low temperature (277-283 K) and to crystallize elastase, glucose isomerase, and lysozyme with TGP. We also found that TGP clearly increased the number of elastase, glucose isomerase, and lysozyme crystals. This approach will provide a wide variety of possibilities for protein crystallization in hydrogels.
  • Gen Sazaki, Harutoshi Asakawa, Ken Nagashima, Shunichi Nakatsubo, Yoshinori Furukawa
    CRYSTAL GROWTH & DESIGN 13 (4) 1761 - 1766 1528-7483 2013/04 [Refereed][Not invited]
     
    Ice crystal surfaces melt at temperatures below 0 degrees C, and then quasi-liquid layers (QLLs) are formed. However, revealing the dynamic behavior of QLLs, which dominates the surface properties of ice crystals at temperatures near the melting point, remains an experimental challenge. Here, we demonstrate the similarities and differences in the generation mechanisms of two types of QLL phases, which show different morphologies and dynamics. We directly visualized the appearance of round liquidlike droplets (alpha-QLLs) and thin liquidlike layers (beta-QLLs) on ice basal faces by advanced optical microscopy, which can allow visualization of the individual elementary steps on basal faces. We found that alpha-QLLs always appear at outcrops of dislocations, and that beta-QLLs emerge from crystal surfaces where many microdefects are embedded. These results clearly demonstrate the similar function that strain induces the appearance of both types of QLLs. We also found that beta-QLLs are spontaneously formed at interfaces between basal faces and alpha-QLLs, when the diameter of the alpha-QLLs becomes larger than several tens of micrometers. This result arose from the different structures of alpha- and beta-QLLs: the beta-QLLs probably have a structure intermediate between those of basal faces and alpha-QLLs, resulting in a reduction of the total interfacial free energy.
  • Gen Sazaki, Zepeda Salvador, Shunichi Nakatsubo, Yoshinori Furukawa
    JOURNAL OF THE JAPANESE SOCIETY FOR FOOD SCIENCE AND TECHNOLOGY-NIPPON SHOKUHIN KAGAKU KOGAKU KAISHI 60 (8) 445 - 449 1341-027X 2013 [Refereed][Not invited]
     
    Molecular-level understanding of ice crystal surfaces holds the key to unlocking the secrets of various fields. To observe ice crystal surfaces at the molecular level, we developed an advanced optical microscope, and succeeded in visualizing individual elementary steps of 0.37 nm in height on ice basal faces. Utilizing this microscope, we also attempted to visualize the surface melting processes of ice crystals. We found the presence of two types of surface liquid phases (quasi-liquid layer phases) that exhibit different morphologies and dynamics on ice basal faces.
  • Hiroshi Y. Yoshikawa, Yoichiroh Hosokawa, Ryota Murai, Gen Sazaki, Tomoya Kitatani, Hiroaki Adachi, Tsuyoshi Inoue, Hiroyoshi Matsumura, Kazufumi Takano, Satoshi Murakami, Seiichiro Nakabayashi, Yusuke Mori, Hiroshi Masuhara
    CRYSTAL GROWTH & DESIGN 12 (9) 4334 - 4339 1528-7483 2012/09 [Refereed][Not invited]
     
    We developed a spatially precise, soft microseeding method for the production of single protein crystals that are suitable for X-ray crystallographic studies. We used focused femtosecond laser pulses to produce, via multiphoton absorption processes, seed crystals from small regions (similar to 1 mu m(2)) of crystals. Hen egg-white lysozyme seed crystals, produced in this manner, grew to be single crystals without any deterioration in their crystallinity. We also validated the technique using polycrystals for the membrane protein, acriflavine resistance protein B, for which single crystals are very difficult to obtain. In addition, we found that the shape of a tetragonal lysozyme crystal prepared from the seed could be controlled by altering the time interval between the initiation of crystallization and laser ablation. We also tried to comprehend the mechanism of femtosecond laser-induced microseeding. We visualized the ablated surfaces of the lysozyme crystals by atomic force microscopy and by laser confocal microscopy combined with differential interference microscopy. The results obtained in this study clearly demonstrate that femtosecond laser ablation of protein crystals is based on a photomechanical process, which ejects crystal fragments with little thermal damage. Femtosecond laser ablation is indeed very promising to produce high quality protein seed crystals from polycrystals or cracked crystals that are not suitable for X-ray diffraction studies.
  • Gen Sazaki, Alexander E. S. Van Driessche, Guoliang Dai, Masashi Okada, Takuro Matsui, Fermin Otalora, Katsuo Tsukamoto, Kazuo Nakajima
    PROTEIN AND PEPTIDE LETTERS 19 (7) 743 - 760 0929-8665 2012/07 [Refereed][Not invited]
     
    To start systematically investigating the quality improvement of protein crystals, the elementary growth processes of protein crystals must be first clarified comprehensively. Atomic force microscopy (AFM) has made a tremendous contribution toward elucidating the elementary growth processes of protein crystals and has confirmed that protein crystals grow layer by layer utilizing kinks on steps, as in the case of inorganic and low-molecular-weight compound crystals. However, the scanning of the AFM cantilever greatly disturbs the concentration distribution and solution flow in the vicinity of growing protein crystals. AFM also cannot visualize the dynamic behavior of mobile solute and impurity molecules on protein crystal surfaces. To compensate for these disadvantages of AFM, in situ observation by two types of advanced optical microscopy has been recently performed. To observe the elementary steps of protein crystals noninvasively, laser confocal microscopy combined with differential interference contrast microscopy (LCM-DIM) was developed. To visualize individual mobile protein molecules, total internal reflection fluorescent (TIRF) microscopy, which is widely used in the field of biological physics, was applied to the visualization of protein crystal surfaces. In this review, recent progress in the noninvasive in situ observation of elementary steps and individual mobile protein molecules on protein crystal surfaces is outlined.
  • Mihoko Maruyama, Hisato Kawahara, Gen Sazaki, Syou Maki, Yoshinori Takahashi, Hiroshi Y. Yoshikawa, Shigeru Sugiyama, Hiroaki Adachi, Kazufumi Takano, Hiroyoshi Matsumura, Tsuyoshi Inoue, Satoshi Murakami, Yusuke Mori
    CRYSTAL GROWTH & DESIGN 12 (6) 2856 - 2863 1528-7483 2012/06 [Refereed][Not invited]
     
    To grow protein crystals of better quality, there still exists an open question whether a solution flow should be suppressed or intentionally introduced. To obtain a comprehensive understanding of the effects of a solution flow, we directly measured the velocities of individual elementary steps (on {110} faces of tetragonal lysozyme crystals) under a forced solution flow, for the first time, by laser confocal microscopy combined with differential interference contrast microscopy. When we used crystals grown by a two-dimensional (2D) nucleation growth mechanism in a solution of commercial lysozyme (98.5% purity, from Seikagaku Co.), while increasing the solution flow rate, the step velocity decreased monotonically. We confirmed that this decrease in the step velocity with flow rate was due to the enhancement of the mass transfer of impurity (mainly covalently bonded dimer), by the observation using a lysozyme further purified (dimer was removed). In contrast, when we used crystals grown by a spiral growth mechanism in a commercial lysozyme solution, with increasing the flow rate, the step velocity increased and had the maximum at the flow rate of 10 mu m/s; and then decreased monotonically. Also, the step velocity was 2-4 times higher than in the case of the 2D nucleation growth. These results demonstrate that the growth of spiral steps is less affected by impurities because the density of spiral steps is much higher than that of 2D island ones.
  • Mike Sleutel, Gen Sazaki, Alexander E. S. Van Driessche
    CRYSTAL GROWTH & DESIGN 12 (5) 2367 - 2374 1528-7483 2012/05 [Refereed][Not invited]
     
    The morphology and step kinetics of 2D islands and spiral hillocks of lysozyme crystals growing from purified and contaminated solutions were determined and compared. It was found that the morphology and step dynamics of spiral hillocks of lysozyme crystals are less affected by the presence of impurities in the growth solution as compared to steps generated by 2D nucleation. These observations could be satisfactorily explained considering the terrace exposure time of spiral hillocks (tau(sp)) and 2D islands (tau(2D)) and the characteristic impurity adsorption time (tau(i)). For lysozyme, overlapping time scales of terrace exposure and impurity adsorption exist and tau(i) approximate to tau(sp) < tau(2D). Hence, when crystal growth is dominated by spiral hillocks, less impurities are adsorbed onto the crystal surface and a more pure crystal lattice is formed. Although spiral hillocks reduce the effect of impurities, they do play a significant role in the mechanism of step bunching.
  • Shigeru Sugiyama, Mihoko Maruyama, Gen Sazaki, Mika Hirose, Hiroaki Adachi, Kazufumi Takano, Satoshi Murakami, Tsuyoshi Inoue, Yusuke Mori, Hiroyoshi Matsumura
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 134 (13) 5786 - 5789 0002-7863 2012/04 [Refereed][Not invited]
     
    High-throughput protein X-ray crystallography offers a significant opportunity to facilitate drug discovery. The most reliable approach is to determine the three-dimensional structure of the protein ligand complex by soaking the ligand in apo crystals. However, protein apo crystals produced by conventional crystallization in a solution are fatally damaged by osmotic shock during soaking. To overcome this difficulty, we present a novel technique for growing protein crystals in a high-concentration hydrogel that is completely gellified and exhibits high strength. This technique allowed us essentially to increase the mechanical stability of the crystals, preventing serious damage to the crystals caused by osmotic shock. Thus, this method may accelerate structure-based drug discoveries.
  • Gen Sazaki, Salvador Zepeda, Shunichi Nakatsubo, Makoto Yokomine, Yoshinori Furukawa
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 109 (4) 1052 - 1055 0027-8424 2012/01 [Refereed][Not invited]
     
    Ice plays crucially important roles in various phenomena because of its abundance on Earth. However, revealing the dynamic behavior of quasi-liquid layers (QLLs), which governs the surface properties of ice crystals at temperatures near the melting point, remains an experimental challenge. Here we show that two types of QLL phases appear that exhibit different morphologies and dynamics. We directly visualized the two types of QLLs on ice crystal surfaces by advanced optical microscopy, which can visualize the individual 0.37-nm-thick elementary steps on ice crystal surfaces. We found that they had different stabilities and different interactions with ice crystal surfaces. The two immiscible QLL phases appeared heterogeneously, moved around, and coalesced dynamically on ice crystal surfaces. This picture of surface melting is quite different from the conventional picture in which one QLL phase appears uniformly on ice crystal surfaces.
  • Ryugo Tero, Gen Sazaki, Tom Ujihara, Tsuneo Urisu
    LANGMUIR 27 (16) 9662 - 9665 0743-7463 2011/08 [Refereed][Not invited]
     
    Hierarchic structure and anomalous diffusion on submicrometer scale were introduced into an artificial cell membrane, and the spatiotemporal dependence of lipid diffusion was visualized on nanostructured oxide surfaces. We observed the lipid diffusion in supported lipid bilayers (SLBs) on step-and-terrace TiO2(100) and amorphous SiO2/Si surfaces by single molecule tracking (SMT) method. The SMT at the time resolution of 500 mu s to 30 ms achieved observation of the lipid diffusion over the spatial and temporal ranges of 100 nm/millisecond to 1 mu m/second. The temporal dependence of the diffusion coefficient in the SLB on TiO2(100) showed that the crossover from anomalous diffusion to random diffusion occurred around 10 ms. The surface fine architecture on substrates will be applicable to induce hierarchic structures on the order of 100 nm or less, which correspond to the microcompartment size in vivo.
  • Ryugo Tero, Gen Sazaki, Toru Ujihara, Tsuneo Urisu
    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 242 0065-7727 2011/08 [Refereed][Not invited]
  • Shigeru Sugiyama, Mika Hirose, Noriko Shimizu, Mayumi Niiyama, Mihoko Maruyama, Gen Sazaki, Ryota Murai, Hiroaki Adachi, Kazufumi Takano, Satoshi Murakami, Tsuyoshi Inoue, Yusuke Mori, Hiroyoshi Matsumura
    JAPANESE JOURNAL OF APPLIED PHYSICS 50 (2) 0021-4922 2011/02 [Refereed][Not invited]
     
    High-accuracy X-ray diffraction measurements of protein crystals are an important process to determine three-dimensional structures. Investigators must manipulate crystals in X-ray diffraction measurement. Protein crystals are exposed to evaporation during manipulation, and their exposure to evaporation for a long time causes serious damage. Recently, we have developed a novel technique of protein crystallization using a semi-solid agarose gel (SSAG), which demonstrated several desirable merits such as the growth of crystals with high quality, growth with a high nucleation rate, and the possibility of automated crystal capture. To further assess the merits of SSAG-grown crystals, we evaluated the effects of evaporation on the quality of SSAG-grown crystals using X-ray diffraction and subsequent structural analyses. The results demonstrate that the SSAG-grown crystals showed a high tolerance to evaporation, compared with the solution-grown crystals. These comparative experiments also demonstrate the practical advantages of efficient protection by the SSAG surrounding the protein crystals. (C) 2011 The Japan Society of Applied Physics
  • Guoliang Dai, Gen Sazaki, Takuro Matsui, Katsuo Tsukamoto, Kazuo Nakajima, Qi Kang, Wenrui Hu
    CRYSTAL GROWTH & DESIGN 11 (1) 88 - 92 1528-7483 2011/01 [Refereed][Not invited]
     
    The adsorption/desorption behavior of mobile solute molecules at a solution-crystal interface has been explored using crystals of model protein hen egg-white lysozyme (HEWL) and fluorescent-labeled HEWL (F-HEWL) molecules. We have tracked the transient processes occurring during adsorption/desorption of identical F-HEWL molecules on a tetragonal HEWL crystal surface by single-molecule visualization using a total internal reflection fluorescent microscope and pulsed discontinuous laser illumination. We found an induction period (similar to 70 min) after which the number density of F-HEWL molecules adsorbed mainly on steps increased linearly with the adsorption time. We show direct evidence that the residence time of molecules on the crystal surface gradually increases during the transition process from a solute species to the crystal after successive multistep processes.
  • Gen Sazaki, Salvador Zepeda, Shunichi Nakatsubo, Etsuro Yokoyama, Yoshinori Furukawa
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 107 (46) 19702 - 19707 0027-8424 2010/11 [Refereed][Not invited]
     
    Due to the abundance of ice on earth, the phase transition of ice plays crucially important roles in various phenomena in nature. Hence, the molecular-level understanding of ice crystal surfaces holds the key to unlocking the secrets of a number of fields. In this study we demonstrate, by laser confocal microscopy combined with differential interference contrast microscopy, that elementary steps (the growing ends of ubiquitous molecular layers with the minimum height) of ice crystals and their dynamic behavior can be visualized directly at air-ice interfaces. We observed the appearance and lateral growth of two-dimensional islands on ice crystal surfaces. When the steps of neighboring two-dimensional islands coalesced, the contrast of the steps always disappeared completely. We were able to discount the occurrence of steps too small to detect directly because we never observed the associated phenomena that would indicate their presence. In addition, classical two-dimensional nucleation theory does not support the appearance of multilayered two-dimensional islands. Hence, we concluded that two-dimensional islands with elementary height (0.37 and 0.39 nm on basal and prism faces, respectively) were visualized by our optical microscopy. On basal and prism faces, we also observed the spiral growth steps generated by screw dislocations. The distance between adjacent spiral steps on a prism face was about 1/20 of that on a basal face. Hence, the step ledge energy of a prism face was 1/20 of that on a basal face, in accord with the known lower-temperature roughening transition of the prism face.
  • Alexander E. S. Van Driessche, Juan Manuel Garcia-Ruiz, Jose Manuel Delgado-Lopez, Gen Sazaki
    CRYSTAL GROWTH & DESIGN 10 (9) 3909 - 3916 1528-7483 2010/09 [Refereed][Not invited]
     
    In this work we studied the kinetics of gypsum crystals growing from aqueous solutions as a function of temperature and supersaturation. Laser confocal differential interference contrast microscopy (LCM-DIM) and atomic force microscopy (A FM) were used to observe in situ the step advancement and the evolution of the surface morphology of the {010} face. We found that, for the experimental conditions used in this study, 2D nucleation is the main step generation mechanism, even at low supersaturations, and only a few spiral hillocks were observed. Due to the elongated morphology of 2D islands along the c-axis and the frequent nucleation of multilayer 2D islands, {010} faces growing from a supersatured solution developed a "hill and valley" topography. This type of surface topography is observed at all temperatures. The step kinetic coefficient, beta(st), was determined in the temperature range 20-80 degrees C, and a steep increment in the kinetic coefficient is found with increasing temperature. From these data, the activation barrier for incorporation of building units in the (010) face was determined to be 70.7 +/- 5.0 kJ/mol. Analysis of the kinetic data shows that at low temperatures (<= 40 degrees C) growth of the {010) face is dominated by a mixed regime and at higher temperatures (>40 degrees C) growth is controlled solely by diffusion.
  • Yoshihisa Suzuki, Gen Sazaki, Masamitsu Matsumoto, Makoto Nagasawa, Kazuo Nakajima, Katsuhiro Tamura
    CRYSTAL GROWTH & DESIGN 10 (4) 2020 - 2020 1528-7483 2010/04 [Refereed][Not invited]
  • Toshiyuki Chatake, Gen Sazaki, Tatsuhiko Kikkou, Satoru Fujiwara, Takuya Ishikawa, Osamu Matsumoto, Yukio Morimoto
    CRYSTAL GROWTH & DESIGN 10 (3) 1090 - 1095 1528-7483 2010/03 [Refereed][Not invited]
     
    We propose a technique for DNA crystallization using the thermal reversible process of DNA. A double-stranded DNA (dsDNA) can be converted into two single-stranded DNAs (ssDNAs) at high temperatures to improve its water solubility. Thus, this thermal conversion can be utilized for increasing the solubility of DNA crystals by changing solute species. We investigated the solubility of the crystals of a DNA hexamer d(CGCGCG) and their melting temperature, at which thermal conversion occurs from it dsDNA to ssDNAs or vice versa. A van't Hoff plot showed two crystallization processes with it change in temperature dependency of the solubility at around 315 K. This result almost corresponded to the melting temperature (322 K) measured by UV spectroscopy. These Findings suggest that the conversion from a dsDNA to ssDNAs results in an increase in solubility. Using this temperature-controlled technique, single crystals of the DNA hexamer could be obtained from a small amount of DNA samples; X-ray assessment demonstrated that these crystals were high grade. This easy-to-apply technique would be superior to the conventional vapor diffusion technique in that it allows the solubility of DNA crystals to be controlled with no need for expensive Setups.
  • Jaime Gomez-Morales, Angeles Hernandez-Hernandez, Gen Sazaki, Juan Manuel Garcia-Ruiz
    CRYSTAL GROWTH & DESIGN 10 (2) 963 - 969 1528-7483 2010/02 [Refereed][Not invited]
     
