Research activity information

• Oct. 2019 公益社団法人日本表面真空学会, 技術賞, 超ミクロンスケール系に適用可能な 新しい量子輸送シミュレーション手法の開発

  石関圭輔, 笹岡健二, 小鍋 哲, 相馬聡文, 山本貴博


• May 2009 IEEE International Meeting for Future of Electron Devices, Kansai (IMFEDK), Best Paper Award, Influence of Edge Roughness on the Performance of Graphene Nano-Ribbon Devices

  SOUMA Satofumi, OGAWA Matsuto, YAMAMOTO Takahiro, WATANABE Kazuyuki

• (GaAs/InAs)–GaAsSb digital alloy type-II superlattice for extended short-wavelength infrared detection

  Takashi Kato, Makoto Murata, Sundararajan Balasekaran, Yasuhiro Iguchi, Yojiro Nakayama, Satofumi Souma

  GaInAs–GaAsSb type-II superlattices (T2SLs) on an InP substrate are promising candidates for an optical absorption layer in the extended short-wavelength region (2–3 μm), offering more flexibility in designing a cutoff wavelength compared to strained GaInAs bulk material. However, T2SL-based photodetectors inherently suffer from lower quantum efficiency (QE) due to the reduced overlap of the wavefunctions of the conduction and valence bands in the optical matrix element of the T2SL. To improve QE, a (GaAs/InAs)–GaAsSb digital alloy T2SL, which replaces the GaInAs random alloy layer in the GaInAs–GaAsSb T2SL with a GaAs/InAs digital alloy, has been proposed recently by an empirical tight-binding calculation. This paper presents a demonstration of a fabricated photodetector using the (GaAs/InAs)–GaAsSb digital alloy grown on an InP substrate by molecular beam epitaxy and shows that the average QE in the wavelength region of 2.3–2.6 μm is approximately 1.6 times higher than that of a conventional GaInAs–GaAsSb T2SL photodetector. Furthermore, the dark-current density of the digital alloy photodetector is lower than that of the GaInAs–GaAsSb T2SL photodetector despite having a longer cutoff wavelength.

  Last, AIP Publishing, Oct. 2024, Applied Physics Letters, 125(16) (16)

  [Refereed]

  Scientific journal


• Simulation of Qubits Confined in Pseudo Magnetic Field Generated by Strained Graphene Nanoribbon

  Yusuke Hayashi, Satofumi Souma

  IEEE, Sep. 2024, 2024 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), 1 - 4

  [Refereed]

  International conference proceedings


• Simulation of graphene surface plasmon propagation based on tight-binding method and finite-difference time-domain method

  Satofumi Souma, Shota Ogisawa

  Nov. 2023, IEICE Tech. Rep., vol. 123, no. 250, SDM2023-68, pp. 26-30, Nov. 2023., Japanese

  [Invited]


• Quantum transport simulation of synaptic FETs based on two-dimensional semiconductors

  Takuya Ishibashi, Satofumi Souma

  IEEE, Sep. 2023, 2023 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD)

  [Refereed]

  International conference proceedings


• Tight-binding simulation of graphene nanoantenna based on Boltzmann equation and finite difference time-domain method

  Shota Ogisawa, Satofumi Souma

  IEEE, Sep. 2023, 2023 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD)

  [Refereed]

  International conference proceedings


• Optical properties of (GaAs/InAs)–GaAsySb1−y digital alloy superlattices in the short-wavelength infrared region calculated by an sp3d5s* tight-binding method

  Takashi Kato, Satofumi Souma

  Last, Springer Science and Business Media LLC, May 2023, Applied Physics A, 129(6) (6), English

  [Refereed]

  Scientific journal


• A proposal of quantum computing algorithm to solve Poisson equation for nanoscale devices under Neumann boundary condition

  Shingo Matsuo, Satofumi Souma

  Elsevier BV, Feb. 2023, Solid-State Electronics, 200, 108547 - 108547, English

  [Refereed]

  Scientific journal


• Exploring the Application of Gate-Type Quantum Computational Algorithm for Music Creation and Performance

  Satofumi Souma

  Springer International Publishing, Dec. 2022, Quantum Computer Music, 83 - 103

  [Refereed][Invited]

  In book


• SISPAD2022 Review

  相馬聡文

  Nov. 2022, 信学技報, vol. 122, no. 247, SDM2022-77, pp. 61-67, 2022年11月.

  [Invited]


• A study on the development of nanoscale device simulation method based on the use of gate-type quantum computing algorithm

  Satofumi Souma, Shingo Matsuo, Takuya Ishibashi

  Nov. 2022, IEICE Tech. Rep., vol. 122, no. 247, SDM2022-69, pp. 23-27, Nov. 2022.

  [Invited]

  Symposium


• An interface trap charge model for simulation of graphene-based synaptic field effect transistors

  Reon Oshio, Satofumi Souma

  AIP Publishing, Jan. 2022, Journal of Applied Physics, 131(2) (2), 024301 - 024301, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Improved tight-binding parameters of III-V semiconductor alloys and their application to type-II superlattices

  Akitaka Sawamura, Takashi Kato, Satofumi Souma

  A simple tight-binding method for ternary semiconductor alloys is generalized to calculate the properties of the semiconductor alloys accurately. Specifically independently adjustable parameters, which represent compositional disorder, are incorporated in all the ternary tight-binding parameters. Energy levels and effective masses agree well with the reference values only by the proposed method. We have applied the method to calculate the band gaps and a spectrum of the absorption coefficient of (InAs)/(GaInSb) type-II superlattices. The calculated band-gaps agree well with the experimental ones and we could well reproduce the shape of the absorption coefficient spectrum calculated by an empirical pseudopotential scheme.

  Last, IOP Publishing, Dec. 2021, Japanese Journal of Applied Physics, English

  [Refereed]

  Scientific journal


• Acceleration of nonequilibrium Green's function simulation for nanoscale devices by applying machine-learning model

  相馬聡文

  Nov. 2021, 信学技報, vol. 121, no. 235, SDM2021-65, IEICE-121, 66 - 71, Japanese

  [Invited]

  Symposium


• Neural network model for implementation of electron–phonon scattering in nanoscale device simulations based on NEGF method

  Satofumi Souma, Matsuto Ogawa

  IEEE, Sep. 2021, 2021 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), English

  [Refereed]

  International conference proceedings


• Transient performance analysis of graphene FET gated via ionic solid by numerical simulations based on tight-binding method and Nernst–Planck–Poisson equations

  Koki Arihori, Matsuto Ogawa, Satofumi Souma (Kobe Univ ), Junko Sato-Iwanaga, Masa-aki Suzuki (Panasonic Corporation)

  Corresponding, AIP Publishing, Aug. 2021, Journal of Applied Physics, 130(8) (8), 084302 - 084302, English

  [Refereed]

  Scientific journal


• High-Temperature Operation of a Quantum Cascade Laser With Definite Parity of the Wave Functions

  Takashi Kato, Hiroki Mori, Hiroyuki Yoshinaga, Satofumi Souma

  Last, Institute of Electrical and Electronics Engineers (IEEE), May 2021, IEEE Photonics Technology Letters, 33(10) (10), 507 - 510, English

  [Refereed]

  Scientific journal


• SISPAD2022 Review

  相馬聡文

  Nov. 2020, 信学技報, vol. 120, no. 239, SDM2020-22, pp. 1-4, 2020年11月.

  [Invited]


• Transient simulation of graphene FET gated by electrolyte medium

  Koki Arihori, Matsuto Ogawa, Satofumi Souma (Kobe Univ.), Junko Sato-Iwanaga, Masa-aki Suzuki (Panasonic Corporation)

  Corresponding, IEEE, Sep. 2020, 2020 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), English

  [Refereed]

  International conference proceedings


• Tight-binding simulation of optical gain in h-BCN for laser application

  Daisuke Maki, Matsuto Ogawa, Satofumi Souma

  IEEE, Sep. 2020, 2020 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), English

  [Refereed]

  International conference proceedings


• Impact of electron–phonon scattering on the strain-induced current-blocking effect in graphene field-effect transistors

  Satofumi Souma and Matsuto Ogawa

  2020, Journal of Applied Physics 127, 094304 (2020)

  [Refereed]

  Link to Kobe Univ. Repository (Kernel)


• Acceleration of nonequilibrium Green's function simulation for nanoscale FETs by applying convolutional neural network model

  Satofumi Souma, Matsuto Ogawa

  2020, IEICE Electronics Express, Vol.17, No.4, 1–6, 2020

  [Refereed]

  Link to Kobe Univ. Repository (Kernel)


• Study of an application of non-parabolic complex band structures to the design for mid-infrared quantum cascade lasers

  Takashi Kato, Satofumi Souma

  Last, 2019, J. Appl. Phys. 125, 073101 (2019)

  [Refereed]


• Nearest-neighbor sp(3)d(5)s* tight-binding parameters based on the hybrid quasi-particle self-consistent GW method verified by modeling of type-II superlattices

  Akitaka Sawamura, Jun Otsuka, Takashi Kato, Takao Kotani, Satofumi Souma

  We report the determination of parameters in the nearest-neighbor sp(3)d(5)s* tight-binding (TB) model for nine binary compound semiconductors which consist of Al, Ga, or In and of P, As, or Sb based on the hybrid quasi-particle self-consistent GW (QSGW) calculations. We have used the determination parameters to calculate band structures and related properties of the compounds in the bulk phase relevant to mid-infrared applications and of the type-II (InAs)/(GaSb) superlattices. For the type-II (InAs)/(GaSb) superlattices with various superlattice periods, good agreement with photoluminescence measurements on the band gaps has been confirmed. Furthermore, two aspects of the band gap properties from other calculations have been reproduced: the band gap energies rising up to some superlattice periods and shrinking beyond them asymptotically. In both the bulk phase and the superlattices, erroneous flat valence bands have appeared within the nearest-neighbor sp(3)s* TB model. The present TB model has eliminated these artifacts, which are potential obstacles to design advanced superlattices. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

  Last, OPTICAL SOC AMER, Jun. 2018, OPTICAL MATERIALS EXPRESS, 8(6) (6), 1569 - 1584, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• 超ミクロンスケール系に適用可能な新しい量子輸送シミュレーション手法の開発

  石関 圭輔, 笹岡 健二, 小鍋 哲, 相馬 聡文, 山本 貴博

  2018, 表面と真空 61 pp. 360-365 (2018)

  [Refereed]


• Quantum decoherence in electronic current flowing through carbon nanotubes induced by thermal atomic vibrations

  Keisuke Ishizeki, Kenji Sasaoka, Satoru Konabe, Satofumi Souma, Takahiro Yamamoto

  2018, Jpn. J. Appl. Phys. 57, pp. 065102 1-4 (2018)

  [Refereed]


• sp3s* tight-binding calculation of band edges and effective masses of InAs/GaSb superlattices with different interface structures

  Takashi Kato, Satofumi Souma

  Last, 2018, Superlattices and Microstructures, 122, 492 (2018)

  [Refereed]


• Super-micron-scale atomistic simulation for electronic transport with atomic vibration: Unified approach from quantum to classical transport (vol 96, 035428, 2017)

  Keisuke Ishizeki, Kenji Sasaoka, Satoru Konabe, Satofumi Souma, Takahiro Yamamoto

  AMER PHYSICAL SOC, Dec. 2017, PHYSICAL REVIEW B, 96(23) (23), English

  [Refereed]


• Time dependent quantum dynamical study of laser induced current switching in graphene

  Satofumi Souma, Takashi Akiyama, Kenji Sasaoka, Matsuto Ogawa

  We present a numerical study on the effect of laser light irradiation on the electronic transport through single layer graphene. We employed the wave packet quantum dynamics method to take into account the effect of laser light with circular polarization irradiated only through the finite channel region of graphene device. Our simulations have shown that the transmission through graphene can be switched off by irradiating the circularly polarized laser light, in a way consistent with the generation of dynamical band gap by the circularly polarized light predicted previously. It has also been suggested that the presence of irradiation induced remote valley away from the Dirac point importantly influences the current switching.

  Institute of Electrical and Electronics Engineers Inc., Oct. 2017, International Conference on Simulation of Semiconductor Processes and Devices, SISPAD, 2017-, 213 - 216, English

  [Refereed]

  International conference proceedings


• Effect of strain on electron mobility in graphene

  Hideki Hirai, Matsuto Ogawa, Satofumi Souma

  We present a numerical study on the effect of mechanical strain on the electron mobility and the averaged electron velocity of graphene, where the graphene is assumed to be suspended and the phonon scattering is the dominant scattering mechanism. By employing the tight-binding formalism to describe the electronic band structure in the presence of strain and the Boltzmann transport equation to describe the non-equilibrium carrier transport in the presence of phonon scattering, the electron mobility was found to decrease nonlinearly with increasing the strain.

  Institute of Electrical and Electronics Engineers Inc., Oct. 2017, International Conference on Simulation of Semiconductor Processes and Devices, SISPAD, 2017-, 209 - 212, English

  [Refereed]

  International conference proceedings


• Effects of effective equations for channel electrons on FET : comparative analysis of the degree of degradation of potential profile and quantum tunneling currentFET

  Hashimoto Yuki, Ogawa Matsuto, Souma Satofumi

  The Japan Society of Applied Physics, Aug. 2017, JSAP Annual Meetings Extended Abstracts, 2017.2, 2786 - 2786, Japanese


• Super-micron-scale atomistic simulation for electronic transport with atomic vibration: Unified approach from quantum to classical transport

  Keisuke Ishizeki, Kenji Sasaoka, Satoru Konabe, Satofumi Souma, Takahiro Yamamoto

  We develop a powerful simulation method that can treat electronic transport in a super-micron-scale open system with atomic vibration at finite temperature. As an application of the developed method to realistic materials, we simulate electronic transport in metallic single-walled carbon nanotubes from nanometer scale to micrometer scale at room temperature. Based on the simulation results, we successfully identify two different crossovers, namely, ballistic to diffusive crossover and coherent to incoherent crossover, simultaneously and with equal footing, from which the mean free path and the phase coherence length can be extracted clearly. Moreover, we clarify the scaling behavior of the electrical resistance and the electronic current in the crossover regime.

  AMER PHYSICAL SOC, Jul. 2017, PHYSICAL REVIEW B, 96(3) (3), 035428, English

  [Refereed]

  Scientific journal


• Nearest-neighbor sp(3)s* tight-binding parameters based on the hybrid quasi-particle self-consistent GW method verified by modeling of type-II superlattices

  Akitaka Sawamura, Jun Otsuka, Takashi Kato, Takao Kotani, Satofumi Souma

  We report the determination of parameters for the nearest-neighbor sp(3)s* tight-binding (TB) model for GaP, GaAs, GaSb, InP, InAs, and InSb at 0, 77, and 300K based on the hybrid quasi-particle self-consistent GW (QSGW) calculation and their application to a type II (InAs)/(GaSb) superlattice. The effects of finite temperature have been incorporated empirically by adjusting the parameter for blending the exchange-correlation terms of the pure QSGW method and local density approximation, in addition to the usage of experimental lattice parameters. As expected, the TB band gap shrinks with temperature and asymptotically with superlattice period when it is large. In addition, a bell curve in the band gap in the case of small superlattice period and slight and remarkable anisotropy in effective masses of electron and hole, both predicted by the hybrid QSGW method, respectively, are reproduced. Published by AIP Publishing.

  Last, AMER INST PHYSICS, Jun. 2017, JOURNAL OF APPLIED PHYSICS, 121(23) (23), English

  [Refereed]

  Scientific journal


• Modulations of thermal properties of graphene by strain-induced phonon engineering

  TADA Kento, FUNATANI Takashi, KONABE Satoru, SASAOKA Kenji, OGAWA Matsuto, SOUMA Satofumi, YAMAMOTO Takahiro

  Modulation of the thermal properties of graphene due to strain-induced phononic band engineering was theoretically investigated by first-principles calculations based on the density functional theory. The high-energy phonon modes are found to exhibit softening owing to the strain, whereas a low-energy acoustic mode (out-of-plane mode) exhibits hardening. Moreover, the dispersion relation of the out-of-plane mode associated with the strain essentially changes from quadratic (∝ k²) to linear (∝ k). Accordingly, the temperature dependence of the low-temperature specific heat also changes from linear (∝ T) to quadratic (∝ T²).

  Institute of Physics, 2017, Jpn. J. Appl. Phys, 56(2) (2), 025102 - 25102, English

  [Refereed]

  Scientific journal


• Performance simulation of FET made of graphene-based lateral heterostructures

  HASHIMOTO YUKI, ICHIHARA KEISUKE, TANAKA MIKU, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  The Japan Society of Applied Physics, Sep. 2016, JSAP Annual Meetings Extended Abstracts, 2016.2, 3518 - 3518, Japanese


• Quantitative estimation of the momentum-relaxation length and the phase-relaxation length for metallic carbon nanotubes by electric transport simulation over one million atoms

  Ishizeki Keisuke, Sasaoka Kenji, konabe satoru, souma satofumi, Yamamoto Takahiro

  金属CNTはLSIの銅配線の代替材料として注目を集めている。CNT配線の長さは、ナノ～マイクロメートル程度であるが、これらを包括的に扱える計算手法は存在せず、CNT配線の精密設計が困難な状況である。本研究では、100万原子を超える系にも適応可能な電子輸送シミュレータを開発し、ナノ～マイクロメートルの長さのCNTの電子輸送をシームレスに取り扱い、CNTの運動量緩和長と位相緩和長の精密評価に成功した。

  The Surface Science Society of Japan, 2016, Abstract of annual meeting of the Surface Science of Japan, 36, 353 - 353, Japanese


• 歪みグラフェンを用いたディラック電子エンジニアリング素子のシミュレーション

  相馬 聡文, 田中 未来, 市原圭祐, 迫田 翔太郎, 笹岡 健二, 小川 真人

  Nov. 2015, SMD2015-89, 29, Japanese

  [Invited]


• Spin Blocker Using the Interband Rashba Effect in Symmetric Double Quantum Wells

  S. Souma, A. Sawada, H. Chen, Y. Sekine, M. Eto, T. Koga

  We propose a lateral spin-blockade device that uses the interband Rashba effect in a symmetric double quantum well (QW), where the Rashba effect in the conventional sense vanishes because of its inversion symmetry. The interband Rashba effect manifests itself in the off-diagonal term (represented by the parameter eta) in the QW space using the bonding and antibonding basis [Esmerindo Bernardes, John Schliemann, Minchul Lee, J. Carlos Egues, and Daniel Loss, Phys. Rev. Lett. 99, 076603 (2007)]. In such a system, spin selection is possible by tuning the device length, gate electric field and in-plane magnetic field. We particularly show illustrative mechanisms using a one-dimensional model with k = (k(F), 0), where the selected spin can be blocked completely in the presence of the in-plane magnetic field. While the inclusion of the finite k(y) and/or the gate electric field deteriorates the spin polarization P, finite values remain for P (P>11%). Our proposal can also be regarded as an effective way of enhancing a variation of the Rashba-Edelstein effect, the generation of bulk spin polarization by electric current, based on semiconductor band engineering technology.

