Efficient Room-Temperature Operation of a Quantum Dot Spin-Polarized Light-Emitting Diode under High-Bias Conditions
Kohei Etou, Satoshi Hiura, Soyoung Park, Junichi Takayama, Agus Subagyo, Kazuhisa Sueoka, Akihiro Murayama
Physical Review Applied, 19, 2, American Physical Society (APS), 21 Feb. 2023
Scientific journal

Room-Temperature Spin-Transport Properties in an In0.5Ga0.5As Quantum Dot Spin-Polarized Light-Emitting Diode
Kohei Etou, Satoshi Hiura, Soyoung Park, Kazuya Sakamoto, Junichi Takayama, Agus Subagyo, Kazuhisa Sueoka, Akihiro Murayama
Physical Review Applied, 16, 1, American Physical Society (APS), 14 Jul. 2021, [Peer-reviewed]
Scientific journal

Relationship between rheological properties and actin filaments of single cells investigated by atomic force microscopy
Ryosuke Tanaka, Maki Sawano, Yuki Fujii, Kaori Kuribayashi-Shigetomi, Agus Subagyo, Kazuhisa Sueoka, Takaharu Okajima
Japanese Journal of Applied Physics, 59, SN, SN1010, SN1010, IOP Publishing, 01 Aug. 2020, [Peer-reviewed]
Scientific journal

Electron-transfer-induced metallic electronic states in a H/Fe3O4(001) film subsurface
Satoshi Hiura, Agus Subagyo, Akihiro Murayama, Kazuhisa Sueoka
Applied Physics Express, 12, 5, 055502, 055502, IOP Publishing, 01 May 2019, [Peer-reviewed]
Scientific journal

Visualising the dynamics of live pancreatic microtumours self-organised through cell-in-cell invasion
Yukiko Miyatake, Kaori Kuribayashi-Shigetomi, Yusuke Ohta, Shunji Ikeshita, Agus Subagyo, Kazuhisa Sueoka, Akira Kakugo, Maho Amano, Toshiyuki Takahashi, Takaharu Okajima, Masanori Kasahara
Scientific Reports, 8, 1, Springer Science and Business Media LLC, 19 Dec. 2018, [Peer-reviewed]
English, Scientific journal, Pancreatic ductal adenocarcinoma (PDAC) reportedly progresses very rapidly through the initial carcinogenesis stages including DNA damage and disordered cell death. However, such oncogenic mechanisms are largely studied through observational diagnostic methods, partly because of a lack of live in vitro tumour imaging techniques. Here we demonstrate a simple live-tumour in vitro imaging technique using micro-patterned plates (micro/nanoplates) that allows dynamic visualisation of PDAC microtumours. When PDAC cells were cultured on a micro/nanoplate overnight, the cells self-organised into non-spheroidal microtumours that were anchored to the micro/nanoplate through cell-in-cell invasion. This self-organisation was only efficiently induced in small-diameter rough microislands. Using a time-lapse imaging system, we found that PDAC microtumours actively stretched to catch dead cell debris via filo/lamellipoedia and suction, suggesting that they have a sophisticated survival strategy (analogous to that of starving animals), which implies a context for the development of possible therapies for PDACs. The simple tumour imaging system visualises a potential of PDAC cells, in which the aggressive tumour dynamics reminds us of the need to review traditional PDAC pathogenesis.

Origami-based self-folding of co-cultured NIH/3T3 and HepG2 cells into 3D microstructures
Qian He, Takaharu Okajima, Hiroaki Onoe, Agus Subagyo, Kazuhisa Sueoka, Kaori Kuribayashi-Shigetomi
Scientific Reports, 8, 1, Springer Science and Business Media LLC, 14 Dec. 2018, [Peer-reviewed]
Scientific journal

Temporal Variation in Single-Cell Power-Law Rheology Spans the Ensemble Variation of Cell Population
PingGen Cai, Ryosuke Takahashi, Kaori Kuribayashi-Shigetomi, Agus Subagyo, Kazuhisa Sueoka, John M. Maloney, Krystyn J. Van Vliet, Takaharu Okajima
Biophysical Journal, 113, 3, 671, 678, Elsevier BV, 08 Aug. 2017, [Peer-reviewed]
Scientific journal

Direct observation of subsurface charge ordering in Fe3O4(001) by scanning tunneling microscopy/spectroscopy
Satoshi Hiura, Akira Ikeuchi, Masafumi Jochi, Riku Yamazaki, Sotaro Takahashi, Agus Subagyo, Akihiro Murayama, Kazuhisa Sueoka
Applied Physics Express, 10, 4, 045701, 045701, IOP Publishing, 01 Apr. 2017, [Peer-reviewed]
Scientific journal

酸化と酵素切断がLDLの物性に与える影響(Physical properties of low-density lipoprotein after oxidation or proteolytic enzyme treatment)　　　　　　　　　　　　　　　
Takeda Seiji, Subagyo Agus, Hui Shu-Ping, Fuda Hirotoshi, Sueoka Kazuhisa, Chiba Hitoshi
生物物理, 56, Suppl.1-2, S290, S290, (一社)日本生物物理学会, Oct. 2016
English

Mapping cell-to-cell variations in power-law rheology investigated by multifrequency force modulation atomic force microscopy
M. Sawano, R. Tanaka, R. Takahashi, K. Kurubayashi-Shigetomi, A. Subagyo, K. Sueoka, T. Okajima
MOLECULAR BIOLOGY OF THE CELL, 27, AMER SOC CELL BIOLOGY, 2016, [Peer-reviewed]
English, International conference proceedings

Elastic modulus of low-density lipoprotein as potential indicator of its oxidation
Seiji Takeda, Agus Subagyo, Shu-Ping Hui, Hirotoshi Fuda, Rojeet Shrestha, Kazuhisa Sueoka, Hitoshi Chiba
ANNALS OF CLINICAL BIOCHEMISTRY, 52, 6, 647, 653, SAGE PUBLICATIONS INC, Nov. 2015, [Peer-reviewed]
English, Scientific journal, Background Evaluation of low-density lipoprotein oxidation is important in the risk assessment of cardiovascular disease. Atomic force microscope is widely used to evaluate the physical properties including stiffness on a single-particle scale. In this study, the effect of low-density lipoprotein oxidation on the low-density lipoprotein stiffness was investigated using an atomic force microscope.
Methods Isolated low-density lipoprotein particles with or without oxidation were densely bound to an Au substrate on mica, and then pressed and deformed by the atomic force microscope tip. The stiffness of each low-density lipoprotein particle was estimated as the elastic modulus obtained by the force curve analysis. Biochemical change of low-density lipoprotein due to oxidation was studied by electrophoresis.
Results and conclusion The elastic modulus of low-density lipoprotein particles ranged between 0.1 and 2MPa. The oxidation of low-density lipoprotein increased the number of low-density lipoprotein particles with smaller elastic moduli, indicating the decrease in low-density lipoprotein stiffness. The elastic modulus of low-density lipoprotein might be potentially useful to evaluate low-density lipoprotein oxidation.

