渡邉　孝信

ISSN：18820778

概要：© 2017 The Japan Society of Applied Physics.We clarified the mechanism of oxygen (O-)-ion migration at a high-k/SiO2 interface, which is a possible origin of the flat-band voltage shift in metal/high-k gate stacks. The oxygen density difference accommodation model was reproduced by a molecular dynamics simulation of an Al2O3/SiO2 structure, in which O- ions migrate from the higher oxygen density side to the lower one. We determined that the driving force of the O--ion migration is the short-range repulsion between ionic cores. The repulsive force is greater in materials with a higher oxygen density, pushing O- ions to the lower oxygen density side.

ISSN：00036951

概要：© 2017 Author(s).We experimentally investigated the dipole layer formation at Al2O3/AlFxOy (x:y = 1:1 and 1:2.5) interfaces, which would be explicable by considering the anion density difference as the key parameter to determine the dipole direction at the dielectric interface with different anions. Molecular dynamics (MD) simulation of Al2O3/AlF3 demonstrates a preferential migration of O from Al2O3 to AlF3 compared with F to the opposite direction which suggests that anion migration due to the density difference could determine the direction of the dipole layer formed at this interface. In addition, charge separation due to the difference in the anion valences could have certain effect simultaneously.

ISSN：00214922

概要：© 2017 The Japan Society of Applied Physics. The evaluation of strain states in silicon nanowires (Si NWs) is important not only for the surrounding gate field-effect transistors but also for the thermoelectric Si NW devices to optimize their electric and thermoelectric performance characteristics. The strain states in Si NWs formed by different oxidation processes were evaluated by UV Raman spectroscopy. We confirmed that a higher tensile strain was induced by the partial presence of a tetraethyl orthosilicate (TEOS) SiO2 layer prior to the thermal oxidation. Furthermore, in order to measure biaxial stress states in Si NWs accurately, we performed water-immersion Raman spectroscopy. It was confirmed that the anisotropic biaxial stresses in the Si NWs along the length and width directions were compressive and tensile states, respectively. The Si NW with a TEOS SiO2 layer on top had a larger strain than the Si NW surrounded only by thermal SiO2.

概要：© 2014 IEEE.We demonstrate that the image force effects in low-dimensional Si are highly controllable to achieve the best possible performance of the gate-all-around (GAA) Schottky barrier tunneling FET (SB-TFET). Our finite element electrostatic calculation shows that the image potential lowers near the metal source/drain, whereas it rises in the proximity of the gate insulator. Moreover, the drain induced barrier lowering (DIBL) of GAA-SB-TFET is suppressed by the image forces in a thin Si nanowire of about 4.0nm diameter.

ISSN：0021-4922

概要：Silicon nanowire Schottky barrier tunnel field effect transistors (NW-SBTFETs) are promising structures for high performance devices. In this study, we fabricated NW-SBTFETs to investigate the effect of nanowire structure on the device characteristics. The NW-SBTFETs were operated with a backgate bias, and the experimental results demonstrate that the ON current density is enhanced by narrowing the width of the nanowire. We confirmed using the Fowler–Nordheim plot that the drain current in the ON state mainly comprises the quantum tunneling component through the Schottky barrier. Comparison with a technology computer aided design (TCAD) simulation revealed that the enhancement is attributed to the electric field concentration at the corners of cross-section of the NW. The study findings suggest an effective approach to securing the ON current by Schottky barrier width modulation.

ISSN：0021-4922

概要：We show the electric dipole layer formed at a high-k/SiO2interface can be explained by the imbalance between the migration of oxygen ions and metal cations across the high-k/SiO2interface. Classical molecular dynamics (MD) simulations are performed for Al2O3/SiO2, MgO/SiO2, and SrO/SiO2interfaces. The simulations qualitatively reproduce the experimentally observed flatband voltage (VFB) shifts of these systems. In the case of the Al2O3/SiO2interface, a dipole layer is formed by the migration of oxygen ions from the Al2O3side to the SiO2side. By way of contrast, opposite dipole moments appear at the MgO/SiO2and SrO/SiO2interfaces, because of a preferential migration of metal cations from the high-k oxide toward the SiO2layer in the course of the formation of a stable silicate phase. These results indicate that the migrations of both oxygen ions and metal cations are responsible for the formation of the dipole layer in high-k/SiO2interfaces.