  Lead, AMER PHYSICAL SOC, Sep. 2015, PHYSICAL REVIEW APPLIED, 4(3) (3), 034010 1 - 9, English

  [Refereed]

  Scientific journal


• Strain-induced modulation of an isotropic photoconductivity in graphene

  Amir Mehdipour, Kenji Sasaoka, Matsuto Ogawa, Satofumi Souma

  We present a numerical study of the effect of in-plane uniaxial strain on the photoconductivity of graphene, where special attention is paid to the dependences of the photoconductivity on the direction of the strain, the strength of the strain, and the polarization direction in lineally polarized light irradiated perpendicularly to graphene. Our calculations showed that the anisotropic feature of the photoconductivity predicted for unstrained graphene is strongly modulated by applying strain. In particular, it was found that the estimation of anisotropy factors, defined by the ratio between the diagonal conductivities along the strain direction for two different light polarizations theta(p) = 0 and pi/2 relative to the strain axis, enables us to not only determine the strain ratio but also obtain information about the crystal orientation along which the strain is applied. (C) 2014 The Japan Society of Applied Physics

  IOP PUBLISHING LTD, Nov. 2014, JAPANESE JOURNAL OF APPLIED PHYSICS, 53(11) (11), 115103 1 - 7, English

  [Refereed]

  Scientific journal


• Simulation-based design of a strained graphene field effect transistor incorporating the pseudo magnetic field effect

  Satofumi Souma, Masayuki Ueyama, Matsuto Ogawa

  We present a numerical study on the performance of strained graphene-based field-effect transistors. A local strain less than 10% is applied over a central channel region of the graphene to induce the shift of the Dirac point in the channel region along the transverse momentum direction. The left and the right unstrained graphene regions are doped to be either n-type or p-type. By using the atomistic tight-binding model and a Green's function method, we predict that the gate voltage applied to the central strained graphene region can switch the drain current on and off with an on/off ratio of more than six orders of magnitude at room temperature. This is in spite of the absence of a bandgap in the strained channel region. Steeper subthreshold slopes below 60mV/decade are also predicted at room temperature because of a mechanism similar to the band-to-band tunneling field-effect transistors. (C) 2014 AIP Publishing LLC.

  AMER INST PHYSICS, May 2014, APPLIED PHYSICS LETTERS, 104(21) (21), 213505 1 - 4, English

  [Refereed]

  Scientific journal


• Pure spin current induced by adiabatic quantum pumping in zigzag-edged graphene nanoribbons

  Satofumi Souma, Matsuto Ogawa

  We show theoretically that pure spin current can be generated in zigzag edged graphene nanoribbons through the adiabatic pumping by edge selective pumping potentials. The origin of such pure spin current is the spin splitting of the edge localized states, which are oppositely spin polarized at opposite edges. In the proposed device, each edge of the ribbon is covered by two independent time-periodic local gate potentials with a definite phase difference, inducing the edge spin polarized current. When the pumping phase difference is opposite in sign between two edges, the total charge currents is zero and the pure edge spin current is generated. (C) 2014 AIP Publishing LLC.

  AMER INST PHYSICS, May 2014, APPLIED PHYSICS LETTERS, 104(18) (18), 108103 1 - 4, English

  [Refereed]

  Scientific journal


• Proposal of simplified model for absorption coefficients in quantum dot array based intermediate band solar cell structure

  Amir Mehdipour, Kenji Sasaoka, Matsuto Ogawa, Satofumi Souma

  We propose a simplified theoretical model to analyze the absorption coefficients in quantum dot intermediate band solar cell (QD-IBSC) structure. Our theoretical model, based on the multiband tight-binding Hamiltonian including the conduction, valence, and the intermediate band, can capture some essential features in the actual QD-IBSC such as the absorption path dependence of the absorption strength and the line shape of the absorption spectrum in spite of its simplicity. The main feature of this model is its ability to be applied to any QD-IBSC system regardless of the geometrical parameters (QDs shapes and spacing) or the base materials by changing the relevant coupling parameters. The proposed simplified should be of useful for the semi-quantitative understanding and modeling of QD-IBSC.

  IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG, 2014, IEICE ELECTRONICS EXPRESS, 11(17) (17), 1 - 11, English

  [Refereed]

  Scientific journal


• Numerical simulation of current noise caused by potential fluctuation in nanowire FET with an oxide trap

  Yuki Furubayashi, Matsuto Ogawa, Satofumi Souma

  We present a theoretical study on the temporal current fluctuation in nanowire FET caused by the presence of a single gate oxide trap through the Coulomb interaction. Our calculations based on the scattering theoretical formulation of the current noise showed that the presence of the trap level in the gate insulator gives rise to the enhancement of the noise at a specific gate voltage. The peak position of the noise is related to the capacitive coupling strengths of the trap to the channel and the gate electrode, suggesting that the current noise can be used to measure such physical quantifies.

  IEEE, 2014, 2014 INTERNATIONAL CONFERENCE ON SIMULATION OF SEMICONDUCTOR PROCESSES AND DEVICES (SISPAD), 201 - 204, English

  [Refereed]

  International conference proceedings


• Intermediate band electron wave function localization effect on the efficiency limits of InAs/GaAs quantum dot solar cell

  MEHDIPOUR Amir, SASAOKA Kenji, OGAWA Matsuto, SOUMA Satofumi

  神戸大学大学院工学研究科, 2014, Memoirs of the Graduate Schools of Engineering and System Informatics Kobe University, 6, 18 - 24, English

  [Refereed]

  Research institution

  Link to Kobe Univ. Repository (Kernel)


• Effect of lateral strain on gate induced control of electrical conduction in single layer graphene device

  Satofumi Souma, Yusuke Ohmi, Matsuto Ogawa

  We study numerically the effect of various types of in-plane strain on the electronic transport property in the single layer graphene connected to two metallic electrodes, with the special attention to the dependences on the gate voltage, channel length, the type of strain, and the strength of the strain. Our calculations have shown that the combination of the shear and the armchair-directional strain can be used to obtain a clear threshold behavior in the gate voltage dependence of the current as expected from the previously reported strain induced bandgap opening. Moreover, we predict the strain induced increase of the current density for small strain regime. © 2013 Springer Science+Business Media New York.

  Jun. 2013, Journal of Computational Electronics, 12(2) (2), 170 - 174, English

  [Refereed]

  Scientific journal


• Influence of geometrical deformation and electric field on transport characteristics through carbon nanotubes

  Masaaki Mouri, Matsuto Ogawa, Satofumi Souma

  We study computationally the electronic transport properties through mechanically squashed zigzag carbon nanotubes (CNTs) under the uniform electric field perpendicular to the tube axis, based on the tight-binding molecular dynamics method for the structural analysis and the Landauer-Buttiker's formalism for the transport analysis. Our simulations show that the band gaps of the zigzag carbon nanotubes exhibit nonlinear decrease as increasing the deformation ratio in the presence of the external perpendicular electric field, in contrast to the case of zero electric field, where the band gap decreases linearly as increasing the deformation ratio. Such properties allow us to tune the sensitivity of the electromechanical response in CNT devices by applying the external electric field. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4768449]

  AMER INST PHYSICS, Dec. 2012, JOURNAL OF APPLIED PHYSICS, 112(11) (11), 114328 - 1-114328-5, English

  [Refereed]

  Scientific journal


• Tight-binding molecular dynamics study of mechanical and electronic properties in twisted graphene nanoribbons

  SOUMA Satofumi, KAINO Shozo, OGAWA Matsuto

  Sep. 2012, Proc. of Int. Conf. on Simulation of Semiconductor Processes and Devices 2012, 133 - 136, English

  [Refereed]

  International conference proceedings


• Fast Perturbative Treatment for Efficient Nano-Scale Device Simulation Based on Bridge-Function Pseudo-Spectral Method

  SAITO Yuta, FUJIKAWA Hiroki, SOUMA Satofumi, OGAWA Matsuto

  Sep. 2012, Proc. of Int. Conf. on Simulation of Semiconductor Processes and Devices 2012, 384 - 387, English

  [Refereed]

  International conference proceedings


• Analysis of tunneling characteristics through hetero interface of InAs/Si nanowire tunneling field effect transistors

  MIYOSHI Yasuaki, OGAWA Matsuto, SOUMA Satofumi, NAKAMURA Hajime

  Sep. 2012, Proc. of Int. Conf. on Simulation of Semiconductor Processes and Devices 2012, 368 - 371, English

  [Refereed]

  International conference proceedings


• Beating Analysis of Shubnikov de Haas Oscillation in In0.53Ga0.47As Double Quantum Well toward Spin Filter Applications

  Takaaki Koga, Toru Matsuura, Sebastien Faniel, Satofumi Souma, Shunsuke Mineshige, Yoshiaki Sekine, Hiroki Sugiyama

  We recently determined the values of intrinsic spin-orbit (SO) parameters for In(0.52)Al(0.48)AS/In0.53Ga0.47As(10 nm)/In0.52Al0.48As (InGaAs/InAlAs) quantum wells (QW), lattice-matched to (001) InP, from the weak localization/antilocalization analysis of the low-temperature magneto-conductivity measurements [I]. We have then studied the sub-band energy spectra for the InGaAs/InAlAs double QW system from beatings in the Shubnikov de Haas (SdH) oscillations. The basic properties obtained here for the double QW system provides useful information for realizing nonmagnetic spin-filter devices based on the spin-orbit interaction [2].

  IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG, May 2012, IEICE TRANSACTIONS ON ELECTRONICS, E95C(5) (5), 770 - 776, English

  [Refereed]

  Scientific journal


• Strain induced modulation of switching behavior in carbon nanotube tunneling field effect transistors

  Takashi Nakano, Matsuto Ogawa, Satofumi Souma

  We study numerically the effect of axial strain on the band structure of semiconducting carbon nanotubes (CNTs) and the transport characteristics of CNT based band-to-band tunneling field effect transistors (CNT-TFETs). By making use of empirical tight-binding method and the non-equilibrium Green's function formalism, we found that applying the axial tensile strain can dramatically suppresses the off-leakage current in CNT-TFETs, and makes the subthreshold swing steeper. Such improvement of the device performance can be understood qualitatively to be caused by the band gap modulation in the CNT channel region. © 2012 IEEE.

  2012, IMFEDK 2012 - 2012 International Meeting for Future of Electron Devices, Kansai, 138 - 139, English

  [Refereed]

  International conference proceedings


• Numerical simulation of transport properties in InAs/Si heterojunction nanowire tunneling field effect transistors

  Y. Miyoshi, M. Ogawa, S. Souma, H. Nakamura

  Electronic transport in InAs/Si heterojunction nanowire (NW) band-to-band tunneling field-effect transistors (TFETs) is studied numerically using the non-equilibrium Green's function formalism based on the sp 3 s* d 5 tight-binding Hamiltonian. Our analyses have shown that TFETs based on the InAs/Si heterojunction NW have superior properties compared with those based on the Si and InAs homojunction NWs in obtaining the higher on-current, lower leakage current as well as the steeper subthreshold swing. The physical origin behind such superiority can be successfully understood by analyzing the complex band structures and the local densities of states. © 2012 IEEE.

  2012, IMFEDK 2012 - 2012 International Meeting for Future of Electron Devices, Kansai, 108 - 109, English

  [Refereed]

  International conference proceedings


• Theory of finite temperature Josephson transport through a ferromagnetic insulator

  Shuhei Nakamura, Satofumi Souma, Matsuto Ogawa, Shiro Kawabata

  We predict an anomalous 0-pi transition in Josephson junctions with a ferromagnetic-insulator (FI) barrier. Previously it was found that the ground state of such junctions alternates between 0 and pi states when the thickness of FI is increasing by a single atomic layer. By solving the Bogoliubov de-Gennes equation and using the Furusaki-Tsukada formula, we show that similar 0-pi transition can be also induced by increasing temperature T. Therefore the existence of p state can be experimentally confirmed by simply observing the nonmonotonic T dependence of the Josephson critical current. (C) 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of ISS Program Committee

  ELSEVIER SCIENCE BV, 2012, ADVANCES IN SUPERCONDUCTIVITY XXIV, 27, 308 - 311, English

  [Refereed]

  International conference proceedings


• Parity induced edge-current saturation and current distribution in zigzag-edged graphene nano-ribbon devices

  Satofumi Souma, Matsuto Ogawa, Takahiro Yamamoto, Kazuyuki Watanabe

  We show computationally that the current-voltage characteristics of the zigzag-edged graphene nanoribbon (ZGNR) with the even width exhibit remarkable current saturation behavior in spite of the absence of the bandgap. Mechanism of such current-saturation behavior can be understood to be originated from the symmetries of the wavefunctions corresponding to the edge states in ZGNR. We further demonstrate that the current-voltage characteristics of ZGNR can be drastically changed even by the presence of a single lattice vacancy, with the strong dependence on the position of the vacancy. The origin of such properties is intuitively understood by analyzing the transmission probabilities through such systems.

  SPRINGER, Jun. 2011, JOURNAL OF COMPUTATIONAL ELECTRONICS, 10(1-2) (1-2), 35 - 43, English

  [Refereed]

  Scientific journal


• Erratum: Parity induced edge-current saturation and current distribution in zigzag-edged graphene nano-ribbon devices (Journal of Computational Electronics DOI:10.1007/s10825-011-0352-0)

  Satofumi Souma, Matsuto Ogawa, Takahiro Yamamoto, Kazuyuki Watanabe

  Jun. 2011, Journal of Computational Electronics, 10(1-2) (1-2), 269, English

  [Refereed]

  Scientific journal


• Impact of Native Interface Asymmetry and Electric Field on Spin-splitting in Narrow Gap Semiconductor Hetrostructures

  Satofumi Souma, Matsuto Ogawa

  Based on the atomistic tight-binding method with intra-atomic spin-orbit coupling, we study computationally the effect of atomic scale interface asymmetry on the spin-polarization of transmission peaks through InAs/AlSb double barrier resonant tunneling heterostructures. Our calculations show the significant anisotropic zero-magnetic-field spin-splitting of the resonant transmission peak even in the absence of the external electric field, demonstrating the importance of the barrier material and the atomic scale detail of the hetero interfaces on the spin-splitting. Moreover, our calculations have predicted that such interface induced anisotropy of the spin-splitting can be cancelled out by applying the external electric field, leading to the Dresselhaus-type isotropic spin-splitting behavior.

  KOREAN PHYSICAL SOC, May 2011, JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 58(5) (5), 1251 - 1255, English

  [Refereed]

  Scientific journal


• Bridge-function pseudospectral method for quantum mechanical simulation of nano-scaled devices

  Yuta Saitou, Takeshi Nakamori, Satofumi Souma, Matsuto Ogawa

  In this paper we show the effectiveness and powerfulness of a pseudospectral method (PSM) with newly developed bridge-functions, which ensure the continuity of physical quantities, for the solution of the 3D Schrödinger equation, Poisson's equation, in addition, non-equilibrium Green's function (NEGF) on equal footing with high accuracy and negligible computational overheads. By comparing with the results of the conventional finite difference method (FDM) with same numbers of mesh, the present method is found to be 60 times faster with higher accuracy. © 2011 IEEE.

  2011, International Conference on Simulation of Semiconductor Processes and Devices, SISPAD, 311 - 314, English

  [Refereed]

  International conference proceedings


• Analysis of geometrical structure and transport property in InAs/Si heterojunction nanowire tunneling field effect transistors

  Yasuaki Miyoshi, Matsuto Ogawa, Satofumi Souma, Hajime Nakamura

  Band-to-band tunneling (BTBT) field-effect transistors (FETs) is one of the promisng strategies in reducing the leakage current and improving the subthreshold characteristics compared with the conventional metal-oxide- semiconductor field-effect transistors (MOSFETs). However, BTBT-FETs have an intrinsic drawback of small on-current. We explore numerically the possibility of using the InAs/Si heterojunction nanowire (NW) to resolve such intrinsic difficulty in BTBT-FETs, and found that the use of the InAs/Si heterojunction nanowire is advantageous in increasing the on-current compared with the Si homojunction nanowires. © 2011 IEEE.

  2011, International Conference on Simulation of Semiconductor Processes and Devices, SISPAD, 227 - 230, English

  [Refereed]

  International conference proceedings


• Tight binding modeling of intermediate band solar cells based on InAs/GaAs quantum dot arrays

  Amir Mehdipour, Matsuto Ogawa, Satofumi Souma

  We study the electronic structure of vertically stacked cubic quantum dots for the purpose of exploring the efficient design of quantum dot intermediate solar cells. We analyzed the dependence of the miniband levels and widths on the number of quantum dots as well as the inter-dot spacing by combining the finite element method and tight-binding method. Regarding the calculated energy band structure, the detailed balance model has been employed and the conversion efficiency has been estimated to be 56.3%. © 2011 IEEE.