Correlation between OH density and Fe electronic states of H/Fe3O4(001) film surfaces studied by scanning tunneling microscopy/spectroscopy
Satoshi Hiura, Akira Ikeuchi, Soraya Shirini, Agus Subagyo, Kazuhisa Sueoka
JAPANESE JOURNAL OF APPLIED PHYSICS, 54, 8, 08LB02, IOP PUBLISHING LTD, Aug. 2015, [Peer-reviewed]
English, Scientific journal, We report two types of adsorption structures in H/Fe3O4(001) film surfaces and the correlation between OH density and Fe electronic states, which have been studied by scanning tunneling microscopy/spectroscopy (STM/STS). Two types of bright protrusions (BPs), whose lengths along the atomic rows are different, are observed in the STM images. The shorter and longer BPs consist of Fe atoms with one and with two OH groups neighbor, respectively. In addition, STS measurements show the higher local density of states (LDOS) just below the Fermi level of Fe atoms with increasing neighboring OH groups. The variation can be attributed to the difference in the gain of electrons from H atoms, which is due to the difference in the number of neighboring OH groups. These results reveal that surface OH density is a factor for determining the LDOS just below the Fermi level of surface Fe atoms. (C) 2015 The Japan Society of Applied Physics

Effect of adsorbed H atoms on the Fe electronic states of Fe3O4(001) film surfaces
Satoshi Hiura, Akira Ikeuchi, Soraya Shirini, Agus Subagyo, Kazuhisa Sueoka
PHYSICAL REVIEW B, 91, 20, 205411, AMER PHYSICAL SOC, May 2015, [Peer-reviewed]
English, Scientific journal, We report the presence of OH groups on the surfaces of ultrahigh-vacuum-prepared Fe3O4(001) films by means of x-ray photoelectron spectroscopy (XPS). In addition, the variations of Fe electronic states induced by H atoms adsorbed on a Jahn-Teller distorted Fe3O4(001) surface have been studied using in situ scanning tunneling microscopy and scanning tunneling spectroscopy (STS). The obtained XPS spectra of the films have demonstrated the presence of surface OH groups. The STS spectra measured on Fe sites with and without neighboring OH groups have indicated that adsorbed H and their neighboring Fe atoms behave as electron-donor and electron-trapping sites, respectively. This phenomenon changes the Fe atoms from a semiconducting to a metalliclike nature. These local electronic state modifications are related to the occupation of Fe 3d states just below the Fermi level, corresponding to an Fe2+-like state. The orbital occupation can be explained by the gain of electrons from the adsorbed H atoms.

Size dependence of electron spin dephasing in InGaAs quantum dots
Y. Q. Huang, Y. Puttisong, I. A. Buyanova, X. J. Yang, A. Subagyo, K. Sueoka, A. Murayama, W. M. Chen
APPLIED PHYSICS LETTERS, 106, 9, 93109, AMER INST PHYSICS, Mar. 2015, [Peer-reviewed]
English, Scientific journal, We investigate ensemble electron spin dephasing in self-assembled InGaAs/GaAs quantum dots (QDs) of different lateral sizes by employing optical Hanle measurements. Using low excitation power, we are able to obtain a spin dephasing time T-2* (in the order of ns) of the resident electron after recombination of negative trions in the QDs. We show that T-2* is determined by the hyperfine field arising from the frozen fluctuation of nuclear spins, which scales with the size of QDs following the Merkulov-Efros-Rosen model. This scaling no longer holds in large QDs, most likely due to a breakdown in the lateral electron confinement. (C) 2015 AIP Publishing LLC.

High-throughput measurements of single cell rheology by atomic force microscopy
Kaori Kuribayashi-Shigetomi, Ryosuke Takahashi, Agus Subagyo, Kazuhisa Sueoka, Takaharu Okajima
Hyper Bio Assembler for 3D Cellular Systems, 57, 67, Springer Japan, 01 Jan. 2015, [Peer-reviewed]
English, In book, The compliant mechanical properties of single cells have been extensively investigated and these properties are known to exhibit a strong dependence on the surrounding environments and also cell types, functions and conditions. An understanding of the cell behavior is important for applications of tissue engineering. Accurate rheological measurements are essential to elucidate the mechanisms of cell integrity and fluidity and are also key to mechanically identifying and separating single cells for cellular and tissue engineering. Of the various existing nano-and micro-rheology techniques, atomic force microscopy (AFM) shows great potential as a minimally invasive method. AFM allows mechanical measurements to be performed without the need for chemical modifications, via nano-scale contact between the AFM probe and the cell surface. In this chapter, we describe a recent advance in which micro-fabricated substrates are used for high-speed, automated AFM rheological measurements on size-and position-controlled cells.

Growth-temperature dependence of optical spin-injection dynamics in self-assembled InGaAs quantum dots
Takafumi Yamamura, Takayuki Kiba, Xiaojie Yang, Junichi Takayama, Agus Subagyo, Kazuhisa Sueoka, Akihiro Murayama
JOURNAL OF APPLIED PHYSICS, 116, 9, 94309, AMER INST PHYSICS, Sep. 2014, [Peer-reviewed]
English, Scientific journal, The growth-temperature dependence of the optical spin-injection dynamics in self-assembled quantum dots (QDs) of In0.5Ga0.5As was studied by increasing the sheet density of the dots from 2 x 10(10) to 7 x 10(10) cm(-2) and reducing their size through a decrease in growth temperature from 500 to 470 degrees C. The circularly polarized transient photoluminescence (PL) of the resulting QD ensembles was analyzed after optical excitation of spin-polarized carriers in GaAs barriers by using rate equations that take into account spin-injection dynamics such as spin-injection time, spin relaxation during injection, spin-dependent state-filling, and subsequent spin relaxation. The excitation-power dependence of the transient circular polarization of PL in the QDs, which is sensitive to the state-filling effect, was also examined. It was found that a systematic increase occurs in the degree of circular polarization of PL with decreasing growth temperature, which reflects the transient polarization of exciton spin after spin injection. This is attributed to strong suppression of the filling effect for the majority-spin states as the dot-density of the QDs increases. (C) 2014 AIP Publishing LLC.

Anomalous spectral dependence of optical polarization and its impact on spin detection in InGaAs/GaAs quantum dots
Y. Puttisong, Y. Q. Huang, I. A. Buyanova, X. J. Yang, A. Subagyo, K. Sueoka, A. Murayama, W. M. Chen
APPLIED PHYSICS LETTERS, 105, 13, 132106, AMER INST PHYSICS, Sep. 2014, [Peer-reviewed]
English, Scientific journal, We show that circularly polarized emission light from InGaAs/GaAs quantum dot (QD) ensembles under optical spin injection from an adjacent GaAs layer can switch its helicity depending on emission wavelengths and optical excitation density. We attribute this anomalous behavior to simultaneous contributions from both positive and negative trions and a lower number of photo-excited holes than electrons being injected into the QDs due to trapping of holes at ionized acceptors and a lower hole mobility. Our results call for caution in reading out electron spin polarization by optical polarization of the QD ensembles and also provide a guideline in improving efficiency of spin light emitting devices that utilize QDs. (C) 2014 AIP Publishing LLC.

Atomic force microscopy measurements of mechanical properties of single cells patterned by microcontact printing
Ryosuke Takahashi, Satoshi Ichikawa, Agus Subagyo, Kazuhisa Sueoka, Takaharu Okajima
ADVANCED ROBOTICS, 28, 7, 449, 455, TAYLOR & FRANCIS LTD, Apr. 2014, [Peer-reviewed]
English, Scientific journal, To investigate the mechanical properties of adherent cells under conditions where cell-to-cell interaction can be prevented and controlled, we used microcontact printing to pattern single cells without intercellular contacts and measured them with a custom-built atomic force microscopy (AFM) system. The motorized AFM system can measure individual cells over a large spatial range, enabling the measurement of cells in a microarray format. We tested single fibroblast cells and found that the power-law of their complex shear modulus is not significantly influenced by cell-to-cell contact. This method is effective for obtaining high-throughput measurements on single cells.

