Directory of Researchers
| SOUMA Satofumi |  |
| Graduate School of Engineering / Department of Electrical and Electronic Engineering | |
| Associate Professor | |
| Physics |
Researcher Profile and Settings
Affiliation
＜Faculty / Graduate School / Others＞
Graduate School of Engineering / Department of Electrical and Electronic Engineering＜Related Faculty / Graduate School / Others＞
Faculty of Engineering / Department of Electrical and Electronic Engineering
Teaching
- Office for the Promotion of International Exchange, 2022, Elements of Continuum Mechanics
- Office for the Promotion of International Exchange, 2022, Elements of Thermodynamics
- Faculty of Engineering / Department of Electrical and Electronic Engineering, 2022, Quantum Physics and Electronics
- Faculty of Engineering / Department of Electrical and Electronic Engineering, 2022, Creative Seminar
- Faculty of Engineering / Department of Electrical and Electronic Engineering, 2022, Electromagnetic Wave Theory A
- Faculty of Engineering / Department of Electrical and Electronic Engineering, 2022, Electrical and Electronics Engineering Laboratory ⅢA
- Faculty of Engineering / Department of Electrical and Electronic Engineering, 2022, Electrical and Electronics Engineering Laboratory Ⅲ
- Faculty of Engineering / Department of Electrical and Electronic Engineering, 2022, Electromagnetic Wave Theory
- Faculty of Engineering / Department of Electrical and Electronic Engineering, 2022, Electromagnetic Wave Theory B
- Faculty of Engineering / Department of Electrical and Electronic Engineering, 2022, Electrical and Electronics Engineering Laboratory ⅢB
- Graduate School of Engineering / Department of Electrical and Electronic Engineering, 2022, Quantum Materials Physics and Engineering
- Graduate School of Engineering / Department of Electrical and Electronic Engineering, 2022, Advanced Electrical and Electronics Seminar
- Graduate School of Engineering / Department of Electrical and Electronic Engineering, 2022, Quantum Devices Ⅱ
Research Activities
Research Interests
- Semiconductor device modeling and simulation
- Atomic layer material electronics
- Quantum transport theory
- Development of atomistic device simulator
- Non equilibrium Green's function method
- Neuromorphic computing device
- Quantum computing device and algorithm
Research Areas
- Manufacturing technology (mechanical, electrical/electronic, chemical engineering) / Electronic devices and equipment
Committee Memberships
- Apr. 2021 - Present, International Conference on Solid State Devices and Materials (SSDM), Program Committee (Area 1)
- Apr. 2018 - Present, IMFEDK (International Meeting for Future of Electron Devices, Kansai), Program Committee
- Apr. 2017 - Present, JST グローバルサイエンスキャンパス（GSC）事業-実施機関：神戸大学, 実施担当者
- Apr. 2017 - Present, SISPAD (International Conference on Simulation of Semiconductor Processes and Devices), Conference Committee
- Apr. 2017 - Present, 応用物理学会シリコンテクノロジー分科会システムデバイスロードマップ（SDRJ）委員会, 委員
- Apr. 2017 - Present, 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委員会, 幹事
- Apr. 2015 - Present, VSLI-TSA (International Symposium on VLSI Technology, Systems and Applications), Technical Program Committee
- Oct. 2012 - Mar. 2016, 半導体技術ロードマップ委員会（STRJ), 専門委員
- Apr. 2013 - Mar. 2015, 応用物理学会関西支部, 幹事
Awards
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
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
Published Papers
- Elsevier BV, Feb. 2023, Solid-State Electronics, 200, 108547 - 108547, English
[Refereed]
Scientific journal
- Springer International Publishing, Dec. 2022, Quantum Computer Music, 83 - 103
[Refereed][Invited]
In book
- Nov. 2022, 信学技報, vol. 122, no. 247, SDM2022-77, pp. 61-67, 2022年11月.
[Invited]
- Nov. 2022, IEICE Tech. Rep., vol. 122, no. 247, SDM2022-69, pp. 23-27, Nov. 2022.
[Invited]
Symposium
- AIP Publishing, 10 Jan. 2022, Journal of Applied Physics, 131 (2), 024301 - 024301, English
[Refereed]
Scientific journal
Abstract 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, 17 Dec. 2021, Japanese Journal of Applied Physics, English[Refereed]
Scientific journal
- Nov. 2021, 信学技報, vol. 121, no. 235, SDM2021-65, IEICE-121, 66 - 71, Japanese
[Invited]
Symposium
- IEEE, 27 Sep. 2021, 2021 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), English
[Refereed]
International conference proceedings
- Corresponding, AIP Publishing, 28 Aug. 2021, Journal of Applied Physics, 130 (8), 084302 - 084302, English
[Refereed]
Scientific journal
- Last, Institute of Electrical and Electronics Engineers (IEEE), 15 May 2021, IEEE Photonics Technology Letters, 33 (10), 507 - 510, English
[Refereed]
Scientific journal
- Nov. 2020, 信学技報, vol. 120, no. 239, SDM2020-22, pp. 1-4, 2020年11月.