  2011, IMFEDK 2011 - 2011 International Meeting for Future of Electron Devices, Kansai, 36 - 37, English

  [Refereed]

  International conference proceedings


• Analysis of electronic structure in quantum dot arrays for intermediate band solar cells

  Akihito Kurome, Ryosuke Morigaki, Satofumi Souma, Matsuto Ogawa

  Intermediate band solar cells (IBSCs) have been proposed as highly efficient third generation photovoltaic devices. Quantum dot (QD) arrays produce mini-bands that are separated by a region of zero density of states from other states in the conduction band. Additional absorption from the valence band to the IB and the IB to the conduction band allows two photons with energies below the energy gap to be harvested in generating one electron-hole pair. We present a theoretical study of the electronic and optical properties of the IB formed by an InAs/GaAs QD arrays. The calculations are based on effective-mass approximation and finite element method. Theoretical results of the mini-band width variation with the period of the QD arrays in the z direction are presented. © 2011 IEEE.

  2011, IMFEDK 2011 - 2011 International Meeting for Future of Electron Devices, Kansai, 114 - 115, English

  [Refereed]

  International conference proceedings


• Effect of uniaxial strain on the electronic transport in single layer graphene

  Yusuke Ohmi, Matsuto Ogawa, Satofumi Souma

  We study the effect of the various types of strain on the electronic band structure and the transport characteristics in graphene. It has been found that the combination of shear and armchair uniaxial deformation is an effective way to open the band gap, meaning the efficient controllability of the electronic current through graphene © 2011 IEEE.

  2011, IMFEDK 2011 - 2011 International Meeting for Future of Electron Devices, Kansai, 126 - 127, English

  [Refereed]

  International conference proceedings


• Spin currents in semiconductor nanostructures:A nonequilibrium Green function approach

  NIKOLIC B. K, ZARBO L. P, SOUMA Satofumi

  Mar. 2010, Oxford Handbook of Nanoscience and Technology, pp. 814-865, English

  [Refereed]


• Spin-polarization in InAs/AlSb double barrier resonant tunneling structures: influence of barrier material and interface structure

  Satofumi Souma, Matsuto Ogawa

  We present a study on the atomistic simulation of the spin-polarized transmissions through InAs/AlSb double barrier resonant tunneling heterostructures. By making use of the atomistic sp3s* tight binding Hamiltonian including the intra-atomic spin-orbit interaction and the recursive Green's function method, we obtain the significant anisotropic zero-magnetic-field spin-splitting of the resonant transmission peak in the absence of the external electric field, demonstrating the importance of the barrier material and the atomic scale detail of the hetero interfaces on the spin-splitting.

  ELSEVIER SCIENCE BV, 2010, PROCEEDINGS OF THE 14TH INTERNATIONAL CONFERENCE ON NARROW GAP SEMICONDUCTORS AND SYSTEMS, 3(2) (2), 1287 - 1290, English

  [Refereed]

  International conference proceedings


• グラフェンナノエレクトロニクス素子の開発に向けて-素子シミュレーションと素子作成・物性評価

  相馬 聡文, 小川 真人, 山本 貴博, 渡辺 一之, 長汐 晃輔

  アグネ技術センタ-, Jan. 2010, 固体物理 Vol. 45 No. 1 pp.63-76, Vol 45, No. 1, pp. 63-76(1) (1), 63 - 76, Japanese

  [Refereed]


• Effect of interface structure on current spin-polarization in narrow gap semiconductor heterostructures

  SOUMA Satofumi, OGAWA Matsuto

  Dec. 2009, Physica E, Available online 1 December 20, English

  [Refereed]

  Scientific journal


• Simulation of Graphene Nanoribbon Spin-Filter Device with Spin-Density Functional Tight-Binding Method

  Satofumi Souma, Matsuto Ogawa, Takahiro Yamamoto, Kazuyuki Watanabe

  We study the spin filtering characteristics of the zigzag-edged graphene nanoribbon spin filtering device, applying the spin-density functional tight-binding method and the non-equilibrium Green's function method. Our simulations have shown that the spin filtering effect can be controlled by applying the side-gate voltages that effectively induce the transverse electric fields. Influence of an edge lattice vacancy on the spin-filtering effect is also discussed.

  IEEE, 2009, IWCE-13: 2009 13TH INTERNATIONAL WORKSHOP ON COMPUTATIONAL ELECTRONICS, pp. 81-84, 81 - +, English

  [Refereed]

  International conference proceedings


• Device physics and simulation techniques for nanoscale SOI-MOSFETs

  H. Tsuchiya, Y. Yamada, S. Souma, M. Ogawa

  The silicon-based planar CMOS technology is expected to face fundamental limits in the near future, and therefore, new types of nanoscale devices are being investigated aggressively. To understand the device physics and assess their performance limits, new types of simulation techniques considering quantum mechanical phenomena, carrier's ballistic transport and atomistic effects are also needed. In this paper, we present our recent approaches toward the quantum and atomistic transport modeling, and make a performance projection of emerging nano-MOS transistors employing new device structures and new channel materials. ©The Electrochemical Society.

  2009, ECS Transactions, 19(4) (4), 211 - 220, English

  [Refereed]

  International conference proceedings


• 2D Quantum Mechanical Simulation of Gate-Leakage Current in Double-Gate n-MOSFETs

  Satoru Muraoka, Ryota Mukai, Satofumi Souma, Matsuto Ogawa

  The direct gate leakage current in double-gate n-type MOSFETs with physical gate lengths of 10 nm is investigated. This work uses a combination of a two-dimensional non-equilibrium Green's function (NEGF) based upon a real-space expansion method and Poisson's equation, which are solved self-consistently. In the conventional 1D analysis of the gate leakage current, an optical potential or an imaginary energy has been necessary to broaden the energy level in the triangular quantum well for reduction of computational costs. It is found that, however, different from the results in the conventional 1D analysis, peaks in the current density energy spectra, equivalently the energy levels, are broadened even under zero drain bias condition due to the quantum mechanical scatterings in the presence of the source and drain electrodes. This fact proves that the optical potential used in the conventional 1D simulation merely models the effect of the existence of the electrodes and the 2D analysis gives more sound results.

  IEEE, 2009, 2009 INTERNATIONAL CONFERENCE ON SIMULATION OF SEMICONDUCTOR PROCESSES AND DEVICES, 297 - 300, English

  [Refereed]

  International conference proceedings


• Numerical simulation of electronic transport in zigzag-edged graphene nano-ribbon devices

  Satofumi Souma, Matsuto Ogawa, Takahiro Yamamoto, Kazuyuki Watanabe

  We present a numerical study of the current-voltage characteristics in zigzag-edged graphene nano-ribbon (Z-GNR) devices. Our calculations employing the non-equilibrium Green's function method and the density-functional tight-binding method show that the Z-GNR with transverse symmetry can exhibit remarkable current saturation behavior in spite of the absence of the bandgap. We further demonstrate that the saturation current can be controlled by the additional doping in the channel region. The mechanism of such current saturation can be explained in terms of the symmetry of the wavefunctions corresponding to the conduction and the valence bands in Z-GNR.

  SPRINGER, Sep. 2008, JOURNAL OF COMPUTATIONAL ELECTRONICS, 7(3) (3), 390 - 393, English

  [Refereed]

  Scientific journal


• グラフェンナノリボンを用いた新規デバイスの提案とシミュレーション

  SOUMA Satofumi, OGAWA Mtsuto, YAMAMOTO Takahiro, WATANABE Kazuyuki

  Jul. 2008, シリコンテクノロジー, No.103, pp. 15-20, Japanese


• Dimensional transitions of density of states and heat capacity in spherical quantum dots

  Seung Joo Lee, Hee Chang Jeon, Tae Won Kang, Satofumi Souma

  We evaluate analytically and numerically the density of states (DOS) and the heat capacity in a spherical quantum dot formed by a spherical thin barrier. The control of the spherical barrier thickness or the potential barrier height is found to cause the dimensional transition from the three-dimensional (3D) behavior to the quasi-zero dimensional (Q0D) behavior in the DOS and the heat capacity. When the barrier is thick enough, the DOS shows the Q0D-like behavior but when the barrier is thin enough to allow electrons to tunnel through it, the temperature dependence of the heat capacity exhibits quite a distinct behavior depending on the electron density. Explicit numerical plots are given in the low density regime.

  WORLD SCIENTIFIC PUBL CO PTE LTD, Jun. 2008, INTERNATIONAL JOURNAL OF MODERN PHYSICS B, 22(15) (15), 2373 - 2382, English

  [Refereed]

  Scientific journal


• Transitions of density of states and heat capacity in spherical quantum structure formed by a thin barrier

  Seung Joo Lee, Hee Chang Jeon, Tae Won Kang, Satofumi Souma

  We present a theoretical study of the density of states (DOS) and the heat capacity in a spherical quantum dot formed by a spherical thin barrier. The control of the spherical barrier thickness or the potential barrier height is found to cause the dimensional transition from the three-dimensional (3D) behavior to the quasi-zero dimensional (Q0D) behavior in the DOS and the heat capacity. When the barrier is thick enough the DOS shows the Q0D-like behavior but when the barrier is thin enough to allow electrons to tunnel through it, the temperature dependence of the heat capacity exhibits quite distinct behavior depending on the electron density. (C) 2007 Elsevier B.V. All rights reserved.

  ELSEVIER SCIENCE BV, Apr. 2008, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 40(6) (6), 2198 - 2200, English

  [Refereed]

  Scientific journal


• Non-equilibrium Green's function method for modeling quantum electron transport in nano-scale devices with anisotropic multiband structure

  Helmy Fitriawan, Matsuto Ogawa, Satofumi Souma, Tanroku Miyoshi

  Aggressive scaling of devices has reduced device dimensions into nanometer scale in which the single-band effective mass model is inadequate to simulate quantum transport in such devices. Thus it motivates the use of more realistic full band structures in quantum transport simulations. In this study we perform the analysis of multiband quantum transport in nanoscale devices based on a non-equilibrium Green's function (NEGF) formalism coupled self-consistently with the Poisson equation. The empirical nearest neighbor sp(3)s* tight binding approximation (TBA), where the couplings among atomic orbitals of the host crystal are taken into account, is employed to obtain a realistic multiband structure. The effects of non-parabolic bandstructure as well as anisotropic features of Si are studied and analyzed. Our multiband simulation results on potential and current profiles show significant differences, especially in higher applied bias, with those of conventional effective mass model where only parabolic singleband is considered in the simulation.

  SPRINGER, Feb. 2008, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 19(2) (2), 107 - 110, English

  [Refereed]

  Scientific journal


• Quantum electron transport modeling in uniaxially strained silicon channel of double-gate MOSFETs

  Helmy Fitriawan, Matsuto Ogawa, Satofumi Souma, Tanroku Miyoshi

  This paper reports the calculation of quantum electron transport in double-gate metal oxide semiconductor field effects transistors (MOSFETs) with uniaxially strained silicon channel. The calculation is formulated based on multiband non-equilibrium Green's function (NEGF) method coupled self-consistently with the Poisson equation. The empirical sp(3)s* tight binding approximation (TBA) model with nearest neighbor coupling is employed to obtain more realistic band structure in the formulation. We compare the carrier transport characteristics of simulated MOSFETs with strained channel to those of without strain. The simulation results show that the presence of uniaxially strain induce the current enhancement in the devices. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  WILEY-V C H VERLAG GMBH, 2008, PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 1, 5(1) (1), 74 - 77, English

  [Refereed]

  International conference proceedings


• Fullband simulation of nano-scale MOSFETs based on a non-equilibrium Green's function method

  Helmy Fitriawan, Matsuto Ogawa, Satofumi Souma, Tanroku Miyoshi

  The analysis of multiband quantum transport simulation in double-gate metal oxide semiconductor field effects transistors (DG-MOSFETs) is performed based on a non-equilibrium Green's function (NEGF) formalism coupled self-consistently with the Poisson equation. The empirical sp(3)s. tight binding approximation (TBA) with nearest neighbor coupling is employed to obtain a realistic multiband structure. The effects of non-parabolic bandstructure as well as anisotropic features of Si are studied and analyzed. As a result, it is found that the multiband simulation results on potential and current profiles show significant differences, especially in higher applied bias, from those of conventional effective mass model.

  IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG, Jan. 2008, IEICE TRANSACTIONS ON ELECTRONICS, E91C(1) (1), 105 - 109, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Analysis of direct tunneling current from quasi-bound states in n-MOSFET based on non-equilibrium Green's function

  Satoru Muraoka, Satofumi Souma, Matsuto Ogawa

  Gate-leakage current from quasi-bound states in highly scaled metal-oxide-semiconductor devices has been investigated by using a non-equilibrium Green's function method. We have taken account of the realistic band structure of Si with anisotropic effective masses. This study also presents a model for the efficient simulation of gate-leakage current with open boundaries where no escape time or life time has been assumed contrary to the conventional analysis [1]. We have added optical potential to the on-site energies only above the conduction band edge in the substrate electrode. The optical potential induces energy broadening in the triangle potential to calculate the density of states properly.

  IEEE, 2008, SISPAD: 2008 INTERNATIONAL CONFERENCE ON SIMULATION OF SEMICONDUCTOR PROCESSES AND DEVICES, pp. 221-224, 221 - 224, English

  [Refereed]

  International conference proceedings


• Quantum electron transport modeling in uniaxially strained silicon channel of double-gate MOSFETs

  Helmy Fitriawan, Matsuto Ogawa, Satofumi Souma, Tanroku Miyoshi

  This paper reports the calculation of quantum electron transport in double-gate metal oxide semiconductor field effects transistors (MOSFETs) with uniaxially strained silicon channel. The calculation is formulated based on multiband non-equilibrium Green's function (NEGF) method coupled self-consistently with the Poisson equation. The empirical sp3 s* tight binding approximation (TBA) model with nearest neighbor coupling is employed to obtain more realistic band structure in the formulation. We compare the carrier transport characteristics of simulated MOSFETs with strained channel to those of without strain. The simulation results show that the presence of uniaxially strain induce the current enhancement in the devices. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA.

  2008, Physica Status Solidi (C) Current Topics in Solid State Physics, 5(1) (1), 74 - 77, English

  [Refereed]

  International conference proceedings


• Quantum electron transport modeling in double-gate MOSFETs based on multiband non-equilibrium Green's function method

  Helmy Fitriawan, Matsuto Ogawa, Satofumi Souma, Tanroku Miyoshi

  The formulation and calculation of quantum electron transport in double-gate metal oxide semi-conductor field effect transistors (DGMOSFETs) is presented based on multiband non-equilibrium Green's function (NEGF) formalism. In the formulation we employ the empirical sp(3)s(*) tight-binding approximation (TBA) with nearest neighbor coupling to obtain a realistic fullband structure. The multiband NEGF is performed self-consistently with the Poisson equation to acquire the effect of space charge density. We compare the non-parabolicity feature of bandstructure with that of parabolic effective mass model. Due to the difference in energy dispersion relation, we have found that the results of multiband simulations are quite different with those based on conventional effective mass model. (c) 2007 Elsevier B.V. All rights reserved.

  ELSEVIER SCIENCE BV, Dec. 2007, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 40(2) (2), 245 - 248, English

  [Refereed]

  Scientific journal


• Multiband simulation of uniaxially stressed silicon MOSFETs based on non-equilibrium Green’s function method

  FITRIAWAN Helmy, SOUMA Satofumi, OGAWA Matsuto

  Sep. 2007, Extended Abstact of 2007 Int. Conf. on Solid State Devices andMaterials, pp. 52-53, English

  International conference proceedings


• Analysis of quantum transport in nano-scale silicon

  IMAGO Hiroshi, MIZUTANI Atsushi, SHIMIZU Takayuki, FITRIAWAN Helmy, OGAWA Matsuto, SOUMA Satofumi, MIYOSHI Tanroku

  Apr. 2007, Proc. 2007 Int. Meetingfor Future of Electron Devices, Kansai, pp.107-108, English

  International conference proceedings


• Imaging mesoscopic spin Hall flow: Spatial distribution of local spin currents and spin densities in and out of multiterminal spin-orbit coupled semiconductor nanostructures

  BK Nikolic, LP Zarbo, S Souma

  We introduce the concept of bond spin currents, which describe the spin transport between two sites of the lattice model of a multiterminal spin-orbit (SO) coupled semiconductor nanostructure, and express them in terms of the spin-dependent nonequilibrium (Keldysh) Green functions for the Landauer setup where the nanostructure is attached to many semi-infinite ideal leads terminating in macroscopic thermalizing reservoirs. This formalism is applied to obtain the spatial distribution of microscopic spin currents in a clean phase-coherent two-dimensional electron (2DEG) gas with the Rashba type of SO coupling attached to four external leads. Together with the corresponding spatial profiles of the steady-state spin density, such visualization of the phase-coherent spin flow allow us to resolve several key issues for the understanding of microscopic mechanisms which generate pure spin Hall currents in the transverse leads of ballistic devices due to the flow of unpolarized charge current through their longitudinal leads: (i) while bond spin currents are nonzero locally within the SO coupled sample and neighboring region of the leads even in equilibrium (when all leads are at the same potential), the total spin currents obtained by summing the bond spin currents over any cross section within the leads are zero, so that no spin is actually transported by such equilibrium spin currents; (ii) when the device is brought into a nonequilibrium state (supporting steady-state charge current) by applying the external voltage difference between its longitudinal leads, only the wave functions (or Green functions) around the Fermi energy contribute to the total spin current through a given transverse cross section; (iii) the total spin Hall current is not conserved within the SO coupled region-however, it becomes conserved and physically well-defined quantity in the ideal leads where it is, furthermore, equal to the spin current obtained within the multiprobe Landauer-Buttiker scattering formalism in linear response regime. The spatial profiles of the local spin currents and stationary flowing spin densities crucially depend on whether the sample is smaller or greater than the spin precession length, thereby demonstrating its essential role as the characteristic mesoscale for the spin Hall effect in ballistic multiterminal semiconductor nanostructures. Although the static spin-independent disorder reduces the magnitude of the total spin current in the leads, the bond spin currents and spin densities remain nonzero throughout the whole diffusive 2DEG sample.

