Researcher basic information

• M. Eng., Hokkaido University
• D. Eng., Hokkaido University

• https://researchmap.jp/shiramine0166634?lang=en

• https://jglobal.jst.go.jp/detail?JGLOBAL_ID=200901058065210939

• 200901058065210939

• 透過型電子顕微鏡
• 分子線エピタキシー
• Transmission Electron Microscopy
• Molecular Beam Epitaxy

• Nanotechnology/Materials, Crystal engineering
• Nanotechnology/Materials, Applied physical properties

• Bachelor's degree program, School of Engineering
• Master's degree program, Graduate School of Engineering
• Doctoral (PhD) degree program, Graduate School of Engineering

Research activity information

• Tip artifact in atomic force microscopy observations of InAs quantum dots grown in Stranski–Krastanow mode
  Ken-ichi Shiramine; Shunichi Muto; Tamaki Shibayama; Norihito Sakaguchi; Hideki Ichinose; Tamotsu Kozaki; Seichi Sato; Yoshiaki Nakata; Naoki Yokoyama; Masafumi Taniwaki
  Journal of Applied Physics, 101, 3, AIP Publishing, 01 Feb. 2007, [Peer-reviewed]
  Scientific journal, The tip artifact in atomic force microscopy (AFM) observations of InAs islands was evaluated quantitatively. The islands were grown in the Stranski–Krastanow mode of molecular beam epitaxy. The width and height of the islands were determined using transmission electron microscopy (TEM) and AFM. The average [1¯10] in-plane width and height determined using TEM excluding native oxide were 22 and 7nm, respectively; those determined using AFM including the oxide were 35 and 8nm, respectively. The difference in width was due to the oxide and the tip artifact. The sizes including the oxide were deduced from TEM observations to be a width of 27nm and a height of 6nm with correction for the thickness of the oxide. The residual difference of 8nm between the width determined using AFM and that determined using TEM including the oxide was ascribed to the tip artifact. The results enable us to determine the actual size of the islands from their AFM images.
• Critical cluster size of InAs quantum dots formed by Stranski-Krastanow mode,
  Shiramine, Ken-ichi; Itoh, Tomohiko; Muto, Shunichi
  J. Vac. Sci. Technol. B, 22, 2, 642, 646, 2004, [Peer-reviewed]
  English, Scientific journal, The number of In atoms in a critical cluster, i*, in Stranski-Krastanow (S-K) mode of InAs islands was determined to be 1-10. The i* was determined using an activation energy EA of 2.0 eV determined from an Arrhenius plot of the saturated density of InAs islands formed on a GaAs (001) surface by S-K mode of molecular beam epitaxy [K. Shiramine et al., J. Cryst. Growth 242, 332 (2002)], and an activation energy of 1.6 eV for migration (surface diffusion) of In adatoms, inferred from other references. The common value ~2.0 eV of EA in S-K mode was ascribed to the small i*.
• Size, density, and shape of InAs quantum dots in closely stacked multilayers grown by the Stranski-Krastanow made,
  Shiramine, Ken-ichi; Muto, Shunichi; Shibayama, Tamaki; Takahashi, Heishichiro; Kozaki, Tamotsu; Sato, Seichi; Nakata, Yoshiaki; Yokoyama, Naoki
  J. Vac. Sci. Technol. B, 21, 5, 2054, 2059, 2003, [Peer-reviewed]
  English, Scientific journal, Closely stacked multilayer structures of InAs islands with intermediate-layer thicknesses d of 3, 6, 10, and 20 nm were grown by the Stranski-Krastanow mode of molecular beam epitaxy and were observed using transmission electron microscopy (TEM) and atomic force microscopy (AFM). The multilayers consisted of five InAs layers each of a thickness of 1.8 monolayers and four GaAs layers each of a thickness d. Columns of coherent islands were observed by cross-sectional TEM. Changes in the size and density of the islands with d, determined by AFM, could be explained in terms of (i) change in the vertical pairing probability of islands, (ii) detachment of In from the top of the island, and (iii) surface segregation of In. The observed AFM images of the islands were elliptical. Their major axis was in the [110] direction, and the length of the minor axis was 80% of that of the major axis.
• Adatom migration in Stranski-Krastanow growth of InAs quantum dots
  K Shiramine; T Itoh; S Muto; T Kozaki; S Sato
  JOURNAL OF CRYSTAL GROWTH, 242, 3-4, 332, 338, Jul. 2002, [Peer-reviewed]
  English, Scientific journal
• Quantum gates using tunneling electron spins of a quantum-dot chain
  S. Muto; H. Sasakura; S. Adachi; Y. Kajiwara; K. Shiramine
  Physica E, 13, 616, 619, 2002, [Peer-reviewed]
  English, Scientific journal
• TEM observation of threading dislocations in InAs self-assembled quantum dot structure
  K Shiramine; Y Horisaki; D Suzuki; S Itoh; Y Ebiko; S Muto; Y Nakata; N Yokoyama
  JOURNAL OF CRYSTAL GROWTH, 205, 4, 461, 466, Sep. 1999, [Peer-reviewed]
  English, Scientific journal
• Scaling properties of InAs/GaAs self-assembled quantum dots
  Y Ebiko; S Muto; D Suzuki; S Itoh; H Yamakoshi; K Shiramine; T Haga; K Unno; M Ikeda
  PHYSICAL REVIEW B, 60, 11, 8234, 8237, Sep. 1999, [Peer-reviewed]
  English, Scientific journal
• Exchange interaction of optically created electrons in coupled quantum dots
  S Itoh; S Muto; Y Ebiko; H Sasakura; K Shiramine
  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS, 38, 8B, L917, L919, Aug. 1999, [Peer-reviewed]
  English, Scientific journal
• Volume distributions of InAs GaAs self-assembled quantum dots by Stranski-Krastanow mode
  Y Ebiko; S Muto; D Suzuki; S Itoh; K Shiramine; T Haga; Y Nakata; Y Sugiyama; N Yokoyama
  JOURNAL OF CRYSTAL GROWTH, 201, 1150, 1153, May 1999, [Peer-reviewed]
  English, Scientific journal
• Volume distribution of InAs/GaAs self-assembled quantum dots
  Y Ebiko; S Muto; S Itoh; D Suzuki; H Yamakosi; K Shiramine; T Haga
  COMPOUND SEMICONDUCTORS 1998, 162, 445, 450, 1999, [Peer-reviewed]
  English, Scientific journal
• Threading dislocations in multilayer structure of InAs self-assembled quantum dots
  K Shiramine; Y Horisaki; D Suzuki; S Itoh; Y Ebiko; S Muto; Y Nakata; N Yokoyama
  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, 37, 10, 5493, 5496, Oct. 1998, [Peer-reviewed]
  English, Scientific journal
• Island size scaling in InAs/GaAs self-assembled quantum dots
  Y Ebiko; S Muto; D Suzuki; S Itoh; K Shiramine; T Haga; Y Nakata; N Yokoyama
  PHYSICAL REVIEW LETTERS, 80, 12, 2650, 2653, Mar. 1998, [Peer-reviewed]
  English, Scientific journal