    The nucleation and polymorphism of calcium carbonate have been studied using a microdevice named the crystallization mushroom. This setup allows carrying out precipitation experiments reproducibly by the vapor diffusion sitting drop technique. Within the range of concentrations investigated (from 10 to 500 mmol/L CaCl(2) and from 1 to 25 mmol/L NH(4)HCO(3)), the dominant polymorph to appear first in the drops wits calcite, or mixtures of calcite and vaterite followed by aragonite. Additionally, amorphous calcium carbonate (ACC) was not observed. The order of appearance of the polymorphs in the droplets is explained by intrinsic features of the crystallization mushroom, that is, the slow increase in the ionic activity product caused by slow diffusion of NH(3) and CO(2) gases, which favors the least soluble phase calcite to crystallize before other more soluble polymorphs. The appearance of calcite its the first nucleating dominant polymorph in the drops allowed us to calculate its surface free energy from induction time measurements assuming the mononuclear nucleation model. The experimentally calculated result of 35 mJ/m(2) is lower than the value predicted for homogeneous nucleation. The cause is the existence of heterogeneous nucleation taking place at the air-solution and solution-support interfaces.
  • Ryota Murai, Hiroshi Y. Yoshikawa, Yoshinori Takahashi, Mihoko Maruyama, Shigeru Sugiyama, Gen Sazaki, Hiroaki Adachi, Kazufumi Takano, Hiroyoshi Matsumura, Satoshi Murakami, Tsuyoshi Inoue, Yusuke Mori
    APPLIED PHYSICS LETTERS 96 (4) 0003-6951 2010/01 [Refereed][Not invited]
     
    We found that the use of a gel solution with agarose enhanced femtosecond laser-induced nucleation and produced hen egg white lysozyme crystals at three to five times lower supersaturation than those by the femtosecond laser or agarose alone. The fast fluorescence imaging of the protein in the gel solution revealed that cavitation bubbles created high-concentration regions at the focal point, which could be the trigger for protein nucleation. The lower diffusions of protein molecules in agarose gel retained the high-concentration regions for a longer time, and facilitated the nucleation.
  • T. Fujiwara, Y. Suzuki, G. Sazaki, K. Tamura
    INTERNATIONAL CONFERENCE ON HIGH PRESSURE SCIENCE AND TECHNOLOGY, JOINT AIRAPT-22 AND HPCJ-50 215 1742-6588 2010 [Refereed][Not invited]
     
    We successfully measured equilibrium temperatures T(e) of tetragonal hen egg-white lysozyme crystals under high pressure by in situ observation of steps on the {110} faces of the crystals. The dependence of T(e) on the concentration of lysozyme corresponds to that of the solubility C(e) on temperature. The precision of the solubility determined in this study is significantly higher than that in previous works. One T(e) could be measured during short time less than 70 minutes. This method for solubility measurements of protein crystals under high pressure is the fastest one at this stage.
  • Gen Sazaki
    PROGRESS IN BIOPHYSICS & MOLECULAR BIOLOGY 101 (1-3) 45 - 55 0079-6107 2009/11 [Refereed][Not invited]
     
    From the latter half of the 90s, many studies of the effects of magnetic fields on protein crystallization have been carried out. It has been found that the crystallization of proteins under both homogeneous and inhomogeneous (gradient) magnetic fields enhances the quality of protein crystals. The quality enhancement is attributed to the magnetic orientation of protein crystals and the magnetic suppression of buoyancy convection in protein solutions. The magnetic fields also affect the kinetics of protein crystallization and hence change the habit of protein crystals. In this review, the effects of magnetic fields on protein crystallization, their mechanisms and indispensable future studies are outlined. (C) 2009 Elsevier Ltd. All rights reserved.
  • Yoshihisa Suzuki, Gen Sazaki, Masamitsu Matsumoto, Makoto Nagasawa, Kazuo Nakajima, Katsuhiro Tamura
    CRYSTAL GROWTH & DESIGN 9 (10) 4289 - 4295 1528-7483 2009/10 [Refereed][Not invited]
     
    We have succeeded in the first direct observation under high pressure of the elementary steps (7.2 nm high) on {011} faces of glucose isomerase (GI) crystals, by using a laser confocal microscope combined with a differential interference contrast microscope (LCM-DIM) and a specially designed high-pressure vessel with a sapphire window of 1 mm thickness. The images of elementary steps taken under 50 MPa exhibited a sufficiently high contrast level for subsequent studies of crystal growth. By in situ observations, we directly confirmed that, irrespective of pressure, {011} faces of GI crystals grew by two-dimensional (2D) nucleation growth of the polynucleation type, and that pressure did not affect growth morphology. We measured the solubility of GI crystals under high pressure by observing in situ the growth and dissolution of elementary steps and ridges on the crystals. The resulting solubility curve exhibited much higher precision than those determined by interferometry, and revealed a significant decrease in solubility with increasing pressure. We also measured the 2D nucleation rates of 2D islands and the velocities of elementary steps under high pressure.
  • Alexander E. S. Van Driessche, Gen Sazaki, Guoliang Dai, Fermin Otalora, Jose A. Gavira, Takuro Matsui, Izumi Yoshizaki, Katsuo Tsukamoto, Kazuo Nakajima
    CRYSTAL GROWTH & DESIGN 9 (7) 3062 - 3071 1528-7483 2009/07 [Refereed][Not invited]
     
    We measured noninvasively step velocities of elementary two-dimensional (2D) islands on {110} faces of tetragonal lysozyme crystals, under various supersaturations, by laser confocal microscopy combined with differential interference contrast microscopy. We studied the correlation between the effects of protein impurities on the growth of elementary steps and their adsorption sites on a crystal surface, using three kinds of proteins: fluorescent-labeled lysozyme (F-lysozyme), covalently bonded dimers of lysozyme (dimer), and a 18 kDa polypeptide (18 kDa). These three protein impurities suppressed the advancement of the steps. However, they exhibited different supersaturation dependencies of the Suppression of the step velocities. To clarify the cause of this difference, we observed in situ the adsorption sites of individual molecules of F-lysozyme and fluorescent-labeled dimer (F-dimer) on the crystal surface by single-molecule visualization. We found that F-lysozyme adsorbed preferentially on steps (i.e., kinks), whereas F-dimer adsorbed randomly on terraces. Taking into account the different adsorption sites of F-lysozyme and F-dimer, we could successfully explain the different effects of the impurities on the step velocities. These observations strongly suggest that 18 kDa also adsorbs randomly on terraces. Seikagaku lysozyme exhibited a complex effect that could not alone be explained by the two major impurities (dimer and 18 kDa) present in Seikagaku lysozyme, indicating that trace amounts of other impurities significantly affect the step advancement.
  • Mihoko Maruyama, Katsuo Tsukamoto, Gen Sazaki, Yoshihiro Nishimura, Peter G. Vekilov
    CRYSTAL GROWTH & DESIGN 9 (1) 127 - 135 1528-7483 2009/01 [Refereed][Not invited]
     
    The regulation of calcite mineralization by chiral biological molecules is one of the fundamental unresolved issues at the interface between biological, geological, and physical sciences. Here we address the role of chirality of L-aspartic acid (L-Asp), a model additive, in the regulation of the growth of calcite crystals. We apply phase-shift interferometry to nonintrusively monitor in-situ the morphology of the surface and quantify the velocity of propagation of the edges of the unfinished crystal layers, the steps, during crystallization. We show that L-Asp leads to several-fold increase in the step velocity, in all directions, at low supersaturations, and several-fold decrease in the step velocity at high supersaturations. L-Asp also introduces asymmetry in the velocity of steps related by mirror symmetry, however, of <= 10%. To explain the complex effects of L-Asp and, likely, of other biological regulators of calcite crystallization, we show that prior to incorporation into steps, calcium and carbonate ions adsorb on the terraces and diffuse toward the steps. L-Asp accelerates the surface diffusion toward the steps, an achiral process, likely because of rearrangement by L-Asp of the structure of the water coating the calcite crystal surface. Importantly, L-Asp delays by similar to 20x the incorporation of calcite ions into the steps, the only chiral process in the calcite crystallization mechanism, likely by blocking a significant fraction of the kinks. We show that the low asymmetry between the two chiral directions is due to suppression of chirality by the symmetric surface supply fields of the steps. The results and analyses presented here suggest that the chiral effects of biogenerated molecules on crystallization may be too weak to determine the biological or nonbiological origin of minerals.
  • Guoliang Dai, Xingyu Liu, Gen Sazaki, Xiaogang Zhang
    JOURNAL OF CRYSTAL GROWTH 311 (3) 548 - 552 0022-0248 2009/01 [Refereed][Not invited]
     
    The investigation of the effect of micro impurity on crystal growth by optical microscopy has been validated. The results showed that the growth rate of a lysozyme crystal was affected even if the concentration of impurity of fluorescent-labeled lysozyme (abbreviation, F-lysozyme) was very small. Different concentrations of F-lysozyme had different effects on crystal growth rate. The growth rate decreased much more as F-lysozyme concentration increased. The density of incorporated F-lysozyme on different grown layers of a lysozyme crystal during crystal growth was obtained from the results of flat-bottomed etch pits density. (C) 2008 Elsevier B.V. All rights reserved.
  • Hiroshi Y. Yoshikawa, Ryota Murai, Shigeru Sugiyama, Gen Sazaki, Tornoya Kitatani, Yoshinori Takahashi, Hiroaki Adachi, Hiroyoshi Matsumura, Satoshi Murakami, Tsuyoshi Inoue, Kazufumi Takano, Yusuke Mori
    JOURNAL OF CRYSTAL GROWTH 311 (3) 956 - 959 0022-0248 2009/01 [Refereed][Not invited]
     
    We have performed femtosecond laser-induced nucleation of protein in agarose gel to study the crystallization dynamics. The use of agarose gel facilitates the monitoring of laser-induced crystallization from the focal point, because the gel forms a highly viscous solution at low supersaturation and thereby suppresses the diffusion of laser-induced bubbles and microcrystals. We succeeded in monitoring the crystallization process from the focal point in the time range from microseconds to days. In addition, by combining an agarose gel system with fluorescence imaging, we revealed that the shrinking of laser-induced cavitation bubbles causes a local increase of protein concentration, which could be the trigger for protein nucleation. (c) 2008 Elsevier B.V. All rights reserved.
  • The adsorption of protein molecules at a crystal/solution interface observed by an improved TIRFM
    Guoliang Dai, Gen Sazaki
    2009 3RD INTERNATIONAL CONFERENCE ON BIOINFORMATICS AND BIOMEDICAL ENGINEERING, VOLS 1-11 2382 - + 2009 [Refereed][Not invited]
     
    We have improved the ordinary total internal reflection fluorescence microscopy (TIRFM). Two improvements have been achieved, one is the interface between opaque material and solution can be observed, another is the interface far away (usually several ten micro meters) the objective lens can be observed. By this improved TIRFM, the adsorption of protein molecules at a crystal/solution interface had been successfully observed. We have obtained the results of relationship between the amount of adsorbed protein molecules on bunched steps and the height of bunched steps of a protein crystal.
  • Alexander E. S. Van Driessche, Fermin Otalora, Gen Sazaki, Mike Sleutel, K. Tsukamoto, Jose A. Gavira
    CRYSTAL GROWTH & DESIGN 8 (12) 4316 - 4323 1528-7483 2008/12 [Refereed][Not invited]
     
    The relative merits and domains of application of three observation techniques (atomic force microscopy, Michelson interferometry, and laser confocal microscopy with differential interference contrast microscopy) for the investigation of crystal growth kinetics are discussed in the context of protein crystallization. Growth rate measurements on the same system under identical experimental conditions using different techniques show differences up to 5-fold in growth rate and a different behavior of growth rate as a function of supersaturation. These results are discussed in terms of differences in mass transport at the crystal interface during data collection in the first case and as data processing artifacts in the second. Guidelines are provided for the selection of the optimal observation technique in crystal growth studies as a function of the specific problem under investigation, showing that AFM is best suited for nanometere-size, slow processes; LCM-DIM for nanometer-micrometer size, slow and medium processes; and PSMI for micrometer size, fast processes.
  • Hiroshi Y. Yoshikawa, Ryota Murai, Syou Maki, Tomoya Kitatani, Shigeru Sugiyama, Gen Sazaki, Hiroaki Adachi, Tsuyoshi Inoue, Hiroyoshi Matsumura, Kazufumi Takano, Satoshi Murakami, Takatomo Sasaki, Yusuke Mori
    APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING 93 (4) 911 - 915 0947-8396 2008/12 [Refereed][Not invited]
     
    We have investigated femtosecond laser-induced nucleation of hen egg-white lysozyme (HEWL) as a function of the laser pulse energy and pulse time width. This is the first recorded study to confirm that the femtosecond laser-induced nucleation of HEWL can be induced at a specific threshold laser energy. The threshold energy is comparable to that of cavitation bubble generation. The results strongly suggest that morphological changes in the solution are key factors for protein nucleation.
  • Alexander E. S. Van Driessche, Fermin Otalora, Jose A. Gavira, Gen Sazaki
    CRYSTAL GROWTH & DESIGN 8 (10) 3623 - 3629 1528-7483 2008/10 [Refereed][Not invited]
     
    The joint effect of agarose gel and impurities on hen egg white lysozyme crystal growth kinetics was investigated in situ by comparing the two-dimensional (2D) nucleation rate and the step velocity of crystals growing from free and gelled (agarose) solutions having two different levels of purity: highly purified (99.99% pure) and commercial grade (98.5% pure). The 2D nucleation rate and step velocity were measured on {110} faces of tetragonal lysozyme crystals using laser confocal microscopy combined with differential interference contrast microscopy (LCM-DIM). 2D nucleation rates are enhanced by the presence of gel fibers that act as heterogeneous nucleation sites. These results also show that the specific surface energies are similar for the gel fiber/crystal interface and for the gel fiber/solution interface. This is consistent with the observed incorporation of agarose fibers into the lysozyme crystal lattice and the small effect of gel fibers on step velocity. 2D nucleation in the presence of both gel and impurities is also enhanced but not as much as for gelled purified solutions. The presence of agarose has an almost negligible effect on the step velocity in purified solutions but significantly modifies the step velocity in crystals growing from impure solutions, shifting these values closer to the velocities measured in purified solutions. This velocity increase corresponds to a 7-fold reduction in the concentration of adsorbed impurities at the crystal surface with respect to ungelled experiments. This direct evidence of the diffusive impurity filtering concept is also consistent with the qualitative observations on 2D island morphologies.
  • Gen Sazaki, Masashi Okada, Takuro Matsui, Tomonobu Watanabe, Hideo Higuchi, Katsuo Tsukamoto, Kazuo Nakajima
    CRYSTAL GROWTH & DESIGN 8 (6) 2024 - 2031 1528-7483 2008/06 [Refereed][Not invited]
     
    We directly observed the diffusion of individual fluorescence-labeled protein molecules at an interface between a solution and a protein crystal using a single-molecule visualization technique, by which we can observe individual molecules with fluorescence labels. We simulated the diffusion behavior of mobile solute molecules at a solution-crystal interface, using fluorescence-labeled lysozyme and tetragonal lysozyme crystals. We found that the molecules diffused along the crystal surface 4-5 orders of magnitude slower (diffusion coefficient (6.9 +/- 1.2) x 10(-15) m(2)/S) than in a bulk solution, indicating that the molecules strongly interacted with molecules that were aligned at the crystal surface. This result denotes that slow two-dimensional diffusion inside a range of interactions from the crystal surface is a general picture of surface diffusion at an interface between an aqueous solution and a hydrophilic crystal surface. In addition, the number density of the molecules at the interface was 3 orders of magnitude higher than that estimated from a concentration of a bulk solution, demonstrating that interaction from the crystal surface drastically condensed the molecules at the interface. The average residence time and average diffusion length of the molecules at the interface were 0.47 s and 0.11 mu m, respectively.
  • Kozo Fujiwara, Kensaku Maeda, Noritaka Usami, Gen Sazaki, Yoshitaro Nose, Akiko Nomura, Toetsu Shishido, Kazuo Nakajima
    ACTA MATERIALIA 56 (11) 2663 - 2668 1359-6454 2008/06 [Refereed][Not invited]
     
    We directly observed the transition of crystal growth behavior of Si in a low undercooling region. We succeeded in observing the initiation of faceted dendrite growth from a portion of parallel twins with increasing degrees of undercooling. The critical undercooling for growing a faceted dendrite was experimentally determined to be Delta T= 10 K. We also confirmed that parallel twins associated with faceted dendrite growth were formed between grain boundaries and not at grain boundaries during melt growth. The parallel-twin formation was explained in terms of a model of twin formation on the {111} facet plane at the growth interface. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
  • Itsuo Hanasaki, Hiroto Takahashi, Gen Sazaki, Kazuo Nakajima, Satoyuki Kawano
    JOURNAL OF PHYSICS D-APPLIED PHYSICS 41 (9) 0022-3727 2008/05 [Refereed][Not invited]
     
    Interactions between protein molecules and inorganic substrates were studied both experimentally and numerically to obtain fundamental insight into the assembly of biomacromolecules for engineering applications. We experimentally traced individual fluorescent-labelled lysozyme (F-lysozyme) molecules, diffusing in the vicinity of interfaces between a protein solution and oxidized Si( 1 0 0) and glass plates. The results indicate that diffusion coefficients of F-lysozyme molecules on both substrates are more than three orders of magnitude smaller than those in a bulk solution. The molecular dynamics simulations reveal a drastically diminished diffusion coefficient of lysozyme on the substrates of pure Si( 1 1 1) and oxidized Si( 1 0 0) with a hydroxy-terminated surface compared with that in bulk solution due to molecular adsorption behaviour on the substrate, which is in good agreement with experimental results. Furthermore, full atomistic description of the behaviour provides detailed information of deformation due to the adsorption process. Lysozyme on pure Si( 1 1 1) undergoes substantial deformation whereas that on oxidized Si( 1 0 0) does not, which indicates the importance of substrate surface condition to preserve the structure, i.e. functionality of adsorbed biomolecules.
  • S. Nishikata, G. Sazaki, J. T. Sadowski, A. Al-Mahboob, T. Nishihara, Y. Fujikawa, S. Suto, T. Sakurai, K. Nakajima
    PHYSICAL REVIEW B 76 (16) 1098-0121 2007/10 [Refereed][Not invited]
     