  AMER PHYSICAL SOC, Feb. 2006, PHYSICAL REVIEW B, 73(7) (7), English

  [Refereed]

  Scientific journal


• Electronic transport properties of graphitic ribbons under finite bias voltages

  SOUMA Satofumi, YAMAMOTO Takahiro, WATANABE Kazuyuki

  Jan. 2006, e-Journal of Surface Science and Nanotechnology, Vol.4, pp.78-83, English

  [Refereed]

  Scientific journal


• Mesoscopic spin Hall effect in multiprobe ballistic spin-orbit-coupled semiconductor bridges

  BK Nikolic, LP Zarbo, S Souma

  We predict that unpolarized charge current driven through the longitudinal leads attached to ballistic quantum-coherent two-dimensional electron gas (2DEG) in semiconductor heterostructure will induce a pure spin current, which is not accompanied by any net charge flow, in the transverse voltage probes. Its magnitude can be tuned by the Rashba spin-orbit (SO) coupling and, moreover, it is resilient to weak spin-independent scattering off impurities within the metallic diffusive regime. While the polarization vector of the spin transported through the transverse leads is not orthogonal to the plane of 2DEG, we demonstrate that only two components (out-of-plane and longitudinal) of the transverse spin current are signatures of the spin Hall effect in four-probe Rashba spin-split semiconductor nanostructures. The linear response spin Hall current, obtained from the multiprobe Landauer-Buttiker scattering formalism generalized for quantum transport of spin, is the Fermi-surface determined nonequilibrium quantity whose scaling with the 2DEG size L reveals the importance of processes occurring on the spin precession mesoscale L-SO (on which spin precesses by an angle pi)-the out-of-plane component of the transverse spin current exhibits quasioscillatory behavior for L less than or similar to L-SO (attaining the maximum value in 2DEGs of the size L-SO x L-SO), while it reaches the asymptotic value in the macroscopic regime L > L-SO. Furthermore, these values of the spin Hall current can be manipulated by the measuring geometry defined by the attached leads.

  AMER PHYSICAL SOC, Aug. 2005, PHYSICAL REVIEW B, 72(7) (7), English

  [Refereed]

  Scientific journal


• Numerical study of ferromagnetism in diluted magnetic semiconductor quantum-wells

  S Souma, SJ Lee, TW Kang

  We study the ferromagnetism in III-V diluted magnetic semiconductor (DMS) quantum-wells theoretically and numerically taking into account the occupation of multiple sub-bands by holes in quantum wells. Starting from the mean-field theory of carrier-induced ferromagnetism in III-V DMS along with the exchange-correlation interaction of holes within the local spin density approximation, we found that the ferromagnetic transition temperature T-c of DMS quantum-wells exhibits step-function-like dependence on the hole density, reflecting the quasi-two-dimensional nature of systems. Moreover, the temperature dependence of the spin polarization shows quite distinct characteristics depending on the hole density.

  WORLD SCIENTIFIC PUBL CO PTE LTD, Jul. 2005, INTERNATIONAL JOURNAL OF MODERN PHYSICS B, 19(19) (19), 3151 - 3160, English

  [Refereed]

  Scientific journal


• Nonequilibrium spin hall accumulation in ballistic semiconductor nanostructures

  BK Nikolic, S Souma, LP Zarbo, J Sinova

  We demonstrate that the flow of a longitudinal unpolarized current through a ballistic two-dimensional electron gas with Rashba spin-orbit coupling will induce a nonequilibrium spin accumulation which has opposite signs for the two lateral edges and is, therefore, the principal observable signature of the spin Hall effect in two-probe semiconductor nanostructures. The magnitude of its out-of-plane component is gradually diminished by static disorder, while it can be enhanced by an in-plane transverse magnetic field. Moreover, our prediction of the longitudinal component of the spin Hall accumulation, which is insensitive to the reversal of the bias voltage, offers direct evidence to differentiate experimentally between the extrinsic, intrinsic, and mesoscopic spin Hall mechanisms.

  AMERICAN PHYSICAL SOC, Jul. 2005, PHYSICAL REVIEW LETTERS, 95(4) (4), English

  [Refereed]

  Scientific journal


• Decoherence of transported spin in multichannel spin-orbit-coupled spintronic devices: Scattering approach to spin-density matrix from the ballistic to the localized regime

  BK Nikolic, S Souma

  By viewing current in the detecting lead of a spintronic device as being an ensemble of flowing spins corresponding to a mixed quantum state, where each spin itself is generally described by an improper mixture generated during the transport where it couples to other degrees of freedom due to spin-orbit (SO) interactions or inhomogeneous magnetic fields, we introduce the spin-density operator associated with such current and express it in terms of the spin-resolved Landauer transmission matrix of the device. This formalism, which provides a complete description of coupled spin-charge quantum transport in open finite-size systems attached to external probes, is employed to understand how initially injected pure spin states, comprising fully spin-polarized current, evolve into the mixed ones corresponding to a partially polarized current. We analyze particular routes that diminish spin coherence (signified by decay of the off-diagonal elements of the current spin-density matrix) in two-dimensional-electron-gas-based devices due to the interplay of the Rashba and/or Dresselhaus SO coupling and (i) scattering at the boundaries or lead-wire interface in ballistic semiconductor nanowires; or (ii) spin-independent scattering off static impurities in both weakly and strongly disordered nanowires. The physical interpretation of spin decoherence in the course of multichannel quantum transport in terms of the entanglement of spin to an effectively zero-temperature "environment" composed of open orbital conducting channels offers insight into some of the key challenges for spintronics: controlling decoherence of transported spins and emergence of partially coherent spin states in all-electrical spin manipulation schemes based on the SO interactions in realistic semiconductor structures. In particular, our analysis elucidates why operation of both ballistic and nonballistic spin-field-effect transistors, envisaged to exploit Rashba and Rashba+Dresselhaus SO coupling, respectively, would demand single-channel transport as the only setup ensuring complete suppression of (D'yakonov-Perel'.-type) spin decoherence.

  AMER PHYSICAL SOC, May 2005, PHYSICAL REVIEW B, 71(19) (19), English

  [Refereed]

  Scientific journal


• Spin hall current driven by quantum interferences in mesoscopic Rashba rings

  S Souma, BK Nikolic

  We propose an all-electrical nanostructure where pure spin current is induced in the transverse voltage probes attached to a quantum-coherent ballistic one-dimensional ring when unpolarized charge current is injected through its longitudinal leads. Tuning of the Rashba spin-orbit coupling in a semiconductor heterostructure hosting the ring generates quasiperiodic oscillations of the predicted spin-Hall current due to spin-sensitive quantum-interference effects caused by the difference in the Aharonov-Casher phase accumulated by opposite spin states. Its amplitude is comparable to that of the spin-Hall current predicted for finite-size (simply connected) two-dimensional electron gases, while it gets reduced gradually in wide two-dimensional rings or due to spin-independent disorder.

  AMER PHYSICAL SOC, Mar. 2005, PHYSICAL REVIEW LETTERS, 94(10) (10), English

  [Refereed]

  Scientific journal


• Transitions of dimensional states in quantum dots formed by spherical barrier

  SJ Lee, TW Kang, S Souma, SK Noh, JC Woo

  The control of the spherical barrier thickness or height is found to cause the dimensional transitions from the three dimensional (3D) behavior to the quasi-zero dimensional (Q0D) behavior in the density of states (DOS) and the heat capacity. When the barrier is thick enough such that the DOS shows the Q0D-like signature but is still thin enough to allow electrons to tunnel it, the temperature dependence of the heat capacity exhibits quite distinct behavior depending on the electron density.

  AMER INST PHYSICS, 2005, Physics of Semiconductors, Pts A and B, 772, 793 - 794, English

  [Refereed]

  International conference proceedings


• Molecular like states in coupled magnetic quantum dots

  S Souma, SJ Lee, TW Kang, G Ihm, KJ Chang

  We report a computational study of coupled magnetic quantum dots, which are the magnetic analogue of the conventional electrically coupled quantum dots. In order to study that problem, we calculated the conductance of the narrow 2DEG in which two magnetic quantum dots are located. The calculated conductance shows several double anti-resonance-dips, which are due to the formation of the molecular like states which are extended over those two magnetic quantum dots. This is also shown by the local density of states which is given explicitly by the form of images.

  AMER INST PHYSICS, 2005, Physics of Semiconductors, Pts A and B, 772, 735 - 736, English

  [Refereed]

  International conference proceedings


• Comparative Study of Time-Dependent and Scattering-State Ab Initio Calculations for Field Emission

  Araidai Masaaki, Souma Satofumi, Watanabe Kazuyuki

  We perform time-dependent (TD) and scattering-state (SS) ab-inito calculations for simulating the field emission (FE) of Na surfaces to explore the applicability of the two schemes. The amplitude of emission current is evaluated more reliably by SS than TD methods, because the former treats the steady-state electron tunneling faithfully but the latter utilizes transient electron dynamics. In contrast with the evaluation of current amplitude, the TD method is more suitable than the SS one for revealing the electronic-state origin of FE, because the TD method can directly determine the time evolution of all wave functions caused by an electric field. Thus, the TD and SS methods are found to play a complementary role in the FE study. [DOI: 10.1380/ejssnt.2005.457]

  The Surface Science Society of Japan, 2005, e-Journal of Surface Science and Nanotechnology, Vol.3, pp.457-460(3) (3), 457 - 460, English

  [Refereed]

  Scientific journal


• Modulating unpolarized current in quantum spintronics: Visibility of spin-interference effects in multichannel Aharonov-Casher mesoscopic rings

  S Souma, BK Nikolic

  The conventional unpolarized current injected into a quantum-coherent semiconductor ring attached to two non-magnetic external leads can be modulated from perfect conductor to perfect insulator limit via electrically tunable Rashba spin-orbit (SO) coupling, thereby avoiding the usage of any ferromagnetic elements or external magnetic fields. This requires that ballistic propagation of electrons, whose spin precession is induced by the topological Aharonov-Casher phase accumulated by the spin wave function during a cyclic evolution, takes place through a single conducting channel ensuring that electronic quantum state remains a pure separable one in the course of transport. We study the fate of such spin-sensitive quantum interference effects as more than one orbital conducting channel becomes available for quantum transport. Although the conductance of multichannel rings, in general, does not go all the way to zero at any value of the SO coupling, some degree of current modulation survives. We analyze possible scenarios that can lead to reduced visibility of the destructive spin interference effects that are responsible for the zero conductance at particular values of the Rashba interaction: (i) the transmitted spin states remain fully coherent, but conditions for destructive interference are different in different channels; (ii) the transmitted spins end up in partially coherent quantum state arising from entanglement to the environment composed of orbital degrees of freedom of the same particle to which the spin is attached.

  AMER PHYSICAL SOC, Nov. 2004, PHYSICAL REVIEW B, 70(19) (19), English

  [Refereed]

  Scientific journal


• On the two magnetic quantum dots in a two dimensional electron gas

  LEE S. J, KANG T. W, IHM G, CHANG K. J, SOUMA Satofumi

  Sep. 2004, UZBEK JOURNAL OF PHYSICS, Volume 6, Number 5&6, pp.334-3, English

  [Refereed]

  Scientific journal


• Magnetic quantum dots and magnetic edge states

  SJ Lee, S Souma, G Ihm, KJ Chang

  Starting with defining the magnetic edge state in a magnetic quantum dot, which becomes quite popular nowadays conjunction with a possible candidate for a high density memory device or spintronic materials, various magnetic nano-quantum structures are reviewed in detail. We study the magnetic edge states of the two dimensional electron gas in strong perpendicular magnetic fields. We find that magnetic edge states are formed along the boundary of the magnetic dot, which is formed by a nonuniform distribution of magnetic fields. These magnetic edge states circulate either clockwise or counterclockwise, depending on the number of missing flux quanta, and exhibit quite different properties, as compared to the conventional ones which are induced by electrostatic confinements in the quantum Hall system. We also find that a close relation between the quantum mechanical eigenstates and the classical trajectories in the magnetic dot. When a magnetic dot is located inside a quantum wire, the edge-channel scattering mechanism by the magnetic quantum dot is very different from that by electrostatic dots. Here, the magnetic dot is formed by two different magnetic fields inside and outside the dot. We study the ballistic edge-channel transport and magnetic edge states in this situation. When the inner field is parallel to the outer one, the two-terminal conductance is quantized and shows the features of a transmission barrier and a resonator. On the other hand, when the inner field-is reversed, the conductance is not quantized and all channels can be completely reflected in some energy ranges. The difference between the above two cases results from the distinct magnetic confinements. We also describe successfully the edge states of magnetic quantum rings and others in detail. (C) 2003 Elsevier B.V. All rights reserved.

  ELSEVIER SCIENCE BV, Apr. 2004, PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, 394(1) (1), 1 - 40, English

  [Refereed]

  Scientific journal


• Effects of multi-subband occupation and electric field in ferromagnetic semiconductor quantum wells

  S Souma, SJ Lee, TW Kang

  Ferromagnetism in III-V diluted magnetic semiconductor (DMS) quantum wells is studied theoretically paying special attention to the occupation of multiple subbands by holes and the effect of static electric field perpendicular to the well plane. Our calculations show that the ferromagnetic transition temperature T, of DMS quantum-well exhibits step-function-like dependence on the carrier concentration, reflecting the quasi-two-dimensional nature of systems. The T, can be sensitively controlled by the application of electric field when the hole density is small so as to occupy only a few subbands. (C) 2003 Elsevier B.V. All rights reserved.

  ELSEVIER SCIENCE BV, Mar. 2004, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 21(2-4) (2-4), 1037 - 1040, English

  [Refereed]

  Scientific journal


• Controlling Decoherence of Transported Quantum Spin Information in Semiconductor Spintronics

  Branislav K. Nikolic and Satofumi Souma

  2004, REALIZING CONTROLLABLE QUANTUM STATES Proceedings of the International Symposium on Mesoscopic Superconductivity and Spintronics - In the Light of Quantum Computation, World Scientific (2005)

  [Refereed]


• Effects of magnetic quantum dots on magnetoconductance in quantum wires

  S Souma, SJ Lee, N Kim, TW Kang, G Ihm, KS Yi, A Suzuki

  We present a theoretical study of electronic transport in quantum wires (narrow two-dimensional electron gas) with array of magnetic quantum dots. Each magnetic quantum dot is defined by a small circular region where the strength of perpendicular magnetic field is modulated. By making use of a newly developed calculation method based on the gauge transformations, we calculated the conductance as a function of the external perpendicular magnetic field. Our numerical calculations show that the magnetoconductance is very sensitive to the number of magnetic quantum dots in the field region where the direction of the net magnetic field in dot regions is antiparallel to the external magnetic field.

  KLUWER ACADEMIC/PLENUM PUBL, Apr. 2003, JOURNAL OF SUPERCONDUCTIVITY, 16(2) (2), 339 - 342, English

  [Refereed]

  Scientific journal


• Transitions of the density of states in cylindrical quantum box

  SJ Lee, S Souma, N Kim, TW Kang, G Ihm, JC Woo, A Suzuki

  We study the density of states in a cylindrical quantum box formed by a cylindrical penetrable barrier and a planer penetrable double barrier perpendicular to the cylinder. The control of the cylindrical barrier thickness or height is found to cause the 3D-Q1D and Q2D-QOD transitions if the strength of the planer double barrier is zero and infinity, respectively. In the transient regime of the 3D-Q1D (Q2D-QOD) transition, we found the presence of the Q2D (Q1D) like crossover regime, in which the tunneling motion through the cylindrical barrier is interpreted to provide the "free" degree of freedom to the DOS.

  NOVA SCIENCE PUBLISHERS, INC, 2003, SIMILARITY IN DIVERSITY, 27 - 34, English

  [Refereed]

  International conference proceedings


• Dimensional crossover in cylindrical quantum-box structures formed by penetrable barriers

  S Souma, SJ Lee, N Kim, TW Kang

  We study the density of states (DOS) in a cylindrical quantum box formed by a cylindrical penetrable barrier and a planer penetrable double barrier perpendicular to the cylinder. The control of the cylindrical barrier thickness or height is found to cause the dimensional transitions from a three-dimensional (3D) DOS to a quasi-one-dimensional (Q1D) DOS and from a quasi-two-dimensional (Q2D) DOS to a quasi-zero-dimensional (Q0D) DOS, if the strength of the planer double barrier is zero and infinity, respectively. In between the 3D and the Q1D (Q2D and Q0D) limiting regimes, we found the presence of a Q2D (Q1D) like crossover regime. (C) 2002 American Institute of Physics.

  AMER INST PHYSICS, Dec. 2002, JOURNAL OF APPLIED PHYSICS, 92(11) (11), 6927 - 6929, English

  [Refereed]

  Scientific journal


• Dimensional crossover of the density of states in cylindrically confined systems

  S Souma, SJ Lee, TW Kang

  Within the context of a simplified model,we study the density of states (DOS) in a cylindrical region surrounded by a cylindrical penetrable barrier, within the context of a simplified model. It is shown that the DOS in the cylindrical region exhibits a smooth transition from a three-dimensional (3D)-type energy dependence to a quasi-one-dimensional (Q1D)-type (sawtooth-like) energy dependence with increasing strength of the cylindrical potential barrier. Interestingly, in a transient region between the 3D and the Q1D behaviors, the DOS shows a quasi-two-dimensional (Q2D)-type (staircase-like) energy dependence in a certain narrow energy range.