• Indium Adatom Migration in InAs/GaAs Quantum-Dot Growth
  SHIRAMINE Ken-ichi; ITOH Tomohiko; MUTO Shunichi; KOZAKI Tamotsu; SATO Seichi, Extended abstracts of the ... Conference on Solid State Devices and Materials, 2001, 658, 659, 25 Sep. 2001
  English
• Quantum computing using electron spins in a quantum-dot-chain
  Sasakura H.; Adachi S.; Shiramine K.; Muto S., Meeting abstracts of the Physical Society of Japan, 56, 2, 547, 547, 03 Sep. 2001
  The Physical Society of Japan (JPS), Japanese
• Volume distributions of InAs/GaAs self-assembled quantum dots by Stranski-Krastanow mode of molecular beam epitaxy
  S. Muto; Y. Ebiko; D. Suzuki; S. Itoh; K. Shiramine; T. Haga; Y. Nakata; Y. Sugiyama; N. Yokoyama, Materials Science in Semiconductor Processing, 1, 2, 131, 140, 1998
  Elsevier Ltd, English

• 応用物理学実験Ⅰ, 2024年, 学士課程, 工学部
• 応用物理学実験Ⅱ, 2024年, 学士課程, 工学部

• 日本結晶成長学会
• 応用物理学会
• Japanese Association for Crystal Growth
• Japan Society of Applied Physics