ISSN：2188-5303

概要：We demonstrate that the parallel computing with graphic processing unit (GPU) effectively accelerates a particle-based carrier transport simulation called EMC/MD method. The simulation speed is increased by parallelizing the point-to-point Coulomb's force calculation, which is sufficient to accomplish a device characteristic simulation of nanostructured metal-oxide-semiconductor field effect transistor (MOSFET) including source and drain diffusion regions. The EMC/MD simulation powered by GPU computing is a useful tool to investigate the statistical variability analysis of nano-scale transistors.

ISSN：1098-0121

ISSN：1520-5827

概要：:A large-scale molecular dynamics simulation was carried out in order to investigate the adsorption mechanism of ribosomal protein L2 (RPL2) onto a silica surface at various pH values. RPL2 is a constituent protein of the 50S large ribosomal subunit, and a recent experimental report showed that it adsorbs strongly to silica surfaces and that it can be used to immobilize proteins on silica surfaces. The simulation results show that RPL2, especially domains 1 (residues 1-60) and 3 (residues 203-273), adsorbed more tightly to the silica surface above pH 7. We found that a major driving force for the adsorption of RPL2 onto the silica surface is the electrostatic interaction and that the structural flexibility of domains 1 and 3 may further contribute to the high affinity.

ISSN：0021-4922

ISSN：0021-4922

ISSN：0743-7463

ISSN：0021-4922

ISSN：1569-8025

ISSN：19385862

概要：© The Electrochemical Society.We have newly developed the interatomic potential of Si, Ge or Ge, Sn mixed systems to reproduce the lattice constant, phonon frequency, and phonon dispersion relations in the bulk pure group IV crystal and group IV alloys by molecular dynamics (MD) simulation. The phonon dispersion relation is derived from the dynamical structure factor which is calculated by the space-time Fourier transform of atomic trajectories in MD simulation. The newly designed potential parameter set reproduces the experimental data of lattice constant and phonon frequency in Si, Ge, Sn, and SiGe. Furthermore, the Sn concentration dependence of the phonon frequency, which are not yet clarified, is calculated with three type assumptions of lattice constant in GeSn alloy. This work enables us to predict the elastic and phonon related properties of bulk group IV alloys.

ISSN：0021-4922

ISSN：0021-4922

ISSN：2162-8769

ISSN：0026-2714

ISSN：0021-4922

ISSN：0021-4922

ISSN：03885321

概要：This article reports the results of real-time scanning tunneling microscopy (STM) observation of Au+ ion irradiation effects on high-temperature Si surface, which was achieved by our original ion gun and STM combined system. Sequential STM images of a Si(111)-7×7 surface kept at 500oC were obtained before, during, and after Au+ ion irradiation with 3 keV. Vacancy islands, which are two-dimensional clusters of surface vacancies, and 5×2-Au structures were formed on the surface and their size were changed during the subsequent thermal treatment. This method enables us to count exact numbers of vacancies and Au atoms on the surface by measuring the sizes of vacancy islands and 5×2-Au reconstructions. The timescale of the growth of the 5×2-Au domain suggests that the implanted Au atoms diffuse to the surface almost without interacting with point defects induced by the ion irradiation.

ISSN：0913-5685

概要：ナノMOSFETにおいて形成されるとされる縦波光学(LO)フォノンが滞留した非平衡熱分布,いわゆるホットスポットの熱散逸過程を分子動力学(MD)シミュレーションにより調査した.Bulk-FinとSOI-Fin構造における熱拡散過程を比較し,埋め込み酸化膜(BOX)層がその拡散速度に与える影響を調査した.BOX膜厚を原子層レベルで変化させFin部からSi基板への熱拡散過程を解析したところ,Fin構造ではBOX層の厚さが1原子層であっても大きな熱の拡散バリアになることが分かった.これは,音響フォノンのSi基板への拡散がBOX層の存在により阻害され,その熱がFin中に滞留してしまうこどが原因であることが判明した.本結果は,デバイスの自己発熱効果の対策として,ナノ構造中にSi領域でできた熱の通り道を確保する必要があることを示している.