3P169 Multi-frequency modulation atomic force microscopy for the high-speed measurement of single cell rheology(Cell biology,Poster,The 52th Annual Meeting of the Biophysical Society of Japan(BSJ2014))
Ryosuke Takahashi, Kaori Kuribayashi-Shigetomi, Agus Subagyo, Kazuhisa Sueoka, Takaharu Okajima
Seibutsu Butsuri, 54, 1, S277, The Biophysical Society of Japan General Incorporated Association, 2014
English

3P189 Movement of nucleus in cells cultured on micro-patterned substrates(Cell biology,Poster,The 52th Annual Meeting of the Biophysical Society of Japan(BSJ2014))
Xinfeng Zhu, Kaori Kuribayashi-Shigetomi, Pinggen Cai, Agus Subagyo, Kazuhisa Sueoka, Takaharu Okajima
Seibutsu Butsuri, 54, 1, S280, The Biophysical Society of Japan General Incorporated Association, 2014
English

1P053 Mechanical properties of oxidized low-density lipoprotein particles disclosed with AFM(01C. Protein : Property,Poster,The 52nd Annual Meeting of the Biophysical Society of Japan(BSJ2014))
Takeda Seiji, Subagyo Agus, Hui Shu-Ping, Fuda Hirotoshi, Sueoka Kazuhisa, Chiba Hitoshi
Seibutsu Butsuri, 54, 1, S149, The Biophysical Society of Japan General Incorporated Association, 2014
English

Temporal Change in Complex Shear Modulus of Cells: An Atomic Force Microscopy Study
PingGen Cai, Ryosuke Takahashi, Kaori Kuribayashi-Shigetomi, Agus Subagyo, Kazuhisa Sueoka, Takaharu Okajima
2014 INTERNATIONAL SYMPOSIUM ON MICRO-NANOMECHATRONICS AND HUMAN SCIENCE (MHS), 1, 3, IEEE, 2014, [Peer-reviewed]
English, International conference proceedings, To sort living cells according to our needs, it is important to understand how degree cell property measured for cell sorting fluctuates in time. Mechanical property of cells is one of essential indicators for cell sorting. Thus, in this study, we attempted to measure a time evolution of viscoelastic property such as complex shear modulus, G* of single cells adhered on substrates using atomic force microscopy (AFM). We observed that the G* largely fluctuated in time even the cells are placed on substrates in a confined condition. This indicates that in mechanical cell sorting, mechanical fluctuations of cells should be carefully estimated so that cells are precisely separated by taking the measured data involving cell fluctuations into account.

Atomic Force Microscopy for Mapping Mechanical Property of the Whole Cell Assembly
Ryosuke Tanaka, Yuki Fujii, Junpei Kikkawa, Kaori Kuribayashi-Shigetomi, Agus Subagyo, Kazuhisa Sueoka, Takaharu Okajima
2014 INTERNATIONAL SYMPOSIUM ON MICRO-NANOMECHATRONICS AND HUMAN SCIENCE (MHS), 1, 2, IEEE, 2014, [Peer-reviewed]
English, International conference proceedings, Cells rapidly undergo cell division during the embryogenesis. Such dynamic behaviors of cells during the embryogenesis are considered to be strongly associated with their mechanical properties such as cell-cell mechanical interactions and cell stiffness. However, the interplay between the morphogenesis and the mechanical property of whole cell assembly during the developmental process has not been well understood. To exploring the mechanism of forming the whole cell assembly, we proposed atomic force microscopy (AFM) combined with a microarray technique, which allows us to map mechanical property of the whole cell assembly. In this AFM setup, the cell assembly is randomly directed in the microarray well, and thus the average mechanical property of the whole cell assembly can be reconstructed from mapping images obtained from different cell assemblies.

Quantitative Rheological Measurements of Confluent Cell Using Atomic Force Microscopy
Ryosuke Takahashi, Kaori Kuribayashi-Shigetomi, Agus Subagyo, Kazuhisa Sueoka, Takaharu Okajima
2014 INTERNATIONAL SYMPOSIUM ON MICRO-NANOMECHATRONICS AND HUMAN SCIENCE (MHS), 1, 3, IEEE, 2014, [Peer-reviewed]
English, International conference proceedings, Rheological properties of cells are associated with various cell functions and thus are considered to be an indicator for diagnosing cell disease. Atomic force microscopy (AFM) is a powerful tool for quantifying the mechanical properties of isolated single cells. For example, our AFM technique reported previously revealed that the complex shear modulus of single cells exhibited a large cell-to-cell variation which depended on frequency. By contrast, rheological properties of cell population such as cells in confluent condition have been less understood. Thus, it is valuable to investigate how quantitatively the AFM technique can be applied to cell population such as cells in confluent condition. As a result, rheological properties of cells in confluent conditions can be relatively rapidly measured by our AFM setup modifying a force modulation AFM mode. This suggests that the AFM technique is useful for diagnosing not only single cells but also cell population and cell assembly.

Scanning Tunneling Microscopy Study of an Altered Fe3O4(001) Thin Films Surface by Hydrogen Adsorption
HIURA SATOSHI, IKEUCHI AKIRA, SHIRINI SORAYA, SUBAGYO AGUS, SUEOKA KAZUHISA
e-Journal Surf Sci Nanotechnol (Web), 12, 26-30 (J-STAGE), 2014, [Peer-reviewed]
English

Ultrafast spin tunneling and injection in coupled nanostructures of InGaAs quantum dots and quantum well
Xiao-Jie Yang, Takayuki Kiba, Takafumi Yamamura, Junichi Takayama, Agus Subagyo, Kazuhisa Sueoka, Akihiro Murayama
APPLIED PHYSICS LETTERS, 104, 1, 12406, AMER INST PHYSICS, Jan. 2014, [Peer-reviewed]
English, Scientific journal, We investigate the electron-spin injection dynamics via tunneling from an In0.1Ga0.9As quantum well (QW) to In0.5Ga0.5As quantum dots (QDs) in coupled QW-QDs nanostructures. These coupled nanostructures demonstrate ultrafast (5 to 20 ps) spin injection into the QDs. The degree of spin polarization up to 45% is obtained in the QDs after the injection, essentially depending on the injection time. The spin injection and conservation are enhanced with thinner barriers due to the stronger electronic coupling between the QW and QDs. (C) 2014 AIP Publishing LLC.

Temperature dependence of the dynamics of optical spin injection in self-assembled InGaAs quantum dots
KIBA TAKAYUKI, YANG XIAO-JIE, YAMAMURA TAKAFUMI, KUNO YUKI, SUBAGYO AGUS, SUEOKA KAZUHISA, MURAYAMA AKIHIRO
Appl Phys Lett, 103, 8, 082405-082405-5, 082405, AIP Publishing, 19 Aug. 2013, [Peer-reviewed]
English, Scientific journal

High-throughput measurements of cell mechanics using atomic force microscopy with micro-patterned substrates.
Ryosuke Takahashi, Kaori Kuribayashi-Shigetomi, Masahiro Tsuchiya, Agus Subagyo, Kazuhisa Sueoka, Takaharu Okajima
International Symposium on Micro-NanoMechatronics and Human Science, MHS 2013, Nagoya, Japan, November 10-13, 2013, 1, 3, IEEE, 2013, [Peer-reviewed]
International conference proceedings

Noncontact Atomic Force Microscopy Observation of Fe3O4(001) Surface
Mizuno Taichi, Hosoi Hirotaka, Subagyo Agus, Oishi Suguru, Ikeuchi Akira, Hiura Satoshi, Sueoka Kazuhisa
Jpn J Appl Phys, 51, 8, 08KB03, 08KB03-4, The Japan Society of Applied Physics, 25 Aug. 2012, [Peer-reviewed]
English, Fe3O4 is one of the important oxide materials and its surface structure should be well understood to enable application of this material. We report the first noncontact atomic force microscopy (NC-AFM) results for Fe3O4(001) thin films. The observed films were grown homoepitaxially on magnetite thin films substrate. A low-energy electron diffraction pattern shows the well-known (\sqrt{2}\times \sqrt{2})R45° reconstructed structure. The observed minimum step height is 0.21 nm, corresponding to the distance between the same planes. We obtain two types of atomic-scale NC-AFM images. One image shows bright protrusions along the [100] and [010] directions at intervals of 0.84 nm corresponding to a unit cell of the (\sqrt{2}\times \sqrt{2})R45° reconstructed structure. The other image shows a more detailed atomic structure with 0.6 and 0.3 nm corrugations.