  KOREAN PHYSICAL SOC, Jun. 2002, JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 40(6) (6), 1051 - 1055, English

  [Refereed]

  Scientific journal


• Local density of states and scattering matrix in quasi-one-dimensional systems

  S Souma, A Suzuki

  Mathematical relations between the local density of states (LDOS) and the scattering matrix (i.e., transmission and reflection amplitudes) for quasi-one-dimensional systems are derived in the presence of static uniform magnetic fields. Starting from the definition of the LDOS expressed by the Green's function, we derive the formulas for the LDOS in terms of the functional derivative of the scattering matrix or the Friedel phase with respect to a scattering potential.

  AMERICAN PHYSICAL SOC, Mar. 2002, PHYSICAL REVIEW B, 65(11) (11), English

  [Refereed]

  Scientific journal


• Magneto-conductance in Quantum Wires with Array of Magnetic Quantum Dots

  S. Souma, S.J. Lee, N. Kim, T.W. Kang, G. Ihm, J.C.Woo, and A. Suzuki

  2002, Proceedings of the 26th International Conference on the Physics of Semiconductors, Edinburgh 2002

  [Refereed]


• Dephasing due to voltage probes in quantum wires with antidot potential

  S Souma, A Suzuki

  The effect of phase-breaking due to the presence of voltage probes is investigated theoretically through a study of the conductance oscillation caused by inter-edge scattering between the circular edge-states around an antidot and those localized edge-states along the system boundaries on both sides of a conductor.

  AMER INST PHYSICS, 2000, STATISTICAL PHYSICS, 519, 569 - 571, English

  [Refereed]

  International conference proceedings


• Interedge scattering in mesoscopic Corbino disks near the ballistic regime

  S Souma, A Suzuki

  We study the effect of impurities on the conductance of mesoscopic Corbino disks placed in a uniform magnetic field, where noninteracting electrons are transmitted from inner to outer edge coherently. The magnetoconductance is calculated numerically by applying the Landauer-Buttiker formula for an annular two-dimensional electron gas system. The results are interpreted in terms of the classical picture of cyclotron orbits. [S0163-1829(99)08547-1].

  AMER PHYSICAL SOC, Dec. 1999, PHYSICAL REVIEW B, 60(23) (23), 15928 - 15936, English

  [Refereed]

  Scientific journal


• Transmission phases in quantum wires with an antidot potential subjected to a high magnetic field

  Satofumi Souma and Akira Suzuki

  1999, Journal of the Korean Physical Society, vol. 39 No. 3, September 2001, pp. 553-557

  [Refereed]


• Effect of phase breaking scattering in quantum wires with an antidot potential

  Satofumi Souma and Akira Suzuki

  1999, Proceedings of the 5th International Workshop on Similarity in Diversity, edited by H. Hara, T. Toyoda and T. Morita, (1999) P.183-187

  [Refereed]


• Effect of impurity scattering in nanoscale Corbino disks

  S Souma, A Suzuki

  We have studied electrical conductance of nanoscale Corbino disks having single delta-function impurities. Kirczenow [J. Phys.: Condens. Matter 6, L583 (1994)] predicted that the conductance G in ballistic Corbino disks at zero temperature is quantized in odd integer multiples of 2e(2/)h. We found that the same feature of conductance quantization as in the case of ballistic Corbino disks can be seen in the presence of single repulsive delta-function impurity in nanoscale Corbino disks, regardless of the impurity strength. For an attractive delta-function impurity, however, G decreases significantly at the energy levels of quasibound states formed in the effective confining potential. This indicates that the presence of evanescent modes strongly affects the scattering of propagating waves by single attractive delta-function impurity. This feature appears distinctively in the first step of the conductance for weak impurity whereas for strong impurity in the second or subsequent steps, depending on the strength of the impurity.

  Lead, AMER PHYSICAL SOC, Aug. 1998, PHYSICAL REVIEW B, 58(8) (8), 4649 - 4655, English

  [Refereed]

  Scientific journal


• Evanescent modes and impurity scattering in nano-scale Corbino disks

  Satofumi Souma and Akira Suzuki

  1998, Statistical Physics, Experiments, Theories and Computer Simulation, Proceedings of the 2nd Tohwa University International Meeting, edited by M. Tokuyama and I. Oppenheim, (1998) P. 196.

  [Refereed]

• Investigation of Quantum Computing Algorithms for Quantum Transport Simulation Based on the Time-Dependent Open System Schrödinger Equation

  Satofumi Souma

  The 72st JSAP Spring Meeting, 2025, Mar. 2025

  Poster presentation


• Numerical Simulation of Photoconductivity in Monolayer Transition Metal Dichalcogenides for Optoelectronic Applications

  Akira Nakanishi, Satofumi Souma

  The 2024 International Meeting for Future of Electron Devices, Kansai, Nov. 2024, English, International conference

  Poster presentation


• Theoretical analysis of photo-induced conductivity in TMDC and black phosphorus

  Akira Nakanishi, Satofumi Souma

  The 85th JSAP Autumn Meeting, 2024, Sep. 2024

  Poster presentation


• Study on the Application of Quantum Computing Algorithms for Semiconductor Device Simulation

  Satofumi Souma, Takuya Ishibashi

  The 71st Japan Society of Applied Physics (JSAP) Spring Meeting, Mar. 2024

  Oral presentation


• Construction and Analysis of Performance Data for Understanding Skill Acquisition and Forgetting in Piano Performance

  Yusei Maeba, Satofumi Souma, Yoshinari Takegawa

  The 139th Music and Computer Research Presentation, Mar. 2024

  Poster presentation


• Development of an Optimal Fingering Suggestion System for Beginner Viola Players

  Onka Hirayama, Satofumi Souma

  The 139th Music and Computer Research Presentation, Mar. 2024

  Poster presentation


• Simulation of spin qubits in silicon double quantum dot with magnetic gradient and valley splitting

  Yusuke Hayashi, Satofumi Souma

  The 2023 International Meeting for Future of Electron Devices, Kansai, Nov. 2023, English

  Poster presentation


• 強束縛近似法と有限差分時間領域法に基づくグラフェン表面プラズモン伝搬のシミュレーション

  相馬聡文, 扇澤祥太

  電子情報通信学会 シリコン材料・デバイス研究会「プロセス・デバイス・回路シミュレーションおよび一般」, Nov. 2023

  [Invited]

  Invited oral presentation


• 強束縛近似法に基づくグラフェン状物質の電子状態解析のための変分量子アルゴリズムの実装及び変分量子回路構成の検討

  石橋 拓也, 相馬 聡文

  2023年 第84回応用物理学会秋季学術講演会, Sep. 2023


• Quantum Computers and the Quantum Future Society

  Satofumi Souma

  The 40th (FY 2023) Kobe University Faculty of Engineering Public Lecture "Engineering Contributing to the SDGs" – June 10, 2023, Jun. 2023

  Public discourse


• 半導体ナノワイヤ中の二重量子ドットを用いたスピン量子ビットのゲート制御に関するシミュレーション

  林雄介, 相馬聡文

  応用物理学会関西支部 2023年度 第1回講演会, Jun. 2023


• Application of machine learning and quantum computational algorithm for semiconductor device simulations

  Satofumi Souma

  2022 GIST International Workshop for Accelerating Intelligence Semiconductor & AI, Dec. 2022, English

  Invited oral presentation


• Improvisational Music Generation Performance Embodying Quantum Interactions

  Satofumi Souma

  The 14th Annual Conference of the Japanese Association for the Study of Musical Improvisation, Nov. 2022

  Oral presentation


• SISPAD2022レビュー

  相馬 聡文

  電子情報通信学会シリコン材料・デバイス研究会, Nov. 2022

  [Invited]

  Invited oral presentation


• ゲート式量子コンピューティングアルゴリズムを援用したナノスケールデバイスシミュレーション手法の検討

  相馬聡文 松尾信吾 石橋拓也

  電子情報通信学会シリコン材料・デバイス研究会, Nov. 2022

  [Invited]

  Invited oral presentation


• 量子計算アルゴリズムを援用した強束縛近似法に基づく グラフェン状物質の電子状態解析手法の検討

  石橋拓也, 相馬聡文

  応用物理学会関西支部講演会, Nov. 2022

  Poster presentation


• ナノワイヤp-n接合構造におけるポアソン方程式の数値解法のためのゲート型量子コンピューティングアルゴリズムの提案

  松尾 信吾, 相馬 聡文

  2022年第83回応用物理学会秋季学術講演会, Sep. 2022

  Poster presentation


• 二次元半導体を用いたトンネル電界効果トランジスタのための低計算負荷シミュレーションモデルの開発及び回路シミュレーションとの連携

  山口 航輔、相馬 聡文

  2022年第83回応用物理学会秋季学術講演会, Sep. 2022

  Poster presentation


• A proposal of quantum computing algorithm to solve Poisson equation for nanoscale devices under Neumann boundary condition

  Shingo Matsuo, Satofumi Souma

  2022 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD2022), Sep. 2022, English

  Oral presentation


• Scattering matrix-based low computational cost model for the device and circuit co-simulation of phosphorene tunnel field-effect transistors

  Kosuke Yamaguchi, Satofumi Souma

  2022 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD2022), Sep. 2022, English

  Poster presentation


• Quamtum transport simulation-based design of synaptic FET and circuit simulation

  Satofumi Souma, Reon Oshio

  JSAP Silicon technology division 236th reseach meeting, Jul. 2022, Japanese

  Oral presentation


• A Study on the Potential of Improvisational Music Generation Based on Quantum Algorithms

  Satofumi Souma

  The 13th Annual Conference of the Japanese Association for the Study of Musical Improvisation, Jan. 2022, Japanese

  Oral presentation


• Exploring the Application of Gate-type Quantum Computational Algorithm for Music Creation and Performance

  Satofumi Souma

  1st International Symposium on Quantum Computing and Musical Creativity, Nov. 2021, English, International conference

  Oral presentation


• Development of device and circuit simulation framework based on phosphorene tunnel field-effect transistors

  Kosuke Yamaguchi, Satofumi Souma

  The 2021 International Meeting for Future of Electron Devices, Kansai, Nov. 2021, English

  Poster presentation


• Implementation of gate-type quantum computing algorithm to solve Poisson equation for semiconductor nanowire p-n junction

  Shingo Matsuo, Satofumi Souma

  The 2021 International Meeting for Future of Electron Devices, Kansai, Nov. 2021, English

  Poster presentation


• 非平衡グリーン関数法に基づくナノスケールデバイスシミュレーションの機械学習を用いた高速化

  相馬聡文

  電子情報通信学会シリコン材料・デバイス研究会, Nov. 2021, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• 量子コンピューティングアルゴリズムに基づく音楽作成手法の提案とアプリケーション開発

  相馬 聡文

  IPA 量子コンピューティング技術実践講座（ゲート式）, Nov. 2021, Japanese, Japan, Domestic conference

  [Invited]

  Invited oral presentation


• 光ゲート効果を用いたグラフェン光センサにおける電子‐ フォノン散乱の影響に関する理論解析

  相田 晋吾, 相馬 聡文

  応用物理学会関西支部 2021 年度 第 2 回講演会, Oct. 2021, Japanese

  Poster presentation


• ゲート式量子コンピューティングアルゴリズムを援用したナノスケールデバイスシミュレーション手法の検討

  松尾 信吾, 石橋 拓也, 相馬 聡文

  2021年 第82回応用物理学会秋季学術講演会, Sep. 2021, Japanese

  Poster presentation


• 二次元半導体をチャネル材料としたトンネル電界効果トランジスタの 電気伝導特性及び回路ミュレーション

  山口 航輔, 相馬 聡文

  2021年 第82回応用物理学会秋季学術講演会, Sep. 2021, Japanese

  Poster presentation


• 光ゲート効果を用いたグラフェン光センサのシミュレーション

  相田 晋吾, 相馬 聡文

  2021年 第82回応用物理学会秋季学術講演会, Sep. 2021

  Poster presentation


• フォスフォレンをチャネル材料としたトンネル電界効果トランジスタの電気伝導特性 シミュレーション

  山口 航輔, 相馬 聡文

  応用物理学会関西支部 2021 年度 第 1 回講演会, Apr. 2021, Japanese

  Poster presentation


• Application of deep neural network for the simulation of nanoscale FETs based on non-equilibrium Green's function method

  Satofumi Souma, Matsuto Ogawa

  The 8th Asian Conference on Crystal Growth and Crystal Technology, Mar. 2021, English

  Oral presentation


• Consideration of scattering process in nanoscale device simulation based on top of barrier model

  Ren Tanaka, Matsuto Ogawa, Satofumi Souma

  IEEE IMFEDK 2020 Satellite event for young researchers, Nov. 2020, English

  Poster presentation


• Simulation of graphene photodetectors incorporating the photo-gating effect

  Shingo Aida, Matsuto Ogawa, Satofumi Souma

  IEEE IMFEDK 2020 Satellite event for young researchers, Nov. 2020, English

  Poster presentation


• Tight-binding simulation of optical gain in h-BCN for laser application

  Daisuke Maki, Matsuto Ogawa, Satofumi Souma

  2020 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), Sep. 2020, English

  Poster presentation


• Transient simulation of graphene FET gated by electrolyte medium

  Koki Arihori, Matsuto Ogawa, Satofumi Souma, Junko Sato-Iwanaga, Masa-aki Suzuki

  020 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), Sep. 2020, English

  Oral presentation


• Application of convolutional neural network for nanoscale device simulations based on nonequilibrium Greens function method

  Satofumi Souma

  2020 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD). Workshop “Combination of TCAD and Machine Learning”, Sep. 2020, English

  [Invited]

  Invited oral presentation


• 電解質媒体をゲート制御に用いたグラフェンFETの過渡応答特性シミュレーション

  有堀 光貴, 岩永 順子, 鈴木 正明, 小川 真人, 相馬 聡文

  2020年第67回応用物理学会春季学術講演会, Mar. 2020, Japanese

  Poster presentation


• h-BCNを活性層に用いた半導体レーザーの光増幅利得における層数依存性に関する数値解析

  牧 大介, 小川 真人, 相馬 聡文

  2020年第67回応用物理学会春季学術講演会, Mar. 2020, Japanese

  Poster presentation


• 畳み込みニューラルネットワークを応用したナノスケールデバイスシミュレーションの高速化に関する検討

  相馬 聡文, 小川 真人

  2020年第67回応用物理学会春季学術講演会, Mar. 2020, Japanese

  Oral presentation


• Simulation of Graphene FET Gated by Ionic Liquid

  Koki Arihori, Matsuto Ogawa, Satofumi Souma, Junko Sato-Iwanaga

  International Meeting for Future of Electron Devices, Kansai (IMFEDK 2019), Nov. 2019, English

  Poster presentation


• Simulation of Optical Gain in Semiconductor Laser Structure with h-BCN Active Layer

  Daisuke Maki, Matsuto Ogawa, Satofumi Souma

  International Meeting for Future of Electron Devices, Kansai (IMFEDK 2019), Nov. 2019, English

  Poster presentation


• ナノスケールデバイスシミュレーションのための機械学習の応用に関する検討

  相馬 聡文, 有堀 光貴, 牧 大介, 小川 真人

  2019年第80回応用物理学会秋季学術講演会, Sep. 2019, Japanese

  Oral presentation


• h-BCNを活性層に用いた半導体レーザーの光増幅利得シミュレーション

  牧 大介, 小川 真人, 相馬 聡文

  応用物理学会関西支部2019年度第1回講演会, Jun. 2019

  Poster presentation


• イオン液体をゲート制御に用いたグラフェン FET の電気伝導特性シミュレーション

  有堀 光貴, 小川 真人, 相馬 聡文

  応用物理学会関西支部2019年度第1回講演会, Jun. 2019

  Poster presentation


• ナノスケールデバイスシミュレーションのための非平衡グリーン関数法と障壁高さモデルの比較検討

  SOUMA SATOFUMI, 岡 直左, 外田 祐也, 清水 良馬, OGAWA MATSUTO

  第66回応用物理学会春季学術講演会, Mar. 2018, Japanese, 東京, Domestic conference

  Poster presentation


• グラフェン状物質における光誘起電流のシミュレーション

  土井 信行, OGAWA MATSUTO, SOUMA SATOFUMI

  第65回応用物理学会春季学術講演会, Mar. 2018, Japanese, 東京, Domestic conference

  Poster presentation


• テラヘルツ素子応用に向けたグラフェンナノリボンの電磁波応答に関する数値シミュレーション

  石橋 純, SASAOKA KENJI, 山本 貴博, OGAWA MATSUTO, SOUMA SATOFUMI

  応用物理学会関西支部平成29年度第3回講演会, Nov. 2017, Japanese, 京都市, Domestic conference

  Poster presentation


• テラヘルツ素子応用に向けたグラフェンナノリボンFETの動的特性に関する数値シミュレーション

  中井 雄紀, SASAOKA KENJI, 山本 貴博, OGAWA MATSUTO, SOUMA SATOFUMI

  応用物理学会関西支部平成29年度第2回講演会, Nov. 2017, Japanese, 京都市, Domestic conference

  Poster presentation


• 二次元原子膜h-BCNをチャネルとしたFETにおける電気伝導特性の原子配置依存性

  生水出 浩斗, OGAWA MATSUTO, SOUMA SATOFUMI

  第78回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference

  Poster presentation


• 二次元原子膜h-BCNの光吸収特性における原子配置依存性

  栗原 健汰, 岡本 一希, OGAWA MATSUTO, SOUMA SATOFUMI

  第86回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference

  Poster presentation


• 光照射されたグラフェン状物質の電気伝導に関する理論解析

  土井 信行, OGAWA MATSUTO, SOUMA SATOFUMI

  第82回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference

  Poster presentation


• ポテンシャル制御の劣化度合いと量子トンネル電流の比較解析によるチャネル電子の有効方程式がFET特性に及ぼす影響の解明

  橋本 悠希, OGAWA MATSUTO, SOUMA SATOFUMI

  第80回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference

  Poster presentation


• シリケイン及びゲルマナンMOSFETのトンネル電流を考慮したバリスティック輸送特性

  岡 直左, OGAWA MATSUTO, SOUMA SATOFUMI

  第84回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference

  Poster presentation


• グラフェンとグラフェン状物質h-BCNの超格子構造の電気伝導特性シミュレーション

  石原 友也, OGAWA MATSUTO, SOUMA SATOFUMI

  第79回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference

  Poster presentation


• グラフェン/h-BCNへテロ超格子構造における長波長光吸収特性の理論解析による評価

  栗原 健汰, 岡本 一希, OGAWA MATSUTO, SOUMA SATOFUMI

  第85回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference

  Poster presentation


• Siナノワイヤ型FETの伝達特性における散乱に起因した1次元効果の重要性

  清水 良馬, OGAWA MATSUTO, SOUMA SATOFUMI

  第83回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference

  Poster presentation


• Black phosphorus FETの異方的電気伝導特性におけるトンネル効果の影響

  外田 祐也, OGAWA MATSUTO, SOUMA SATOFUMI

  第81回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference

  Poster presentation


• グラフェン状物質h-BCNの電気伝導特性シミュレーション

  生水出 浩斗, OGAWA MATSUTO, SOUMA SATOFUMI

  応用物理学会関西支部平成29年度第1回講演会, May 2017, Japanese, 姫路市, Domestic conference

  Poster presentation


• グラフェン状物質h-BCNの光吸収特性シミュレーション

  岡本一希, OGAWA MATSUTO, SOUMA SATOFUMI

  応用物理学会関西支部平成29年度第3回講演会, May 2017, Japanese, 姫路市, Domestic conference

  Poster presentation


• グラフェン/h-BCN超格子構造の電気伝導特性シミュレーション

  石原 友也, OGAWA MATSUTO, SOUMA SATOFUMI

  応用物理学会関西支部平成29年度第4回講演会, May 2017, Japanese, 姫路市, Domestic conference

  Poster presentation


• グラフェン/h-BCN超格子構造の光吸収特性シミュレーション

  栗原 健汰, OGAWA MATSUTO, SOUMA SATOFUMI

  応用物理学会関西支部平成29年度第2回講演会, May 2017, Japanese, 姫路市, Domestic conference

  Poster presentation


• 二次元原子膜を用いた光検出器に関する理論解析,第64回応用物理学会春季学術講演会

  土井 信行, 福富 惇一朗, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  第64回応用物理学会春季学術講演会, Mar. 2017, Japanese, 横浜市, Domestic conference