[Invited]
- Corresponding, IEEE, 23 Sep. 2020, 2020 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), English
[Refereed]
International conference proceedings
- IEEE, 23 Sep. 2020, 2020 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), English
[Refereed]
International conference proceedings
- 2020, Journal of Applied Physics 127, 094304 (2020)
[Refereed]
- 2020, IEICE Electronics Express, Vol.17, No.4, 1–6, 2020
[Refereed]
- Last, 2019, J. Appl. Phys. 125, 073101 (2019)
[Refereed]
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), 1569 - 1584, English[Refereed]
Scientific journal
- 2018, 表面と真空 61 pp. 360-365 (2018)
[Refereed]
- 2018, Jpn. J. Appl. Phys. 57, pp. 065102 1-4 (2018)
[Refereed]
- Last, 2018, Superlattices and Microstructures, 122, 492 (2018)
[Refereed]
- AMER PHYSICAL SOC, Dec. 2017, PHYSICAL REVIEW B, 96 (23), English
[Refereed]
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., 25 Oct. 2017, International Conference on Simulation of Semiconductor Processes and Devices, SISPAD, 2017-, 213 - 216, English[Refereed]
International conference proceedings
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., 25 Oct. 2017, International Conference on Simulation of Semiconductor Processes and Devices, SISPAD, 2017-, 209 - 212, English[Refereed]
International conference proceedings
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), 035428, English[Refereed]
Scientific journal
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), English[Refereed]
Scientific journal
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), 025102 - 25102, English[Refereed]
Scientific journal
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- Nov. 2015, SMD2015-89, 29, 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
[Invited]
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), 034010 1 - 9, English[Refereed]
Scientific journal
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), 115103 1 - 7, English[Refereed]
Scientific journal
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), 213505 1 - 4, English[Refereed]
Scientific journal
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), 108103 1 - 4, English[Refereed]
Scientific journal
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), 1 - 11, English[Refereed]
Scientific journal
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
- 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
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), 170 - 174, English[Refereed]
Scientific journal
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), 114328 - 1-114328-5, English[Refereed]
Scientific journal
- Sep. 2012, Proc. of Int. Conf. on Simulation of Semiconductor Processes and Devices 2012, 133 - 136, EnglishTight-binding molecular dynamics study of mechanical and electronic properties in twisted graphene nanoribbons
[Refereed]
International conference proceedings
- Sep. 2012, Proc. of Int. Conf. on Simulation of Semiconductor Processes and Devices 2012, 384 - 387, EnglishFast Perturbative Treatment for Efficient Nano-Scale Device Simulation Based on Bridge-Function Pseudo-Spectral Method
[Refereed]
International conference proceedings
- Sep. 2012, Proc. of Int. Conf. on Simulation of Semiconductor Processes and Devices 2012, 368 - 371, EnglishAnalysis of tunneling characteristics through hetero interface of InAs/Si nanowire tunneling field effect transistors
[Refereed]
International conference proceedings
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), 770 - 776, English[Refereed]
Scientific journal
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
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
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
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), 35 - 43, English[Refereed]
Scientific journal
- Jun. 2011, Journal of Computational Electronics, 10 (1-2), 269, English
[Refereed]
Scientific journal
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), 1251 - 1255, English[Refereed]
Scientific journal
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
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
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
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
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
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), 1287 - 1290, English[Refereed]
International conference proceedings
- 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), 63 - 76, Japanese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
[Refereed]
- Dec. 2009, Physica E, Available online 1 December 20, EnglishEffect of interface structure on current spin-polarization in narrow gap semiconductor heterostructures
[Refereed]
Scientific journal
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
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), 211 - 220, English[Refereed]
International conference proceedings
- 2D Quantum Mechanical Simulation of Gate-Leakage Current in Double-Gate n-MOSFETs
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
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), 390 - 393, English[Refereed]
Scientific journal
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), 2373 - 2382, English[Refereed]
Scientific journal
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), 2198 - 2200, English[Refereed]
Scientific journal
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), 107 - 110, English[Refereed]
Scientific journal
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), 74 - 77, English[Refereed]
International conference proceedings
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), 105 - 109, English[Refereed]
Scientific journal
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
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), 74 - 77, English[Refereed]
International conference proceedings
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), 245 - 248, English[Refereed]
Scientific journal