概要：

Nano composite (NC) materials have a great potential to improve characteristics of electrical rotating machinery insulation systems. In order to understand the contribution of the NC materials on the insulation characteristics, a fundamental study which used semi-conductor field technologies is shown in this paper. The thin NC film is formed on a silicon substrate by a spin coating method. The silica particle dispersion in epoxy is analyzed by SEM. Furthermore, the insulation breakdown is measured and the nanoscale breakdown spots are investigated by STM. The results show that a NC which has a potential of actual application is developed and that the nanoscale method seems to be effective for evaluating NC materials.

概要：© 2017 IEEE. A new device architecture of micro thermoelectric generator (μ-TEG) is proposed. The μ-TEG utilizes silicon nanowires as the thermoelectric (TE) material, and it can be fabricated by the CMOS-compatible process. It is driven by an 'evanescent thermal field' exuding around a heat flow perpendicular to the substrate. We demonstrate experimentally that the TE power increases in the shorter TE leg lengths. The results show that the TE power density is scalable by miniaturizing and integrating the proposed structure.

ISSN：00036951

概要：© 2017 Author(s). We have found experimentally an anomalous thermoelectric characteristic of an n-type Si nanowire micro thermoelectric generator (μTEG). The μTEG is fabricated on a silicon-on-insulator wafer by electron beam lithography and dry etching, and its surface is covered with a thermally grown silicon dioxide film. The observed thermoelectric current is opposite to what is expected from the Seebeck coefficient of n-type Si. The result is understandable by considering a potential barrier in the nanowire. Upon the application of the temperature gradient across the nanowire, the potential barrier impedes the diffusion of thermally activated majority carriers into the nanowire, and it rather stimulates the injection of thermally generated minority carriers. The most plausible origin of the potential barrier is negative charges trapped at the interface between the Si nanowire and the oxide film. We practically confirmed that the normal Seebeck coefficient of the n-type Si nanowire is recovered after the hydrogen forming gas annealing. This implies that the interface traps are diminished by the hydrogen termination of bonding defects. The present results show the importance of the surface inactivation treatment of μTEGs to suppress the potential barrier and unfavorable contribution of minority carriers.

概要：© 2017 IEEE. Energy harvester is a key device for realizing trillion sensors network society. Thermoelectric generator (TEG) is regarded as the ultimate energy harvester to provide semipermanent power from heat energies via Seebeck effect. The recent discovery of the superior thermoelectric (TE) property of silicon nanowires (Si-NWs) opens the way for Si-based TEGs. In this paper, a very simple device architecture of Si-based micro TEG is proposed. It can be fabricated by the CMOS-compatible process, and the TE power density is found to be scalable by miniaturizing and integrating the structure.

ISSN：00218979

概要：© 2017 Author(s). We demonstrate that the nickelidation (nickel silicidation) reaction rate of silicon nanowires (SiNWs) surrounded by a thermally grown silicon dioxide (SiO 2 ) film is enhanced by post-oxidation annealing (POA). The SiNWs are fabricated by electron beam lithography, and some of the SiNWs are subjected to the POA process. The nickelidation reaction rate of the SiNWs is enhanced in the samples subjected to the POA treatment. Ultraviolet Raman spectroscopy measurements reveal that POA enhances compressive strain and lattice disorder in the SiNWs. By considering these experimental results in conjunction with our molecular dynamics simulation analysis, we conclude that the oxide-induced lattice disorder is the dominant origin of the increase in the nickelidation rate in smaller width SiNWs. This study sheds light on the pivotal role of lattice disorders in controlling metallic contact formation in SiNW devices.

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口頭発表（招待・特別）開催地：東京

開催地：三島

口頭発表（招待・特別）

口頭発表（招待・特別）

口頭発表（招待・特別）開催地：熱海