• 量子効果によるスピン保存の研究
  科学研究費助成事業
  2007 - 2007
  武藤 俊一; 白峰 賢一
  量子効果は通常デジタル情報処理においては不確定性原理のためにマイナスであるとされている。例えば、1つの電子スピンのメモリを想定すると、その緩和がexp(-γt)の形をとる限り、測定してリフレッシュしてもメモリ持続時間が長くなることはない。しかしながら、短い時間では指数関数型の緩和からのズレがありexp(-αt^2)となることが知られている。このことを用いて短い時間で測定(観測)を繰り返せば、いわゆる「量子ゼノン効果」によりズレが持続し、メモリを飛躍的に永くすることができる(例えばM. C. Fischer et. al. Phys. Rev. Lett. 87(2001)040402)。更に、量子情報処理で確立している量子誤り補正を応用することもできる。また量子情報処理と異なり、多数決処理のような手法と量子誤り補正との組み合わせにより全く新しいメモリ保持の可能性も開ける可能性がある。
  本研究では特に量子Zeno効果による電子スピンのデジタルなメモリ延伸の可能性を調べるために1スピンの非指数関数的減衰を観測することを目的とし実験的検討を行った。
  スピンの安定に存在する量子構造の形成を検討した。具体的にはSi不純物を添加した量子井戸構造の作製を行った。また、電極により量子ドット中の電荷状態を制御するために、量子ドットを含むダイオード構造を試作した。更に、bright excitonとdark excitonにより逆ラムダ遷移を実現するために、フォークト配置での励起子エネルギーの磁場依存性を測定し、2つの遷移間のエネルギー差が400μeV程度と非常に大きな中性励起子を選別することに成功した。
  日本学術振興会, 萌芽研究, 北海道大学, 19656001
• Quantum information processing using nuclear spin orientation in a single quantum dot
  Grants-in-Aid for Scientific Research
  2006 - 2007
  MUTO Shunichi; ADACHI Satoru; TSUCHIYA Takuma; SHIRAMINE Kenichi
  In this project, we did a feasibility study of memory applications of quantum mechanically superposed states of an ensemble of nuclear spins. In other words, we tried to clarify the possibility of quantum information storage using quantum bit (qubit) conversion of a photon to an ensemble of nuclear spins mediated by a single electron spin through hyperfine interaction. For this purpose, we had to realize the situation where energy at the flip-flop of electron and nuclear spins is conserved, that is, the cancellation of external magnetic field and the effective nuclear field.
  In 2006, we studied the formation of nuclear field as functions of intensity and degree of circular polarization of excitation light on a single InAlAs/GaAs quantum dot (QD). As a result, we observed hysteresis in the nuclear magnetic field as a function of intensity of the excitation light which is circularly polarized. We can interpret this phenomenon as a nuclear spin switching and we concluded that the cancellation of external magnetic field and the effective nuclear field was realized. This is a condition necessary for the electron nuclear spin qubit conversion.
  In 2007, we advanced our study to include the magnetic field dependence. Upon increasing field the nuclear field increased to a certain threshold value above which the nuclear field discontinuously decreased. Comparison with theoretical calculations tells us that the nuclear field completely cancelled the external magnetic field. Unfortunately, however, this nuclear field is determined by the balance of the formation and destruction of nuclear spin polarization, and is not indicating the perfect polarization or the nuclear dark state both of which can be used for the electron nuclear spin qubit conversion. This shows that the current status of InAlAs QD is not suitable for the qubit conversion and either enhancement of nuclear spin formation or reduction of spin deformation is needed.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 18360001
• Quantum computation using optical control of electron spins in quantum dots
  Grants-in-Aid for Scientific Research
  2002 - 2005
  MUTO Shunichi; ADACHI Satoru; TODA Yasunori; SHIRAMINE Kenichi; YOH Kanji
  An electron spin in a quantum dot is one of important candidates to be used for future large scale quantum computing. We have already proposed a set of universal quantum gates using photon-assisted tunneling and its coulomb blockade. In this project, we have done various experimental studies on the feasibility of this proposal. Also, the quantum computing is required to be connected to the photonic quantum infromation processing. Therefore we proposed a scheme to cunvert a photon qubit and an electron spin qubit and experimentally evaluated this proposal.
  Before experiments, we did computer simulation of our universal gates and found that the experimental demonstration of the CNOT gateis possible ifthe coheraice of an electron spin is largo-than 100 ps.
  Then, we developed a measurem ent technology based on the four-wave-mixing FWM to detarmine the electron spin coherence. We applied this to the spin relaxation measurements of electrons in a quantum well for which the pump -probe technique is established. The result of the new method, i.e. spin-diffracted FWM gave the same result as the pump -probe, indicating the validity of the method. We then, applied this to the ensemble of InAlAs/AlGaAs quantum dots and found that the longest coherence of these dots is as long as 7 ns. This value is much longer than those in the conventional method using streak-camera and indicates that the measurements of resonant excitation and dedection such as ours are necessary for precise determination of spin coherence instead of the non-resonant measurements such as those using streak-camers.