Atomically Resolved Observations of Antiphase Domain Boundaries in Epitaxial Fe3O4 Films on MgO(001) by Scanning Tunneling Microscopy
Ikeuchi Akira, Hiura Satoshi, Mizuno Taichi, Kaji Eisaku, Subagyo Agus, Sueoka Kazuhisa
Jpn J Appl Phys, 51, 8, 08KB02, 08KB02-5, The Japan Society of Applied Physics, 25 Aug. 2012, [Peer-reviewed]
English, We have studied the surface atomic configurations around antiphase domain boundaries (APBs) in epitaxial magnetite (Fe3O4) thin films on MgO(001) by scanning tunneling microscopy (STM). The observed surface of the Fe3O4 films is the B-plane terminating surface with the (\sqrt{2}\times\sqrt{2})R45^{\circ} reconstruction. Several variations of APBs are observed by STM at atomic resolution. The observed APBs are categorized into a APBs labeled by three different phase shift vectors: in-plane 1/4[110], in-plane 1/2[100], and out-of-plane 1/4[101]. We discussed how these APBs appear on the surface. The proportions of the APBs with 1/4[110], 1/2[100], and 1/4[101] shifts are about 38, 1, and 61%, respectively, in our experiment.

Direct observation of dynamic force propagation between focal adhesions of cells on microposts by atomic force microscopy
A. Okada, Y. Mizutani, A. Subagyo, H. Hosoi, M. Nakamura, K. Sueoka, K. Kawahara, T. Okajima
Appl. Phys. Lett., 99, 26, 263703-1, 263703-3, AMER INST PHYSICS, 26 Dec. 2011, [Peer-reviewed]
English, Scientific journal, We investigated dynamic force propagation between focal adhesions of fibroblast cells cultured on polydimethylsiloxane micropost substrates, by atomic force microscopy. Live cells were mechanically modulated by the atomic force microscopy probe bound to cell apical surfaces at 0.01-0.5 Hz, while microposts served as a force sensor at basal surfaces. We observed that cells exhibited rheological behavior at the apical surface but had no apparent out-of-phase response at the basal surface, indicating that the dynamic force propagating through cytoskeletal filaments behaves in an elastic manner. Moreover, the direction of the propagated force was observed to be intimately associated with the prestress. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3672225]

Calculation method of reflectance distributions for computer-generated holograms using the finite-difference time-domain method
Tsubasa Ichikawa, Yuji Sakamoto, Agus Subagyo, Kazuhisa Sueoka
APPLIED OPTICS, 50, 34, H211, H219, OPTICAL SOC AMER, Dec. 2011, [Peer-reviewed]
English, Scientific journal, The research on reflectance distributions in computer-generated holograms (CGHs) is particularly sparse, and the textures of materials are not expressed. Thus, we propose a method for calculating reflectance distributions in CGHs that uses the finite-difference time-domain method. In this method, reflected light from an uneven surface made on a computer is analyzed by finite-difference time-domain simulation, and the reflected light distribution is applied to the CGH as an object light. We report the relations between the surface roughness of the objects and the reflectance distributions, and show that the reflectance distributions are given to CGHs by imaging simulation. (C) 2011 Optical Society of America

A method of Calculating Reflectance Distributions for CGH with FDTD using the Structure of Actual Surfaces
Ichikawa Tsubasa, Sakamoto Yuji, Subagyo Agus, Sueoka Kazuhisa
PRACTICAL HOLOGRAPHY XXV: MATERIALS AND APPLICATIONS, 7957, 2011, [Peer-reviewed]

Holders for in situ treatments of scanning tunneling microscopy tips.
Ishida N, Subagyo A, Ikeuchi A, Sueoka K
The Review of scientific instruments, 80, 9, 093703, Sep. 2009, [Peer-reviewed]

Surface magnetic structure of epitaxial magnetite thin films grown on MgO(001)
Kaji Eisaku, Subagyo Agus, Arita Masashi, Sueoka Kazuhisa
JOURNAL OF APPLIED PHYSICS, 105, 7, 01 Apr. 2009, [Peer-reviewed]

Needle-type field-effect transistor based on carbon nanotube derivative without lithography process
Takeda Seiji, Nakamura Motonori, Subagyo Agus, Ishii Atsushi, Sueoka Kazuhisa, Mukasa Koichi
SENSORS AND ACTUATORS B-CHEMICAL, 132, 1, 9, 12, 28 May 2008, [Peer-reviewed]

Inhomogeneous surface electronic properties and charge ordering in epitaxial Fe3O4 films on MgO(001)
A. Subagyo, Y. Sasaki, H. Oka, K. Sueoka
physica status solidi (b), 244, 12, 4482, 4485, Wiley, Dec. 2007, [Peer-reviewed], [Lead author]
Scientific journal

A pH sensor based on electric properties of nanotubes on a glass substrate.
Takeda S, Nakamura M, Ishii A, Subagyo A, Hosoi H, Sueoka K, Mukasa K
Nanoscale research letters, 2, 4, 207, 212, Springer, Mar. 2007, [Peer-reviewed]
English, We fabricated a pH-sensitive device on a glass substrate based on properties of carbon nanotubes. Nanotubes were immobilized specifically on chemically modified areas on a substrate followed by deposition of metallic source and drain electrodes on the area. Some nanotubes connected the source and drain electrodes. A top gate electrode was fabricated on an insulating layer of silane coupling agent on the nanotube. The device showed properties of an n-type field effect transistor when a potential was applied to the nanotube from the top gate electrode. Before fabrication of the insulating layer, the device showed that the p-type field effect transistor and the current through the source and drain electrodes depend on the buffer pH. The current increases with decreasing pH of the CNT solution. This device, which can detect pH, is applicable for use as a biosensor through modification of the CNT surface.

Large area magnetic domain imaging of magnetite films with Spin-SEM
Eisaku Kaji, Agus Subagyo, Kazuhisa Sueoka
Physica Status Solidi (C) Current Topics in Solid State Physics, 4, 12, 4364, 4367, 2007, [Peer-reviewed]
English, International conference proceedings, The surface crystallographic structure and magnetic structure of magnetite thin films epitaxially grown on a MgO(001) substrate were investigated by means of a scanning tunnelling microscope (STM), magnetic force microscope (MFM) and Spin-polarized scanning electron microscopy (Spin-SEM). The STM investigation and MFM measurement were performed in-situ and in an ambient condition, respectively. After exposing the sample to air, a Spin-SEM image was acquired. Spin-dependent contrasted SEM images could be obtained after cleaning the sample surfaces. The cleaning procedure is annealing the sample at 250°C in an ultra high vacuum (UHV) below 3 × 10-8 Pa for 3 hours. The STM observation indicates the thin films have antiphase domains and the observed MFM images reflect a cease in micromagnetic domain structures. Spin-SEM images indicate that large-scale magnetic inhomogeneity of a few μm is the inhomogeneity of the perpendicular magnetic moments of the films. Due to the spatial resolution limitation of our Spin-SEM system, the correlation between the fine and coarse magnetic structures of the thin films induced by the antiphase domain boundaries is not clear, however, we have suggested the annealing process alone in a UHV makes the spin configuration of the thin films visible using a conventional Spin-SEM system. © 2007 WILEY-VCH Verlag GmbH &
Co. KGaA.