- Sep. 2007, Extended Abstact of 2007 Int. Conf. on Solid State Devices andMaterials, pp. 52-53, EnglishMultiband simulation of uniaxially stressed silicon MOSFETs based on non-equilibrium Green’s function method
International conference proceedings
- Apr. 2007, Proc. 2007 Int. Meetingfor Future of Electron Devices, Kansai, pp.107-108, EnglishAnalysis of quantum transport in nano-scale silicon
International conference proceedings
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), English[Refereed]
Scientific journal
- Jan. 2006, e-Journal of Surface Science and Nanotechnology, Vol.4, pp.78-83, English
[Refereed]
Scientific journal
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), English[Refereed]
Scientific journal
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), 3151 - 3160, English[Refereed]
Scientific journal
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), English[Refereed]
Scientific journal
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), English[Refereed]
Scientific journal
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), English[Refereed]
Scientific journal
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
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
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), 457 - 460, English[Refereed]
Scientific journal
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), English[Refereed]
Scientific journal
- Sep. 2004, UZBEK JOURNAL OF PHYSICS, Volume 6, Number 5&6, pp.334-3, EnglishOn the two magnetic quantum dots in a two dimensional electron gas
[Refereed]
Scientific journal
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 - 40, English[Refereed]
Scientific journal
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), 1037 - 1040, English[Refereed]
Scientific journal
- 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
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), 339 - 342, English[Refereed]
Scientific journal
- Transitions of the density of states in cylindrical quantum box
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
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), 6927 - 6929, English[Refereed]
Scientific journal
- Dimensional crossover of the density of states in cylindrically confined systems
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), 1051 - 1055, English[Refereed]
Scientific journal
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), English[Refereed]
Scientific journal
- 2002, Proceedings of the 26th International Conference on the Physics of Semiconductors, Edinburgh 2002Magneto-conductance in Quantum Wires with Array of Magnetic Quantum Dots
[Refereed]
- Dephasing due to voltage probes in quantum wires with antidot potential
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
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), 15928 - 15936, English[Refereed]
Scientific journal
- 1999, Journal of the Korean Physical Society, vol. 39 No. 3, September 2001, pp. 553-557Transmission phases in quantum wires with an antidot potential subjected to a high magnetic field
[Refereed]
- 1999, Proceedings of the 5th International Workshop on Similarity in Diversity, edited by H. Hara, T. Toyoda and T. Morita, (1999) P.183-187Effect of phase breaking scattering in quantum wires with an antidot potential
[Refereed]
- Effect of impurity scattering in nanoscale Corbino disks
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), 4649 - 4655, English[Refereed]
Scientific journal
- 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.Evanescent modes and impurity scattering in nano-scale Corbino disks
[Refereed]
- Jul. 2008, シリコンテクノロジー, No.103, pp. 15-20, Japanese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
- Mar. 2010, Oxford Handbook of Nanoscience and Technology, pp. 814-865, EnglishSpin currents in semiconductor nanostructures:A nonequilibrium Green function approach
[Refereed]
Presentations
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- 日本音楽即興学会 第14回大会, 27 Nov. 2022量子的な関わり合いをカタチにする即興的音楽生成パフォーマンス
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- 電子情報通信学会シリコン材料・デバイス研究会, 11 Nov. 2022SISPAD2022レビュー
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- 2022 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD2022), 08 Sep. 2022, EnglishA proposal of quantum computing algorithm to solve Poisson equation for nanoscale devices under Neumann boundary condition
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- 2022 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD2022), 07 Sep. 2022, EnglishScattering matrix-based low computational cost model for the device and circuit co-simulation of phosphorene tunnel field-effect transistors
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- JSAP Silicon technology division 236th reseach meeting, 22 Jul. 2022, JapaneseQuamtum transport simulation-based design of synaptic FET and circuit simulation
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- 日本音楽即興学会 第13回大会, 10 Jan. 2022, Japanese量子的アルゴリズムに基づく即興的音楽生成の可能性に関する一考察
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- 1st International Symposium on Quantum Computing and Musical Creativity, 19 Nov. 2021, English, International conferenceExploring the Application of Gate-type Quantum Computational Algorithm for Music Creation and Performance
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- The 2021 International Meeting for Future of Electron Devices, Kansai, 18 Nov. 2021, EnglishDevelopment of device and circuit simulation framework based on phosphorene tunnel field-effect transistors
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- The 2021 International Meeting for Future of Electron Devices, Kansai, 18 Nov. 2021, EnglishImplementation of gate-type quantum computing algorithm to solve Poisson equation for semiconductor nanowire p-n junction
Poster presentation
- 電子情報通信学会シリコン材料・デバイス研究会, 12 Nov. 2021, Japanese, Domestic conference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
[Invited]