    Single-monolayer high pentacene (Pn) dendrites grown on a hydrogen-terminated Si(111) surface [H-Si(111)] under ultrahigh vacuum were observed by low-energy electron microscopy and microbeam low-energy electron diffraction analyses. We determined the epitaxial structure (type I) inside a unique polycrystalline domain structure of such dendrites, each of which has six equivalent epitaxial orientations of Pn two-dimensional (2D) unit cells. There are three sets of these cells, which are rotated +/- 120 degrees relative to each other. Domain boundaries inside each dendrite were successfully observed by scanning tunneling microscopy. In addition, we found another epitaxial relation (type II): the polycrystalline domain structure and lattice parameters are similar to those of the type-I dendrite; however, the 2D unit cells of the type-II dendrite are rotated approximately 90 degrees relative to those of the type-I dendrite. These results suggest that the crystal structure of the dendrites on H-Si(111) is determined mainly by the interaction between Pn molecules. Each dendrite is composed of domains that are exclusively of type I or II. The so-called point-on-line coincidences are found between the Pn 2D lattices of types I and II, and H-Si(111). The higher commensurability of the type-I dendrites than the type-II dendrites results in a higher probability of type-I dendrite formation. Moreover, for both the type-I and type-II dendrites, we found supercell structures. We estimated the minimum interface energy between the dendrite and H-Si(111) from an island's free energy, which is necessary to reproduce the growth of a single-monolayer high dendrite.
  • Alexander E. S. Van Driessche, Gen Sazaki, Fermin Otalora, Francisco M. Gonzalez-Rico, Peter Dold, Katsuo Tsukamoto, Kazuo Nakajima
    CRYSTAL GROWTH & DESIGN 7 (10) 1980 - 1987 1528-7483 2007/10 [Refereed][Not invited]
     
    We observed two-dimensional (2D) nucleation behavior on {110} and {101} faces of tetragonal crystals of model protein lysozyme by laser confocal microscopy combined with differential interference contrast microscopy (LCM-DIM). We measured, for the first time directly and noninvasively, the 2D nucleation rates using 99.99% pure lysozyme, 98.5% pure lysozyme (Seikagaku Co.), and 99.99% pure lysozyme with intentionally added impure proteins (fluorescent-labeled lysozyme, covalently bonded dimer of lysozyme, and IS kDa polypeptide). We found that 2D nucleation was the dominant growth mechanism under conditions adopted in this study, and the 2D nucleation occurred randomly on the entire crystal surface irrespective of supersaturation within the range of sigma = ln(C/C-e) = 0-1.4, where C is a bulk lysozyme concentration and C, the solubility (crystal size: 0.2-0.3 mm). Repeated 2D nucleation, which continued for 3-4 layers, was also observed mainly when the impure proteins were present. In addition, multilayered 2D islands were formed after the adsorption of relatively large foreign particles on the crystal surface. From the comparison between the 2D nucleation rates determined on the {110} faces with and without the impure proteins, we concluded that homogeneous 2D nucleation occurred under a higher supersaturation range (sigma > 0.8), irrespective of the presence of the impurities. In contrast, under a lower supersaturation range (sigma < 0.8), we found that significant heterogeneous 2D nucleation dominated the growth mainly when the impure proteins were present. The {101} faces exhibited more significant heterogeneous 2D nucleation induced by smaller amounts of impurities than in the case of the {110} faces. We also determined the ledge free energies of the homogeneous and heterogeneous nucleation. Within the experimental conditions used in this study, we could not find significant dependence of the ledge free energies of the heterogeneous nucleation on the kinds of impure proteins.
  • Hiroki Kato, Takumi Taoka, Susumu Nishikata, Gen Sazaki, Taro Yamada, Ryszard Czajka, Andrzej Wawro, Kazuo Nakajima, Atsuo Kasuya, Shozo Suto
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 46 (9A) 5701 - 5705 0021-4922 2007/09 [Refereed][Not invited]
     
    We propose an improved wet chemical process for preparing a high-quality hydrogen-terminated Si(111)-(1 x 1) surface and show an atomically ordered and ultraclean surface without carbon and oxygen contamination. The vibrational properties and surface morphology are investigated by high-resolution electron energy loss spectroscopy (HREELS), atomic force microscopy (AFM), and scanning tunneling microscopy (STM). The HREELS spectra and images of AFM and STM reveal the precise aqueous NH4F etching process of Si(111) and indicate the high controllability of steps and terraces at the atomic scale. The surface cleanliness and morphology strongly depend on the etching time. At the etching time of 10 min, we obtain an ultraclean and atomically ordered surface with wide terraces of 36 +/- 17 nm step distance. It is confirmed by AFM and STM that 1.0% ammonium sulfite is useful for removing dissolved oxygen in the 40% NH4F etching solution and for preparing a high-quality H:Si(I I I)-(I x 1) surface with a low density of etch pits. The onset of tunneling current and the gap of 1.39 eV are measured by scanning tunneling spectroscopy. There is no peak at -1.3 eV in comparison with the previous report.
  • H. Yoshikawa, T. Adachi, G. Sazaki, T. Mastui, K. Nakajima, H. Masuhara
    JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS 9 (8) S164 - S171 1464-4258 2007/08 [Refereed][Not invited]
     
    Optical trapping of silver nanoparticles dispersed with rhodamine 6G (R6G) and NaCl in water gives surface-enhanced hyper-Raman scattering (SEHRS) of R6G. In this paper we have measured the SEHRS spectrum in the R6G concentration range between 10(-7) and 10(-11) M. SEHRS intensity and signal-to-noise ratio show clear differences at the lower R6G concentrations than similar to 10(-9) M, indicating that the number of R6G in a trapped silver aggregate approaches the single-molecule level. This trapping SEHRS technique is applied for the detection of lysozyme molecules labelled with tetramethylrhodamine dye.
  • K. Fujiwara, K. Maeda, N. Usami, G. Sazaki, Y. Nose, K. Nakajima
    SCRIPTA MATERIALIA 57 (2) 81 - 84 1359-6462 2007/07 [Refereed][Not invited]
     
    We propose a simple model to explain formation mechanism of parallel twins that are related to Si-facetted dendrite growth, and attempt to confirm its validity by in situ observations. The model involves the formation of a twin boundary at the {1 111 facet plane on the growth interface followed by formation of another twin parallel to the first one. Subsequently, a facetted dendrite grows parallel to the facet plane in this model. This growth behavior was successfully observed by growth experiments. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
  • Kenji Furuta, Tetsuo Okutsu, Gen Sazaki, Izumi Yoshizaki, Hiroaki Horiuchi, Tetsuya Shimizu, Masaki Yamamoto, Yoshihito Tanaka, Hiroshi Hiratsuka
    CHEMISTRY LETTERS 36 (6) 714 - 715 0366-7022 2007/06 [Refereed][Not invited]
     
    We investigate light-induced crystallization mechanism of hen egg-white lysozyme. Photochemical intermediate radical has been expected to form cluster which grows to nucleus. To confirm the nucleation process that the radical grows to the crystal, SDS-PAGE, crystallization experiments were carried out. Covalent-bonded dimer was produced by photochemical reaction, and it grows to the crystal. We conclude that the dimer plays the role of the smallest stable cluster in early stage of the crystallization process.
  • Susumu Nishikata, Gen Sazaki, Toshihiko Takeuchi, Noritaka Usami, Shozo Suto, Kazuo Nakajima
    CRYSTAL GROWTH & DESIGN 7 (2) 439 - 444 1528-7483 2007/02 [Refereed][Not invited]
     
    We investigate thin film crystals of an organic semiconductor, pentacene (Pn), grown on hydrogen-terminated Si(111) (H-Si(111)) surfaces with various interstep distances to elucidate the effects of vicinal steps of H-Si(111) on the growth of the Pn layers. By observing the morphology of the thin films with atomic force microscopy, we conclude that the vicinal steps induce significant anisotropy in the growth of the first layers of Pn: dendritic branches evolve in a lower-terrace side (the Si[11 (2) over bar] direction), but a compact shape appears in an upper-terrace side (the Si[(1) over bar(1) over bar2] direction), although the first layers grow in an isotropic shape on a flat H-Si(111) surface. Furthermore, the growth of the first layers is much faster in the lower-terrace-side direction than in the upper-terrace-side direction. The anisotropy of the growth increases with decreasing interstep distances of H-Si(111), in particular <= 10 nm. Since such anisotropic growth was observed in a similar way irrespective of the directions of an incident Pn molecular beam, we conclude that the cause of the anisotropic growth is not the anisotropy of the surface diffusion and admolecule distribution of Pn molecules. Under the substrate temperature of 30-90 degrees C, the degree of the anisotropy remained constant within experimental error.
  • J. T. Sadowski, G. Sazaki, S. Nishikata, A. Al-Mahboob, Y. Fujikawa, K. Nakajima, R. M. Tromp, T. Sakurai
    PHYSICAL REVIEW LETTERS 98 (4) 0031-9007 2007/01 [Refereed][Not invited]
     
    We have observed, by use of low-energy electron microscopy, the first direct evidence of self-driven polycrystallization evolved from a single nucleus in the case of epitaxial pentacene growth on the Si(111)-H terminated surface. In this Letter we demonstrate that such polycrystallization can develop in anisotropic systems (in terms of crystal structure and/or the intermolecular interactions) when kinetic growth conditions force the alignment of the intrinsic preferential growth directions along the density gradient of diffusing molecules. This finding gives new insight into the crystallization of complex molecular systems, elucidating the importance of nanoscale control of the growth conditions.
  • Takuro Matsui, Gen Sazaki, Hironori Hondoh, Yoshiki Matsuura, Toshitaka Nakada, Kazuo Nakajima
    JOURNAL OF CRYSTAL GROWTH 293 (2) 415 - 422 0022-0248 2006/08 [Refereed][Not invited]
     
    To study the effects of impure proteins, i.e. proteins with heterogeneous features that are minor constituents within "purified" protein solutions, on the crystallization of target proteins, and in particular the effects of such impurities on intermolecular contacts, we modified only the e-amino group of the N-terminal lysine of hen egg-white lysozyme with a fluorescent reagent, tetramethylrhodamine-5-isothiocyanate (5-TRITC), which has a high detection sensitivity. We then investigated the effects of the fluorescent-labeled lysozyme (Flysozyme) on the nucleation and growth of tetragonal and monoclinic lysozyme crystals. In the tetragonal and monoclinic crystals, the fluorescent labels were located at molecular surfaces of lysozyme inside and outside of the intermolecular contact areas, respectively. We found that addition of a low concentration (0.02 mg/ml) of F-lysozyme significantly suppressed nucleation of the tetragonal crystals but had no effect on that of the monoclinic crystals. In contrast, addition of a higher concentration (0.05 mg/ml) of F-lysozyme significantly promoted the heterogeneous nucleation of both polymorphs. In addition, the decrease in the growth rate of the tetragonal crystal by Flysozyme was much more significant than that of the monoclinic one, although the effective distribution coefficients of F-lysozyme for the tetragonal and monoclinic crystals were similar (2.9 and 3.2, respectively). These results clearly indicate that inhibiting the formation of specific intermolecular contacts plays a crucial role in the effects of impure proteins. (c) 2006 Elsevier B.V. All rights reserved.
  • P. Dold, E. Ono, K. Tsukamoto, G. Sazaki
    JOURNAL OF CRYSTAL GROWTH 293 (1) 102 - 109 0022-0248 2006/07 [Refereed][Not invited]
     
    The step velocity on {110} faces of tetragonal lysozyme crystals has been measured in situ by high-resolution phase contrast microscopy. The movement of the steps shows a distinct anisotropy with respect to the growth velocity and the interaction with impurities. Under high-purity conditions (using lysozyme of 99.99% purity), the step velocity nu(step) in the < 110 > direction exceeds the one in the < 001 > direction by a factor of 6. Spiral hillocks as well as 2D islands show an elongated, lens shaped morphology with pronounced tips in the < 110 > direction. The ratio of nu(step) < 1110 >/nu(step) < 001 > is reduced to approximate to 2-4 when commercial grade lysozyme (purity: 98.5%) is used. The morphology of the hillocks/islands changes from the lens-shaped one to a rounded one. The step velocity into the fast growing < 110 > direction is significantly more affected by impurities than the growth into the < 001 > direction. The step velocity of monolayer islands (5.6 nm in height), of multilayer islands and of growth spirals is similar within the accuracy of the measurements. On the topside, the crystal is exposed to protein solution of approximate to 0.5 mm width. This results in convective mass transport conditions. On the backside of the crystal, there is a small gap of a few hundred nanometers. Within this gap, the crystal is growing under diffusive transport conditions. Changing the focus position from the topside of the crystal to the backside, the growth can be observed on the same crystal under convective as well as under diffusive conditions. Using commercial grade lysozyme, the growth velocity is higher under diffusive conditions than under convectively dominated ones. The morphology of the islands grown from a commercial grade solution under diffusive mass transport conditions is similar to the island morphology obtained otherwise only from high-purity solutions. Using high-purity solution, the step velocity and the island morphology does not differ as a function of the mass transport conditions. These results prove the extension of the depletion zone of the impurities and the reduced transport of impurities toward the growing interface under diffusive transport conditions. (c) 2006 Elsevier B.V. All rights reserved.
  • G Watari, N Usami, Y Nose, K Fujiwara, G Sazaki, K Nakajima
    THIN SOLID FILMS 508 (1-2) 163 - 165 0040-6090 2006/06 [Refereed][Not invited]
     
    Exposure of GeH4 on Si was attempted at various temperatures to establish growth conditions for high-quality Ge on Si or Si-on-insulator, which could be utilized for on-chip 1.3-1.55 mu m photodetectors. The grown film was found to be not pure-Ge but Ge-rich SiGe, and Si composition in the film increased with the rise of the growth temperature. This behavior could be utilized for growth of Ge on a compositionally graded SiGe buffer layer just by decreasing growth temperature. In fact, a preliminary experiment in order to obtain such a structure was successfully demonstrated by decreasing temperature from 700 to 500 degrees C at a rate of -6.7 degrees C/min. (c) 2005 Elsevier B.V. All rights reserved.
  • G Sazaki, K Tsukamoto, S Yai, M Okada, K Nakajima
    CRYSTAL GROWTH & DESIGN 5 (5) 1729 - 1735 1528-7483 2005/09 [Refereed][Not invited]
     
    We attempted to visualize defects in a tetragonal lysozyme crystal in situ by laser confocal microscopy combined with differential interference contrast microscopy (LCM-DIM). Birefringence microscopy (BM) and phase-contrast microscopy (PCM) were also employed for the in situ observations. LCM-DIM enabled us to observe the {1 10} surfaces of the crystals and visualize the strain fields around the dislocations normal to a light beam with sufficient contrast during growth for the first time. Relatively large inclusions (60 to 300 mu m) inside the crystal could also be visualized during growth, with the use of BM and PCM. We found that the dislocations appeared in bundles and were probably generated at the periphery of the relatively large inclusions inside the crystal. The existence of the dislocations was confirmed by etching experiments, in which we observed two kinds of etch pits: those with a point bottom and those with a flat bottom; the former corresponded to the dislocations inside the crystal and the latter corresponded to microdefects. Two different critical undersaturations existed above which the point-bottomed and flat-bottomed etch pits started to appear. The critical undersaturation for the point-bottomed etch pits was definitely less than that for the flat-bottomed ones. In the central region of the spiral growth hillock were many point-bottomed etch pits corresponding to the dislocations but not contributing to the formation of spiral growth steps. Although the point-bottomed etch pits were formed in only the central region of the spiral growth hillock, the flat-bottomed ones were randomly formed all over the {110} surfaces.
  • T Ujihara, S Munetoh, K Kusunoki, K Kamei, N Usami, K Fujiwara, G Sazaki, K Nakajima
    THIN SOLID FILMS 476 (1) 206 - 209 0040-6090 2005/04 [Refereed][Not invited]
     
    Liquid-phase epitaxial (LPE) growth, on silicon carbide. simultaneously covers macroscale defects, e.g., micropipes, and improves the quality of the crystal. In this study, an epi-layer grown over a macrodefect was evaluated by micro-Raman scattering spectroscopy. Before the growth process, the density of the stacking fault was high and the carrier density spatially inhomogeneous in the vicinity of the macrodefects. On the other hand, after growth, the layer over the macrodefect displayed good quality; the density of the stacking fault was less than that before growth and the homogeneity of the carrier density improved. (c) 2004 Elsevier B.V. All rights reserved.
  • Y Suzuki, G Sazaki, T Matsui, K Nakajima, K Tamura
    JOURNAL OF PHYSICAL CHEMISTRY B 109 (8) 3222 - 3226 1520-6106 2005/03 [Refereed][Not invited]
     
    The growth and dissolution rates of glucose isomerase crystals (11 0 11 face) were measured in situ at 0.1 and 100 MPa. From these data, we determined that the solubilities at 25 degreesC were C-e = 3.1 +/- 0.9 and 2.6 +/- 0.5 mg mL(-1) at 0.1 and 100 MPa, respectively. At the same supersaturation of sigma = 2.5 (or ln(C/C-e), C = the concentration of glucose isomerase, C-e = the solubility) and temperature (T = 25 degreesC), the growth rate under 100 MPa was 7.6 times larger than that under 0.1 MPa. This result shows, for the first time, a kinetic acceleration of the growth rates of protein crystals with increasing pressure. The growth rates vs sigma data fitted well with a two-dimensional nucleation growth model of a polynucleation type. The fitting results indicate that the acceleration is mainly due to the decrease in the molecular surface energy of the glucose isomerase crystal with pressure.
  • S Saijo, Y Yamada, T Sato, N Tanaka, T Matsui, G Sazaki, K Nakajima, Y Matsuura
    ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY 61 207 - 217 0907-4449 2005/03 [Refereed][Not invited]
     