Large area magnetic domain imaging of magnetite films with Spin-SEM
Kaji Eisaku, Subagyo Agus, Sueoka Kazuhisa
PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 4, NO 12, 4, 12, 4364, 4367, 2007, [Peer-reviewed]

Correlation between Surface Structure and Charge Ordering in Magnetite(001) Studied by Scanning Tunneling Microscopy and Spectroscopy
Subagyo Agus, Sueoka Kazuhisa
PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY, 61, 1102, 1106, 2007, [Peer-reviewed]
International conference proceedings

Spin-Polarized Scanning Tunneling Microscopy Study on Charge Ordering of Reconstructed Fe3O4(001) Film Surfaces
Agus Subagyo, Kazuhisa Sueoka
Japanese Journal of Applied Physics, 45, 3B, 2255, 2258, IOP Publishing, 27 Mar. 2006, [Peer-reviewed], [Lead author]
English, Scientific journal, Fe3O4(001) film surfaces having a ($\sqrt{2} \times \sqrt{2}$)$R$45° reconstruction are studied by scanning tunneling microscopy (STM) and spin-polarized STM (SP-STM). The reconstruction is induced by ordered arrays of oxygen vacancy at B-terminated surfaces as revealed by STM. Fe cation rows having a wavelike structure oriented along the [110] direction with a separation of 0.6 nm are observed. A single Fe cation with a 0.3 nm periodicity within the cation rows is resolved. Instead of a single Fe cation, SP-STM imaged an alternation of high and low corrugations representing Fe3+–Fe3+ dimers and Fe2+–Fe2+ dimers, respectively. The resolving of Fe dimers having different spin states by SP-STM is due to the contribution of spin-polarized tunneling current. The Fe3+–Fe3+ and Fe2+–Fe2+ dimers have a separation of about 0.6 nm in the [110] direction, while in the [$1\bar{1}0$] direction these dimers alternate by about 0.65 and 0.55 nm. The separation is consistent with the wavelike row structure on the ($\sqrt{2}\times \sqrt{2}$)$R$45° reconstructed Fe3O4(001) film surfaces.

Directional diffusion of K atoms on a gaas(110) surface
Ishida Nobuyuki, Subagyo Agus, Sueoka Kazuhisa
INTERNATIONAL JOURNAL OF NANOSCIENCE, VOL 5, NO 6, 5, 6, 895, +, WORLD SCIENTIFIC PUBL CO PTE LTD, 2006, [Peer-reviewed]
English, International conference proceedings, We performed STM measurements on the K/GaAs(110) surface with high K coverage. The K atoms gradually disappeared while scanning the tip over the surface at negative sample bias voltage. The phenomenon strongly occurred over the scanning area and can be explained by the field-induced surface diffusion from the scanning area to radial direction. Considering the interaction between the dipole moment of the adsorbed K atoms and the electric field, we discuss the relationship between the static and induced dipole moment of K atoms on a GaAs(110) surface.

Local electronic properties of domain boundaries on c(2 x 2) Fe(001) thin film surfaces
Oka Hirofumi, Subagyo Agus, Sueoka Kazuhisa
INTERNATIONAL JOURNAL OF NANOSCIENCE, VOL 5, NO 6, 5, 6, 935, +, 2006, [Peer-reviewed]

Defect-Induced Charge Freezing on Epitaxial Fe3O4(001) Film Surfaces Studied by Spin-Polarized Scanning Tunneling Microscopy
Agus Subagyo, Kazuhisa Sueoka
Japanese Journal of Applied Physics, 44, 7B, 5447, 5450, IOP Publishing, 26 Jul. 2005, [Peer-reviewed], [Lead author]
English, Scientific journal, We report the role of atom defects on the charge freezing of Fe3O4(001) surfaces studied by spin-polarized scanning tunneling microscopy (SP-STM) using a Ni tip. Epitaxially grown Fe3O4(001) films on a MgO(001) substrate were used as samples. Atomically flat surfaces are obtained by annealing in an ultrahigh vacuum and in oxygen. The surfaces exhibit a $(\sqrt{2}\times\sqrt{2})R45$° reconstruction as revealed by STM with a W tip. STM images indicate surface termination at B-sites. An atomic structure with a 0.3 nm periodicity is observed within the cation rows that are aligned along the [110] direction. SP-STM images show a pronouncedly different periodicity of 1.2 nm on areas having surface defects such as cation vacancies. This corrugation with a 1.2 nm periodicity can be attributed to a charge localization of Fe3+ and Fe2+ ions that are trapped by cation vacancies and then isolated from the electron hopping process. The results also indicate the important role of oxygen vacancies in modifying the 1.2 nm periodicity.

In situ Conductance Measurement of a Limited Number of Nanoparticles during Transmission Electron Microscopy Observation
HIROSE Ryusuke, ARITA Masashi, HAMADA Kouichi, TAKAHASHI Yasuo, SUBAGYO Agus
Jpn J Appl Phys Part 2, 44, 24-27, L790-L792, L792, INSTITUTE OF PURE AND APPLIED PHYSICS, 10 Jul. 2005, [Peer-reviewed]
English, A technique for measuring the conductance of a small number of particles during transmission electron microcopy (TEM) observation is demonstrated. By using a custom-designed TEM holder, an Au tip was brought into contact with Fe nanodots contained in a SrF2 film deposited on another Au tip. The conductance shows Coulomb-blockade-like characteristics even at room temperature.

Reconstruction and charge ordering of epitaxial Fe3O4(001) films
Agus Subagyo, Kazuhisa Sueoka, Koichi Mukasa
Journal of Magnetism and Magnetic Materials, 290-291, 1037, 1039, Elsevier BV, Apr. 2005, [Peer-reviewed], [Lead author]
Scientific journal

Anti-phase domains and charge ordering on epitaxial magnetite films studied by spin-polarized scanning tunneling microscopy
Agus Subagyo, Kazuhisa Sueoka
INTERMAG ASIA 2005: Digests of the IEEE International Magnetics Conference, 350, IEEE Computer Society, 2005
English, International conference proceedings

Magnetic imaging with scanning probe microscopy
K Sueoka, A Subagyo, H Hosoi, K Mukasa
NANOTECHNOLOGY, 15, 10, S691, S698, IOP PUBLISHING LTD, Oct. 2004, [Peer-reviewed]
English, Scientific journal, We review our research on the application of scanning tunnelling microscopy (STM) and non-contact atomic force microscopy (NC-AFM) for magnetic imaging in high spatial resolution even down to the atomic scale. In the first part, we propose a new experimental scheme of spin-polarized STM (SP-STM) with a GaAs spin probe to obtain a large contribution of spin-polarized electrons in the tunnelling current. This is yielded by injecting the spin-polarized photo-excited electrons in an optically pumped GaAs tip into the spin-polarized empty states near the Fermi level of a bcc-Fe(001) surface. According to the bandgap energy of GaAs and the surface state of the sample observed at 0.4 eV above the Fermi level, the spin-dependant electron injection can be achieved by applying a sample bias voltage of -1 V. The tunnel current in the positive bias region depends on the helicity of the circular polarized pumping light, and is modified when the applied magnetic field is reversed. Mapping the current asymmetry provides a spin-dependent SP-STM image. In the second part, we describe the progress towards spin imaging with NC-AFM. The spin imaging can be achieved by detecting short-range magnetic interaction such as exchange interaction between a ferromagnetic tip and a magnetic sample. We demonstrate the capabilities of NC-AFM by imaging the spin structure of an antiferromagnetic NiO(001) surface on the atomic scale. The cross-sectional line profiles of the atomically resolved images obtained using several ferromagnetic tips (Fe, Ni) were analysed by adding the atomic corrugation amplitude on the basis of the periodicity of the image. The results of the analysis show that the difference of the neighbouring maxima depends on the crystal direction. On the other hand, no significant indication of the directional dependency can be seen on the images obtained by using a non-magnetic Si tip. The directional dependency coincides with the antiferromagnetic spin alignment of the NiO(001) surface.