Invited oral presentation
- IPA 量子コンピューティング技術実践講座（ゲート式）, 05 Nov. 2021, Japanese, Japan, Domestic conference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
[Invited]
Invited oral presentation
- 応用物理学会関西支部 2021 年度 第 2 回講演会, 15 Oct. 2021, Japanese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
Poster presentation
- 2021年 第82回応用物理学会秋季学術講演会, 23 Sep. 2021, Japanese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
Poster presentation
- 2021年 第82回応用物理学会秋季学術講演会, 23 Sep. 2021, Japanese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
Poster presentation
- 2021年 第82回応用物理学会秋季学術講演会, 23 Sep. 2021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
Poster presentation
- 応用物理学会関西支部 2021 年度 第 1 回講演会, 23 Apr. 2021, Japanese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
Poster presentation
- The 8th Asian Conference on Crystal Growth and Crystal Technology, Mar. 2021, EnglishApplication of deep neural network for the simulation of nanoscale FETs based on non-equilibrium Green's function method
Oral presentation
- IEEE IMFEDK 2020 Satellite event for young researchers, Nov. 2020, EnglishConsideration of scattering process in nanoscale device simulation based on top of barrier model
Poster presentation
- IEEE IMFEDK 2020 Satellite event for young researchers, Nov. 2020, EnglishSimulation of graphene photodetectors incorporating the photo-gating effect
Poster presentation
- 2020 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), Sep. 2020, EnglishTight-binding simulation of optical gain in h-BCN for laser application
Poster presentation
- 020 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), Sep. 2020, EnglishTransient simulation of graphene FET gated by electrolyte medium
Oral presentation
- 2020 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD). Workshop “Combination of TCAD and Machine Learning”, Sep. 2020, EnglishApplication of convolutional neural network for nanoscale device simulations based on nonequilibrium Greens function method
[Invited]
Invited oral presentation
- 2020年第67回応用物理学会春季学術講演会, 12 Mar. 2020, Japanese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
Poster presentation
- 2020年第67回応用物理学会春季学術講演会, 12 Mar. 2020, Japaneseh-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
Poster presentation
- 2020年第67回応用物理学会春季学術講演会, 12 Mar. 2020, Japanese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
Oral presentation
- International Meeting for Future of Electron Devices, Kansai (IMFEDK 2019), 14 Nov. 2019, EnglishSimulation of Graphene FET Gated by Ionic Liquid
Poster presentation
- International Meeting for Future of Electron Devices, Kansai (IMFEDK 2019), 14 Nov. 2019, EnglishSimulation of Optical Gain in Semiconductor Laser Structure with h-BCN Active Layer
Poster presentation
- 2019年第80回応用物理学会秋季学術講演会, 18 Sep. 2019, Japanese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
Oral presentation
- 応用物理学会関西支部2019年度第1回講演会, 20 Jun. 2019h-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
Poster presentation
- 応用物理学会関西支部2019年度第1回講演会, 20 Jun. 2019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
Poster presentation
- 第66回応用物理学会春季学術講演会, Mar. 2018, Japanese, 東京, Domestic conference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
Poster presentation
- 第65回応用物理学会春季学術講演会, Mar. 2018, Japanese, 東京, Domestic conference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
Poster presentation
- 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
Poster presentation
- 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
Poster presentation
- 第78回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference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
Poster presentation
- 第86回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference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
Poster presentation
- 第82回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference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
Poster presentation
- 第80回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference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
Poster presentation
- 第84回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference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
Poster presentation
- 第79回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference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
Poster presentation
- 第85回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conference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
Poster presentation
- 第83回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conferenceSi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
Poster presentation
- 第81回 応用物理学会秋季学術講演会, Sep. 2017, Japanese, 福岡市, Domestic conferenceBlack 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
Poster presentation
- 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
Poster presentation
- 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グラフェン状物質h-BCNの光吸収特性シミュレーション
Poster presentation
- 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
Poster presentation
- 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
Poster presentation
- 第64回応用物理学会春季学術講演会, Mar. 2017, Japanese, 横浜市, Domestic conference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
Poster presentation
- 第77回 応用物理学会秋季学術講演会,, Sep. 2016, Japanese, 新潟市, Domestic conference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
Poster presentation
- 第77回 応用物理学会秋季学術講演会,, Sep. 2016, Japanese, 新潟市, Domestic conference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
Poster presentation
- 第77回 応用物理学会秋季学術講演会,, Sep. 2016, Japanese, 新潟市, Domestic conference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
Poster presentation
- 第77回 応用物理学会秋季学術講演会,, Sep. 2016, Japanese, 新潟市, Domestic conference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
Poster presentation
- 第77回 応用物理学会秋季学術講演会,, Sep. 2016, Japanese, 新潟市, Domestic conferenceSi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
Poster presentation
