Yoshio Oshita

Orientation Dependence of Silicon Oxidation Ratio in High-Pressure Water Vapor

We investigated the relative oxidation rates of single-crystalline Si substrates with various orientations to study the formation of thermally grown oxide films on multicrystalline Si at low temperatures in high-pressure water vapor. The oxidation rates depended greatly on the Si substrate orientation, but the increasing pressure did not change the proportion of their relative oxidation ratio even though the oxidation rate was accelerated by the pressure. On the basis of our modeling of the Si surface structure, we consider that the dependence of oxidation ratio on substrate Si orientation depends in turn on interface atomic density for a structure that has one or two Si–O bonds.

Migration of the aluminium enhanced crystal growth process from quartz to glass using EBEP-CVD

The use of aluminium precursor films has already been shown to enhance the as-deposited grain size of silicon films on quartz substrates as grown by electron beam excited plasma chemical vapour deposition (EBEP-CVD). In this paper, the process is successfully migrated from quartz substrates to Corning 1737, low cost glass. The move to low cost substrates is essential for the viability of the process in producing silicon films suitable for low cost photovoltaics. Thin aluminium layers are evaporated onto Corning 1737 substrates prior to EBEP-CVD deposition of silicon at 400-600/spl deg/C. Subsequent analysis by X-ray diffraction shows increases in as-deposited grain sizes up to 40 nm, exceeding results achieved on quartz; without aluminium the as-deposited grain size is around 5 nm. The grain size enhancement is dependant on the silicon deposition temperature and the substrate cleaning regime. There is also an apparent correlation between the silicon aluminium grain sizes.

Ion Beam Induced Effects in RF Plasma Chemical Vapor Deposition Deposited Hydrogenated Amorphous Carbon Thin Films

Boron ions of 65 keV are bombarded into hydrogenated a-carbon films deposited by radio frequency plasma chemical vapor deposition technique. Ion beam current dependence studies on the physical properties of a-C films for a fixed boron dose of 1×1016 ions/cm2 reveal the reduction in resistivity, whereas the optical gap is found to be unaffected. The structural phase transition accompanied by the reduction in the optical gap and resistivity takes place when the ion dose is increased. These changes are due to the production of defect levels and localized heating effects during the ion implantation process.