    A novel method has been developed to improve protein-crystal perfection during crystallization in a high magnetic field and structural studies have been undertaken. The three-dimensional structure of orthorhombic hen egg-white (HEW) lysozyme crystals grown in a homogeneous and static magnetic field of 10 T has been determined and refined to a resolution of 1.13 Angstrom and an R factor of 17.0%. The 10 T crystals belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 56.54 (3), b = 73.86 (6), c = 30.50 (2) Angstrom and one molecule per asymmetric unit. A comparison of the structures of the 0 T and 10 T crystals has been carried out. The magnitude of the structural changes, with a root-mean-square deviation value of 0.75 Angstrom for the positions of all protein atoms, is similar to that observed when an identical protein structure is resolved in two different crystalline lattices. The structures remain similar, with the exception of a few residues e.g. Arg68, Arg73, Arg128 and Gln121. The shifts of the arginine residues result in very significant structural fluctuations, which can have large effects on a protein's crystallization properties. The high magnetic field contributed to an improvement in diffraction intensity by (i) the displacement of the charged side chains of Arg68 and Arg73 in the flexible loop and of Arg128 at the C-terminus and (ii) the removal of the alternate conformations of the charged side chains of Arg21, Lys97 or Arg114. The improvement in crystal perfection might arise from the magnetic effect on molecular orientation without structural change and differences in molecular interactions. X-ray diffraction and molecular-modelling studies of lysozyme crystals grown in a 10 T field have indicated that the field contributes to the stability of the dihedral angle. The average difference in conformational energy has a value of -578 U mol(-1) per charged residue in favour of the crystal grown in the magnetic field. For most protein atoms, the average B factor in the 10 T crystal shows an improvement of 1.8 Angstrom(2) over that for the 0 T control; subsequently, the difference in diffraction intensity between the 10 T and 0 T crystals corresponds to an increase of 22.6% at the resolution limit. The mosaicity of the 10 T crystal was better than that of the 0 T crystal. More highly isotropic values of 0.0065, 0.0049 and 0.0048degrees were recorded along the a, b and c axes, respectively. Anisotropic mosaicity analysis indicated that crystal growth is most perfect in the direction that corresponds to the favoured growth direction of the crystal, and that the crystal grown in the magnetic field had domains that were three times the volume of those of the control crystal. Overall, the magnetic field has improved the quality of these crystals and the diffracted intensity has increased significantly with the magnetic field, leading to a higher resolution.
  • Elizabeth Nieto-Mendoza, Bernardo A. Frontana-Uribe, Gen Sazaki, Abel Moreno
    JOURNAL OF CRYSTAL GROWTH 275 (1-2) E1437 - E1446 0022-0248 2005/02 [Refereed][Not invited]
     
    Investigations on electromigration phenomena for protein crystallization in gels and solution using a crystal growth cell with multiple electrodes at constant current (2 mu A per circuit) are discussed. In this work, the advantages and disadvantages of different electrode dispositions number, and electrode connections inside the cell are shown. A pH change effect was discarded as the main factor affecting the selective growth of the crystals at the cathode and the fact is explained in terms of electromigration phenomena. Additionally, controlled potential experiments were carried out in order to avoid parasitic reactions observed at constant current, resulting in an increase of reproducibility and better control of crystal growth. (C) 2004 Elsevier B. V. All rights reserved.
  • G Sazaki, T Fujino, N Usami, T Ujihara, K Fujiwara, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 273 (3-4) 594 - 602 0022-0248 2005/01 [Refereed][Not invited]
     
    On flat and off-cut Si(1 1 1) substrates terminated with monohydride, thin film crystals of organic semiconductor perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) were grown by molecular beam epitaxy (MBE) and were observed by atomic force microscopy (AFM). The thin film crystals on the hydrogen-terminated Si(1 1 1) surface (H-Si(1 1 1)) have a mesa-type island shape. On the flat H-Si(1 1 1) (average step distance > 500 rim, off-angle < 0.04degrees), with an increase in a thin film thickness, the size and number of the PTCDA islands were increased and decreased, respectively. These results show that the islands coalesced during the growth. After the coalescence of the islands, some islands became single crystals and the others became polycrystals. The ratio of the single crystal islands was estimated from the shapes of the islands. We found that the ratio of the single crystal islands after the coalescence was 48% and this value was much larger than a probability (1/6) estimated from an epitaxial relation. This result suggests that Ostwald ripening occurred in the PTCDA/H-Si(1 1 1) system. The PTCDA thin film crystals were also grown on the off-cut H-Si(1 1 1) (average step distance = 10 nm, off-angle = 1.8degrees). The number of the islands was much larger than that on the flat H-Si(1 1 1) and this result shows that the vicinal steps on the surface can work as effective nucleation sites. Coalescence of the islands was also observed on the off-cut H-Si(I 1 1). After the coalescence, the ratio of the single crystal islands on the off-cut H-Si(1 1 1) was 10% larger than that on the flat H-Si(1 1 1). This result shows that the orientation of the PTCDA islands can be controlled using the vicinal steps on the Substrate surface. (C) 2004 Elsevier B.V. All rights reserved.
  • K Nakajima, Y Azuma, N Usami, G Sazaki, T Ujihara, K Fujiwara, T Shishido, Y Nishijima, T Kusunoki
    INTERNATIONAL JOURNAL OF MATERIALS & PRODUCT TECHNOLOGY 22 (1-3) 185 - 212 0268-1900 2005 [Refereed][Not invited]
     
    Growth of binary and ternary single crystals which have complete miscibility in the phase diagrams, have been studied by several newly developed methods such as the liquid encapsulated Czochralski, Bridgman, and multi-component zone melting methods for InGaAs bulk crystals, and the multi-component zone melting methods and Bridgman methods for Ge-rich and Si-rich SiGe bulk crystals. Crystals grown by these methods are compared with each other, to find the proper growth conditions to obtain single crystals with uniform composition. Techniques for the precise control of the temperature at the growing interface and for the continuous supply of the depleted solute elements to the growth melt were developed. InGaAs bulk crystals with uniform composition were obtained by the multicomponent zone melting method. Si-rich and Ge-rich SiGe bulk crystals with uniform composition were obtained in the Ge compositional range from 10 to 78%. The advanced technologies to obtain the InGaAs and SiGe bulk crystals with much higher-quality are discussed in this paper.
  • K Fujiwara, N Usami, Y Nose, G Sazaki, K Nakajima
    Conference Record of the Thirty-First IEEE Photovoltaic Specialists Conference - 2005 1081 - 1083 0160-8371 2005 [Refereed][Not invited]
     
    We investigated crystal growth behaviors of silicon melt by using an in-situ monitoring system consisting of a furnace and a microscope. Morphology of solid/liquid interface and directional growth processes of polycrystalline silicon were directly observed. We found two kinds of grain expanding mechanisms. It is suggested that we can control a dominant orientation on a wafer surface of polycrystalline silicon by controlling those two mechanisms during casting method.
  • T Shishido, S Okada, Y Ishizawa, K Kudou, K Iizumi, Y Sawada, H Horiuchi, K Inaba, T Sekiguchi, J Ye, S Miyashita, A Nomura, T Sugawara, K Obara, M Oku, K Fujiwara, T Ujihara, G Sazaki, N Usami, S Kohiki, Y Kawazoe, K Nakajima
    JOURNAL OF ALLOYS AND COMPOUNDS 383 (1-2) 319 - 321 0925-8388 2004/11 [Refereed][Not invited]
     
    Single crystals of CrSi2 were obtained in the form of hexagonal prisms by the solution growth method using molten tin as a flux. The maximum size of the crystal is about 0.3 mm in diameter and 25 mm in length. The crystal structure of CrSi2 has hexagonal symmetry with space group P6(2)22 and the lattice parameters are a = 0.425(2) nm and c = 0.6375(1) nm, respectively. The crystals are semiconducting. The value of the micro-Vickers hardness for the {1100} face with hexagonal symmetry is 11.2 +/- 0.4 GPa. Weight gain of the crystals heated up to 1473 K in air is negligible. (C) 2004 Elsevier B.V. All rights reserved.
  • K Kutsukake, N Usami, T Ujihara, K Fujiwara, G Sazaki, K Nakajima
    APPLIED PHYSICS LETTERS 85 (8) 1335 - 1337 0003-6951 2004/08 [Refereed][Not invited]
     
    We investigated the microscopic strain fluctuation in strained-Si grown on SiGe-on-insulator (SGOI) and SiGe virtual substrates, and clarified the origins of the strain fluctuation in the strained-Si film. A periodic strain fluctuation, which reflects a cross-hatch pattern of the substrate, was observed in the sample on the virtual substrate. On the other hand, a featureless strain fluctuation with suppressed amplitude was observed in the sample on SGOI substrate. By analyzing the correlation of the Raman peak positions of the Si-Si modes in strained-Si and SiGe, the dominant mechanism of the strain fluctuation in the strained Si film was found to be the compositional fluctuation in underlying SiGe for the sample on SGOI, and the strain fluctuation reflecting the cross-hatch pattern for the sample on the virtual substrate, respectively. (C) 2004 American Institute of Physics.
  • K Fujiwara, Y Obinata, T Ujihara, N Usami, G Sazaki, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 266 (4) 441 - 448 0022-0248 2004/06 [Refereed][Not invited]
     
    We investigated the grain growth behaviors of polycrystalline silicon during directional growth from melt. Two types of grain growth behaviors were directly observed using an in situ monitoring system. In the first, when the moving velocity of solid-liquid growth interface is slow and the interfacial morphology is flat, a grain with a plane of lower surface energy with respect to the growth direction expands to lateral direction. In the second, when the interface moves fast and it has an irregular shape because of the differences of the growth rate among grains, a faster growing grain competitively expands to lateral direction covering the slower one. We suggested that the undercooling at the growth front is the key parameter to divide those growth behaviors. (C) 2004 Elsevier B.V. All rights reserved.
  • T Ujihara, E Kanda, K Obara, K Fujiwara, N Usami, G Sazaki, A Alguno, T Shishido, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 266 (4) 467 - 474 0022-0248 2004/06 [Refereed][Not invited]
     
    We investigated the effects of growth temperature on the surface morphology of silicon layers grown by liquid phase epitaxy method on a (1 1 1) oriented silicon substrate in a relatively low-temperature range from 600degreesC to 900degreesC using Au-Bi alloy solvent. Layers are formed in the following growth sequence: (1) commencing in the form of initial nuclei as starting points of growth, (2) these structures grow along lateral and vertical directions as island structures, and (3) coalesce each other. Moreover, it was made clear that flat layers tend to cover the substrate completely at high growth temperature, in order to clarify the main factor that influences the surface morphology, an empirical model of the growth process was constructed. As a result, the temperature dependence of the surface morphology mainly depends on the temperature dependence of the preferential growth direction of Si on Si (1 1 1). (C) 2004 Elsevier B.V. All rights reserved.
  • Effects of high pressure on the solubility and growth kinetics of monoclinic lysozyme crystals
    T Asai, Y Suzuki, G Sazaki, K Tamura, T Sawada, K Nakajima
    CELLULAR AND MOLECULAR BIOLOGY 50 (4) 329 - 334 0145-5680 2004/06 [Refereed][Not invited]
     
    Average growth rates of the (0 1 0) and (0 (1) over bar0) faces (R-<0 1 0>) of monoclinic lysozyme crystals were measured in situ under 0.1 and 100 MPa. From the dependence of the growth rates on the lysozyme concentration, we determined the solubility of the crystal as a function of temperature at 0.1 and 100 MPa. The solubility increased with an increase in pressure. From the comparison between the growth rates under 0.1 and 100 MPa at the same supersaturation level, we found that the growth rates of the monoclinic lysozyme crystals kinetically increase with an increase in pressure. Supersaturation dependencies of the growth rates under 0.1 and 100 MPa were well fitted with a two-dimensional (2D) nucleation growth model of a birth-and-spread type. The fitting results suggest that the increase in the growth rates with pressure can be explained by the decrease in the average ledge surface energy of 2D island, the average distance between the kinks on a step and the activation energies in the incorporation processes of solute molecules.
  • A Alguno, N Usami, T Ujihara, K Fujiwara, G Sazaki, K Nakajima, K Sawano, Y Shiraki
    APPLIED PHYSICS LETTERS 84 (15) 2802 - 2804 0003-6951 2004/04 [Refereed][Not invited]
     
    We report on the effects of spacer thickness on the external quantum efficiency (EQE) of the solar cells with Ge islands embedded into the intrinsic region of the Si-based p-i-n diode. The EQE response of the solar cells in the near-infrared region is dependent on the spacer thickness that separates the layers of self-assembled Ge islands. It was found that the EQE response has an optimum value when the spacer thickness can sustain a good vertical ordering of islands. On the other hand, random nucleation of islands due to a thicker spacer layer exhibits an inferior EQE response. Furthermore, a drastic decrease of the EQE response of the solar cells for a thinner spacer layer was observed. (C) 2004 American Institute of Physics.
  • A Moreno, G Sazaki
    JOURNAL OF CRYSTAL GROWTH 264 (1-3) 438 - 444 0022-0248 2004/03 [Refereed][Not invited]
     
    In this work, the effects of an internal electric field (a direct current) on the crystallization of hen egg-white lysozyme were investigated. The crystallization was carried out in solution and gel placed in a crystallization cell. This crystallization growth cell has two parallel Pt electrodes (0.2 mm diameter and 15 mm length), and those electrodes were in contact with crystallization media. A direct current of 2.0 muA was applied (1.9 x 10(-3)V) for 8 h in solution and 12 h in gel media. During the crystallization, no generation of gas was observed. Lysozyme crystals appeared only around the cathode (negatively charged electrode), while amorphous precipitation was observed around the anode (positively charged electrode). By applying the direct current, the number of the deposited crystals was significantly decreased, and consequently the size of the crystals was increased. The direct current also decreased the induction time of nucleation. No significant change in pH was observed during the crystallization. The deposition of the crystals only around the cathode and the decrease in the induction time can be explained by an opposite polarity of the lysozyme molecules and the electrodes and by interactions between the lysozyme molecules and the Cl- in the vicinity of the electrodes. Electric potential generated by an electric field would be also responsible for the decrease in the number of the deposited crystals. (C) 2004 Elsevier B.V. All rights reserved.
  • K Kutsukake, N Usami, K Fujiwara, T Ujihara, G Sazaki, K Nakajima, BP Zhang, Y Segawa
    APPLIED SURFACE SCIENCE 224 (1-4) 95 - 98 0169-4332 2004/03 [Refereed][Not invited]
     
    We report on fabrication of SiGe single crystal film on insulator by a simple approach including a growth of a thin Ge film on a commercially available Sol substrate, formation of a SiO2 protective layer, and rapid thermal annealing (RTA) in an Ar atmosphere. Homogeneity of the local Si fraction in SiGe-on-insulator (SGOI) was found to be closely connected with the SiGe phase diagram, and RTA below the solidus line is required to obtain homogeneous SGOI. In spite of the high annealing temperature beyond the melting point of Ge, obtained SGOI was revealed to be single crystalline as evidenced by electron back scattering pattern analysis. (C) 2003 Elsevier B.V All rights reserved.
  • N Usami, A Alguno, K Sawano, T Ujihara, K Fujiwara, G Sazaki, Y Shiraki, K Nakajima
    THIN SOLID FILMS 451 604 - 607 0040-6090 2004/03 [Refereed][Not invited]
     
    We fabricated Si-based solar cell with stacked Ge islands grown via the Stranski-Krastanov growth mode in the intrinsic layer of pin diodes. The onset of the external quantum efficiency in the near infrared regime was extended up to approximately 1.4 mum for the solar cells with stacked Ge islands. The quantum efficiency was found to increase with increasing number of stacking, showing that a part of electron-hole pairs generated within Ge islands was separated by the internal electric field and contributed to the photocurrent. Increase of the processing temperature for the impurity diffusion was found to bring blue-shift of the band gap through the intermixing of Si and Ge as well as the deformation of Ge islands. Therefore, low-temperature process was suggested to be necessary for further enhancement of quantum efficiency in the near infrared regime. (C) 2003 Elsevier B.V. All rights reserved.
  • K Fujiwara, Y Obinata, T Ujhara, N Usami, G Sazaki, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 262 (1-4) 124 - 129 0022-0248 2004/02 [Refereed][Not invited]
     
    Melt growth behavior of polycrystalline silicon was observed using a newly developed in-situ monitoring system consisting of a furnace and a microscope. It is possible to perform a directional growth from seed crystal or crucible wall and to observe the growth interface by using this system. Differences of growth rate or interfacial morphology among each grain of polycrystalline silicon were observed during melt growth. The Mullins-Sekerka instability of growth interface was also observed in a silicon melt for the first time. This observation system is confirmed to become a useful tool for revealing the growth mechanism of polycrystalline silicon. (C) 2003 Elsevier B.V. All rights reserved.
  • G Sazaki, T Fujino, JT Sadowski, N Usami, T Ujihara, K Fujiwara, Y Takahashi, E Matsubara, T Sakurai, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 262 (1-4) 196 - 201 0022-0248 2004/02 [Refereed][Not invited]
     
    Surface of an off-cut Si(1 1 1) substrate with an average step distance of 100 Angstrom was terminated with monohydride. On this substrate, thin film crystals of organic semiconductor PTCDA were grown by molecular beam epitaxy (MBE). Surface of the thin film crystals on the hydrogen-terminated Si(1 1 1) surface (H-Si(1 1 1)) were observed using ultra-high vacuum scanning tunneling microscopy (UHV-STM) and atomic force microscopy (AFM). The PTCDA thin film crystals had an island shape of Volmer-Weber type. From the direction of the vicinal steps of the substrate [1 (1) over bar 0], we determined the size and orientation of the PTCDA thin film crystals on the H-Si(1 1 1). Long-axis of the two-dimensional (2D) unit cell of the thin film crystals matches the vector (6, 2) of the H-Si(1 1 1) surface. We proposed two conceivable epitaxial relations: one is ((6)(2/3) (2)(11/3)) and the other is point-on-line coincidence. 2D unit cells of the thin film crystals have widely stretched structure (2-10%), and the island growth of Volmer-Weber type is probably due to this large lattice misfit. (C) 2003 Elsevier B.V. All rights reserved.
  • G Sazaki, T Matsui, K Tsukamoto, N Usami, T Ujihara, K Fujiwara, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 262 (1-4) 536 - 542 0022-0248 2004/02 [Refereed][Not invited]
     