- 第77回 応用物理学会秋季学術講演会,, Sep. 2016, Japanese, 新潟市, Domestic conference,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
Poster presentation
- 19th International Conference on Superlattices, Nanostructures and Nanodevices,, Jul. 2016, English, Hong Kong, International conferenceComputational study on the performance of locally strained graphene devices: transport and wave packet dynamics simulations
[Invited]
Poster presentation
- 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
Oral presentation
- 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
Poster presentation
- 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
Poster presentation
- 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
Poster presentation
- 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
Poster presentation
- 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
[Invited]
Invited oral presentation
- 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
Poster presentation
- 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
Oral presentation
- 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
Oral presentation
- 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
Public discourse
- 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
Poster presentation
- International Symposium on Recent Progress of Photonic Devices and Material, Nov. 2014, English, 神戸市, International conferencePhotoconductivity-based strain sensing in graphene
Poster presentation
- 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
Public discourse
- 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
Public discourse
- 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
Public discourse
- 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
Poster presentation
- 第77回応用物理学会秋季学術講演会, Sep. 2014, Japanese, 札幌市, Domestic conference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
Poster presentation
- 第79回応用物理学会秋季学術講演会, Sep. 2014, Japanese, 札幌市, Domestic conference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
Poster presentation
- 第78回応用物理学会秋季学術講演会, Sep. 2014, Japanese, 札幌市, Domestic conference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
Poster presentation
- 第76回応用物理学会秋季学術講演会, Sep. 2014, Japanese, 札幌市, Domestic conference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
Poster presentation
- 第75回応用物理学会秋季学術講演会, Sep. 2014, Japanese, 札幌市, Domestic conference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
Poster presentation
- 第80回応用物理学会秋季学術講演会, Sep. 2014, Japanese, 札幌市, Domestic conference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
Poster presentation
- International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), 2014, Sep. 2014, English, 横浜市, International conferenceNumerical simulation of current noise caused by potential fluctuation in nanowire FET with an oxide trap
[Invited]
Poster presentation
- 東京理科大学セミナー講演, Jun. 2014, Japanese, 東京, Domestic conference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
Public discourse
- Meeting abstracts of the Physical Society of Japan, 05 Mar. 2014, Japanese, The Physical Society of Japan (JPS)28pPSA-72 Transient response simulations of scattering states under time-dependent gate voltage
- 日本物理学会, Mar. 2014, Japanese, Domestic conference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
Poster presentation
- 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 conferenceNumerical Simulations for Time-evolving Electronic States in a Nanoscale System with and without Wide Band Limit Approximation
Poster presentation
- 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
Oral presentation
- 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
Poster presentation
- 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
Oral presentation
- 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
Poster presentation
- 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
Poster presentation
- 日本物理学会 2013年秋季大会, Sep. 2013, Japanese, 徳島市, Domestic conferenceグラフェンの熱物性における面内歪みの影響
Oral presentation
- 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
Poster presentation
- 5th International Conference on Recent Progress in Graphene Research, Sep. 2013, English, 東京, International conferenceWave-packet dynamics study of electronic transport in graphene irradiated by circularly polarized light
[Invited]
Poster presentation
- 5th International Conference on Recent Progress in Graphene Research, Sep. 2013, English, 東京, Domestic conferenceEffect of lateral strain on electronic transport in graphene: interplay between band gap formation and pseudo magnetic field effect
[Invited]
Oral presentation
- 5th International Conference on Recent Progress in Graphene Research, Sep. 2013, English, 東京, International conferenceEffect of in-plane strain on thermal properties of graphene
[Invited]
Poster presentation
- 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 conferenceEffect of in-plane strain on thermal properties of graphene
Poster presentation
- 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
[Invited]
Invited oral presentation
- 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
[Invited]
Oral presentation
- 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
[Invited]
Invited oral presentation
- International Workshop on Computational Electronics 2013, Jun. 2013, English, 奈良市, International conferenceQuantum Dynamical Simulation of Photo-Induced Graphene Switch
[Invited]
Poster presentation
- International Workshop on Computational Electronics 2013, Jun. 2013, English, 奈良市, International conferenceEffect of Axial Strain on Switching Behavior of Carbon Nanotube Tunneling Field Effect Transistors
[Invited]
Poster presentation
- Meeting abstracts of the Physical Society of Japan, 26 Mar. 2013, Japanese, The Physical Society of Japan (JPS)28pPSA-5 Numerical analysis of current noise caused by potential fluctuation in semiconductor nanowires II
- 日本物理学会第６８回年次大会, Mar. 2013, Japanese, 東広島市, Domestic conference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
