No abstract

Surface C/Si ratio was demonstrated as a useful indicator for the control of in-wafer distribution of thickness and carrier concentration in 4H-SiC homo-epitaxial films on large-diameter wafers. Close investigation of the dependence of growth rate and carrier concentration on the radial distance from the center of the 150 mm wafer revealed that the actual C/Si ratio just above the wafer: surface C/Si ratio, is quite different to the introduced C/Si ratio. In-wafer distribution of thickness and carrier concentration in the epitaxial films can be explained by the surface C/Si ratio, which suggests that the surface C/Si ratio could be a useful indicator for the precise control of uniform growth on large-diameter wafers. It is also found that two types of SiC films, one with extremely low defect density and the other with low pit density, both with highly uniform growth rate and carrier concentration, could be grown by controlling of the surface C/Si ratio on the whole wafers.

A silicon carbide chemical vapor deposition reactor cleaning process was designed by managing and utilizing the temperature increase due to the exothermic reaction heat produced by the chemical reaction between chlorine trifluoride gas and a particle-type polycrystalline silicon carbide layer. The main issues were (i) the initial susceptor temperature, (ii) the exothermic reaction heat, and (iii) the heat transport from the susceptor surface for reducing the peeling of the susceptor coating film. The important parameter was the initial susceptor temperature for performing the moderate etching of the silicon carbide layer and the local etching at the contact point between the silicon carbide particles and the susceptor surface. The 30-μm-thick particle-type polycrystalline silicon carbide layer could be detached and cleaned in two minutes.

The solubility of cholesterol in the binary solubilizates system (cholesterol and -sitosterol) of a sodium taurodeoxycholate solution decreased to almost half of that in the single cholesterol system. On the other hand, the cholesterol solubilities in other binary other systems (cholesterol and certain aromatics) of those solutions were the same as that of the single cholesterol system. The results of competitive solubilization between sterols and aromatics suggested that both were solubilized at different solubilization sites of a micelle. Their molecular dynamics and solubilization sites were measured by the 1 H NMR method. The rotating-frame nuclear Overhauser effect and exchange spectroscopy (ROESY) contour plot of aromatics solubilized micellar solution exhibited direct cross-peaks between the aromatics and bile salt of 19-methyl protons. The observed ROESY spectra of the sterol-solubilized solutions were almost identical to those of the pure micellar solution. The spin-lattice relaxation time (T 1 ) for aromatics solubilized in the micellar solutions increased for 18-, 19-, and 21-methyl protons of the bile salt in comparison with those of a pure micellar solution, which indicated that the micellar core changed to a loosely packed state owing to the penetration of aromatics. On the other hand, the T 1 values for sterols solubilized in micelles were lesser than those for pure micellar solutions for almost all proton positions, which suggested that the sterols were compatible with the micelle. These results indicated that the aromatics were solubilized in micellar palisade layer interacting with bile salt of methyl protons, whereas, the sterols were solubilized to match the micellar structure via the steroids interaction.in parentheses are the calculated ones. -Sitosterol was purchased from Tama Biological, Japan, and its high purity was confirmed Fig. 2. Solubility change of cholesterol, -sitosterol, and aromatic compounds in a single solubilizate system (left-hand side) and solubilizate of cholesterol and other compounds in a binary mixed system (right-hand side) in a 15 mM NaTDC solution. K. Matsuoka et al.

No abstract