    Surface micro-topography of the {110} faces of tetragonal lysozyme crystals was observed in situ by laser confocal microscopy (LCM) combined with differential interference contrast microscopy (DIM). We could observe two-dimensional (213) nucleation and subsequent growth of the 2D islands in real time. When steps of neighboring 2D islands coalesced, the contrast of the steps disappeared completely and the 2D islands merged smoothly. This result proved that the height of the steps observed by LCM combined with DIM was always the same and these steps were elementary ones (5.6 nm high). The combination of LCM and DIM was necessary to observe elementary steps with sufficient contrast. The elementary steps on a spiral growth hillock could also be observed using the LCM-DIM system, although their contrast was much smaller than that of the 2D islands because of much smaller inter-step distance. (C) 2003 Elsevier B.V. All rights reserved.
  • G Sazaki, A Moreno, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 262 (1-4) 499 - 502 0022-0248 2004/02 [Refereed][Not invited]
     
    Novel effects of combining the magnetic and internal electric fields on protein crystallization were studied in this report. Homogeneity in crystal size and ratio of magnetically orientated crystals were significantly increased, when a homogeneous magnetic field of 10T and an internal electric field (a direct current of 2 muA) were applied to the crystallization of hen egg-white lysozyme at the same time. When the directions of the magnetic field and the electric current were parallel, there were not significant effects observed. This result suggests that the Lorenz force is responsible for the coupling effects of the magnetic and internal electric fields. (C) 2003 Elsevier B.V. All rights reserved.
  • N Usami, WG Pan, K Fujiwara, T Ujihara, G Sazaki, K Nakajima
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 43 (2B) L250 - L252 0021-4922 2004/02 [Refereed][Not invited]
     
    The grain boundary character distribution of multicrystalline SiGe (mc-SiGe) solar cells with microscopic compositional distribution was revealed to have a significant effect on the photovoltaic performance of solar cells. This was clarified by comparing the photovoltaic performance of small-area (approximate to0.02 cm(2)) solar cells fabricated in a large-area solar cell with their local structures. With increasing fraction of random grain boundaries in a small-area solar cell, the conversion efficiency was found to decrease. On the other hand, Sigma3 grain boundaries are found to be dominant in a solar cell with good performance. These results suggest that the development of a crystal growth technique that fully controls the grain boundary character distribution is the key to improving the conversion efficiency of the solar cell based on multicrystalline semiconductors.
  • K Nakajima, T Ujihara, N Usami, K Fujiwara, G Sazaki, T Shishido
    JOURNAL OF CRYSTAL GROWTH 260 (3-4) 372 - 383 0022-0248 2004/01 [Refereed][Not invited]
     
    The strain, surface and interface energies of the SiGe/Si (SiGe grown on Si) heterostructure system with and without misfit dislocations were calculated for the Frank-van der Merwe (FM), Stranski-Krastanov (SK) and Volmer-Weber (VW) growth modes essentially based on the three kinds of fundamental and simple structures. The free energies for each growth mode were derived from these energies, and it was determined as a function of the composition and layer thickness of SiGe on Si. By comparison of the free energies, the phase diagrams of the FM, SK and VW growth modes for the SiGe/Si system were determined. The (111) and (100) reconstructed surfaces were selected for this calculation. From the phase diagrams, it was found for the growth of SiGe on Si that the layer-by-layer growth such as the FM mode was easy to be obtained when the Ge composition is small, and the island growth on a wetting layer such as the SK mode was easy to be obtained when the Ge composition is large. The VW mode is energetically stable in the Ge-rich compositional range, but it is difficult for the VW mode to appear in the actual growth of SiGe on Si because the VW region is right above the SK region. The regions of the SK and VW modes for the (111) heterostructure are larger than those for the (100) one because the strain energy of the (111) face is larger than that of the (100) face. The regions of the SK and VW modes for the heterostructure with misfit dislocations are narrower than those for the one without misfit dislocations because the strain energy is much released by misfit dislocations. The phase diagrams roughly explain the behavior of the FM and SK growth modes of SiGe on Si. (C) 2003 Elsevier B.V. All rights reserved.
  • T Sato, S Hara, T Matsui, G Sazaki, S Saijo, T Ganbe, N Tanaka, Y Sugano, M Shoda
    ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY 60 149 - 152 0907-4449 2004/01 [Refereed][Not invited]
     
    The dye-decolorizing peroxidase DyP is a key enzyme in the decolorizing fungus Thanatephorus cucumeris Dec 1 that degrades azo and antraquinone dyes. The gene dyp from T. cucumeris Dec 1, which has low homology to other peroxidase genes, was cloned and transformed into Aspergillus oryzae and glycosylated DyP was expressed at high levels. Purified DyP was deglycosylated using GST Endo F1 and then crystallized in a strong magnetic field ( 10 T) at 283 K using ammonium sulfate as precipitant. X-ray diffraction data to 2.96 Angstrom resolution collected from a native crystal at the Photon Factory ( Tsukuba, Japan) showed that the crystal belonged to the hexagonal space group P6(5)22, with unit-cell parameters a = b = 136.15, c = 363.46 Angstrom. The asymmetric unit of the crystal contained four DyP molecules, with a corresponding Matthews coefficient (V-M) of 2.50 Angstrom(3) Da(-1) and a solvent content of 51%. Heavy-atom derivatives of DyP have been obtained and electron-density maps have been calculated. The haem is visible and continuous electron density between the haem and protein clearly indicates the location of the proximal histidine ligand.
  • T Ujihara, S Munetoh, K Kusunoki, K Kamei, N Usami, K Fujiwara, G Sazaki, K Nakajima
    SILICON CARBIDE AND RELATED MATERIALS 2003, PRTS 1 AND 2 457-460 633 - 636 0255-5476 2004 [Refereed][Not invited]
     
    We performed homoepitaxial growth of 6H-SiC layers on substrates including micropipes by the LPE method and evaluated the crystal quality by Raman scattering spectroscopy. In particular, we focused on the crystal quality of layers covering micropipes. It was made clear that there is no stress due to morphological macroscopic defects in the crystal over micropipes. Moreover, LPE growth not only closes a micropipe but also reduces the inhomogeneity of carrier density which exists in the area of the micropipe before growth.
  • T Shishido, S Okada, Y Ishizawa, K Kudou, K Iizumi, Y Sawada, H Horiuchi, K Inaba, T Sekiguchi, JH Ye, S Miyashita, A Nomura, T Sugawara, K Obara, Y Murakami, K Fujiwara, T Ujihara, G Sazaki, N Usami, M Oku, Y Yokoyama, S Kohiki, Y Kawazoe, K Nakajima
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 42 (12) 7292 - 7293 0021-4922 2003/12 [Refereed][Not invited]
     
    Single crystals of CrSi2 were obtained in the form of hexagonal prisms by a high-temperature solution growth method using molten tin as a solvent. Their maximum dimensions were approximately 0.3 mm in diameter and 2.5 mm in length. The crystals had hexagonal symmetry with space group P6(2)22 and their lattice parameters were a=0.425(2) nm and c=0.6375(1) nm. The crystals were semi conducting. The value of the micro-Vickers hardness for the {1100} face with hexagonal symmetry was 11.2 +/- 0.4 GPa. The weight gain of the crystals heated to 1473 K in air was negligible.
  • A Alguno, N Usami, T Ujihara, K Fujiwara, G Sazaki, K Nakajima, Y Shiraki
    APPLIED PHYSICS LETTERS 83 (6) 1258 - 1260 0003-6951 2003/08 [Refereed][Not invited]
     
    We report on the performance of solar cells with stacked self-assembled Ge dots in the intrinsic region of Si-based p-i-n diode. These dots were epitaxially grown on p-type Si(100) substrate via the Stranski-Krastanov growth mode by gas-source molecular beam epitaxy. Enhanced external quantum efficiency (EQE) in the infrared region up to 1.45 mum was observed for the solar cells with stacked self-assembled Ge dots compared with that without Ge dots. Furthermore, the EQE was found to increase with increasing number of stacking. These results show that electron-hole pairs generated in Ge dots can be efficiently separated by the internal electric field, and can contribute to the photocurrent without considerable recombination in Ge dots or at Ge/Si interfaces. (C) 2003 American Institute of Physics.
  • N. Usami, A. Alguno, T. Ujihara, K. Fujiwara, G. Sazaki, K. Nakajima, K. Sawano, Y. Shiraki
    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 4 (4) 1468-6996 2003/07 [Refereed][Not invited]
     
    Stacked Ge islands formed via the Stranski-Krastanov growth mode were incorporated into the intrinsic layer of Si-based pin diode to improve the performance of the solar cells in the near-infrared regime. The onset of the external quantum efficiency was extended up to around 1.4 mm for the solar cells with stacked Ge islands. The quantum efficiency was found to increase with increasing number of stacking, and the onset of the photocurrent response was in good agreement with room-temperature photoluminescence energy of the Ge islands. These results manifest that the Ge islands did play a role to increase the quantum efficiency. Furthermore, a part of electron-hole pairs generated within Ge islands was separated by the internal electric field and contribute to the photocurrent. (C) 2003 Elsevier Ltd. All rights reserved.
  • N Usami, T Ichitsubo, T Ujihara, T Takahashi, K Fujiwara, G Sazaki, K Nakajima
    JOURNAL OF APPLIED PHYSICS 94 (2) 916 - 920 0021-8979 2003/07 [Refereed][Not invited]
     
    We report on a theoretical investigation of the elastic strain in an ellipsoidal SiGe inclusion coherently embedded in Si and its influence on the band structure of SiGe. The strain was calculated as a function of the Ge fraction in SiGe and the aspect ratio of the ellipsoid, and utilized to derive the shift of the band edge. When the principal axis of the ellipsoid was chosen to be parallel to [001], the band structure of SiGe was predicted to be Si like regardless of the aspect ratio. The band gap of strained SiGe was also calculated, and the deviation of the aspect ratio from unity was found to be effective to decrease the band gap due to the breaking of the crystal symmetry. These results suggest the importance of controlling strain, shape, and local Ge fraction in multicrystalline SiGe, which we propose as a promising material for solar cell applications. (C) 2003 American Institute of Physics.
  • Y Nagatoshi, G Sazaki, Y Suzuki, S Miyashita, T Matsui, T Ujihara, K Fujiwara, N Usami, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 254 (1-2) 188 - 195 0022-0248 2003/06 [Refereed][Not invited]
     
    Growth processes of the (0 1 1) and (0 (1) over bar 1) faces of an orthorhombic lysozyme crystal were observed in situ under 0.1 and 100 MPa, The growth rates of the (0 1 1) and (0 (1) over bar 1) faces were equal within an experimental error. From the comparison between the growth rates under 0.1 and 100 MPa at the same supersaturation level, we. found that the growth kinetics of the orthorhombic lysozyme crystals significantly decreases with an increase in pressure. Supersaturation dependencies of the growth rates under 0.1 and 100MPa were well fitted with a two-dimensional (2D) nucleation growth model of a birth-and-spread type. The fitting results show that the decrease in the growth kinetics with pressure can be explained by the increase activation energies in the incorporation processes of solute molecules. (C) 2003 Elsevier Science B.V. All rights reserved.
  • S Yanagiya, S Nishikata, G Sazaki, A Hoshino, K Nakajima, T Inoue
    JOURNAL OF CRYSTAL GROWTH 254 (1-2) 244 - 250 0022-0248 2003/06 [Refereed][Not invited]
     
    In order to establish the general way to prepare thin film crystals of organic semiconductors, we studied annealing effects on the heteroepitaxial growth of Cu-phthalocyanine (CuPc) crystallites on KCl {0 0 1} substrate crystals. CuPc was deposited on a cleaved KCl. single crystal by vacuum evaporation (under 10(-4)Torr). Then, the sample was taken out from the vacuum chamber and annealed in the air. On the CuPc as-deposited surface, no clear contrast was observed by scanning electron microscopy (SEM). On the contrary, many needle-like crystallites could be observed after the annealing treatment. Those crystallites were oriented so that their long axis was parallel to the <1 0 0> direction of the KCl substrate. We also investigated the effects of the annealing temperature and annealing duration time to find an optimal annealing condition. (C) 2003 Elsevier Science B.V. All rights reserved.
  • Y Azuma, N Usami, T Ujihara, K Fujiwara, G Sazaki, Y Murakami, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 250 (3-4) 298 - 304 0022-0248 2003/04 [Refereed][Not invited]
     
    We developed an automatic feedback control system of the crystal-melt interface position to keep the temperature at the interface constant during growth, and demonstrate its successful application to grow Ge-rich SiGe bulk crystals with uniform composition. In this system, the position of the crystal-melt interface was automatically detected by analyzing the images captured,using in situ monitoring system based on charge-coupled-devices camera, and the pulling rate of the crucible was corrected at every 1 min. The system was found to be effective to keep the crystal-melt interface position during growth even when the variation of the growth rate is quite large. Especially, the interface position was kept for 470 h during growth of Ge-rich SiGe bulk crystal when we started with a long growth melt of 80 mm. As a result, a 23 mm-long Si(0.22)Geo(0.78) bulk crystal with uniform composition was obtained thanks to the constancy of the growth temperature during growth through the control of the interface position. Our technique opens a possibility to put multicomponent bulk crystal in a practical use. (C) 2002 Elsevier.Science B.V. All rights reserved.
  • T Ujihara, K Obara, N Usami, K Fujiwara, G Sazaki, T Shishido, K Nakajima
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 42 (3A) L217 - L219 0021-4922 2003/03 [Refereed][Not invited]
     
    We investigated the effect of growth temperature on crystal quality of crystalline silicon layers grown by liquid phase epitaxy (LPE) with gold-bismuth binary alloy solvent. The electrical and structural properties were examined by means of minority-carrier lifetime measurement and micro-Raman scattering spectroscopy. Both electrical and structural qualities improve with decreasing growth temperature. In the present study, the lifetime of the silicon layer grown at the lowest temperature was higher than that of monocrystalline silicon substrate though the solvent includes gold which is a well-known strong recombination site. On the other hand, the structural quality of layers is inferior to that of the substrate even at the lowest growth temperature. Thus, the temperature dependence of lifetime was concluded to be mainly due to the reduction of the solubility of gold impurity in the layer rather than the improvement of structural quality.
  • K Kutsukake, N Usami, K Fujiwara, T Ujihara, G Sazaki, BP Zhang, Y Segawa, K Nakajima
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 42 (3A) L232 - L234 0021-4922 2003/03 [Refereed][Not invited]
     
    We report on the fabrication of a homogeneous SiGe-on-insulator as a substrate for strained Si-on-insulator (SOI) metal-oxide-semiconductor field-effect-transistors. The fabrication process includes the growth of a thin Ge film on a commercially available SOI substrate at 100degreesC using a molecular beam epitaxy system, the formation of a SiO2 cap layer by radio-frequency sputtering, and rapid thermal annealing (RTA) in an Ar atmosphere. After RTA at an appropriate temperature, the SiGe-on-insulator with a laterally homogeneous Si fraction was successfully obtained by the formation of epitaxial SiGe on a thin SOI as a seed and interdiffusion of Ge and Si atoms. However, inhomogeneous SiGe films were obtained when the annealing temperature was very high. The conditions for the realization of SiGe with a homogeneous Si fraction were found to be closely related to the phase diagram of the Si-Ge binary alloy.
  • Spatial distribution of composion and strain in multicrystalline SiGe bulk crystal and their impact on solar cell applications
    N Usami, T Takahashi, AC Alguno, K Fujiwara, T Ujihara, T Ichitsubo, G Sazaki, K Nakajima
    PROCEEDINGS OF 3RD WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION, VOLS A-C 98 - 101 2003 [Refereed][Not invited]
     
    We report on microscopic structural characterizations of multicrystalline SiGe (mc-SiGe) bulk crystal, which contains microscopic compositional distribution, and discuss possible influence on solar cell applications. By combining microscopic Raman spectroscopy and energy-dispersive x-ray analysis, the existence of built-in strain and its spatial distribution were experimentally obtained. By a simple calculation assuming ellipsoidal SiGe inclusion coherently embedded in Si-matrix, effect of the built-in strain on the band gap is quantitatively estimated. For example, an ellipsoidal Si0.5Ge0.5 inclusion with an aspect ratio less than 0.10 is predicted to have the similar band gap with unstrained Ge. Therefore, to utilize strain is concluded to be important to realize spectroscopic response in the near infrared regime with minimizing incorporation of Ge.
  • Direct observations of crystal growth from silicon melt
    K Fujiwara, K Nakajima, T Ujihara, N Usami, G Sazaki, H Hasegawa, S Mizoguchi, K Nakajima
    PROCEEDINGS OF 3RD WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION, VOLS A-C 110 - 113 2003 [Refereed][Not invited]
     
    Crystal growth behavior from silicon melt was observed using a confocal scanning laser microscope with an infrared image furnace. The morphology of growth interface changed from planar to facet with increasing growth rate. The facet vanishing process was also observed. It was shown the (111) facet formed at a steady state. The undercooling in front of the facet interface was measured by an infrared camera and found to be almost 7 degrees. The growth behavior from silicon melt was explained by the analytical expression based on two-dimensional nucleation model.
  • Structure and property of directionally grown SiGe multicrystals with microscopic compositional distribution
    K Fujiwara, T Takahashi, N Usami, T Ujihara, G Sazaki, K Nakajima
    PROCEEDINGS OF 3RD WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION, VOLS A-C 158 - 160 2003 [Refereed][Not invited]
     
    Mullticrystalline SiGe with microscopic compositional distributions is an attractive material for a new high efficiency solar cell because it has a possibility to absorb the near infrared light, which is transparent to Si. In this study, structural property and absorption coefficient was investigated for mc-SiGe and those were compared with mcSi. Columnar structure for mc-SiGe was obtained using directional growth method. It was found that the preferential crystallographic orientation of mc-SiGe is {110} plane, which is different from mc-Si. By measuring the absorption coefficient, we demonstrated that the introduction of microscopic compositional distribution in mc-SiGe is an effective way to increase absorption coefficient in longer wavelength. Mc-SiGe is therefore concluded to be promising for enabling the realization of low-cost and highly efficient solar cells.
  • What is the most important growth parameter on crystal quality of the silicon layer by LPE method?
    T Ujihara, K Obara, N Usami, K Fujiwara, G Sazaki, T Shishido, K Nakajima
    PROCEEDINGS OF 3RD WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION, VOLS A-C 1241 - 1244 2003 [Refereed][Not invited]
     