Self-Assembled Low-Dimensional Potassium Structures on GaAs(110)
Ishida Nobuyuki, Subagyo Agus, Hosoi Hirotaka, Sueoka Kazuhisa, Mukasa Koichi
Jpn J Appl Phys, 43, 7, 4557, 4560, Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physics, 15 Jul. 2004, [Peer-reviewed]
English, We investigated the adsorption structures of K atoms on a GaAs(110) surface as a function of coverage by scanning tunneling microscopy. We found three kinds of adsorption structures, namely, the low-density linear chain, the asymmetric chain and the symmetric chain. At the initial stage with low coverage, K atoms form low-density linear and asymmetric chains. With increasing coverage, low-density linear chains disappeared and the number of asymmetric chains increased. At high adsorption coverage, K atoms began to form symmetric chains, so that the symmetric and asymmetric chains coexisted. The strong dependency of the adsorption structure on the coverage is discussed by considering a recent theoretical work.

Atomic Scale Observation of Domain Boundaries onc(2×2) Fe(001) Thin Film Surfaces
Hirofumi Oka, Agus Subagyo, Makoto Sawamura, Kazuhisa Sueoka, Koichi Mukasa
Japanese Journal of Applied Physics, 41, Part 1, No. 7B, 4969, 4972, IOP Publishing, 30 Jul. 2002, [Peer-reviewed]
English, Scientific journal, Scanning tunneling microscopy (STM) measurements reveal that Fe thin films epitaxially grown on a MgO(001) substrate under appropriate conditions have an atomic step-terrace surface with a $c(2\times 2)$ surface reconstruction, and that this surface is often accompanied by line-like patterns along the Fe$\langle 110 \rangle$ direction. We have investigated the electronic properties of the patterns in detail by atomically resolved STM. We found that the pattern is a domain phase boundary of the $c(2\times 2)$ domains, and that the domain boundaries consist of atoms exhibiting a ($1\times 1$) structure. The STM image shows remarkable bias-voltage dependency as indicated by the contrast inversion between the patterns and $c(2\times 2)$ domains as the polarity of the applied bias-voltage is changed, and the contrast achieved its maximum value at $+0.2$ V. This bias-voltage dependency of the patterns can be explained by the existence of surface states which are observed at around 0.2 eV above the Fermi level on the Fe(001) ($1\times 1$) surface and 0.4 eV on the $c(2\times 2)$ domains.

Spin Electronic States and Geometry of Fe Nanowire : Comparison with Au, Pt, Cu, Na, Mg, Al, Si, and Xe Atomic Strands
SAWAMURA Makoto, HOSOI Hirotaka, KIMURA Michiya, EILERS Guido, SUBAGYO Agus, SUEOKA Kazuhisa, MUKASA Koichi
Journal of the Magnetics Society of Japan, 2, 2, 63, 68, The Magnetics Society of Japan (MSJ), 01 May 2002
English, The geometries and spin electronic states of single atomic strands consisting of Fe atoms were studied in comparison with similar strands of Au, Pt, Cu, Na, Mg, Al, Si, and Xe atoms, using first principles molecular orbital methods. Finite cluster models comprising six atoms were constructed. The optimized geometry of the wire was obtained for each element as the wire was elongated. Abnormally long atomic distances were observed in the cases of Fe, Au, Pt, Cu, Na, Mg, and Xe wires, which have shallow and broad s-orbitals in their valence shells. On the other hand, the wires formed from Al and of Siatoms collapsed while growing to lengths in excess of the bulk atomic distances. These atoms have σ-bonds with their neighboring atoms in the wires. Their electronic states create steep and deep potential energy wells, which prohibit long atomic distances.

Growth and characterization of Fe(100)/InAs(100) hybrid structures
H Ohno, K Yoh, T Doi, A Subagyo, K Sueoka, K Mukasa
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B, 19, 6, 2280, 2283, A V S AMER INST PHYSICS, Nov. 2001, [Peer-reviewed]
English, Scientific journal, We report on the growth of planar/patterned Fe thin films on InAs(100) substrates and their subsequent characterization using reflection high-energy electron diffraction, low-energy electron diffraction, superconducting quantum interference device, and four-terminal contact resistance measurements. Epitaxial growth of body-centered-cubic Fe crystal on InAs(100) was verified for growth temperatures of 23 degreesC and 175 degreesC. A patterned Fe wire array showed clear uniaxial shape anisotropy with the easy axis along the wire direction. Its coercive force was found to depend on the growth temperature and the width of the Fe wires. Four-terminal contact resistance measurement of Fe/n-InAs revealed that Fe forms decent ohmic contact to the InAs substrate with a resistivity of the order of 10(-6) Omegacm(2). Samples crown at room temperature showed equally decent or even better magnetic and electrical characteristics than those obtained by higher temperature growth. These results indicate that the Fe/InAs hybrid structures have definite potential for spin-related semiconductor devices with practical process sequences. (C) 2001 American Vacuum Society.

Scanning Tunneling Spectroscopy of $c(2{\times}2)$ Reconstructed Fe Thin-Film Surfaces
Oka Hirofumi, Subagyo Agus, Sawamura Makoto, Sueoka Kazuhisa, Mukasa Kōichi
Jpn J Appl Phys, 40, 6, 4334, 4336, INSTITUTE OF PURE AND APPLIED PHYSICS, 30 Jun. 2001
English, Fe thin films with flat surfaces are obtained on a MgO(001) substrate at a growth temperature of 550 K. The surfaces with atomically flat and wide terraces exhibit a $c(2{\times}2)$ reconstructed structure. To evaluate the effect of impurity atoms at the surface on the surface structures, scanning tunneling spectroscopy (STS), reflection high energy electron diffraction (RHEED) and X-ray photoelectron spectroscopy (XPS) studies were performed. The differential conductivity (${dI/dV}$) spectrum of the $c(2{\times}2)$ Fe(001) thin-film surfaces indicates an intense peak at the sample bias voltage of 0.4 V. Since there is no clear evidence of impurity adatoms forming such a surface structure, we expect that the topmost atoms are Fe, and that the observed peak originates from surface states.

Scanning Tunneling Microscopy Observation of Epitaxial bcc-Fe(001) Surface
Agus Subagyo, Hirofumi Oka, Guido Eilers, Kazuhisa Sueoka, Koichi Mukasa
Japanese Journal of Applied Physics, 39, Part 1, No. 6B, 3777, 3779, IOP Publishing, 30 Jun. 2000, [Peer-reviewed], [Lead author]
English, Scientific journal, We report the first atomic-resolution scanning tunneling microscopy (STM) image of epitaxial bcc-Fe(001) films grown on MgO(001) substrates. A 50-Å-thick Fe film grown at a growth temperature of 550 K formed square pyramidal islands with atomically flat terraces. The terraces were found to range between 5 nm and 20 nm in width separated by monoatomic high steps. The film exhibited a ($1\times 1$) unreconstructed structure at a film thickness below 19 Å; however, a reconstructed surface was found on thicker films. The atomic-resolution STM image and low energy electron diffraction (LEED) observation indicated that the reconstructed structure is a c($2\times 2$) structure.