  Poster presentation


• 任意の方向に歪みが印加されたグラフェンの量子ダイナミクスシミュレーション

  名村 太希, 迫田 翔太郎, 笹岡 健二, OGAWA MATSUTO, SOUMA SATOFUMI

  第77回 応用物理学会秋季学術講演会,, Sep. 2016, Japanese, 新潟市, Domestic conference

  Poster presentation


• シリケイン及びゲルマナンMOSFETのバリスティック輸送特性の結晶方位依存性

  岡 直左, 兼古 志郎, SOUMA SATOFUMI, OGAWA MATSUTO

  第77回 応用物理学会秋季学術講演会,, Sep. 2016, Japanese, 新潟市, Domestic conference

  Poster presentation


• グラフェン状物質の面内ヘテロ構造を用いたFETの性能予測シミュレーション

  橋本 悠希, 市原 圭祐, 田中 未来, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  第77回 応用物理学会秋季学術講演会,, Sep. 2016, Japanese, 新潟市, Domestic conference

  Poster presentation


• グラフェンナノリボンの電子輸送特性に現れる過渡振動現象に関する理論的研究

  中井 雄紀, 石橋 純, 加藤 大喜, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  第77回 応用物理学会秋季学術講演会,, Sep. 2016, Japanese, 新潟市, Domestic conference

  Poster presentation


• Siナノワイヤ型ジャンクションレストランジスタの準バリスティック輸送特性の解析

  清水 良馬, 一居 雅人, SOUMA SATOFUMI, OGAWA MATSUTO

  第77回 応用物理学会秋季学術講演会,, Sep. 2016, Japanese, 新潟市, Domestic conference

  Poster presentation


• ,六方晶系BN基板上グラフェンの電子輸送特性, 第77回 応用物理学会秋季学術講演会

  外田 祐也, 平井 秀樹, SOUMA SATOFUMI, OGAWA MATSUTO

  第77回 応用物理学会秋季学術講演会,, Sep. 2016, Japanese, 新潟市, Domestic conference

  Poster presentation


• Computational study on the performance of locally strained graphene devices: transport and wave packet dynamics simulations

  Satofumi Souma, Kenji Sasaoka, Keisuke Ichihara, Shotaro Sakoda, Yuuki Hashimoto, Taiki Namura, Matsuto Ogawa

  19th International Conference on Superlattices, Nanostructures and Nanodevices,, Jul. 2016, English, Hong Kong, International conference

  [Invited]

  Poster presentation


• 歪み誘起擬似磁場を利用したグラフェンFETの制御における電子-フォノン散乱の影響

  SOUMA SATOFUMI, SASAOKA KENJI, OGAWA MATSUTO

  第63回応用物理学会春季学術講演会, Mar. 2016, Japanese, 東京工業大学大岡山キャンパス, Domestic conference

  Oral presentation


• 歪み印加されたグラフェンナノリボンの過渡電気伝導現象の数値解析

  加藤 大喜, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  第63回応用物理学会春季学術講演会, Mar. 2016, Japanese, 東京工業大学大岡山キャンパス, Domestic conference

  Poster presentation


• 歪みグラフェンp-n接合ダイオードの整流特性に関する量子輸送シミュレーション

  市原 圭祐, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  第63回応用物理学会春季学術講演会, Mar. 2016, Japanese, 東京工業大学大岡山キャンパス, Domestic conference

  Poster presentation


• グラフェンの歪み/無歪み遷移領域におけるガウス波束の伝播に関する量子ダイナミクスシミュレーション

  迫田 翔太郎, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  第63回応用物理学会春季学術講演会, Mar. 2016, Japanese, 東京工業大学大岡山キャンパス, Domestic conference

  Poster presentation


• ディラック電子をキャリアとする電界効果トランジスタのスイッチング性能に関する理論解析

  田中未来, 笹岡健二, 小川真人, SOUMA SATOFUMI

  第76回応用物理学会秋季学術講演会, Feb. 2016, Japanese, 大阪府立大学中百舌鳥キャンパス, Domestic conference

  Poster presentation


• 歪みグラフェンを用いたディラック電子エンジニアリング素子のシミュレーション

  SOUMA SATOFUMI, 田中 未来, 市原 圭祐, 迫田 翔太郎, SASAOKA KENJI, OGAWA MATSUTO

  シリコン材料・デバイス研究会（SDM） プロセス・デバイス・回路シミュレーションおよび一般, Nov. 2015, Japanese, 機械振興会館 （東京）, Domestic conference

  [Invited]

  Invited oral presentation


• 歪みグラフェンp-n接合の電気伝導特性に関する量子輸送シミュレーション

  市原 圭祐, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  第76回応用物理学会秋季学術講演会, Sep. 2015, Japanese, 名古屋国際会議場, Domestic conference

  Poster presentation


• 時間依存波束伝播法を用いた歪みグラフェンの量子ダイナミクスシミュレーション

  迫田 翔太郎, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  第76回応用物理学会秋季学術講演会, Sep. 2015, Japanese, 名古屋国際会議場, Domestic conference

  Oral presentation


• 開放系シュレーディンガー方程式を用いた歪みアームチェア型グラフェンナノリボンの時間依存電気伝導特性の解析

  加藤 大喜, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  第76回応用物理学会秋季学術講演会, Sep. 2015, Japanese, 名古屋国際会議場, Domestic conference

  Oral presentation


• グラフェン状物質をチャネル材料とする電界効果型トランジスタのシミュレーション

  SOUMA SATOFUMI

  鳥取大学物質科学研究会 次世代デバイスと先端シミュレーション, Jan. 2015, Japanese, 鳥取市, Domestic conference

  Public discourse


• 歪み誘起疑似磁場を利用したグラフェンFET のスイッチング性能に関する理論解析

  上山 真之, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  応用物理学会関西支部平成26 年度第２回講演会, Nov. 2014, Japanese, 神戸市, Domestic conference

  Poster presentation


• Photoconductivity-based strain sensing in graphene

  MEHDIPOUR Amir, SASAOKA Kenji, OGAWA Matsuto, SOUMA Satofumi

  International Symposium on Recent Progress of Photonic Devices and Material, Nov. 2014, English, 神戸市, International conference

  Poster presentation


• 歪み誘起疑似磁場を利用したグラフェンFET の準解析的モデル提案

  上山 真之, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  ミニワークショップ 計算科学アプローチによるナノエレクトロニクス研究, Oct. 2014, Japanese, 東京, Domestic conference

  Public discourse


• 擬似磁場効果を利用した歪みグラフェンFET の電流制御機構における構造乱れの影響

  堤 賢一郎, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  ミニワークショップ 計算科学アプローチによるナノエレクトロニクス研究, Oct. 2014, Japanese, 東京, Domestic conference

  Public discourse


• ディラック電子をキャリアとする電界効果型トランジスタのスイッチング特性に関する理論

  田中 未来, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  ミニワークショップ 計算科学アプローチによるナノエレクトロニクス研究, Oct. 2014, Japanese, 東京, Domestic conference

  Public discourse


• ディラック電子とシュレディンガー電子をキャリアとするFET の性能比較シミュレーション

  田中 未来, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  応用物理学会関西支部平成26 年度第２回講演会, Oct. 2014, Japanese, 神戸市, Domestic conference

  Poster presentation


• 歪み誘起擬似磁場を利用したグラフェンＦＥＴの スイッチング機構における構造乱れの影響

  堤 賢一郎, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  第77回応用物理学会秋季学術講演会, Sep. 2014, Japanese, 札幌市, Domestic conference

  Poster presentation


• 複雑な断面形状を持つSi NWMOSFETにおける量子輸送シミュレーション

  森本 剛司, SASAOKA KENJI, SOUMA SATOFUMI, OGAWA MATSUTO

  第79回応用物理学会秋季学術講演会, Sep. 2014, Japanese, 札幌市, Domestic conference

  Poster presentation


• 結合量子ドット構造の光学吸収特性のドット形状依存性

  武藤 庸平, SASAOKA KENJI, SOUMA SATOFUMI, OGAWA MATSUTO

  第78回応用物理学会秋季学術講演会, Sep. 2014, Japanese, 札幌市, Domestic conference

  Poster presentation


• 擬似磁場効果を利用した歪みグラフェンFETの準解析的モデル提案

  上山 真之, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  第76回応用物理学会秋季学術講演会, Sep. 2014, Japanese, 札幌市, Domestic conference

  Poster presentation


• ディラック電子をキャリアとするFETの性能予測シミュレーション

  田中 未来, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  第75回応用物理学会秋季学術講演会, Sep. 2014, Japanese, 札幌市, Domestic conference

  Poster presentation


• サブ60mV/decadeスイッチングを実現する異なるFETゲート制御機構のシミュレーションによる比較解析

  石田 智也, 福嶋 賢介, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  第80回応用物理学会秋季学術講演会, Sep. 2014, Japanese, 札幌市, Domestic conference

  Poster presentation


• Numerical simulation of current noise caused by potential fluctuation in nanowire FET with an oxide trap

  FURUBAYASHI Yuki, OGAWA Matsuto, SOUMA Satofumi

  International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), 2014, Sep. 2014, English, 横浜市, International conference

  [Invited]

  Poster presentation


• グラフェンを材料とする新規素子の提案とシミュレーション

  SOUMA SATOFUMI

  東京理科大学セミナー講演, Jun. 2014, Japanese, 東京, Domestic conference

  Public discourse


• 28pPSA-72 Transient response simulations of scattering states under time-dependent gate voltage

  Sasaoka Kenji, Kato Kazuma, Souma Satofumi, Ogawa Matsuto

  Meeting abstracts of the Physical Society of Japan, Mar. 2014, Japanese, The Physical Society of Japan (JPS)


• 時間依存ゲート電圧による散乱状態の過渡応答シミュレーション

  SASAOKA KENJI, Kazuma Kato, Satofumi Souma, Matsuto Ogawa

  日本物理学会, Mar. 2014, Japanese, Domestic conference

  Poster presentation


• Numerical Simulations for Time-evolving Electronic States in a Nanoscale System with and without Wide Band Limit Approximation

  SASAOKA KENJI, Kazuma Kato, SOUMA SATOFUMI, OGAWA MATSUTO

  International Workshop on Eigenvalue Problems: Algorithms; Software and Applications, in Petascale Computing (EPASA2014), Mar. 2014, English, Tsukuba, Kenji Sasaoka, Kazuma Kato, Satofumi Souma, and Matsuto Ogawa, International conference

  Poster presentation


• 歪み印加を利用したグラフェンの電気伝導制御に関する数値シミュレーション

  SOUMA SATOFUMI, 上山 真之, OGAWA MATSUTO

  第74回応用物理学会秋季学術講演会, Sep. 2013, Japanese, 京田辺市, Domestic conference

  Oral presentation


• 有限要素法を用いたInAs/GaAs量子ドット太陽電池の特性解析

  益原 貴志, Amir Mehdipour, SOUMA SATOFUMI, OGAWA MATSUTO

  第74回応用物理学会秋季学術講演会, Sep. 2013, English, 京田辺市, Domestic conference

  Poster presentation


• 半導体ナノワイヤFETにおけるポテンシャルゆらぎに起因する電流ノイズの数値シミュレーション

  古林 優希, OGAWA MATSUTO, SOUMA SATOFUMI

  第74回応用物理学会秋季学術講演会, Sep. 2013, Japanese, 京田辺市, Domestic conference

  Oral presentation


• 多バンド有効質量近似法を用いたトンネル電界効果トランジスタの数値シミュレーション

  永井 寛人, OGAWA MATSUTO, SOUMA SATOFUMI

  第74回応用物理学会秋季学術講演会, Sep. 2013, Japanese, 京田辺市, Domestic conference

  Poster presentation


• モード結合スペクトル法を用いた量子輸送解析の高速・高精度化に関する研究

  藤川 広樹, SOUMA SATOFUMI, OGAWA MATSUTO

  第74回応用物理学会秋季学術講演会, Sep. 2013, Japanese, 京田辺市, Domestic conference

  Poster presentation


• グラフェンの熱物性における面内歪みの影響

  船谷 宜嗣, 山本 貴博, OGAWA MATSUTO, SOUMA SATOFUMI

  日本物理学会 2013年秋季大会, Sep. 2013, Japanese, 徳島市, Domestic conference

  Oral presentation


• グラフェンにおける歪みの空間的変化を利用したFETの性能に関する研究

  上山 真之, OGAWA MATSUTO, SOUMA SATOFUMI

  第74回応用物理学会秋季学術講演会, Sep. 2013, Japanese, 京田辺市, Domestic conference

  Poster presentation


• Wave-packet dynamics study of electronic transport in graphene irradiated by circularly polarized light

  AKIYAMA Takashi, SASAOKA Kenji, OGAWA Matsuto, SOUMA Satofumi

  5th International Conference on Recent Progress in Graphene Research, Sep. 2013, English, 東京, International conference

  [Invited]

  Poster presentation


• Effect of lateral strain on electronic transport in graphene: interplay between band gap formation and pseudo magnetic field effect

  SOUMA Satofumi, UEYAMA Masayuki, OGAWA Matsuto

  5th International Conference on Recent Progress in Graphene Research, Sep. 2013, English, 東京, Domestic conference

  [Invited]

  Oral presentation


• Effect of in-plane strain on thermal properties of graphene

  FUNATANI Takashi, YAMAMOTO Takahiro, SASAOKA Kenji, OGAWA Matsuto, SOUMA Satofumi

  5th International Conference on Recent Progress in Graphene Research, Sep. 2013, English, 東京, International conference

  [Invited]

  Poster presentation


• Effect of in-plane strain on thermal properties of graphene

  Takashi Funatani, Takahiro Yamamoto, SASAOKA KENJI, OGAWA MATSUTO, SOUMA SATOFUMI

  5th International Conference on Recent Progress in Graphene Research (RPGR2013), Sep. 2013, English, Tokyo, Takashi Funatani, Takahiro Yamamoto, Kenji Sasaoka, Matsuto Ogawa, Satofumi Souma, International conference

  Poster presentation


• グラフェンをチャネル材料とする電界効果型トランジスタの性能評価シミュレーション

  SOUMA SATOFUMI

  第３回フラーレン・ナノチューブ・グラフェン若手研究会, Aug. 2013, Japanese, 吹田市, Domestic conference

  [Invited]

  Invited oral presentation


• 強結合分子動力学法を用いたグラフェンナノリボンの機械的変形と電子状態に関するシミュレーション

  SOUMA SATOFUMI

  応用物理学会シリコンテクノロジー「大規模・高速・原子レベル計算が可能にする新規モデリング技術」研究会, Jul. 2013, Japanese, 東京, International conference

  [Invited]

  Oral presentation


• グラフェンを材料とする新規機能素子デザインとシミュレーション

  SOUMA SATOFUMI

  ワークショップ「機能性ナノ材料開発に役立つ先端シミュレーション」, Jun. 2013, Japanese, 東京, Domestic conference

  [Invited]

  Invited oral presentation


• Quantum Dynamical Simulation of Photo-Induced Graphene Switch

  AKIYAMA Takashi, OGAWA Matsuto, SOUMA Satofumi

  International Workshop on Computational Electronics 2013, Jun. 2013, English, 奈良市, International conference

  [Invited]

  Poster presentation


• Effect of Axial Strain on Switching Behavior of Carbon Nanotube Tunneling Field Effect Transistors

  NAKANO Takashi, NAGAI Hiroto, OGAWA Matsuto, SOUMA Satofumi

  International Workshop on Computational Electronics 2013, Jun. 2013, English, 奈良市, International conference

  [Invited]

  Poster presentation


• 28pPSA-5 Numerical analysis of current noise caused by potential fluctuation in semiconductor nanowires II

  Furubayashi Y., Ogawa M., Souma S.