Oral presentation
- 日本物理学会第６８回年次大会, Mar. 2013, Japanese, 東広島市, Domestic conference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
Poster presentation
- 第６０回応用物理学会春季学術講演会, Mar. 2013, Japanese, 厚木市, Domestic conference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
Poster presentation
- 第６０回応用物理学会春季学術講演会, Mar. 2013, Japanese, 厚木市, Domestic conference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
Poster presentation
- 日本物理学会第６８回年次大会, Mar. 2013, Japanese, 東広島市, Domestic conferenceグラフェンの機械的変形が熱物性に与える影響
Poster presentation
- 2013 American Physical Society March Meeting, Mar. 2013, English, Baltimore, USA, Domestic conferenceSpin blocking effect in symmetric double quantum well due to Rashba spin-orbit coupling
Oral presentation
- 第６０回応用物理学会春季学術講演会, Mar. 2013, Japanese, 厚木市, Domestic conferenceSpin blocking effect in InGaAs/InAlAs double quantum wells due to Rashba spin-orbit coupling
Oral presentation
- 日本物理学会2012年秋季大会, Sep. 2012, Japanese, 横浜市, Domestic conference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
Poster presentation
- 第７３回応用物理学会学術講演会, Sep. 2012, Japanese, 松山市, Domestic conference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
Oral presentation
- 第７３回応用物理学会学術講演会, Sep. 2012, English, 松山市, Domestic conferenceA Theoretical Study of an Influence of a Time Dependent External Field on Electronic Transport in Graphene
Oral presentation
- Meeting abstracts of the Physical Society of Japan, 24 Aug. 2012, Japanese, The Physical Society of Japan (JPS)19aAF-9 Charge and thermal transport in superconductor/ferromagnetic-insulator/normal-metal junctions
- Meeting abstracts of the Physical Society of Japan, 24 Aug. 2012, Japanese, The Physical Society of Japan (JPS)20pPSA-7 Numerical analysis of current noise caused by potential fluctuation in semiconductor nanowires
- 31st International Conference on the Physics of Semiconductors, Aug. 2012, English, Zurich, Switzerland, International conferenceInAs/GaAs quantum dot arrayed-base intermediate band solar cell with multiple intermediate bands
[Invited]
Poster presentation
- 31st International Conference on the Physics of Semiconductors, Aug. 2012, English, Zurich, Switzerland, International conferenceAtomistic Origin of Rashba and Dresselhaus Spin-Orbit Couplings in Narrow Gap Semiconductor Quantum Wells
[Invited]
Poster presentation
- International Conference on Superlattices, Nanostructures, and Nanodevices, Jul. 2012, English, Dresden, Germany, International conferenceEffect of Lateral Strain on the Performance of Single Layer Graphene Field Effect Transistors
[Invited]
Poster presentation
- Meeting abstracts of the Physical Society of Japan, 05 Mar. 2012, Japanese, The Physical Society of Japan (JPS)26pPSB-61 Effect of axial strain on electronic transport in carbon nanotube tunneling field effect transistors
- Meeting abstracts of the Physical Society of Japan, 05 Mar. 2012, Japanese, The Physical Society of Japan (JPS)25aBC-6 Theory of Josepshon π-junction using a ferromagnetic insulator
- Meeting abstracts of the Physical Society of Japan, 05 Mar. 2012, Japanese, The Physical Society of Japan (JPS)27aSB-3 Numerical simulation of spin pumping effect in graphene nanoribbons
- 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強磁性絶縁体を用いたジョセフソンπ接合の理論
Oral presentation
- 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
Oral presentation
- 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
Oral presentation
- 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
Poster presentation
- 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 conferenceSi, 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
Oral presentation
- Workshop on Innovation and Pioneering Technolo-gy 2011 (WINPTech2011), Dec. 2011, English, International conferenceEfficiency Estimation of Intermediate Band Solar Cells Based on InAs/GaAs Quantum Dot Arrays
Poster presentation
- Workshop on Innovation and Pioneering Technolo-gy 2011 (WINPTech2011), Dec. 2011, English, International conferenceEffect of axial strain on electronic transport in carbon nanotube tunneling field effect transistors
Poster presentation
- 第25回量子情報技術研究会 (QIT25), Nov. 2011, Japanese, Domestic conference強磁性絶縁体を用いたジョセフソンπ接合の理論
Poster presentation
- 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歪積層量子ドット構造の電子状態解析
Oral presentation
- 日本物理学会2011年秋季大会, Sep. 2011, Japanese, 日本物理学会, Domestic conference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
Poster presentation
- 日本物理学会2011年秋季大会, Sep. 2011, Japanese, 日本物理学会, Domestic conference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
Poster presentation
- 日本物理学会2011年秋季大会, Sep. 2011, Japanese, 日本物理学会, Domestic conference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
Poster presentation
- 日本物理学会2011年秋季大会, Sep. 2011, Japanese, 日本物理学会, Domestic conferenceグラフェンFETの特性における面内歪みの影響
Poster presentation
- 日本物理学会2011年秋季大会, Sep. 2011, Japanese, 日本物理学会, Domestic conferenceInGaAs二重量子井戸系におけるスピンフィルタ
Oral presentation
- 日本物理学会2011年秋季大会, Sep. 2011, Japanese, 日本物理学会, Domestic conferenceInGaAs二重量子井戸系でのスピン分離とスピンフィルタ効果
Oral presentation
- 第72回応用物理学会学術講演会, Sep. 2011, Japanese, 応用物理学会, Domestic conferenceInAs/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
Oral presentation
- 2011 Int. Conf. on Simu-lation of Semiconductor Processes and Devices, Sep. 2011, English, International conferenceBridge-Function Pseudospectral Method for Quantum Mechanical Simulation of Nano-Scaled Devices
[Invited]
Oral presentation
- 2011 Int. Conf. on Simu-lation of Semiconductor Processes and Devices, Sep. 2011, English, International conferenceAnalysis of geometrical sutructure and transport property in InAs/Si heterojunction nanowire tunneling field effect transistors
[Invited]
Poster presentation
- 2011 Int. Meetingfor Future of Electron Devices, Kansai, May 2011, English, International conferenceTight binding modeling of intermediate band solar cells based on InAs/GaAs quantum dot arrays
[Invited]