    We investigated the effect of growth parameters, growth temperature, growth rate and solvent, on crystal quality of silicon thin layers grown by LPE method. Electrical and structural properties were examined by means of minority-carrier lifetime measurement and micro-Raman scattering spectroscopy. It was made clear that crystal quality strongly depends oil the growth temperature mainly due to equilibrium impurity solubility in the silicon layers. In addition, it is important to choose an appropriate solvent whose Solubility in crystalline silicon is low and effective capture cross section is small. In actual, we successfully grew the silicon layer of which the lifetime was higher than that of monocrystalline silicon crystal as a substrate.
  • Improved quantum efficiency of solar cells with Ge dots stacked in multilayer structure
    A Alguno, N Usami, T Ujihara, K Fujiwara, K Sawano, G Sazaki, Y Shiraki, K Nakajima
    PROCEEDINGS OF 3RD WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION, VOLS A-C 2746 - 2749 2003 [Refereed][Not invited]
     
    We report on the improved external quantum efficiency of solar cells in the infrared region with self-assembled Ge dots stacked in multilayer structure embedded within the intrinsic region of a p-i-n diode. This quantum efficiency was found to increase with increasing number of stacking. This indicates that additional photocarriers are generated in the Ge dots and have a high probability of escaping from the dots and/or at Ge/Si interfaces without significant recombination under the influence of the internal electric field.
  • N Usami, T Takahashi, K Fujiwara, T Ujihara, G Sazaki, Y Murakami, K Nakajima
    JOURNAL OF APPLIED PHYSICS 92 (12) 7098 - 7101 0021-8979 2002/12 [Refereed][Not invited]
     
    We report on growth and characterizations of Si/multicrystalline-SiGe (mc-SiGe) heterostructure as a promising candidate to surpass mc-Si solar cells. Spatial distribution of the status of strain in Si was investigated using microscopic Raman spectroscopy. The strain was found to be strongly influenced by the composition and microstructure of underlying mc-SiGe. Spatial variation of the strain as well as strain relaxation was found to be suppressed by decreasing average Ge composition of underlying SiGe. (C) 2002 American Institute of Physics.
  • Y Suzuki, G Sazaki, K Visuri, K Tamura, K Nakajima, S Yanagiya
    CRYSTAL GROWTH & DESIGN 2 (5) 321 - 324 1528-7483 2002/09 [Refereed][Not invited]
     
    Solubility of glucose isomerase (from Streptomyces rubiginosus) crystals was measured in situ at 0.1 and 100 MPa. An equilibrium temperature of the crystal with the solution of a given concentration was measured using a two-beam interferometer. The solubility of the crystal decreased to about one-ninth with increasing pressure from 0.1 to 100 MPa at 30 degreesC. This means that the supersaturation, sigma (= In C/C-e, C = protein concentration, C-e = solubility), increases significantly with increasing pressure at the same temperature. This strongly suggests that the substantial acceleration of the crystallization of glucose isomerase with increasing pressure reported by Visuri et al. is due to the significant decrease in the solubility. The enthalpy and entropy of the dissolution were estimated from the van't Hoff plots. The volume change accompanying the dissolution took a large positive value as DeltaV = 54 +/- 31 cm(3) mol(-1) at 30 degreesC.
  • K Fujiwara, K Nakajima, T Ujihara, N Usami, G Sazaki, H Hasegawa, S Mizoguchi, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 243 (2) 275 - 282 0022-0248 2002/08 [Refereed][Not invited]
     
    Crystal growth behavior of silicon melt was observed using a confocal scanning laser microscope with an infrared image furnace. The morphology of the growth interface changed from planar to facet with increasing growth rate. The facet vanishing process was also observed. It was shown the (111) facet formed at a steady state. The undercooling in front of the facet interface was measured by an infrared camera and found to be almost 7degrees. The growth behavior of silicon melt was explained by an analytical expression based on a two-dimensional nucleation model. (C) 2002 Elsevier Science B.V. All rights reserved.
  • N Sato, Y Uragami, T Nishizaki, Y Takahashi, G Sazaki, K Sugimoto, T Nonaka, E Masai, M Fukuda, T Senda
    JOURNAL OF MOLECULAR BIOLOGY 321 (4) 621 - 636 0022-2836 2002/08 [Refereed][Not invited]
     
    BphC derived from Pseudomonas sp. strain KKS102 is an extradiol-cleaving catecholic dioxygenase. This enzyme contains a non-heme iron atom and plays an important role in degrading biphenyl/polychlorinated biphenyls (PCBs) in the microbe. To elucidate detailed structures of BphC reaction intermediates, crystal structures of the substrate-free form, the BphC-substrate complex, and the BphC-substrate-NO (nitric oxide) complex were determined. These crystal structures revealed (1) the binding site of the O-2 molecule in the coordination sphere and (2) conformational changes of His194 during the catalytic reaction. On the basis of these findings, we propose a catalytic mechanism for the extradiol-cleaving catecholic dioxygenase in which His194 seems to play three distinct roles. At the early stage of the catalytic reaction, His194 appears to act as a catalytic base, which likely deprotonates the hydroxyl group of the substrate. At the next stage, the protonated His194 seems to stabilize a negative charge on the O-2 molecule located in the hydrophobic O-2-binding cavity. Finally, protonated His194 seems to function as a proton donor, whose existence has been proposed. (C) 2002 Elsevier Science Ltd. All rights reserved.
  • K Nakajima, N Usami, K Fujiwara, Y Murakami, T Ujihara, G Sazaki, T Shishido
    SOLAR ENERGY MATERIALS AND SOLAR CELLS 73 (3) 305 - 320 0927-0248 2002/07 [Refereed][Not invited]
     
    The growth technique and physical properties of SiGe multicrystals with microscopic compositional distribution are demonstrated for new high-efficiency solar cells in which the wavelength dependence of the absorption coefficient can be freely designed by controlling the compositional distribution in the SiGe multicrystals. This growth technique is suitable for the practical casting method, and it is made up of melt growth of SiGe multicrystals with wide and microscopic distribution of the composition from Si to Ge all over the crystals. It is studied how much widely the microscopic compositional distribution in SiGe multicrystals grown from binary Si-Ge melts can be controlled by the melt composition and the cooling process. The range of the microscopic compositional distribution becomes wider as the starting Si concentration in the growth melt becomes larger. SiGe multicrystals with various microscopic compositional distribution can be freely controlled by optimizing the melt composition and the cooling process. The wavelength dependence of the absorption coefficient of such SiGe multicrystals can also be freely designed. Using the experimentally determined absorption coefficient of a SiGe crystal with microscopic compositional distribution, the short circuit photo-current of solar cells was calculated and it is demonstrated that the short circuit photo-current can be much larger for SiGe with microscopic compositional distribution than for SiGe with uniform composition. Si thin film can be easily grown on such a SiGe multicrystal and the Si/SiGe heterostructure can be obtained. These results show that SiGe multicrystals with microscopic compositional distribution are hopeful for new high-efficiency solar cell applications by using the practical casting method. (C) 2002 Elsevier Science B.V. All rights reserved.
  • T Ujihara, K Fujiwara, G Sazaki, N Usami, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 242 (3-4) 313 - 320 0022-0248 2002/07 [Refereed][Not invited]
     
    We established an in situ and simultaneous measurement system for solute distribution and temperature distribution in high-temperature solutions. The system consists of an infrared camera, an X-ray fluorescence spectrometer for concentration measurement and a sample stage with a two-zone heater. A sample holder is composed of some graphite parts with a quartz glass window at the bottom of holder for monitoring the infrared image. Concentration measurements are performed by the X-ray analysis through the graphite lid at the top of the holder. The present system was applied to the in situ measurement of the solute and temperature distributions in the gallium-zinc solution during the crystal growth by the solute supplied zone melting method. We selected the thin sample with the thickness of 500 pm to observe the solute distribution characterized by diffusion process. As a result, we successfully observed the process in which the solute distribution changed and consequently reached the stationary state due to the diffusion in the linear temperature gradient. These results show that the present system can be a powerful tool for actual survey of supercooling and supersaturation. (C) 2002 Elsevier Science B.V. All rights reserved.
  • N Usami, T Takahashi, K Fujiwara, T Ujihara, G Sazaki, Y Murakami, K Nakajima
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 41 (7A) 4462 - 4465 0021-4922 2002/07 [Refereed][Not invited]
     
    Multicrystalline SiGe (mc-SiGe) with microscopic compositional distribution, which has been proposed as a promising material for solar cell applications, was characterized by microscopic Raman spectroscopy. As expected, a strong spatial variation of Raman spectra was observed. However, the compositional distribution obtained by a separate energy-dispersive X-ray analysis did not fully explain the observed spatial variation of Raman spectra. A plausible explanation of the inconsistency is the existence of built-in strain, which originates from the lattice mismatch between Si and Ge.
  • T Ujihara, K Fujiwara, G Sazaki, N Usami, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 241 (3) 387 - 394 0022-0248 2002/06 [Refereed][Not invited]
     
    We propose a new method for determination of interdiffusion coefficient in high temperature solutions. This method can be characterized by the three following facts: the flux of diffusion is temporarily measured by in situ measurement technique for solution concentration in a diffusion cell; the intrinsic diffusion coefficient is derived from the flux on a basis of Fick's first law; the interdiffusion coefficients are evaluated from the intrinsic diffusion coefficients. In practice, the interdiffusion coefficient of GaZn binary system was successfully determined using the present method. (C) 2002 Elsevier Science B.V. All rights reserved.
  • K Nakajima, T Kusunoki, Y Azuma, N Usami, K Fujiwara, T Ujihara, G Sazaki, T Shishido
    JOURNAL OF CRYSTAL GROWTH 240 (3-4) 373 - 381 0022-0248 2002/05 [Refereed][Not invited]
     
    The effect of the supply of depleted Si solute elements on the compositional variation in the Si-rich SiGe bulk crystals was studied using the method which was used to grow Ge-rich SiGe single crystals with a uniform composition. By selecting the proper pulling rate, we can obtain Si-rich Si1-xGex bulk crystals with uniform composition of x = 0.1 without using the supply mechanism of depleted Si solute elements. When the supply mechanism of Si solute elements was used. the initial composition in Si-rich SiGe crystals can be much more easily determined by controlling the growth temperature than that in Ge-rich crystals because the Si seed crystal is not melted down. The supply of Si solute elements is very effective to change the compositional variation even for Si-rich SiGe crystals. (C) 2002 Elsevier Science B.V. All rights reserved.
  • K Nakajima, N Usami, K Fujiwara, Y Murakami, T Ujihara, G Sazaki, T Shishido
    SOLAR ENERGY MATERIALS AND SOLAR CELLS 72 (1-4) 93 - 100 0927-0248 2002/04 [Refereed][Not invited]
     
    The melt-growth conditions to obtain SiGe multicrystals with microscopic compositional distribution are presented. These SiGe multicrystals are useful for new solar cells whose wavelength dependence of the absorption coefficient can be freely designed. The multicrystals with wide compositional distribution from Si to Ge can be grown by a melt growth technique such as the practical casting method. In this work, it was studied as to how much the micro and macroscopic compositional distribution in SiGe multicrystals grown from binary Si-Ge melts could be controlled by the melt composition and the cooling process. Such SiGe multicrystals with wide distribution of the composition would also have wide distribution of the absorption coefficient, and could be hopeful for new solar cell applications using the practical casting method. (C) 2002 Elsevier Science B.V. All rights reserved.
  • G Sazaki, Y Azuma, S Miyashita, N Usami, T Ujihara, K Fujiwara, Y Murakami, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 236 (1-3) 125 - 131 0022-0248 2002/03 [Refereed][Not invited]
     
    We developed an in-situ observation system of the position and temperature at the crystal-solution interface grown under high temperature. A zone furnace of vertical type has an optical window made of quartz glass, and a sample in the furnace can be directly observed from outside through this window. Beam splitter made of an Si single crystal reflects the visible light comming from the sample, and the visible light image is observed using a CCD camera. Infrared light emitted from the sample penetrates the beam splitter, and the infrared image is monitored by an infrared CCD camera (thermoviewer). A growth process of a SiGe mixed crystal was chosen as a model system. Using the newly developed in-situ monitoring system, the position of the growth interface could be monitored with a spatial resolution of 300 mum. Temperature distribution around the growth interface could be determined with a spatial resolution of 230 mum and an accuracy of +8degreesC. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Y Suzuki, G Sazaki, S Miyashita, T Sawada, K Tamura, H Komatsu
    BIOCHIMICA ET BIOPHYSICA ACTA-PROTEIN STRUCTURE AND MOLECULAR ENZYMOLOGY 1595 (1-2) 345 - 356 0167-4838 2002/03 [Refereed][Not invited]
     
    Pressure is expected to be an important parameter to control protein crystallization, since hydrostatic pressure affects the whole system uniformly and can be changed very rapidly. So far, a lot of studies on protein crystallization have been done. Solubility of protein depends on pressure. For instance, the solubility of tetragonal lysozyme crystal increased with increasing pressure, while that of orthorhombic crystal decreased. The solubility of subtilisin increased with increasing pressure. Crystal growth rates of protein also depend on pressure. The growth rate of glucose isomerase was significantly enhanced with increasing pressure. The growth rate of tetragonal lysozyme crystal and subtilisin decreased with increasing pressure. To study the effects of pressure on the crystallization more precisely and systematically, hen egg white lysozyme is the most suitable protein at this stage, since a lot of data can be used. We focused on growth kinetics under high pressure, since extensive studies on growth kinetics have already been done at atmospheric pressure, and almost all of them have explained the growth mechanisms well, The growth rates of tetragonal lysozyme decreased with pressure under the same supersaturation. This means that the surface growth kinetics significantly depends on pressure. By analyzing the dependence of supersaturation on growth rate, it was found that the increase in average ledge surface energy of the two-dimensional nuclei with pressure explained the decrease in growth rate. At this stage, it is not clear whether the increase in surface energy with increasing pressure is the main reason or not. Fundamental studies on protein crystallization under high pressure will be useful for high pressure crystallography and high pressure protein science. (C) 2002 Elsevier Science B.V. All rights reserved.
  • N Usami, Y Azuma, T Ujihara, G Sazaki, K Fujiwara, Y Murakami, K Nakajima
    MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY 89 (1-3) 364 - 367 0921-5107 2002/02 [Refereed][Not invited]
     
    SiGe bulk crystal was grown by the multicomponent zone-melting method equipped with an in situ monitoring system of the position and the temperature at the crystal-solution interface. By utilizing the in situ monitoring system, an attempt was made to control the interface position at a fixed position during growth by balancing the growth rate and the pulling rate of the crystal. This led to realization of SiGe bulk crystal with Ge composition of 0.86 +/- 0.004 over 22 mm in length. However, as growth proceeds. development of small angle boundaries was evidenced by X-ray characterizations. This polycrystallization was found to be accompanied with appearance of deep-level emission in photoluminescence spectra. A preliminary result to grow SiGe with intermediate composition. which is important for Si-based heterostructures. was also performed. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Usami N, Fujiwara K, Ujihara T, Sazaki G, Yaguchi H, Murakami Y, Nakajima K
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 41 (1AB) L37 - L39 0021-4922 2002/01/15 [Refereed][Not invited]
  • G Sazaki, S Miyashita, M Nokura, T Ujihara, K Fujiwara, N Usami, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 234 (2-3) 516 - 522 0022-0248 2002/01 [Refereed][Not invited]
     
    Using a drop experiment facility. Maragnoni convection induced by a temperature gradient in a 7.35 wt% NaCl aqueous solution was observed in situ under microgravity in order to reveal Marangoni effects on the crystallization from aqueous solution in a spaceship. In the drop experiment, after microgravity was achieved, the buoyant convection diminished completely within 1.0 s. Since the flow rate became quite steady after 1.0 s of microgravity, this was regarded as the flow rate of Marangoni convection. The flow rates of Marangoni convection were also measured as a function of the exposure time of the solution surface to the surrounding air, The flow rate decreased exponentially with an increase in the exposure time. This decrease could be explained by a model containing Langmuir type adsorption of the air on the solution surface. Our result suggests that the solution surface would be entirely contaminated by the adsorbed gas molecules within several hours. and Marangoni convection would diminish. (C) 2002 Elsevier Science B.V. All rights reserved.
  • T Ujihara, K Fujiwara, G Sazaki, N Usami, K Nakajima
    JOURNAL OF NON-CRYSTALLINE SOLIDS 312-14 196 - 202 0022-3093 2002 [Refereed][Not invited]
     
    The intrinsic diffusion coefficients in a liquid GaGe alloy were determined using a novel method based on Fick's first law. The mutual and self diffusion coefficients also were derived. The intrinsic diffusion coefficients of both components are similar to each other and so both components equally contribute to the mutual diffusion coefficient. Also, the values of the self diffusion coefficient agree with values reported in the literature. A comparative study of the gallium self diffusion coefficients between the GaGe and GaZn systems indicated that the self diffusion coefficient depends on the second alloy component. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Y Suzuki, T Sawada, S Miyashita, G Sazaki, T Nakada, H Komatsu, T Arao, K Tamura
    TRENDS IN HIGH PRESSURE BIOSCIENCE AND BIOTECHNOLOGY, PROCEEDINGS 19 117 - 122 0921-0423 2002 [Refereed][Not invited]
     
    Using a two-beam interferometer and a high-pressure cell with transparent windows, we measured the solubility of lysozyme crystals under high pressure in situ. The change in the concentration with time during equilibration was measured accurately and continuously starting from a supersaturated state (growth relaxation) and an undersaturated state (dissolution relaxation). The concentration for the dissolution relaxation reached to a constant value in a week, which did not coincide with a concentration for the growth relaxation in a comparable period. From a theoretical point of view, we regarded the asymptotic concentration for the dissolution relaxation as the solubility. The molar enthalpy of thermal denaturation of pressurized (1hour at 100 MPa) sample (lysozyme: 5mg/ml) was also measured with a differential scanning microcalorimeter (DSC). The enthalpy was not different from that of non-pressurized sample. Thus, the effect of the irreversible pressure denaturation of lysozyme up to 100 MPa on the results of our experiments was negligible.
  • Y Suzuki, S Miyashita, T Sawada, G Sazaki, T Nakada, H Komatsu, T Arao, K Tamura
    TRENDS IN HIGH PRESSURE BIOSCIENCE AND BIOTECHNOLOGY, PROCEEDINGS 19 123 - 130 0921-0423 2002 [Refereed][Not invited]
     