  Meeting abstracts of the Physical Society of Japan, Mar. 2013, Japanese, The Physical Society of Japan (JPS)


• 歪み印加グラフェンの電気伝導に関する数値シミュレーション

  SOUMA SATOFUMI, 上山 真之, 西村 英之, 秋山 隆志, OGAWA MATSUTO

  日本物理学会第６８回年次大会, Mar. 2013, Japanese, 東広島市, Domestic conference

  Oral presentation


• 半導体ナノワイヤ構造におけるポテンシャルゆらぎに起因する電流雑音の数値解析II

  古林 優希, OGAWA MATSUTO, SOUMA SATOFUMI

  日本物理学会第６８回年次大会, Mar. 2013, Japanese, 東広島市, Domestic conference

  Poster presentation


• 多バンド有効質量近似法に基づくトンネル電界効果 トランジスタの特性解析

  永井 寛人, 中野 貴史, 三好 泰諒, OGAWA MATSUTO, SOUMA SATOFUMI

  第６０回応用物理学会春季学術講演会, Mar. 2013, Japanese, 厚木市, Domestic conference

  Poster presentation


• レーザー光を照射したグラフェンの電子状態及び電子透過特性に関する理論的研究

  秋山 剛志, OGAWA MATSUTO, SOUMA SATOFUMI

  第６０回応用物理学会春季学術講演会, Mar. 2013, Japanese, 厚木市, Domestic conference

  Poster presentation


• グラフェンの機械的変形が熱物性に与える影響

  船谷 宜嗣, 山本 貴博, OGAWA MATSUTO, SOUMA SATOFUMI

  日本物理学会第６８回年次大会, Mar. 2013, Japanese, 東広島市, Domestic conference

  Poster presentation


• Spin blocking effect in symmetric double quantum well due to Rashba spin-orbit coupling

  SOUMA Satofumi, OGAWA Matsuto, SEKINE Yoshiaki, SAWADA Atsushi, KOGA Takaaki

  2013 American Physical Society March Meeting, Mar. 2013, English, Baltimore, USA, Domestic conference

  Oral presentation


• Spin blocking effect in InGaAs/InAlAs double quantum wells due to Rashba spin-orbit coupling

  SOUMA Satofumi, OGAWA Matsuto, SEKINE Yoshiaki, SUGIYAMA Hiroki, YOKOTA Shoichiro, KOGA Takaaki

  第６０回応用物理学会春季学術講演会, Mar. 2013, Japanese, 厚木市, Domestic conference

  Oral presentation


• 半導体ナノワイヤ構造におけるポテンシャルゆらぎに起因する電流雑音の数値解析

  古林 優希, OGAWA MATSUTO, SOUMA SATOFUMI

  日本物理学会2012年秋季大会, Sep. 2012, Japanese, 横浜市, Domestic conference

  Poster presentation


• 軸方向引張歪みを加えたCNTトンネル電界効果トランジスタの特性解析

  中野 貴史, OGAWA MATSUTO, SOUMA SATOFUMI

  第７３回応用物理学会学術講演会, Sep. 2012, Japanese, 松山市, Domestic conference

  Oral presentation


• A Theoretical Study of an Influence of a Time Dependent External Field on Electronic Transport in Graphene

  秋山 剛志, OGAWA MATSUTO, SOUMA SATOFUMI

  第７３回応用物理学会学術講演会, Sep. 2012, English, 松山市, Domestic conference

  Oral presentation


• 19aAF-9 Charge and thermal transport in superconductor/ferromagnetic-insulator/normal-metal junctions

  Nakamura S., Souma S., Ogawa M., Vasenko Andery S., Kawabata S.

  Meeting abstracts of the Physical Society of Japan, Aug. 2012, Japanese, The Physical Society of Japan (JPS)


• 20pPSA-7 Numerical analysis of current noise caused by potential fluctuation in semiconductor nanowires

  Kobayashi Y., Ogawa M., Souma S.

  Meeting abstracts of the Physical Society of Japan, Aug. 2012, Japanese, The Physical Society of Japan (JPS)


• InAs/GaAs quantum dot arrayed-base intermediate band solar cell with multiple intermediate bands

  MEHDIPOUR Amir, OGAWA Matsuto, SOUMA Satofumi

  31st International Conference on the Physics of Semiconductors, Aug. 2012, English, Zurich, Switzerland, International conference

  [Invited]

  Poster presentation


• Atomistic Origin of Rashba and Dresselhaus Spin-Orbit Couplings in Narrow Gap Semiconductor Quantum Wells

  SOUMA Satofumi, OGAWA Matsuto

  31st International Conference on the Physics of Semiconductors, Aug. 2012, English, Zurich, Switzerland, International conference

  [Invited]

  Poster presentation


• Effect of Lateral Strain on the Performance of Single Layer Graphene Field Effect Transistors

  SOUMA Satofumi, OHMI Yusuke, OGAWA Matsuto

  International Conference on Superlattices, Nanostructures, and Nanodevices, Jul. 2012, English, Dresden, Germany, International conference

  [Invited]

  Poster presentation


• 26pPSB-61 Effect of axial strain on electronic transport in carbon nanotube tunneling field effect transistors

  Nakano Takashi, Ogawa Matsuto, Souma Satofumi

  Meeting abstracts of the Physical Society of Japan, Mar. 2012, Japanese, The Physical Society of Japan (JPS)


• 25aBC-6 Theory of Josepshon π-junction using a ferromagnetic insulator

  Nakamura S., Souma S., Ogawa M., Kawabata S.

  Meeting abstracts of the Physical Society of Japan, Mar. 2012, Japanese, The Physical Society of Japan (JPS)


• 27aSB-3 Numerical simulation of spin pumping effect in graphene nanoribbons

  Souma S., Ogawa M.

  Meeting abstracts of the Physical Society of Japan, Mar. 2012, Japanese, The Physical Society of Japan (JPS)


• 強磁性絶縁体を用いたジョセフソンπ接合の理論

  中村 周平, 相馬 聡文, 小川 真人, 川畑 史郎

  日本物理学会 第67回年次大会, Mar. 2012, Japanese, 日本物理学会, 兵庫県西宮市, Domestic conference

  Oral presentation


• グラフェンの電気伝導におけるレーザー光照射の効果に関する量子ダイナミクスシミュレーション

  坂本 理朗, 小川 真人, 相馬 聡文

  日本物理学会 第67回年次大会, Mar. 2012, Japanese, 日本物理学会, 兵庫県西宮市, Domestic conference

  Oral presentation


• グラフェンナノリボンにおけるスピンポンプ効果に関するシミュレーション

  相馬 聡文, 小川 真人

  日本物理学会 第67回年次大会, Mar. 2012, Japanese, 日本物理学会, 兵庫県西宮市, Domestic conference

  Oral presentation


• カーボンナノチューブを用いたトンネル電界効果トランジスタの特性における歪みの影響

  中野 貴史, 小川 真人, 相馬 聡文

  日本物理学会 第67回年次大会, Mar. 2012, Japanese, 日本物理学会, 兵庫県西宮市, Domestic conference

  Poster presentation


• Si, InAs, InAs/SiナノワイヤトンネルFETにおけるバンド間トンネリング特性の比較

  三好 泰諒, 小川 真人, 相馬 聡文, 中村 肇

  第59回応用物理学関係連合講演会, Mar. 2012, Japanese, 応用物理学会, 東京, Domestic conference

  Oral presentation


• Efficiency Estimation of Intermediate Band Solar Cells Based on InAs/GaAs Quantum Dot Arrays

  MEHEDIPOUR Amir, OGAWA Matsuto, SOUMA Satofumi

  Workshop on Innovation and Pioneering Technolo-gy 2011 (WINPTech2011), Dec. 2011, English, International conference

  Poster presentation


• Effect of axial strain on electronic transport in carbon nanotube tunneling field effect transistors

  NAKANO Takashi, OGAWA Matsuto, SOUMA Satofumi

  Workshop on Innovation and Pioneering Technolo-gy 2011 (WINPTech2011), Dec. 2011, English, International conference

  Poster presentation


• 強磁性絶縁体を用いたジョセフソンπ接合の理論

  中村 周平, 相馬 聡文, 小川 真人, 川畑 史郎

  第25回量子情報技術研究会 (QIT25), Nov. 2011, Japanese, Domestic conference

  Poster presentation


• 歪積層量子ドット構造の電子状態解析

  森垣亮祐, 相馬 聡文, 小川 真人

  第72回応用物理学会学術講演会, Sep. 2011, Japanese, 応用物理学会, Domestic conference

  Oral presentation


• 結合量子ドットを用いた電荷量子ビット制御における格子振動の影響

  斉藤 守由, 小川 真人, 相馬 聡文

  日本物理学会2011年秋季大会, Sep. 2011, Japanese, 日本物理学会, Domestic conference

  Poster presentation


• レーザー光を用いたグラフェンの電気伝導制御に関するシミュレーション

  坂本 理朗, 小川 真人, 相馬 聡文

  日本物理学会2011年秋季大会, Sep. 2011, Japanese, 日本物理学会, Domestic conference

  Poster presentation


• グラフェンナノリボンの電気伝導における引っ張り歪みと外部電界の効果

  貝野 昭造, 小川 真人, 相馬 聡文

  日本物理学会2011年秋季大会, Sep. 2011, Japanese, 日本物理学会, Domestic conference

  Poster presentation


• グラフェンFETの特性における面内歪みの影響

  近江 裕輔, 小川 真人, 相馬 聡文

  日本物理学会2011年秋季大会, Sep. 2011, Japanese, 日本物理学会, Domestic conference

  Poster presentation


• InGaAs二重量子井戸系におけるスピンフィルタ

  向井 肇, 小川 真人, 相馬 聡文, 松浦 徹, 関根 佳明, 古賀 貴亮

  日本物理学会2011年秋季大会, Sep. 2011, Japanese, 日本物理学会, Domestic conference

  Oral presentation


• InGaAs二重量子井戸系でのスピン分離とスピンフィルタ効果

  松浦 徹, 峰重 俊介, 相馬 聡文, 関根 佳明, 古賀 貴亮

  日本物理学会2011年秋季大会, Sep. 2011, Japanese, 日本物理学会, Domestic conference

  Oral presentation


• InAs/Siヘテロ接合ナノワイヤを用いたバンド間トンネルトランジスタの電流特性解析

  三好 泰諒, 小川 真人, 相馬 聡文, 中村 肇

  第72回応用物理学会学術講演会, Sep. 2011, Japanese, 応用物理学会, Domestic conference

  Oral presentation


• Bridge-Function Pseudospectral Method for Quantum Mechanical Simulation of Nano-Scaled Devices

  SAITO Yuta, SOUMA Satofumi, OGAWA Matsuto

  2011 Int. Conf. on Simu-lation of Semiconductor Processes and Devices, Sep. 2011, English, International conference

  [Invited]

  Oral presentation


• Analysis of geometrical sutructure and transport property in InAs/Si heterojunction nanowire tunneling field effect transistors

  MIYOSHI Yasuaki, OGAWA Matsuto, SOUMA Satofumi, NAKAMURA Hajime

  2011 Int. Conf. on Simu-lation of Semiconductor Processes and Devices, Sep. 2011, English, International conference

  [Invited]

  Poster presentation


• Tight binding modeling of intermediate band solar cells based on InAs/GaAs quantum dot arrays

  MEHEDIPOUR Amir, OGAWA Matsuto, SOUMA Satofumi

  2011 Int. Meetingfor Future of Electron Devices, Kansai, May 2011, English, International conference

  [Invited]

  Poster presentation


• Effect of uniaxial strain on the electronic Transport in single layer graphene

  OHMI Yusuke, OGAWA Matsuto, SOUMA Satofumi

  2011 Int. Meetingfor Future of Electron Devices, Kansai, May 2011, English, International conference

  [Invited]

  Poster presentation


• Analysis of electronic structure in quantum dot arrays for intermediate band solar cells

  KUROME AKITO, MORIGAKI Ryosuke, SOUMA Satofumi, OGAWA Matsuto

  2011 Int. Meetingfor Future of Electron Devices, Kansai, May 2011, English, International conference

  [Invited]

  Poster presentation


• 強束縛近似法による Si ナノワイヤの電子状態解析(II) -終端方法の影響-

  MATSUDA Kouji, SOUMA Satofumi, OGAWA Matsuto

  第57回, Mar. 2010, Japanese, 応用物理学会, 神奈川県平塚市, Domestic conference

  Poster presentation


• グラフェントランジスタの輸送特性におけるグラフェン/金属接合の影響

  SOUMA Satofumi, OGAWA Matsuto, YAMAMOTO Takahiro, WATANABE Kazuyuki

  日本物理学会・第65回年次大会, Mar. 2010, Japanese, 日本物理学会, 岡山, Domestic conference

  Poster presentation


• Computational study of molecular vibration and electronic transport in single molecule devices

  MORIHARA Akihiro, OGAWA Matsuto, SOUMA Satofumi

  WINP Tech 2009, Dec. 2009, English, 神戸大学, kobe, International conference

  Poster presentation


• 2D Quantum Mechanical Simulation of Gate-Leakage Current in Double-Gate n-MOSFETs

  MURAOKA Satoru, MUKAI Ryota, OGAWA Matsuto, SOUMA Satofumi

  International Conference on Simulation of Semiconductor Processes and Devices, Sep. 2009, English, IEEE, San Diego, USA, International conference

  [Invited]

  Poster presentation


• Spin-polarization in InAs/AlSb double barrier resonant tunneling structures:

  SOUMA Satofumi, OGAWA Matsuto

  14th International Conference on Narrow Gap Semiconductor and Systems, Jul. 2009, English, 仙台, International conference

  [Invited]

  Oral presentation


• Effect of interface structure on current spin-polarization in narrow gap

  SOUMA Satofumi, OGAWA Matsuto

  14th International Conference on Modulated Semiconductor Structures, Jul. 2009, English, 神戸, International conference

  [Invited]

  Poster presentation


• Simulation of Graphene Nanoribbon Spin-Filter Device with Spin-Density Functional

  SOUMA Satofumi, OGAWA Matsuto, YAMAMOTO Takahiro, WATANABE Kazuyuki

  13th International Workshop on Computational Electronics, May 2009, English, IEEE, Beijing, China, International conference

  [Invited]

  Oral presentation


• Influence of Geometrical Deformation on Transport Characteristics

  MOURI, Masaaki, OGAWA Matsuto, SOUMA Satofumi

  International Meeting for Future of Electron Devices, Kansai, May 2009, English, IEEE, 大阪, International conference

  [Invited]

  Poster presentation


• Influence of Edge Roughness on the Performance of Graphene Nano-Ribbon Devices

  SOUMA Satofumi, OGAWA Matsuto, YAMAMOTO Takahiro, WATANABE Kazuyuki

  International Meeting for Future of Electron Devices, Kansai, May 2009, English, IEEE, 大阪, International conference

  [Invited]

  Oral presentation


• Analysis of the Electronic Structures in Silicon Nano-Structures by

  MATSUDA, Kouji, OGAWA Matsuto, SOUMA Satofumi

  International Meeting for Future of Electron Devices, Kansai, May 2009, English, IEEE, 大阪, International conference

  [Invited]

  Poster presentation


• 強束縛近似法によるSi ナノワイヤにおける電子状態解析

  MATSUDA Kouj, SOUMA Satofumi, OGAWA Matsuto

  第56回, Apr. 2009, Japanese, 応用物理学会, つくば, Domestic conference

  Oral presentation


• カーボンナノチューブにおける圧力の輸送特性への影響

  MOURI, Masaaki, OGAWA Matsuto, SOUMA Satofumi

  第56回, Apr. 2009, Japanese, 応用物理学会, つくば, Domestic conference

  Oral presentation


• ナノグラフェン素子における電流のスピン偏極制御に関する理論解析

  SOUMA Satofumi, OGAWA Mtsuto, YAMAMOTO Takahiro, WATANABE Kazuyuki

  第56回, Mar. 2009, Japanese, 応用物理学会, 筑波, Domestic conference

  Oral presentation


• Spin Dependent Transport in Graphene Nano Ribbon Devices

  SOUMA Satofumi, OGAWA Matsuto, YAMAMOTO Takahiro, WATANABE Kazuyuki

  American Physical, Nov. 2008, English, AmericanPhysical Society, Pittsburgh, USA, International conference

  Poster presentation


• Computational modeling of graphene nano-ribbon spin devices based on spin-density-functional tight-binding method

  SOUMA Satofumi, OGAWA Matsuto, YAMAMOTO Takahiro, WATANABE Kazuyuki

  Int. Symposium on, Nov. 2008, English, 会津若松, International conference

  [Invited]

  Oral presentation


• Analysis of Direct Tunneling Current from Quasi-Bound States in n-MOSFET Based on

  MURAOKA Satoru, SOUMA Satofumi, OGAWA Matsuto

  2008 International, Nov. 2008, English, 箱根, International conference

  [Invited]

  Poster presentation


• グラフェンナノリボン素子におけるスピン輸送に関する理論解析

  SOUMA Satofumi, OGAWA Mtsuto, YAMAMOTO Takahiro, WATANABE Kazuyuki

  日本物理学会, Sep. 2008, Japanese, 日本物理学会, 盛岡, Domestic conference

  Poster presentation


• Si ナノMOSFET中の量子輸送解析に関する研究

  OKAZAKI Hitoshi, SOUMA Satofumi, OGAWA Matsuto

  第69回応用物理学会学術講演会, Sep. 2008, Japanese, 応用物理学会, 名古屋, Domestic conference

  Poster presentation


• Calculation of strain effecs on the I-V characteristics of ultra small MOSFETs based on NEGF approach

  FITRIAWAN Helmy, SOUMA Satofumi, OGAWA Matsuto

  2008 Int. Conf. on, Sep. 2008, English, 筑波, Domestic conference

  [Invited]