In situ STM observation of the spiral growth in the epitaxial Fe films on MgO(001)
A Subagyo, K Sueoka, K Mukasa
NUCLEATION AND GROWTH PROCESSES IN MATERIALS, 580, 429, 434, MATERIALS RESEARCH SOCIETY, 2000, [Peer-reviewed], [Lead author]
English, International conference proceedings, We reported a scanning tunneling microscopy(STM) observation on the growth mode transition from 2D-nucleation to spiral growth in the epitaxial Fe films on MgO(001). As the growth temperature is increased to above 493 K, a temperature region where the Schwoebel barrier is overcome, the Fe films grow in a 2D-nucleation and growth mode formed atomically flat films. The 2D-nucleation transformed into a spiral growth as increasing film thickness. At a growth temperature of 493 K, the transition of 2D nucleation to the spiral growth was observed at a film thickness of 75 Angstrom. The critical thickness of the emergence of growth transition decreased as the growth temperature is increased.

Growth morphology of epitaxial Fe films on annealed MgO [001] surfaces
A. Subagyo, K. Sueoka, K. Mukasa
IEEE Transactions on Magnetics, 35, 5, 3037, 3039, Institute of Electrical and Electronics Engineers (IEEE), Sep. 1999, [Peer-reviewed], [Lead author]
Scientific journal

Scanning Tunneling Microscopy Study of Surface Structure and Magnetism of Fe Thin Films Grown on MgO (001)
Agus Subagyo, Kazuhisa Sueoka, Koichi Mukasa, Kazunobu Hayakawa
Japanese Journal of Applied Physics, 38, Part 1, No. 6B, 3820, 3825, IOP Publishing, 30 Jun. 1999, [Peer-reviewed], [Lead author]
English, Scientific journal, Substrate preparation procedure dependence of the growth morphology and magnetic properties of 25 ML bcc-Fe(001) thin films epitaxially grown on MgO(001) substrates in a wide range of growth temperature was investigated by means of scanning tunneling microscopy (STM) and superconducting quantum interference device (SQUID). The growth morphology of Fe thin films was uniform both on a polished and on an annealed substrate, but nonuniform on a cleaved substrate. It was very difficult to obtain a flat Fe thin film on the cleaved substrate, and the film became discontinuous at or above a growth temperature of 493 K. At a growth temperature of 550 K, atomically defined terraces of Fe thin films were formed on the annealed substrate but were not formed on the polished substrate. A continuous film grown on the annealed substrate at a temperature of 593 K has a less magnetic anisotropy. The other continuous films have low coercivity of about 8 Oe and a biaxial magnetic anisotropy. The dependency of the growth morphology and magnetic properties of Fe thin films upon substrate preparation procedures concerning the presence of step-terraces on the substrate surface is discussed.

Spin-polarized tunneling between Fe thin films and an optically pumped GaAs probe
K. Sueoka, A. Subagyo, K. Mukasa
Digests of the Intermag Conference, IEEE, 1999
English, International conference proceedings, A GaAs thin film probe for a spin probe was studied by observing clean Fe thin film surfaces. The tunneling current with circular polarization modulation pumping showed both the external magnetic dependency and the position dependency. This indicated that the spin-polarized tunneling occurs between the Fe thin film and the optically pumped GaAs thin film probe.

Growth morphology of epitaxial Fe films on annealed MgO (001) surfaces
Agus Subagyo, Kazuhisa Sueoka, Koichi Mukasa
Digests of the Intermag Conference, IEEE, 1999
English, International conference proceedings, The effects of MgO (001) surface structures to the growth morphology of Fe films were determined by means of atomic force microscopy (AFM), scanning tunneling microscopy (STM) and reflection high energy electron diffraction (RHEED). An evidence for Fe film morphology differences was obtained.

STM Study of a Thin GaAs Tip
SUEOKA Kazuhisa, HOSOYAMA Naoki, SUBAGYO Agus, MUKASA Koichi, HAYAKAWA Kazunobu
Journal of the Surface Science Society of Japan, 19, 8, 522, 526, 日本表面科学会, 10 Aug. 1998, [Peer-reviewed]
Japanese

Silicon MIS Solar Cells by Anodization
Agus SUBAGYO, Yukinari HAYASHI, Susumu TOKUDA, Masaki YOSHINO, Junji NANJO
Denki Kagaku oyobi Kogyo Butsuri Kagaku, 66, 2, 206, 211, The Electrochemical Society of Japan, 05 Feb. 1998, [Peer-reviewed], [Lead author]
Scientific journal

化学先取りシンポジウム 酸化還元電位および硬さ分布からLDLの酸化状態を評価　　　　　　　　　　　　　　　
武田 晴治, アグス・スバギョ, 布田 博敏, 惠 淑萍, 末岡 和久, 千葉 仁志, 臨床化学, 46, Suppl.1, 175, 175, Sep. 2017
(一社)日本臨床化学会, Japanese

LDLの酸化および酵素処理が硬さに与える影響について　　　　　　　　　　　　　　　
武田 晴治, アグス・スバギョ, 布田 博敏, 惠 淑萍, 末岡 和久, 千葉 仁志, 臨床化学, 46, Suppl.1, 329, 329, Sep. 2017
(一社)日本臨床化学会, Japanese

最先端表面分析手法 : 元素分析から電子状態解析まで (特集 進化する最先端計測・解析技術とナノテクノロジープラットフォームによる施設共用)
大塚 俊明, 松尾 保孝, 坂入 正敏, 鈴木 啓太, 上野 貢生, 孫 泉, 三澤 弘明, スバギョ アグス, 末岡 和久, 金属, 86, 12, 1103, 1111, Dec. 2016
アグネ技術センター, Japanese

半導体自己組織化量子ドットへのトンネル効果によるスピン注入;励起スピン密度依存性
YANG Xiaojie, 山村隆文, 木場隆之, 高山純一, SUBAGYO Agus, 末岡和久, 村山明宏, 応用物理学会春季学術講演会講演予稿集(CD-ROM), 61st, 2014

金属強磁性体電極を持つInGaAs量子構造発光ダイオードのEL特性
野村譲, 高山純一, 木場隆之, AGUS Subagyo, 山村隆文, YANG Xiaojie, 末岡和久, 村山明宏, 応用物理学会秋季学術講演会講演予稿集(CD-ROM), 75th, 2014

InGaAs量子ドットと量子井戸の結合スピン状態に対する電界印加効果
高山純一, 木場隆之, 山村隆文, 野村譲, AGUS Subagyo, 末岡和久, 村山明宏, 応用物理学会秋季学術講演会講演予稿集(CD-ROM), 75th, 2014

InGaAs量子井戸から量子ドットへのトンネル効果によるスピン注入ダイナミクス;トンネル障壁厚さ依存性
山村隆文, YANG Xiaojie, 木場隆之, 高山純一, SUBAGYO Agus, 末岡和久, 村山明宏, 応用物理学会秋季学術講演会講演予稿集(CD-ROM), 75th, 2014

Fe電極を用いた量子ドット発光ダイオードのEL特性
佐々木裕也, YANG Xiaojie, 高山純一, 木場隆之, SUBAGYO Agus, 池内昭郎, 末岡和久, 村山明宏, 応用物理学会秋季学術講演会講演予稿集(CD-ROM), 74th, 2013

InGaAs自己組織化量子ドットにおける光スピン注入ダイナミクスの成長温度依存性
山村隆文, YANG Xiaojie, 木場隆之, 高山純一, SUBAGYO Agus, 末岡和久, 村山明宏, 応用物理学会秋季学術講演会講演予稿集(CD-ROM), 74th, 2013

Charge Ordering in a Magnetite Film Surface
SUBAGYO A, SUEOKA K, Magnetics Japan, 3, 4, 174, 179, 01 Apr. 2008, [Lead author]
日本磁気学会, Japanese

Local observation of surface magnetic structures by using STM/STS
OKA H, SUBAGYO Agus, SUEOKA K, 日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan, 28, 0, 149, 149, 21 Sep. 2004
Japanese

20aWD-11 Spin Electronic States of Nanowires under the STM Environment
Sawamura M, Hosoi H, Subagyo A, Sueoka K, Mukasa K, Meeting abstracts of the Physical Society of Japan, 56, 2, 775, 775, 03 Sep. 2001
社団法人日本物理学会, English