Poster presentation
- 2011 Int. Meetingfor Future of Electron Devices, Kansai, May 2011, English, International conferenceEffect of uniaxial strain on the electronic Transport in single layer graphene
[Invited]
Poster presentation
- 2011 Int. Meetingfor Future of Electron Devices, Kansai, May 2011, English, International conferenceAnalysis of electronic structure in quantum dot arrays for intermediate band solar cells
[Invited]
Poster presentation
- 第57回, Mar. 2010, Japanese, 応用物理学会, 神奈川県平塚市, Domestic conference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-
Poster presentation
- 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
Poster presentation
- WINP Tech 2009, Dec. 2009, English, 神戸大学, kobe, International conferenceComputational study of molecular vibration and electronic transport in single molecule devices
Poster presentation
- International Conference on Simulation of Semiconductor Processes and Devices, Sep. 2009, English, IEEE, San Diego, USA, International conference2D Quantum Mechanical Simulation of Gate-Leakage Current in Double-Gate n-MOSFETs
[Invited]
Poster presentation
- 14th International Conference on Narrow Gap Semiconductor and Systems, Jul. 2009, English, 仙台, International conferenceSpin-polarization in InAs/AlSb double barrier resonant tunneling structures:
[Invited]
Oral presentation
- 14th International Conference on Modulated Semiconductor Structures, Jul. 2009, English, 神戸, International conferenceEffect of interface structure on current spin-polarization in narrow gap
[Invited]
Poster presentation
- 13th International Workshop on Computational Electronics, May 2009, English, IEEE, Beijing, China, International conferenceSimulation of Graphene Nanoribbon Spin-Filter Device with Spin-Density Functional
[Invited]
Oral presentation
- International Meeting for Future of Electron Devices, Kansai, May 2009, English, IEEE, 大阪, International conferenceInfluence of Geometrical Deformation on Transport Characteristics
[Invited]
Poster presentation
- International Meeting for Future of Electron Devices, Kansai, May 2009, English, IEEE, 大阪, International conferenceInfluence of Edge Roughness on the Performance of Graphene Nano-Ribbon Devices
[Invited]
Oral presentation
- International Meeting for Future of Electron Devices, Kansai, May 2009, English, IEEE, 大阪, International conferenceAnalysis of the Electronic Structures in Silicon Nano-Structures by
[Invited]
Poster presentation
- 第56回, Apr. 2009, Japanese, 応用物理学会, つくば, Domestic conference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
Oral presentation
- 第56回, Apr. 2009, Japanese, 応用物理学会, つくば, Domestic conference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
Oral presentation
- 第56回, Mar. 2009, Japanese, 応用物理学会, 筑波, Domestic conference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
Oral presentation
- American Physical, Nov. 2008, English, AmericanPhysical Society, Pittsburgh, USA, International conferenceSpin Dependent Transport in Graphene Nano Ribbon Devices
Poster presentation
- Int. Symposium on, Nov. 2008, English, 会津若松, International conferenceComputational modeling of graphene nano-ribbon spin devices based on spin-density-functional tight-binding method
[Invited]
Oral presentation
- 2008 International, Nov. 2008, English, 箱根, International conferenceAnalysis of Direct Tunneling Current from Quasi-Bound States in n-MOSFET Based on
[Invited]
Poster presentation
- 日本物理学会, Sep. 2008, Japanese, 日本物理学会, 盛岡, Domestic conference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
Poster presentation
- 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 conferenceSi ナノMOSFET中の量子輸送解析に関する研究
Poster presentation
- 2008 Int. Conf. on, Sep. 2008, English, 筑波, Domestic conferenceCalculation of strain effecs on the I-V characteristics of ultra small MOSFETs based on NEGF approach
[Invited]
Poster presentation
- 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
[Invited]
Invited oral presentation
- 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グラフェンナノリボンFETの数値シミュレーション
[Invited]
Invited oral presentation
- 日本物理学会, Mar. 2008, Japanese, 日本物理学会, 東京, Domestic conference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
Oral presentation
- 第55回応用物理学関係連合講演会, Mar. 2008, Japanese, 船橋市, Domestic conference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
Oral presentation
- 日本物理学会, Mar. 2008, Japanese, 日本物理学会, 東京, Domestic conference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
Poster presentation
- 第55回応用物理学関係連合講演会, Mar. 2008, English, 船橋市, Domestic conferenceSi ナノMOSFETにおけるフォノン散乱現象の解析
Oral presentation
- 電気関係学会関西支部 連合大会, Nov. 2007, Japanese, 神戸市, Domestic conference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
Oral presentation
- 12th International Workshop on Computational Electronics, Oct. 2007, English, IEEE, Amherst. Mass, International conferenceNumerical simulation of the electronic transport in graphene nano-ribbon devices
[Invited]
Oral presentation
- 12th International Workshop on Computa- tional Electronics, Oct. 2007, English, Massachusetts/USA, International conferenceNumerical simulation of the electronic transport in graphene nano-ribbon devices
[Invited]
Oral presentation
- 12th International Workshop on Computa- tional Electronics, Oct. 2007, English, Massachusetts/USA, International conferenceFullband Green’s function study for quantum electron transport in strained silicon n-MOEFETs
[Invited]
Poster presentation
- 日本物理学会2007年次 大会, Sep. 2007, Japanese, 北海道, Domestic conference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
Oral presentation
- 第68回応用物理学会学術講演会, Sep. 2007, English, 北海道, Domestic conferenceQuantum electron transport modeling in strained MOSFETs based on multiband non-equilibrium
Oral presentation
- 第68回応用物理学会学術講演会, Sep. 2007, Japanese, 北海道, Domestic conferenceCNTへのドーピングによる電子状態変化の解析
Oral presentation
