Simulation of wet oxidation of silicon based on the interfacial silicon emission model and comparison with dry oxidation

Silicon oxidation in wet ambients is simulated based on the interfacial silicon emission model and is compared with dry oxidation in terms of the silicon-atom emission. The silicon emission model enables the simulation of wet oxidation to be done using the oxidant self-diffusivity in the oxide with a single activation energy. The amount of silicon emission from the interface during wet oxidation is smaller than that during dry oxidation. The small emission rate for wet oxidation is responsible for the insignificant initial oxidation enhancement and the linear pressure dependence of the oxidation rate observed in wet oxidation. Using a unified set of parameters, the whole range of oxide thickness is fitted for both (100) and (111) substrates in a wide range of oxidation temperatures (800 °C–1200 °C) and pressures (1–20 atm)

Graphene-Based Nano-Electro-Mechanical Switch with High On/Off Ratio

Locally defined nanomembrane structures can be produced in graphene films on a SiC substrate with atomic steps. The contact conductance between graphene and a metal-coated nanoprobe in scanning probe microscopy can be drastically reduced by inducing local buckling of the membranes. Repeatable current switching with high reproducibility can be realized. The on/off ratio can be varied from about 105 to below 10 by changing the contact force. At a low contact force, the contact conductance changes from 10μS (‘‘ON’’ state) to 100pS (‘‘OFF’’ state). This novel device structure could represent a new path to electrical switching at the nanoscale

Appearance of ferromagnetism in Pt(100) ultrathin films originated from quantum-well states with possibility of small orbital magnetic moment

Ferromagnetism was observed in a Pt(100) ultrathin film deposited on a SrTiO3(100) substrate. The ferromagnetism, which appears in films with thicknesses of 2.2-4.4 nm, periodically changes with a period of approximately 1 nm (5-6 ML) depending on the film thickness. This is consistent with the period derived from the quantum-well states formed in the thin film. X-ray magnetic circular dichroism measurements were conducted to understand the intrinsic nature of the ferromagnetism in the Pt(100) ultrathin films, and contrary to our expectations, the orbital magnetic moment of pure Pt is much smaller than that of the Pt/ferromagnetic multilayer system. These results suggest that the origin of the large magnetic anisotropy in Pt components cannot be explained only by the amount of spin-orbit coupling in Pt.Comment: 7 pages, 4 figure

Enhanced Si and B diffusion in semiconductor-grade SiO 2 and the effect of strain on diffusion

Abstract We present experimental and simulation results of Si self-diffusion and B diffusion in SiO 2 formed directly on Si substrates by thermal oxidation. We show that both Si and B diffusion in SiO 2 are enhanced by SiO generated at the Si/SiO 2 interface and diffusing into SiO 2 . We also show that the existence of high-concentration B in SiO 2 enhances SiO diffusion, which enhances both Si self-diffusion and B diffusion. This correlated diffusion of Si and B in SiO 2 is consistent with the first-principles calculation results, which show that B diffuses via a complex of BSiO with frequent bond exchanges in the SiO 2 network. Furthermore, based on the results, the enhancement of Si self-diffusion and B diffusion in SiO 2 by compressive strain and their retardation by tensile strain are suggested.

Theoretical Simulation of Scanning Tunneling Microscopy/Spectroscopy : Beyond LCAO Approximation

報告番号: 甲08875 ; 学位授与年月日: 1991-03-29 ; 学位の種別: 課程博士 ; 学位の種類: 理学博士 ; 学位記番号: 博理第2351号 ; 研究科・専攻: 理学系研究科物理学専

Electrical control of transient formation of electron-hole coexisting system at silicon metal-oxide-semiconductor interfaces

Abstract Recent observations of macroscopic quantum condensation using electron-hole (e-h) bilayers have activated the research of its application to electronics. However, to the best of our knowledge, no attempts have been made to observe the condensation in silicon, the major material in electronics, due to the lack of technology to form closely-packed and uniform bilayers. Here, we propose a method to meet such requirements. Our method uses the transient response of carriers to a rapid gate-voltage change, permitting the self-organized bilayer formation at the metal-oxide-semiconductor interface with an e-h distance as small as the exciton Bohr radius. Recombination lifetime measurements show that the fast process is followed by a slow process, strongly suggesting that the e-h system changes its configuration depending on carrier density. This method could thus enable controlling the phase of the e-h system, paving the way for condensation and, ultimately, for low-power cryogenic silicon metal-oxide-semiconductor devices