Spin electronic states and geometry of Fe nanowire : Comparison with Au, Pt, Cu, Na, Mg, Al, Si and Xe nanowires
SAWAMURA M, HOSOI H, SUBAGYO A, KIMURA M, EILERES G, SUEOKA K, MUKASA K, 日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan, 25, 0, 258, 258, 01 Sep. 2001
English

28pYQ-1 Spin Electronic States of Nanowires under the STM Environment
Sawamura M, Hosoi H, Kimura M, Eilers G, Subagyo A, Sueoka K, Mukasa K, Meeting abstracts of the Physical Society of Japan, 56, 1, 810, 810, 09 Mar. 2001
社団法人日本物理学会, English

Growth and characterization of Fe(100)/InAs(100) hybrid structures,
OHNO H, YOH K, DOI T, SUBAGYO A, SUEOKA K, MUKASA K, Journal of Vacuum Science and Technology B, 19, 6, 2280, 2283, 2001

Temperature and rate dependence of the growth of Cu films on MgO(001)
Eilers G., Matsuura M., Oka H., Subagyo A., Sueoka K., Mukasa K., Meeting abstracts of the Physical Society of Japan, 55, 2, 765, 765, 10 Sep. 2000
The Physical Society of Japan (JPS), Japanese

SP-STM obsevation of Fe thin films with optically pumped GaAs tips
SUEOKA K, SUBAGYO A, MUKASA K, HAYAKAWA K, 日本応用磁気学会学術講演概要集 = Digest of ... annual conference on magnetics in Japan, 22, 0, 12, a-12-b, 01 Sep. 1998
Japanese

Mapping cell-to-cell variations in power-law rheology investigated by multifrequency force modulation atomic force microscopy　　　　　　　　　　　　　　　
M. Sawano, R. Tanaka, R. Takahashi, K. Kurubayashi-Shigetomi, A. Subagyo, K. Sueoka, T. Okajima
MOLECULAR BIOLOGY OF THE CELL, 2016, AMER SOC CELL BIOLOGY, English
2016 - 2016

Quantitative Rheological Measurements of Confluent Cell Using Atomic Force Microscopy
Ryosuke Takahashi, Kaori Kuribayashi-Shigetomi, Agus Subagyo, Kazuhisa Sueoka, Takaharu Okajima
2014 INTERNATIONAL SYMPOSIUM ON MICRO-NANOMECHATRONICS AND HUMAN SCIENCE (MHS), 2014, IEEE, English
2014 - 2014, Rheological properties of cells are associated with various cell functions and thus are considered to be an indicator for diagnosing cell disease. Atomic force microscopy (AFM) is a powerful tool for quantifying the mechanical properties of isolated single cells. For example, our AFM technique reported previously revealed that the complex shear modulus of single cells exhibited a large cell-to-cell variation which depended on frequency. By contrast, rheological properties of cell population such as cells in confluent condition have been less understood. Thus, it is valuable to investigate how quantitatively the AFM technique can be applied to cell population such as cells in confluent condition. As a result, rheological properties of cells in confluent conditions can be relatively rapidly measured by our AFM setup modifying a force modulation AFM mode. This suggests that the AFM technique is useful for diagnosing not only single cells but also cell population and cell assembly.

Atomic Force Microscopy for Mapping Mechanical Property of the Whole Cell Assembly
Ryosuke Tanaka, Yuki Fujii, Junpei Kikkawa, Kaori Kuribayashi-Shigetomi, Agus Subagyo, Kazuhisa Sueoka, Takaharu Okajima
2014 INTERNATIONAL SYMPOSIUM ON MICRO-NANOMECHATRONICS AND HUMAN SCIENCE (MHS), 2014, IEEE, English
2014 - 2014, Cells rapidly undergo cell division during the embryogenesis. Such dynamic behaviors of cells during the embryogenesis are considered to be strongly associated with their mechanical properties such as cell-cell mechanical interactions and cell stiffness. However, the interplay between the morphogenesis and the mechanical property of whole cell assembly during the developmental process has not been well understood. To exploring the mechanism of forming the whole cell assembly, we proposed atomic force microscopy (AFM) combined with a microarray technique, which allows us to map mechanical property of the whole cell assembly. In this AFM setup, the cell assembly is randomly directed in the microarray well, and thus the average mechanical property of the whole cell assembly can be reconstructed from mapping images obtained from different cell assemblies.

Temporal Change in Complex Shear Modulus of Cells: An Atomic Force Microscopy Study
PingGen Cai, Ryosuke Takahashi, Kaori Kuribayashi-Shigetomi, Agus Subagyo, Kazuhisa Sueoka, Takaharu Okajima
2014 INTERNATIONAL SYMPOSIUM ON MICRO-NANOMECHATRONICS AND HUMAN SCIENCE (MHS), 2014, IEEE, English
2014 - 2014, To sort living cells according to our needs, it is important to understand how degree cell property measured for cell sorting fluctuates in time. Mechanical property of cells is one of essential indicators for cell sorting. Thus, in this study, we attempted to measure a time evolution of viscoelastic property such as complex shear modulus, G* of single cells adhered on substrates using atomic force microscopy (AFM). We observed that the G* largely fluctuated in time even the cells are placed on substrates in a confined condition. This indicates that in mechanical cell sorting, mechanical fluctuations of cells should be carefully estimated so that cells are precisely separated by taking the measured data involving cell fluctuations into account.

Correlation between antiphase boundary defects and surface inhomogeneous properties in magnetite films
Grants-in-Aid for Scientific Research
01 Apr. 2021 - 31 Mar. 2024
アグス スバギョ
初年度では，炭素吸着したマグネタイト表面のスピン偏極度向上の効果を調べるために，申請の段階で実施し始めた通電加熱法の炭素吸着の条件の最適化を図った．また，通電加熱法の炭素吸着の結果を踏まえ，電子ビーム加熱蒸着装置を用いた炭素吸着を検討して実施した．STMやLEED等による原子構造の評価，XPSを用いたマグネタイト組成や炭素吸着時の不純物の評価もおこなった．
マグネタイト試料は，MgO(001)基板にマグネタイト(001)薄膜をエピタキシャル成長させて作成した．マグネタイト薄膜表面は，清浄表面である再構成構造を示すことと，逆位相境界を有することを原子分解STMで確認した．このようなマグネタイト清浄表面上に，通電加熱したグラッシーカーボンフォイルを用いて炭素吸着をおこなった結果，マグネタイト薄膜表面の鉄原子列上に原子レベルの炭素吸着の他に，クラスター状に吸着した炭素もわずかに観察されていた．炭素吸着のない鉄原子上と原子状炭素吸着の局所電子状態を比較すると，吸着炭素上の局所電子状態では新たな状態がみられ，理論計算によって導かれた電子状態におけるスピン偏極したダウンスピンの電子状態と一致した．
均一な炭素吸着した表面を作製するために，炭素吸着チェンバーに通電加熱法の他に電子ビーム加熱蒸着装置を設置した．さらに，炭素吸着のレートを正確に把握するために膜厚モニターも設置した．電子ビーム加熱蒸着装置を用いることにより，通電加熱法より低いレートでの吸着が可能であり，クラスター状の炭素吸着が少なく，より均一な炭素原子吸着したマグネタイト薄膜表面が作製できた．
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 21K04824

電界効果トランジスタ、その製造方法およびバイオセンサ　　　　　　　　　　　　　　　
Patent right, アグス スバギョ, 中村基訓, 山林智明, 高橋理, 菊地洋明, 近藤勝則
PCT/JP2009/007253, 2009
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電界効果トランジスタおよびその製造方法　　　　　　　　　　　　　　　
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