    Normal growth rates of {110} and {101} faces of tetragonal hen egg-white lysozyme crystals were measured in situ under 0.1, 50, and 100 MPa. The solubilities under high pressure enabled us to evaluate supersaturation under high pressure. We found that both growth rates decreased with pressure under the same supersaturation. This means that the surface growth kinetics depends on pressure significantly. The birth and spread model was applied to understand the pressure effects on the growth kinetics. It was found that the increase in the average ledge surface energy of the two-dimensional nuclei with pressure explained the decrease in the growth rate. The molar enthalpy of thermal denaturation of pressurized (1hour at 100 MPa) sample (lysozyme: 5mg/ml) was also measured with a differential scanning microcalorimeter (DSC). The enthalpy was not different from that of non-pressurized sample. Thus, the effect of the irreversible pressure denaturation of lysozyme up to 100 MPa on the results of our experiments was negligible.
  • Y Suzuki, S Miyashita, G Sazaki, T Nakada, T Sawada, H Komatsu
    JOURNAL OF CRYSTAL GROWTH 234 (2-3) 610 - 610 0022-0248 2002/01 [Refereed][Not invited]
  • N Usami, T Takahashi, K Fujiwara, T Ujihara, G Sazaki, Y Murakami, K Nakajima
    CONFERENCE RECORD OF THE TWENTY-NINTH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE 2002 247 - 249 2002 [Refereed][Not invited]
     
    We report on growth and. characterizations of Si/multicrystalline-SiGe (mc-SiGe) heterostructure as a promising candidate to surpass multicrystalline-Si solar cells. A 0.5 mum-thick Si thin film was grown on mc-SiGe using a solid-source molecular beam epitaxy system. Spatial distribution of the status-of strain in S! was found to be strongly dependent on the, composition and microstructure of underlying mc-SiGe. Large strain distribution and partial strain relaxation were revealed in Si on mc-SiGe with average Ge composition of 0.72. On the other hand, almost uniformly strained-Si film was grown on mc-SiGe with average Ge composition of 0.30. To avoid introduction of recombination centers at the Si/SiGe interface, it is necessary to avoid strain relaxation by decreasing average Ge composition in mc-SiGe.
  • T Ujihara, E Kanda, K Fujiwara, G Sazaki, N Usami, Y Murakami, K Kitahara, K Nakajima
    CONFERENCE RECORD OF THE TWENTY-NINTH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE 2002 1339 - 1342 2002 [Refereed][Not invited]
     
    In this study, in order to inquire into the principle of the fabrication of the poly-Si film via the grain growth process, we clarified the grain growth mechanism of the thin film for the solar cell by investigating temporal change of the grain size distribution. Moreover, this process was explained by a theoretical model taking two- and three- dimensional growth modes into account. In addition, the crystal quality. was evaluated using Raman spectroscopy. The quality was very high comparing with the film prepared by the laser annealing technique.
  • T Sato, Y Yamada, S Saijo, T Hori, R Hirose, N Tanaka, G Sazaki, K Nakajima, N Igarashi, M Tanaka, Y Matsuura
    JOURNAL OF CRYSTAL GROWTH 232 (1-4) 229 - 236 0022-0248 2001/11 [Refereed][Not invited]
     
    Orthorhombic crystals of hen egg-white lysozyme (HEWL) were grown under a homogeneous magnetic field of 10 T (B = 10 T). In the magnetic field, crystals were oriented such that their crystallographic c-axes were parallel to the magnetic field, and gave narrower average rocking widths than those grown under 0 T. Crystal quality was evaluated using the full-width at half-maximum (FWHM) of the rocking curve, and the effects of a magnetic field were examined by comparing FWHM of seven crystals grown at 10 T with an equal number grown at 0 T. FWHM values in (10 0 0), (0 8 0), and (0 0 6) reflections decreased by 25%, 38%, and 32%, respectively, and those of general reflections decreased by 7-45 % in crystals grown under high magnetic field. These results show that a magnetic field of 10 T improved the crystal perfection of the orthorhombic lysozyme crystals. At the same time, the maximum resolution limit of X-ray diffraction increased from 1.33 Angstrom for 0 T to 1.13 Angstrom for 10 T. These facts suggest that the application of magnetic field for crystallization might generally have a striking effect in enhancing the diffraction power of protein crystals. (C) 2001 Elsevier Science B.V. All rights reserved.
  • N Usami, Y Azuma, T Ujihara, G Sazaki, K Nakajima, Y Yakabe, T Kondo, K Kawaguchi, S Koh, Y Shiraki, BP Zhang, Y Segawa, S Kodama
    SEMICONDUCTOR SCIENCE AND TECHNOLOGY 16 (8) 699 - 703 0268-1242 2001/08 [Refereed][Not invited]
     
    A detailed study of molecular beam epitaxy of GaAs on homemade SiGe substrates has been performed. It was found that the initial migration-enhanced epitaxy process with As prelayer is crucial to obtain high-quality GaAs. By (004) x-ray diffraction, the lattice mismatch between GaAs and SiGe was demonstrated to be reduced compared with the conventional GaAs/Ge heterostructure. Furthermore, narrower halfwidth of the rocking curve and stronger photoluminescence intensity were found for GaAs on SiGe. These results show that SiGe is a promising material as an alternative substrate to Ge to realize exact lattice matching to GaAs for solar cell applications.
  • T Ujihara, G Sazaki, K Fujiwara, N Usami, K Nakajima
    JOURNAL OF APPLIED PHYSICS 90 (2) 750 - 755 0021-8979 2001/07 [Refereed][Not invited]
     
    We proposed a simple lattice model to describe a solid-liquid interface of silicon based on experimental facts and molecular dynamics simulation results, and evaluated the relationship between the interface structure and the interfacial tension by comparing the model with experimental values. As a result, the entropy was found to give a major contribution to the interfacial tension, and it was revealed that the difference of entropy due to lattice disorder of bulk liquid and interface structure is the dominant factor of the entropy contribution. Moreover, the solid-liquid bond energy, which is crucial to estimate the contribution of the enthalpy, was successfully derived. The present model can be also applied to be the semiconductor material which has a diamond structure or a zinc blende structure. (C) 2001 American Institute of Physics.
  • H Hondoh, G Sazaki, S Miyashita, SD Durbin, K Nakajima, Y Matsuura
    CRYSTAL GROWTH & DESIGN 1 (4) 327 - 332 1528-7483 2001/07 [Refereed][Not invited]
     
    Intermolecular contacts in crystals of monoclinic form hen egg-white lysozyme were analyzed using the macrobond approach. Both the macroscopic crystal morphology and the microscopic morphology observed by atomic force microscopy were explained well using macrobond energies. The features of the advancing steps of the growing surface were related to the step ledge energies. The hydration enthalpy of dissolution of the crystal was estimated using the macrobond energies and the dissolution enthalpy of the crystal obtained from solubility measurements, and showed good agreement with the reported values obtained from thermodynamic measurements.
  • N Usami, Y Azuma, T Ujihara, G Sazaki, S Miyashita, Y Murakami, K Nakajima
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 40 (6A) 4141 - 4144 0021-4922 2001/06 [Refereed][Not invited]
     
    A new growth system, which allows in situ monitoring of the crystal-solution interface, was developed and applied to grow SixGe1-x (x = 0.15) bulk crystal with uniform composition by the multicomponent zone-melting method. By utilizing the system, the dynamical change of the growth rate was evaluated from the nonlinear upward shift of the interface as a function of the growth time. Based on the monitoring, an attempt was made to balance the pulling rate of the ampoule with the growth rate of the crystal, which led to the suppression of the upward shift of the growth interface, Consequently, the compositional uniformity of the crystal in the growth direction was markedly improved.
  • Y Azuma, N Usami, T Ujihara, G Sazaki, Y Murakami, S Miyashita, K Fujiwara, K Nakajima
    JOURNAL OF CRYSTAL GROWTH 224 (3-4) 204 - 211 0022-0248 2001/04 [Refereed][Not invited]
     
    A SiGe bulk crystal with uniform composition was successfully fabricated by clarifying and controlling the growth parameters at the crystal-melt interface. An apparatus was developed for the direct in situ observation and precise control of the interface parameters such as the temperature and the position. The dynamical change of the growth rate of a SiGe bulk crystal in a temperature gradient can be known by utilizing the apparatus. The growing crystal was continuously pulled down at the pulling rate balanced to the growth rate to keep the interface temperature constant, which resulted in the excellent uniformity of the grown crystal. Our technique opened the possibility to incorporate multicomponent semiconductor substrates to the semiconductor heterostructure technology. (C) 2001 Published by Elsevier Science B.V.
  • K Nakajima, T Ujihara, S Miyashita, G Sazaki
    JOURNAL OF APPLIED PHYSICS 89 (1) 146 - 153 0021-8979 2001/01 [Refereed][Not invited]
     
    The thickness-composition phase diagrams of the growth modes were determined for the GaInN-on-GaN (GaInN/GaN) and the GaInN-on-AlN-on-GaN (GaInN/AlN/GaN) structures. For this determination, the strain energy was calculated by considering the stress relaxation due to introduction of misfit dislocations, the surface energy was estimated from bonding enthalpy of the nearest-neighbor bonds on the surface, and the interface energy was estimated by considering both effects of the dangling bonds due to lattice misfit and the abrupt transition of bonding species at the heterointerface. From these phase diagrams, it was found that the layer-by-layer growth such as the Frank-van der Merwe mode was very difficult to obtain for the epitaxial growth of GaInN on GaN when the InN fraction is large. The Volmer-Weber mode is dominant in the phase diagram of the GaInN/GaN structures. The influence of an AlN buffer layer with a larger surface energy was studied by introducing an AlN layer between the GaInN layer and the GaN substrate. It was known that the layer-by-layer growth could be more easily obtained if misfit dislocations were introduced and an AlN layer was used as a buffer. (C) 2001 American Institute of Physics.
  • K Ninomiya, T Yamamoto, T Oheda, K Sato, G Sazaki, Y Matsuura
    JOURNAL OF CRYSTAL GROWTH 222 (1-2) 311 - 316 0022-0248 2001/01 [Refereed][Not invited]
     
    An alpha -amylase originating from a mold Aspergillus oryzae, Taka-amylase A (Mr of 52 kDa, pI of 3.8), has been purified to an electrophoretically single band grade. Crystallization behaviors were investigated using ammonium sulfate and polyethleneglycol 8000 as precipitants. The variations in the morphology of the crystals obtained with changing crystallization parameters are described. Five apparently different crystal forms were obtained, and their morphology and crystallographic data have been determined. Solubility values of four typical forms were measured using a Michelson-type two-beam interferometer. The results of these experiments showed that this protein can be a potentially interesting and useful model for crystal growth study with a gram-amount availability of pure protein sample. (C) 2001 Elsevier Science B.V. All rights reserved.
  • K Nakajima, T Ujihara, G Sazaki, N Usami
    JOURNAL OF CRYSTAL GROWTH 220 (4) 413 - 424 0022-0248 2000/12 [Refereed][Not invited]
     
    In order to know the effects of the surface, interfacial and strain energies on the calculation of the phase diagram, these energies were calculated for the GaxIn1-xAs/InP structure and the Ga-In-As ternary phase diagram for the epitaxial growth of GaInAs on (111) InP was determined. The layer-thickness dependence of the liquidus temperature and solidus composition was determined. It was found that the liquidus and solidus phases were strongly influenced by these energies when the layer thickness was thinner than about 0.06 mum. The consideration of the effects of the surface, interfacial and strain energies is effective to explain the peculiar behavior of the experimental results near the lattice-matched composition (x = 0.47), which is called the latching effect. (C) 2000 Elsevier Science B.V. All rights reserved.
  • N Usami, Y Azuma, T Ujihara, G Sazaki, K Nakajima, Y Yakabe, T Kondo, S Koh, Y Shiraki, B Zhang, Y Segawa, S Kodama
    APPLIED PHYSICS LETTERS 77 (22) 3565 - 3567 0003-6951 2000/11 [Refereed][Not invited]
     
    SiGe bulk crystal fabricated by a multicomponent zone-melting method was used as a substrate for epitaxial growth of GaAs. Compared with conventional GaAs/Ge heterostructure, the lattice mismatch of GaAs/Si0.022Ge0.978 was confirmed to be reduced by a decrease of the peak separation of (400) x-ray diffraction from the epitaxial GaAs layer and the substrate. Furthermore, the linewidth of the rocking curve of GaAs on SiGe was found to be narrower than that of GaAs on Ge. These results show that SiGe is promising material as an alternative substrate to Ge for realization of exactly lattice-matched GaAs/SiGe solar cells. (C) 2000 American Institute of Physics. [S0003-6951(00)01249-3].
  • T Ujihara, G Sazaki, S Miyashita, N Usami, K Nakajima
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 39 (10) 5981 - 5982 0021-4922 2000/10 [Refereed][Not invited]
     
    We proposed an ill situ technique based on X-ray fluorescence spectrometry to measure the composition of a high-temperature solution in a crucible. The sample holder for this technique was composed of carbon, which is transparent to X-rays. Using the present technique, equilibrium compositions of zinc in a gallium solution were measured. The results agreed well with the liquidus curve of the Ga-Zn phase diagram, and thus the validity of this technique was proved.
  • T Sato, Y Yamada, S Saijo, T Hori, R Hirose, N Tanaka, G Sazaki, K Nakajima, N Igarashi, M Tanaka, Y Matsuura
    ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY 56 1079 - 1083 0907-4449 2000/08 [Refereed][Not invited]
     
    Orthorhombic crystals of hen egg-white (HEW) lysozyme were grown in a homogeneous and static magnetic field of 10 T. All crystals grown at 10 T were oriented such that their crystallographic c axes were parallel to the magnetic field direction and showed a narrower average full-width at half-maximum (FWHM) of the rocking curve than those grown at 0 T. Rocking-width measurements were made at the BL-10A station at the Photon Factory, Tsukuba, Japan, using a high-resolution vertical-type four-circle diffractometer. Crystal perfection was evaluated using the FWHM of the rocking curve; the effects of the magnetic field on the quality of the crystals were examined by comparison of the FWHM of seven crystals grown at 10 and 0 T. The FWHMs of the reflections along the a, b and c axes decreased by 23.5, 35.3 and 27.8%, respectively, and those of other general reflections decreased by 17.4-42.2% in the crystals grown at high magnetic field. These results clearly showed that a magnetic field of 10 T improved the crystal perfection of the orthorhombic lysozyme crystals. As a result, the maximum resolution of X-ray diffraction increased from 1.3 Angstrom at 0 T to 1.13 Angstrom at 10 T. The magnetic field also affected the dimensions of the unit cell, increments being 0.2% for the a and c axes and 0.1% for the b axis, respectively. These facts suggest that the application of a high magnetic field during crystallization might result in remarkable enhancements in the diffraction power of protein crystals having magnetic anisotropy.
  • K Nakajima, T Ujihara, S Miyashita, G Sazaki
    JOURNAL OF CRYSTAL GROWTH 209 (4) 637 - 647 0022-0248 2000/02 [Refereed][Not invited]
     
    Many types of structure of the SK mode have possibility to appear as the crystal grows. In order to understand the most stable structure for the SK mode and the minimum-energy path through which the SK mode structure with the smallest free energy appears at each layer-thickness, the strain, surface, and interfacial energies of the GaPSb/GaP system were calculated for the FM, VW and several types of SK mode structures. The free energy for each structure was derived from these energies. By comparison of the free energies of the several types of the SK structure, it is found that the most stable structure of the SK mode is a cluster with four lattice layers or minimum thickness on a wetting layer whose lattice layer increases. As the crystal grows in the SK mode, the path on which only the wetting layer becomes thicker is the most stable. The path on which only the cluster on the wetting layer becomes larger is the most unstable. The thickness-composition phase diagrams for the FM, SKj (j = 1-2) and VW modes were determined for the GaPSb/GaP(1 1 1) system. The area of the SKj region becomes smaller as the cluster height j increases, and that of the VW region becomes larger. In order to compare these phase diagrams, the phase diagram for the case of the SK mode structure whose wetting layer is always one lattice layer thick was determined, and the phase diagram for the SKI mode was also determined by considering the reconstruction of dangling bonds for the calculation of the surface energy. (C) 2000 Elsevier Science B.V. All rights reserved.
  • Y Suzuki, T Sawada, S Miyashita, H Komatsu, G Sazaki, T Nakada
    JOURNAL OF CRYSTAL GROWTH 209 (4) 1018 - 1022 0022-0248 2000/02 [Refereed][Not invited]
     
    The effect of hydrostatic pressure on the solubility of tetragonal hen egg-white lysozyme crystals was measured in situ by a two-beam interferometer combined with a high-pressure optical cell which was newly designed by our group. The change in the concentration with time during equilibration was measured accurately and continuously starting from a supersaturated state (growth relaxation) and an undersaturated state (dissolution relaxation). The solubility value thus measured at 100 MPa was 28% larger than that at 0.1 MPa, and this increase was much smaller than those of previous reports. (C) 2000 Elsevier Science B.V. All rights reserved.
  • S Yanagiya, G Sazaki, SD Durbin, S Miyashita, K Nakajima, H Komatsu, K Watanabe, M Motokawa
    JOURNAL OF CRYSTAL GROWTH 208 (1-4) 645 - 650 0022-0248 2000/01 [Refereed][Not invited]
     
    The growth process of tetragonal lysozyme crystals under static and homogeneous magnetic field of 11 T was observed in situ by using an optical microscope which was specially designed and prepared. This optical system, having a spatial resolution of 0.5 mu m, was used to measure the growth rate of the lysozyme crystals under 0 and 11 T. The effect of the magnetic field of 11 T was to decrease the growth rate of the crystals. The effect of a magnetic field on the dissolution process of the crystal was also investigated. (C) 2000 Elsevier Science B.V. All rights reserved.
  • Y Suzuki, S Miyashita, G Sazaki, T Nakada, T Sawada, H Komatsu
    JOURNAL OF CRYSTAL GROWTH 208 (1-4) 638 - 644 0022-0248 2000/01 [Refereed][Not invited]
     