  We also proposed a new qubit conversion scheme using the nuclear field to realize the degenerate electron levels and energy-split hole levels in a quantum dot. By exerimentally realizing the nuclear field by optically orienting the electron spins in an InAlAs/AlGaAs quantum dot, we found that we can realize the band structure for a qubit conversion between a photon and an dectron spin.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research on Priority Areas, Hokkaido Universigy, 14076201
• Research on the coherent control of electron spins in quantum dots
  Grants-in-Aid for Scientific Research
  2002 - 2003
  MUTO Shunichi; SHIRAMINE Kenichi; TODA Yasunori; ADACHI Satoru; TAKEUCHI Atsushi
  Self-assembled InAlAs/AlGaAs quantum dots are grown by the Stranski-Krastanow mode of Molecular Beam Epitaxy (MBE). We measured the spin relaxation time of the structure under the non-resonant optical excitation by using 80 fs pulses by the titanium sapphire laser at wavelength of 780 nm. We used the right circular polarized light for the excitation of carrires to obtain fixed electron spins. The luminescence from the quantum dots at 10 K was divided into the right circular and the left circular components and was temporary resolved by the streak-scope. While the lifetime of the exciton was about 1 18 ns, the spin relaxation time determined by the decay of the polarization of luminescence was 1.31 us, which is comparable to the lifetime. The result indicates that the major relaxation mechanisms in the quantum well are not effective in the quantum dots and that the quantum dot is a good material for the coherent control of electron spins.
  As the spin-electronisc material for the future generations, wide-gap semiconductors and a polymer was studied with emphasis on the magnetic or spintronic properties.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), HOKKAIDO UNIVERSITY, 14350001
• A RESEARCH ON QUANTUM DOT BASED MATERIAL FOR WAVELENGTH-DIVISION-MULTIPLICATION MEMORY APPLICATIONS
  Grants-in-Aid for Scientific Research
  1997 - 2000
  MUTO Shunichi; YOKOYAMA Naoki; SHIRAMINE Ken-ichi; HAGA Tetsuya; SUGIYAMA Yoshihiro
  Now it is possible to form quantum dots in which electrons show its wavenature as their discrete energy levels. So far, however, the size of the dots is not uniform. This study aim at using those inhomogeneous quantum dots for wave-division-multiplication optical memory based on the fact that quantum dots respond to light with a specific wavelength corresponding to its size.
  We discovered scaling functions of the size distribution and the position distribution of the InAs/GaAs self-assembled quantum dots(SAQDs)grown by molecular beam epitaxy(MBE). This indicates that the mechanism governing the formation of the dots is described by a rather simple picture.
  We studied a possibility to enhance the memory duration using tunneling effect, and confirmed the tunneling of the electrons from InAlAs SAQDs through an AlGaAs tunneling barrier to the AlAs layer. Also, we showed possibilities to increase the effective density of dots using a stacking technique.
  The lattice deformation and atomic diffusion of the InAs/GaAs SAQD were studied by ion channeling method. It was shown that the Ga diffusion depended strongly on the InAs coverage and that there were two regions of growth modes identified : one with larger dots with little Ga diffusion and the other with smaller dots with evident Ga diffusion.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B)., HOKKAIDO UNIVERSITY, 09450001
• 異方性アモルファス半導体の研究
  科学研究費助成事業
  1994 - 1994
  白峰 賢一
  カルコゲン系アモルファス半導体に直線偏光させたバンドギャップ光を照射すると,光学的異方性が生じることが知られている。この現象は、バンドギャップ光が吸収されてアモルファス半導体の構造が変化し、構造が異方的になるためにおこると考えられているが、くわしい機構はわかっていない。この研究では、Ag-As-S系アモルファス半導体に偏光させた光を照射したときにおこる光学的異方性について,定量的に調べた。この系では,Agがイオン化してAg^+になっていることがわかっているので,これまでに研究の対象となっていたAs-S系などとは異なるふるまいをすることが予想された。
  AgAsS_2光ドープ膜とAs_2S_3蒸着膜について実験をおこなった。直線偏光させたHe-Neレーザ光を試料に照射し,He-Neレーザを光源とする偏光解析装置で複屈折を測定した。
  AgAsS_2光ドープ膜の複屈折は,10^5(J/cm^2)の光照射で飽和に達し,そのときの値はΔn=n||-n⊥〜+10^<-2>だった。ここに,n||とn⊥は,それぞれ照射した直線偏光と平行および垂直な電場振動面をもつ直線偏光に対する屈折率をあらわす。As_2S_3蒸着膜の複屈折Δn=-1×10^<-3>だった。この値は,光ドープ膜とくらべると,符号が反対で絶対値は1桁ちがう。偏光照射によって異方的になったAs_2S_3では,吸収端にも異方性があることがすでにわかっている。この研究では,光ドープ膜の吸収端には異方性はみられなかった。光ドープ膜における光誘起異方性は,これまでに知られているAs_2S_3などの光誘起異方性とは別の現象だと考えられる。
  日本学術振興会, 奨励研究(A), 北海道大学, 06750001
• 量子ドットの結晶成長と構造解析
  その他の研究制度
  Competitive research funding
• Crystal growth and structure analysis of quantum dots
  The Other Research Programs
  Competitive research funding