Shin-ichi Kobayashi

Selective germanium epitaxial growth on silicon using CVD technology with ultra-pure gases

Low pressure chemical vapor deposition (LPCVD) experiments of Ge are presented. The results show that Ge epitaxy is possible by the LPCVD technique at low temperatures, if high-purity reactive gases and ultrahigh vacuum (UHV) compatible CVD equipment is used. Epitaxial films can be grown for several deposition parameter combinations. At low GeH4 pressures facet formation can be observed, which originates from a stepflow dominated growth mechanism. At higher partial pressures plain surfaces are obtained due to dangling bond dependent growth, which is verified in a comparison between several Si substrate orientations. Ge CVD reveals perfect Si/SiO2 selectivity and can, therefore, be used as a contact hole filling method as shown by Ge plugs in contact holes.

Deterministic chaos in the hemodynamics of an artificial heart

To analyze the hemodynamic parameters during prosthetic circulation as an entity, non linear mathematical techniques were used. To compare natural and prosthetic circulation, two pneumatically actuated ventricular assist devices were implanted as biventricular bypasses in chronic animal experiments using adult goats to consitute the biventricular bypass complete prosthetic circulation model with ventricular fibrillation. After implantation, these goats were placed in a cage and extubated after waking. All hemodynamic parameters with the natural circulation without biventricular bypass pumping, and the artificial circulation with biventricular bypass pumping under ventricular fibrillation were recorded under awake conditions. By the use of a non linear mathematical technique, the arterial blood pressure waveform was embedded into a four dimensional phase space and projected into three dimensional phase space. The Lyapunov numeric method is used as an adjunct to the graphic analysis of the state space. A phase portrait of the attractor showed a high dimension complex structure, with three dimensional solid torus suggesting deterministic chaos during natural circulation. However, a simple attractor, such as a limit cycle attractor, was observed during artificial circulation. Positive Lyapunov exponents during artificial circulation suggest the lower dimensional chaotic system. Thus, hemodynamic parameters during prosthetic circulation must be carefully controlled when unexpected stimuli are fed from outside.

Initial growth characteristics of germanium on silicon in LPCVD using germane gas

Abstract The growth characteristics in the initial stage of Ge epitaxy on the Si(1 0 0) epitaxial buffer layer have been investigated by ultraclean LPCVD at 350°C using GeH 4 at 0.2 and 12 Pa with H 2 or Ar as a carrier gas. When H 2 was used as a carrier gas, an incubation period was found (about 12 min at 0.2 Pa), during which Ge nuclei were formed on Si. After the incubation period layer growth of Ge film began. In the case where Ar was used as a carrier gas, the incubation period was drastically reduced without any apparent change in the layer growth rate. The nucleus size was larger and the nucleus density was lower in the case of H 2 as carrier gas. These growth characteristics are believed to be caused by the suppression of adsorption and/or decomposition of GeH 4 on the H-terminated Si surface in the case of H 2 .

Algebraic theta functions and the

We study the properties of Eisenstein-Kronecker numbers, which are related to special values of Hecke

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-adic interpolation of Eisenstein-Kronecker numbers

-function of imaginary quadratic fields. We prove that the generating function of these numbers is a reduced (normalized or canonical in some literature) theta function associated to the Poincare bundle of an elliptic curve. We introduce general methods to study the algebraic and

Can the artificial heart make the circulation become fractal

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On the de Rham and p-adic realizations of the elliptic polylogarithm for CM elliptic curves

-adic properties of reduced theta functions for CM abelian varieties. As a corollary, when the prime

Chaotic behavior of hemodynamics with ventricular assist system.

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Development of total artificial heart with economical and durability advantages.

is ordinary, we give a new construction of the two-variable