    Growth kinetics of tetragonal hen egg-white lysozyme crystals under high pressures was studied by in situ measurements. Normal growth rates of {1 1 0} and {1 0 1} faces were measured under 0.1, 50, and 100 MPa. The solubilities under high pressure enabled us to evaluate supersaturation under high pressure. We found that both growth rates decreased with pressure under the same supersaturation. This means that the surface growth kinetics significantly depends on pressure. The birth and spread model was applied to understand the pressure effects on the growth kinetics. It was found that the increase in the average ledge surface energy of the two-dimensional nuclei with pressure explained the decrease in the growth rare. (C) 2000 Elsevier Science B.V. All rights reserved.
  • K Nakajima, T Ujihara, S Miyashita, G Sazaki
    MORPHOLOGICAL AND COMPOSITIONAL EVOLUTION OF HETEROEPITAXIAL SEMICONDUCTOR THIN FILMS 618 285 - 290 0272-9172 2000 [Refereed][Not invited]
     
    The growth of thin films has been categorized into three types namely the Frank-van der Merwe (PM) mode, the Stranski-Krastanov (SK) mode, and the Volmer-Weber (VW) mode. The strain, surface, and interfacial energies were calculated for the three types of growth mode of the GaInN/GaN and GaPSb/GaP systems by considering the effects of the dislocation density and reconstruction of dangling bonds. The phase diagrams of the growth modes were determined for the GaInN/GaN and GaPSb/GaP systems. In the GaInN/GaN system, the VW mode appears in the most region of the phase diagram. The region of the VW mode becomes smaller as the dislocation density increases. In the GaPSb/GaP system, the SK and VW modes appear and the region of these modes becomes larger as the reconstruction ratio increases.
  • Y Nishimura, Y Matsuoka, S Miyashita, H Komatsu, M Motokawa, T Nakada, G Sazaki
    JOURNAL OF CRYSTAL GROWTH 207 (3) 206 - 213 0022-0248 1999/12 [Refereed][Not invited]
     
    Sufficiently large single crystals of Y2Cu2O5 for use in neutron diffraction experiments were successfully grown by the traveling-solvent floating zone method under an oxygen partial pressure of 40-100%. The optimum composition for growth from a high-temperature solution was determined in situ using high-temperature optical microscopy. The growth direction was parallel to the crystallographic b-axis. This crystal exhibited well-defined metamagnetic transitions. (C) 1999 Elsevier Science B.V. All rights reserved.
  • Y Nishimura, S Miyashita, SD Durbin, T Nakada, G Sazaki, H Komatsu
    JOURNAL OF CRYSTAL GROWTH 205 (4) 503 - 509 0022-0248 1999/09 [Refereed][Not invited]
     
    Reliable liquidus lines of SmBa2Cu3Ox in the SmBa2Cu3Ox-Ba7Cu18O25 system under various oxygen partial pressures were determined precisely by in situ observation. The dependence of the liquidus line on oxygen partial pressure was revealed: as the oxygen partial pressure increased, the liquidus shifted to higher temperature. Using this data, SmBa2Cu3Ox crystals were grown. This process was successfully observed in situ by high-temperature optical microscopy. (C) 1999 Elsevier Science B.V. All rights reserved.
  • K Nakajima, S Kodama, S Miyashita, G Sazaki, S Hiyamizu
    JOURNAL OF CRYSTAL GROWTH 205 (3) 270 - 276 0022-0248 1999/08 [Refereed][Not invited]
     
    An improved growth technology was developed to grow Ge-rich SiGe crystals on Ge seeds on the basis of the Multi-component zone melting method. The purpose of growing such a crystal is the preparation of exactly lattice-matched GaAs/SiGe heterostructures for higher-efficiency tandem cells than GaAs/Ge cells. In this method, Si solute elements are continuously supplied from the Si source crystal, and the compositional profile in the SiGe crystal is controlled by the pulling rate. We were successful in preparing a SixGe1-x single crystal with a uniform composition (x = 0.02) following a graded composition (from x = 0 to 0.02). The size of the uniform crystal is 2 cm in length and 1.5 cm in diameter. The combined structure of uniform SiGe/graded SiGe/Ge has two expected merits. A lattice-matched GaAs epitaxial layer can be grown on the SiGe uniform crystal, and the graded composition from Ge (x = 0) to uniform SiGe (x = 0.02) widens the range of absorbed wavelengths of the solar spectrum. (C) 1999 Elsevier Science B.V. All rights reserved.
  • G Sazaki, SD Durbin, S Miyashita, T Ujihara, K Nakajima, M Motokawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 38 (7B) L842 - L844 0021-4922 1999/07 [Refereed][Not invited]
     
    Temperature-driven convection in 25 w% NaCl aqueous solution was observed in situ under a static and homogeneous magnetic field of 10 T. The convection in the solution was visualized using polystyrene latex particles of 5 mu m diameter. A magnetic field of 10 T reduced the velocity of convection by a factor of two. Magnetic damping of convection in an electrolyte solution could be a useful technique to control the growth of crystals such as proteins.
  • S Yanagiya, G Sazaki, SD Durbin, S Miyashita, T Nakada, H Komatsu, K Watanabe, M Motokawa
    JOURNAL OF CRYSTAL GROWTH 196 (2-4) 319 - 324 0022-0248 1999/01 [Refereed][Not invited]
     
    Recent experiments have shown that lysozyme crystallization in a magnetic field of the order of 1 T can result in a significant degree of orientation of the crystals. We present more extensive experimental results and propose a model to account for this phenomenon. Because of the small susceptibility anisotropy of most protein molecules, the orienting effect is unimportant for smaller aggregates, even those much larger than a critical nucleus. However, during sedimentation crystals grow larger and are more likely to become aligned. The degree of orientation thus depends on crystal growth rate and container geometry, in addition to magnetic field strength, as we have confirmed experimentally. (C) 1999 Elsevier Science B.V. All rights reserved.
  • K Kurihara, S Miyashita, G Sazaki, T Nakada, SD Durbin, H Komatsu, T Ohba, K Ohki
    JOURNAL OF CRYSTAL GROWTH 196 (2-4) 285 - 290 0022-0248 1999/01 [Refereed][Not invited]
     
    Concentration of a phosphor-labeled impurity (ovalbumin) incorporated into protein (hen egg white lysozyme) crystals during growth was measured by fluorescence. This technique enabled us to measure the local impurity concentration in a crystal quantitatively. Impurity concentration increased with growth rate, which could not be explained by two conventional models (equilibrium adsorption model and Burton-Prim-Slichter model); a modified model is proposed. Impurity concentration also increased with the pH of the solution. This result is discussed considering the electrostatic interaction between the impurity and the crystallizing species. (C) 1999 Elsevier Science B.V. All rights reserved.
  • G Sazaki, Y Nagatoshi, Y Suzuki, SD Durbin, S Miyashita, T Nakada, H Komatsu
    JOURNAL OF CRYSTAL GROWTH 196 (2-4) 204 - 209 0022-0248 1999/01 [Refereed][Not invited]
     
    Two-beam interferometry was applied to measure lysozyme solubility under high pressure. This rapid method allowed determination of one data point within 3 h. The solubility of tetragonal lysozyme crystals was determined as a function of temperature at 0.1? 50, and 100 MPa, and that of orthorhombic crystals was measured at 0.1 and 100 MPa. The solubility of tetragonal crystals increased with pressure; however, that of orthorhombic crystals decreased. In both cases, the enthalpy and entropy of dissolution decreased with pressure. (C) 1999 Elsevier Science B.V. All rights reserved.
  • T Nakada, G Sazaki, S Miyashita, SD Durbin, H Komatsu
    JOURNAL OF CRYSTAL GROWTH 196 (2-4) 503 - 510 0022-0248 1999/01 [Refereed][Not invited]
     
    Impurity effects on the growth of tetragonal lysozyme crystals have been studied using in situ atomic force microscopy. Commercially available hen egg white lysozyme was characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis with silver staining, and purified by re-crystallization and successive high pressure liquid chromatography. On the (1 1 0) crystal surface, there was no significant difference in morphology between crystals grown in commercial and in purified solutions. On the (1 0 1) surface, however, a large number of small particles were found when the crystal was grown in the commercial solution, while the surface grown in the purified solution was quite smooth. Among the typical residual impurities contained in commercial lysozyme, only covalently bound lysozyme dimer yielded such particles. From measurements of particle separation and an estimate of the critical nucleation size, we infer that the particles reduced the step velocity according to the mechanism described by Cabrera et al. [N. Cabrera, D.A. Vermilyea, in: R.H. Doremus et al. (Eds.) Growth and Perfection of Crystals, 1958, p. 393]. (C) 1999 Elsevier Science B.V. All rights reserved.
  • E Kashimoto, G Sazaki, K Hasegawa, T Nakada, S Miyashita, H Komatsu, K Sato, Y Matsuura, H Tanaka
    JOURNAL OF CRYSTAL GROWTH 186 (3) 461 - 470 0022-0248 1998/03 [Refereed][Not invited]
     
    Well-faceted crystals of concanavalin A were obtained in two different morphologies. Prior to the crystallization, concanavalin A was homogeneously metallized with Mn2+ and Ca2+ cations, Using the metallized samples, we measured the solubility of a well-faceted crystal. The as-grown crystal was bounded by flat faces with high Miller indices. We measured the normal growth rate (R) of these flat faces with respect to the supersaturation (sigma). The R-sigma relation showed that the growth mode corresponded to two-dimensional nucleation growth of a birth and spread type. (C) 1998 Elsevier Science B.V. All rights reserved.
  • G Sazaki, E Yoshida, H Komatsu, T Nakada, S Miyashita, K Watanabe
    JOURNAL OF CRYSTAL GROWTH 173 (1-2) 231 - 234 0022-0248 1997/03 [Refereed][Not invited]
     
    Crystallization of hen egg-white lysozyme and horse-spleen ferritin was carried out under a steady and uniform magnetic field of 10 T and compared with the crystals grown under 0 T. It is clearly demonstrated that a magnetic field reduced the number of nuclei and not only oriented the crystals but also modified the habit of protein crystals. The present experimental result indicates that application of a magnetic field is an efficient method for growing a small number of large crystals.
  • T Nishizawa, T Nakada, Y Kinoshita, S Miyashita, G Sazaki, H Komatsu
    SURFACE SCIENCE 367 (3) L73 - L78 0039-6028 1996/12 [Refereed][Not invited]
     
    In situ atomic force microscopy (AFM) has been applied to study the structure of the Au(111) in sulfuric acid solution. Above 0.88 V versus Ag/AgCl, the Au(111) surface was observed to form an ordered structure having (2/1 1/2) periodicity of the structure agrees with the previous STM experiments, the corrugation of the AFM image was different to the STM images. The AFM image indicates that sulfate anions adsorb on the Au(111) surface with C-2v symmetry.
  • G Sazaki, K Kurihara, T Nakada, S Miyashita, H Komatsu
    JOURNAL OF CRYSTAL GROWTH 169 (2) 355 - 360 0022-0248 1996/11 [Refereed][Not invited]
     
    A novel technique was developed for the rapid solubility measurement of protein crystals (lysozyme) by two-beam interferometry. The merits of this technique are: (1) time saving (less than 2 h to obtain one experimental point), (2) the small amount of the sample (similar to 66 mu l), (3) high accuracy, (4) applicable to the solubility measurement of a metastable phase and (5) insensitive to impurities. The limitations of the present technique are also discussed.
  • K Kurihara, S Miyashita, G Sazaki, T Nakada, Y Suzuki, H Komatsu
    JOURNAL OF CRYSTAL GROWTH 166 (1-4) 904 - 908 0022-0248 1996/09 [Refereed][Not invited]
     
    Using a Michelson interferometer, the concentration-gradient layers around a growing hen-egg-white lysozyme, tetragonal crystal were observed. By measuring by concentration distribution and the normal growth rate, the growth mode and the diffusion coefficient of lysozyme molecules were evaluated. The experimental results indicate that the growth is regulated by two-dimensional nucleation in the supersaturation range of 6 less than or equal to sigma(surf) less than or equal to 20. The diffusion coefficient was nearly constant, 4.9 +/- 0.7 x 10(-11) m(2) s(-1) over a wide supersaturation range, differing from that of supersaturated bulk solutions.
  • T Nakada, S Miyashita, G Sazaki, H Komatsu, AA Chernov
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 35 (1A) L52 - L55 0021-4922 1996/01 [Refereed][Not invited]
     
    Structure forces in n-alcohols (CnH2n+1OH (8 less than or equal to n less than or equal to 12)) on the mica or graphite surfaces were investigated using an atomic force microscope (AFM). The structure force on graphite has a periodicity of similar to 0.5 nm, which is independent of temperature. The structure force on mica has a periodicity of 0.86 nm when T < 40 degrees C which increases linearly with n in the range 1.7 to 2.3 nm when T > 40 degrees C. This phase transition corresponds to a change in the alignment of molecules on the surface from parallel (lying, at T < 40 degrees C) to normal (standing, at T > 40 degrees C).

Books etc

  • Phsyics and Chemistry of Ice 2010
    Hokkaido University Press 2011

Industrial Property Rights

  • 光学顕微鏡と光学的観察方法
    特開2005-309415
  • 有機半導体薄膜のエピタキシャル成長
    特開2005-79535A
  • 水素生成光デバイス
    特開2003-238104

Awards & Honors

  • 2009/11 Japanese Association for Crystal Growth The 26th Best Paper Award
     Development of advanced optical microscopy and elucidation of growth mechanisms of protein crystals at the molecular level 
    受賞者: SAZAKI Gen
  • 2003/10 The Japan Society of Microgravity Application The 1st Young Scientist Award
     Effects of external fields on protein crystallization 
    受賞者: SAZAKI Gen

Research Grants & Projects

  • 多結晶氷の表面融解機構の解明
    平成31年度科学研究費補助金,基盤研究(B)
    Date (from‐to) : 2019/04 -2022/03 
    Author : 佐﨑 元
  • 不凍タンパク質が示す相互作用の解明:拡散・吸着ダイナミクスの蛍光1分子計測
    平成28年度科学研究費補助金,挑戦的萌芽研究
    Date (from‐to) : 2016/04 -2018/03 
    Author : 佐﨑 元
  • 結晶表面上の化学反応を可視化する:氷表面上での酸性ガスの吸着・融解反応の解明
    平成27年度科学研究費補助金,基盤研究(A)
    Date (from‐to) : 2015/04 -2018/03 
    Author : 佐﨑 元
  • 高分解光学観察による氷結晶表面での疑似液体層の動的挙動の解明
    平成23年度科学研究費補助金,基盤研究(A)
    Date (from‐to) : 2011/04 -2015/03 
    Author : 佐﨑 元
  • 水−氷(融液−結晶)界面の分子レベル直接観察:超高感度位相差顕微鏡の開発
    平成24年度科学研究費補助金,挑戦的萌芽研究
    Date (from‐to) : 2012/04 -2014/03 
    Author : 佐﨑 元
  • 不凍タンパク質作用発現機構の解明を目指したその場光観察
    科学技術振興機構:戦略的創造研究推進事業さきがけ
    Date (from‐to) : 2008/10 -2012/03 
    Author : 佐﨑 元
  • 分子レベルその場観察によるタンパク質結晶へのマイクロ欠陥取り込み機構の解明
    平成18年度科学研究費補助金,基盤研究(B)
    Date (from‐to) : 2006/04 -2009/03 
    Author : 佐﨑 元
  • Crystal Growth of Snow and Ice
    Date (from‐to) : 2008
  • タンパク質結晶-溶液界面におけるタンパク質1分子の吸着・脱離・拡散ダイナミクス
    平成17年度科学研究費補助金,特定領域研究(公募研究)
    Date (from‐to) : 2005/04 -2007/03 
    Author : 佐﨑 元
  • 蛍光顕微法を用いた有機半導体薄膜結晶粒間の位相欠陥イメージング
    平成16年度科学研究費補助金,萌芽研究
    Date (from‐to) : 2004/04 -2006/03 
    Author : 佐﨑 元
  • タンパク質結晶成長素過程の1分子その場観察による格子欠陥取り込み機構の解明
    平成16年度科学研究費補助金,基盤研究(B)
    Date (from‐to) : 2004/04 -2006/03 
    Author : 佐﨑 元
  • 環境型バイオデバイス創製のための有機・無機ヘテロエピタキシャル結晶成長技術の開発
    財団法人稲盛財団:平成13年度研究助成
    Date (from‐to) : 2001/04 -2002/03 
    Author : 佐﨑 元
  • 強磁場下でのタンパク質結晶周囲の濃度場観察
    平成12年度科学研究費補助金,奨励研究(A)
    Date (from‐to) : 2000/04 -2002/03 
    Author : 佐﨑 元
  • Development of advanced optical microscopy
    Date (from‐to) : 2002
  • 磁場を利用した微小重力下でのタンパク質の結晶化
    財団法人日本宇宙フォーラム:平成10年度宇宙環境利用に関する公募地上研究 フェーズIA
    Date (from‐to) : 1998/10 -2001/03 
    Author : 佐﨑 元
  • 磁場中の溶液挙動の解明とそれを用いたタンパク質の良質結晶育成
    日本原子力研究所:黎明研究
    Date (from‐to) : 2000/04 -2001/02 
    Author : 佐﨑 元
  • 磁場によるタンパク質の高品位結晶育成
    平成10年度科学研究費補助金,基盤研究(B)
    Date (from‐to) : 1998/04 -2000/03 
    Author : 佐﨑 元
  • 磁場によるタンパク質の高品位単結晶育成
    日本原子力研究所:黎明研究
    Date (from‐to) : 1998/04 -1999/02 
    Author : 佐﨑 元
  • 光干渉法を用いたタンパク質結晶化過程のその場観察
    住友財団:基礎科学研究助成
    Date (from‐to) : 1996/12 -1997/11 
    Author : 佐﨑 元
  • タンパク質(コンカナバリンA)の結晶成長過程の動的研究
    平成7年度科学研究費補助金,奨励研究(A)
    Date (from‐to) : 1995/04 -1996/03 
    Author : 佐﨑 元
  • Crystal Growth of Protein
    Date (from‐to) : 1994

Educational Activities

Teaching Experience

  • Advanced Course in Phase Transition of Planetary Materials
    開講年度 : 2018
    課程区分 : 修士課程
    開講学部 : 理学院
    キーワード : 氷結晶,雪結晶,結晶成長.相転移,ダイナミクス

Committee Membership

  • 2016/08 - Today   Journal of Crystal Growth   Associate Editor


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