  Poster presentation


• グラフェンナノリボンを用いた新規デバイスの提案とシミュレーション

  SOUMA Satofumi, OGAWA Mtsuto, YAMAMOTO Takahiro, WATANABE Kazuyuki

  応用物理学会シリコンテクノロジー分科会モデリング研究会「シリコンCMOSを超える, Jul. 2008, Japanese, 応用物理学, 東京, Domestic conference

  [Invited]

  Invited oral presentation


• グラフェンナノリボンFETの数値シミュレーション

  SOUMA Satofumi, OGAWA Mtsuto, YAMAMOTO Takahiro, WATANABE Kazuyuki

  電気学会「超集積化・環境CMOSデバイス調査専門委員会」, Jul. 2008, Japanese, 電気学会, 東京, Domestic conference

  [Invited]

  Invited oral presentation


• 狭ギャップ半導体共鳴トンネル素子のスピン依存伝導における界面構造の影響

  SOUMA Satofumi, OGAWA Mtsuto

  日本物理学会, Mar. 2008, Japanese, 日本物理学会, 東京, Domestic conference

  Oral presentation


• ナノグラフェン素子における量子輸送シミュレーション

  相馬 聡文, 小川 真人, 山本 貴博, 渡辺 一之

  第55回応用物理学関係連合講演会, Mar. 2008, Japanese, 船橋市, Domestic conference

  Oral presentation


• カーボンナノチューブの輸送特性における圧力と格子欠陥の効果

  MOURI Masaaki, OGAWA Matsuto, SOUMA Satofumi

  日本物理学会, Mar. 2008, Japanese, 日本物理学会, 東京, Domestic conference

  Poster presentation


• Si ナノMOSFETにおけるフォノン散乱現象の解析

  フィトリアワン ヘルミー, 今後 博, 相馬 聡文, 小川 真人

  第55回応用物理学関係連合講演会, Mar. 2008, English, 船橋市, Domestic conference

  Oral presentation


• 歪Si結晶の強束縛近似法による電子状態解析に関する研究

  小原 朋子, 相馬 聡文, 小川 真人

  電気関係学会関西支部 連合大会, Nov. 2007, Japanese, 神戸市, Domestic conference

  Oral presentation


• Numerical simulation of the electronic transport in graphene nano-ribbon devices

  M. Ogawa, Satofumi Souma

  12th International Workshop on Computational Electronics, Oct. 2007, English, IEEE, Amherst. Mass, International conference

  [Invited]

  Oral presentation


• Numerical simulation of the electronic transport in graphene nano-ribbon devices

  SOUMA Satofumi, OGAWA Matsuto, YAMAMOTO Takahiro, WATANABE Kazuyuki

  12th International Workshop on Computa- tional Electronics, Oct. 2007, English, Massachusetts/USA, International conference

  [Invited]

  Oral presentation


• Fullband Green’s function study for quantum electron transport in strained silicon n-MOEFETs

  FITRIAWAN Helmy, SOUMA Satofumi, OGAWA Matsuto

  12th International Workshop on Computa- tional Electronics, Oct. 2007, English, Massachusetts/USA, International conference

  [Invited]

  Poster presentation


• グラフェンナノリボン素子のトランジスタ特性に 関する理論的研究

  相馬 聡文, 小川 真人, 山本 貴博, 渡辺 一之

  日本物理学会2007年次 大会, Sep. 2007, Japanese, 北海道, Domestic conference

  Oral presentation


• Quantum electron transport modeling in strained MOSFETs based on multiband non-equilibrium

  FITRIAWAN Helmy, SOUMA Satofumi, OGAWA Matsuto

  第68回応用物理学会学術講演会, Sep. 2007, English, 北海道, Domestic conference

  Oral presentation


• CNTへのドーピングによる電子状態変化の解析

  前田 琢磨, 相馬 聡文, 小川 真人

  第68回応用物理学会学術講演会, Sep. 2007, Japanese, 北海道, Domestic conference

  Oral presentation


• Numerical study of electronic states in silicon thin films based on empirical tight-binding approach

  ONISHI Kensuke, SOUMA Satofumi, OGAWA Matsuto

  Frontiers in Computational Science of Nanoscale Trans- port in conjunction with Atomistic Workshop 2007, Jun. 2007, English, Tokyo Univ of Science, 東京, International conference

  [Invited]

  Poster presentation


• Electronic structure of substitutional impurity in carbon nanotubes based on a first principle calculation

  Maeda Takuma, SOUMA Satofumi, OGAWA Matsuto

  Frontiers in Computational Science of Nanoscale Trans- port in conjunction with Atomistic Workshop 2007, Jun. 2007, English, Tokyo Univ of Science, 東京, International conference

  [Invited]

  Poster presentation


• Current-voltage chatacteristics and local current distribution in graphene-nano-ribbon devices

  SOUMA Satofumi, OGAWA Matsuto, YAMAMOTO Takahiro, WATANABE Kazuyuki

  Frontiers in Computational Science of Nanoscale Trans- port in conjunction with Atomistic Workshop 2007, Jun. 2007, English, Tokyo Univ of Science, 東京, International conference

  [Invited]

  Poster presentation


• Atomistic simulation of spin-polarized electronic current in resonant tunneling heterostructures

  SOUMA Satofumi, OGAWA Matsuto

  4th International School andConference on Spintronics and Quantum Information Technology (Spintech IV), Jun. 2007, English, Hawaii/USA, International conference

  [Invited]

  Poster presentation


• グラファイトリボンの電気伝導におけるゲート電極の効果

  相馬 聡文, 小川 真人, 山本 貴博, 渡辺 一之

  日本物理学会2007年春季大会, Mar. 2007, Japanese, 鹿児島大学, Domestic conference

  Poster presentation


• Quantum Electron Transport Modeling in Nano-Scale Devices Based on Multiband Non-Equilibrium Green's Funtion Method

  FITRIAWAN Helmy, OGAWA Matsuto, SOUMA Satofumi, MIYOSHI Tanroku

  第54回応用物理学関係連合講演会, Mar. 2007, English, 青山学院大学, Domestic conference

  Oral presentation


• Quantum Electron Transport Modeling in Double-Gate MOSFETs Based on Multiband Non-Equilibrium Green's Function Method

  FITRIAWAN Helmy, OGAWA Matsuto, SOUMA Satofumi, MIYOSHI Tanroku

  Second International Symposium on Nanometer-Scale Quantum Physics, Jan. 2007, English, Tokyo Insititute of Technology, Tokyo, International conference

  [Invited]

  Poster presentation


• Non-Equilibrium Green's Function Method for Modeling Quantum Electron Transport in Nano-Scale Devices with Anisotropic Multiband Structure

  FITRIAWAN Helmy, OGAWA Matsuto, SOUMA Satofumi, MIYOSHI Tanroku

  6th International Conference on Materials for Microelectronics and Nanoengineering, Oct. 2006, English, Cranfield, UK, International conference

  [Invited]

  Poster presentation


• ナノスケールトランジスタにおける電極形状効果と実空間・モード空間展開法の比較

  今後 博, 水谷 篤史, 清水 崇之, Fitriawan Helmy, 相馬 聡文, 小川 真人, 三好 旦六

  第54回応用物理学関係連合講演会, Sep. 2006, Japanese, 青山学院大学, Domestic conference

  Oral presentation


• Rashbaスピン軌道相互作用下のメゾスコピック多端子構造におけるスピンホール流の生成と検出

  相馬 聡文, NIKOLIC Branislav K

  日本物理学会2006年秋季大会, Sep. 2006, Japanese, 千葉大学, Domestic conference

  [Invited]

  Oral presentation


• Quantum Electron Transport Modeling in Nano-Scale Devices Based on Multiband Non-Equilibrium Green's Funtion Method

  FITRIAWAN Helmy, OGAWA Matsuto, SOUMA Satofumi, MIYOSHI Tanroku

  IEICE Technical Committee on Silicon Device and Materials, Sep. 2006, English, Domestic conference

  Oral presentation


• Multiband Simulation of Quantum Electron Transport in Nano-Scale Devices Based on Non-Equilibrium Green's Function

  FITRIAWAN Helmy, OGAWA Matsuto, SOUMA Satofumi, MIYOSHI Tanroku

  2006 International Conference on Solid State Devices and Materials, Sep. 2006, English, Pacifico Yokohama, International conference

  [Invited]

  Poster presentation


• Fullband Simulation of Quantum Electron Transport in Nanoscale Devices

  FITRIAWAN Helmy, OGAWA Matsuto, SOUMA Satofumi, MIYOSHI Tanroku

  第67回応用物理学会学術講演会, Aug. 2006, English, 立命館大学, Domestic conference

  Oral presentation


• グラファイトリボンの有限バイアス電気伝導におけるエッジ状態の役割

  SOUMA Satofumi, YAMAMOTO Takahiro, WATANABE Kazuyuki

  日本物理学会 第61回年次大会, Mar. 2006, Japanese, 松山大学, Domestic conference

  Oral presentation


• タイトバインディング密度汎関数法によるグラファイトリボンの電気伝導解析

  SOUMA Satofumi, YAMAMOTO Takahiro, WATANABE Kazuyuki

  物性研短期研究会 「次世代ナノ・エレクトロニクスのための電子状態計算の基礎理論」, Dec. 2005, Japanese, 東京大学物性研究所, Domestic conference

  Oral presentation


• Nonequilibrium electronic transport in graphitic ribbon bridges

  SOUMA Satofumi, YAMAMOTO Takahiro, WATANABE Kazuyuki

  International Symposium on Molecular Scale Electronics, Dec. 2005, English, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan, International conference

  [Invited]

  Poster presentation


• Electronic transport properties of graphite ribbonbridges under finite bias voltages

  SOUMA Satofumi, YAMAMOTO Takahiro, WATANABE Kazuyuki

  The Forth International Symposium on Surface Science and Nanotechnology, Nov. 2005, English, Ohmiya Sonic City, Saitama, Japan, International conference

  [Invited]

  Poster presentation


• Ab initio scattering state calculation of field emission from nanostructures

  ARAIDAI Masaaki, SOUMA Satofumi, WATANABE Kazuyuki

  The Forth International Symposium on Surface Science and Nanotechnology, Nov. 2005, English, Ohmiya Sonic City, Saitama, Japan, International conference

  [Invited]

  Poster presentation


• グラファイトリボン架橋の有限バイアスでの電気伝導特性

  SOUMA Satofumi, YAMAMOTO Takahiro, WATANABE Kazuyuki

  日本物理学会 2005年秋季大会, Sep. 2005, Japanese, 同志社大学, Domestic conference

  Oral presentation


• Spin Hall current driven by spin-interference in mesoscopic rings with Rashba spin-orbit coupling

  SOUMA Satofumi, NIKOLIC Branislav K

  日本物理学会 2005年秋季大会, Sep. 2005, Japanese, 同志社大学, Domestic conference

  Oral presentation


• Controlling Decoherence of transported spin in semiconductor spintronic devices

  SOUMA Satofumi, NIKOLIC Branislav K

  The 10th Workshop on Similarity in Diversity, Sep. 2005, English, Morito Memorial Hall, Tokyo University of Science, Tokyo, Japan, International conference

  [Invited]

  Oral presentation


• Quantum-coherent spin Hall effect and all-electrical detectors for its experimental observation

  NIKOLIC Branislav K, SOUMA Satofumi

  The third international school and conference on spintronics and quantum information technology, Aug. 2005, English, Awaji Yumebutai International Conference Center, Awaji Island, Hyogo, Japan, International conference

  [Invited]

  Poster presentation


• Mesoscopic spin Hall current and spin accumulation in multiprobe ballistic semiconductor nanostructures

  NIKOLIC Branislav K, ZARBO Liviu P, SOUMA Satofumi

  The third international school and conference on spintronics and quantum information technology, Aug. 2005, English, Awaji Yumebutai International Conference Center, Awaji Island, Hyogo, Japan, International conference

  [Invited]

  Poster presentation

• The Japanese Association for the Study of Musical IMprovisation

  Dec. 2021 - Present


• The Japan Society of Applied Physics

  Feb. 2013 - Present


• IEEE

  Oct. 2010 - Present

• Development of nanoscale device simulation method based on quantum computational algorithm

  相馬 聡文

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Grant-in-Aid for Scientific Research (C), Kobe University, Apr. 2022 - Mar. 2025


• Machine learning assisted simulation and optimization of atomic layer channel based FETs

  相馬 聡文

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Kobe University, Apr. 2019 - Mar. 2021

  機械学習を原子膜デバイスのシミュレーションと最適化設計に応用する事を目的に，これまで，非平衡グリーン関数（NEGF）法に基づくデバイスシミュレーションを畳み込みニューラルネットワーク（CNN）を用いて高速化する手法を確立してきたが，これまでは散乱を考慮しないコヒーレント輸送を前提としていた．より現実的なシミュレーションのためには電子フォノン散乱などの散乱機構を考慮に入れる必要がある．そこで，散乱を考慮したNEGF法に基づくデバイスシミュレーションにおいて機械学習手法，特にニューラルネットワーク（NN）モデルを用いる事によりシミュレーションを高速化する手法についての検討を行った．具体的には，散乱のある場合の電流計算に必要となる非平衡状態での相関グリーン関数（占有状態，非占有状態共）のスペクトル分布（各エネルギー毎の値）が，散乱の無いコヒーレント輸送の場合には大きな計算負荷を要せず（あるいは開発済みのコヒーレント輸送用のNEGF機械学習モデルを用いる事により更に高速に）計算される事，及び，散乱のある場合の上記のスペクトル分布が散乱強度等によって系統的な影響を受ける事に注目し，それらの間の対応関係をNNによって学習させる手法を提案し，この手法によって散乱のある場合の電流がNNモデルによってある程度の精度で低計算負荷に推論可能になる事を明らかにした． 更に，機械学習を用いる事によるデバイス性能予測とデバイス探索のための一般的なフレームワーク検討として，NNを用いる事により，与えられた素子パラメータに対するデバイス特性を直接的に予測するための一般的なモデルを提案し，高い精度で予測可能であることを明らかにした．また，その逆問題として，所望のデバイス性能が与えられた時にそれを実現するデバイスパラメータを抽出するための一般的なモデルも提案，その実用性を示した．


• 脳型コンピュータに向けた超低消費電力FETのための統合型低計算負荷シミュレータの開発と応用

  相馬 聡文

  東芝メモリ奨励研究、キオクシア奨励研究, Feb. 2019 - Mar. 2021, Principal investigator

  Competitive research funding


• 量子ゲート回路を応用した音楽作成システムの開発

  相馬 聡文

  IPA 2018年度未踏ターゲット事業（ゲート式量子コンピュータ部門）, Nov. 2018 - Mar. 2020, Principal investigator

  Competitive research funding


• 発熱・放熱制御と排熱有効利用を実現する超低消費電力デバイスの計算科学的デザイン

  山本 貴博

  科学研究費補助金/基盤研究(B), Apr. 2015 - Mar. 2018

  Competitive research funding


• 京コンピューターを用いたアトミスティック・デバイスシミュレータの開発

  小川 真人

  科学研究費一部基金／基盤研究(B)特設, Apr. 2013 - Mar. 2017

  Competitive research funding


• グラフェンを材料とした新規超低消費電力デバイス制御機構の創出

  相馬 聡文

  科学研究費補助金／萌芽研究, Apr. 2012 - Mar. 2015, Principal investigator

  Competitive research funding


• Confirmation of Mesoscopic Spin Transport in InGaAs Quantum Wells

  KOGA Takaaki, KAWABATA Shiro, SOUMA Satofumi, SAITO Keiji, MATSUURA Toru

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Hokkaido University, 01 Apr. 2011 - 31 Mar. 2014

  For InP-lattice-matched InGaAs quantum wells, we have quantitatively revealed the zero-field spin splitting term. Not only in showing the presence of the Rashba term for the first time which has been the target of controversy for long time, but also we have succeeded in elucidating its size quantitatively. More specifically, we have shown for the first time the linear relation between the Rashba coefficient alpha and the electric field inside the well from the theoretical analysis of the weak antilocalization effect that is seen in the magneto-conductivity data at dilution temperatures. In addition, we have found that the Dresselhaus term in this system is very small. Finally, we have also measured the time-reversal quantum interference effect in a mesoscopic loop array structure that is fabricated in a wafer whose can be varied across zero by gate and demonstrated the effectiveness of the semi-classical approach in theory.


• 密度汎関数法理論に基づく非平衡ナノスケール電気伝導ダイナミクス

  渡邉 聡

  科学研究費補助金/新学術領域研究(研究領域提案型)コンピューティクスによる物質デザイン: 複合相関と非平衡ダイナミクス, Apr. 2010 - Mar. 2014

  Competitive research funding


• 量子輸送シミュレータによる極限シリコン新構造・新材料デバイスの設計

  小川 真人

  科学研究費補助金／基盤研究(B), 2009

  Competitive research funding


• Study on the Optimal Design of Molecular Transistors in Next Generation Based on a Quantum Mechanical Simulation

  OGAWA Matsuto, SOUMA Satofumi

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Kobe University, 2005 - 2008

  スケーリングリミットに近づいたシリコン系デバイスの次世代の代替候補として分子エレクトロニクス材料に焦点を当て,ナノ材料設計及びデバイス設計に関して第一原理電子状態解析とNEGF法に基づき主としてGNR(グラーフェンナノリボン=Carbon系)およびPDT(ポリドデシルチオフェン)系の分子構造に伴う電子状態解析結果とデバイス構造設計によるデバイス特性解析結果,及び解析手法を開発し,PDT系材料のスイッチとしての分子デバイスへの応用が可能となることを明らかにした.シリコン系材料の置換の可能性が開け,次世代ナノ材料・デバイス設計も可能となり,産業技術への展開が可能となると考えられる.


• 原子ノベルの材料特性に基く半導体ナノスピントロニクスデバイスシミュレーターの開発

  相馬 聡文

  科学研究費補助金／特別研究促進費, 2006, Principal investigator

  Competitive research funding