- Frontiers in Computational Science of Nanoscale Trans- port in conjunction with Atomistic Workshop 2007, Jun. 2007, English, Tokyo Univ of Science, 東京, International conferenceNumerical study of electronic states in silicon thin films based on empirical tight-binding approach
[Invited]
Poster presentation
- Frontiers in Computational Science of Nanoscale Trans- port in conjunction with Atomistic Workshop 2007, Jun. 2007, English, Tokyo Univ of Science, 東京, International conferenceElectronic structure of substitutional impurity in carbon nanotubes based on a first principle calculation
[Invited]
Poster presentation
- Frontiers in Computational Science of Nanoscale Trans- port in conjunction with Atomistic Workshop 2007, Jun. 2007, English, Tokyo Univ of Science, 東京, International conferenceCurrent-voltage chatacteristics and local current distribution in graphene-nano-ribbon devices
[Invited]
Poster presentation
- 4th International School andConference on Spintronics and Quantum Information Technology (Spintech IV), Jun. 2007, English, Hawaii/USA, International conferenceAtomistic simulation of spin-polarized electronic current in resonant tunneling heterostructures
[Invited]
Poster presentation
- 日本物理学会2007年春季大会, Mar. 2007, Japanese, 鹿児島大学, Domestic conference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
Poster presentation
- 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 conferenceQuantum Electron Transport Modeling in Nano-Scale Devices Based on Multiband Non-Equilibrium Green's Funtion Method
Oral presentation
- Second International Symposium on Nanometer-Scale Quantum Physics, Jan. 2007, English, Tokyo Insititute of Technology, Tokyo, International conferenceQuantum Electron Transport Modeling in Double-Gate MOSFETs Based on Multiband Non-Equilibrium Green's Function Method
[Invited]
Poster presentation
- 6th International Conference on Materials for Microelectronics and Nanoengineering, Oct. 2006, English, Cranfield, UK, International conferenceNon-Equilibrium Green's Function Method for Modeling Quantum Electron Transport in Nano-Scale Devices with Anisotropic Multiband Structure
[Invited]
Poster presentation
- 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
Oral presentation
- 日本物理学会2006年秋季大会, Sep. 2006, Japanese, 千葉大学, Domestic conferenceRashba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
[Invited]
Oral presentation
- IEICE Technical Committee on Silicon Device and Materials, Sep. 2006, English, Domestic conferenceQuantum Electron Transport Modeling in Nano-Scale Devices Based on Multiband Non-Equilibrium Green's Funtion Method
Oral presentation
- 2006 International Conference on Solid State Devices and Materials, Sep. 2006, English, Pacifico Yokohama, International conferenceMultiband Simulation of Quantum Electron Transport in Nano-Scale Devices Based on Non-Equilibrium Green's Function
[Invited]
Poster presentation
- 第67回応用物理学会学術講演会, Aug. 2006, English, 立命館大学, Domestic conferenceFullband Simulation of Quantum Electron Transport in Nanoscale Devices
Oral presentation
- 日本物理学会 第61回年次大会, Mar. 2006, Japanese, 松山大学, Domestic conference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
Oral presentation
- 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
Oral presentation
- International Symposium on Molecular Scale Electronics, Dec. 2005, English, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan, International conferenceNonequilibrium electronic transport in graphitic ribbon bridges
[Invited]
Poster presentation
- The Forth International Symposium on Surface Science and Nanotechnology, Nov. 2005, English, Ohmiya Sonic City, Saitama, Japan, International conferenceElectronic transport properties of graphite ribbonbridges under finite bias voltages
[Invited]
Poster presentation
- The Forth International Symposium on Surface Science and Nanotechnology, Nov. 2005, English, Ohmiya Sonic City, Saitama, Japan, International conferenceAb initio scattering state calculation of field emission from nanostructures
[Invited]
Poster presentation
- 日本物理学会 2005年秋季大会, Sep. 2005, Japanese, 同志社大学, Domestic conference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
Oral presentation
- 日本物理学会 2005年秋季大会, Sep. 2005, Japanese, 同志社大学, Domestic conferenceSpin Hall current driven by spin-interference in mesoscopic rings with Rashba spin-orbit coupling
Oral presentation
- The 10th Workshop on Similarity in Diversity, Sep. 2005, English, Morito Memorial Hall, Tokyo University of Science, Tokyo, Japan, International conferenceControlling Decoherence of transported spin in semiconductor spintronic devices
[Invited]
Oral presentation
- 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 conferenceQuantum-coherent spin Hall effect and all-electrical detectors for its experimental observation
[Invited]
Poster presentation
- 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 conferenceMesoscopic spin Hall current and spin accumulation in multiprobe ballistic semiconductor nanostructures
[Invited]
Poster presentation
Association Memberships
The Japanese Association for the Study of Musical IMprovisation
Dec. 2021 - PresentThe Japan Society of Applied Physics
Feb. 2013 - PresentIEEE
Oct. 2010 - Present
Research Projects
- 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. 2025Development of nanoscale device simulation method based on quantum computational algorithm
- 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. 2021Machine learning assisted simulation and optimization of atomic layer channel based FETs
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．
- 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
- 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
- 科学研究費補助金/基盤研究(B), Apr. 2015 - Mar. 2018
Competitive research funding
- 科学研究費一部基金／基盤研究(B)特設, Apr. 2013 - Mar. 2017
Competitive research funding
- 科学研究費補助金／萌芽研究, Apr. 2012 - Mar. 2015, Principal investigator
Competitive research funding
- 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
- 科学研究費補助金／基盤研究(B), 2009
Competitive research funding
- 科学研究費補助金／特別研究促進費, 2006, Principal investigator
Competitive research funding