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Rf plasma chemical vapor deposition from silane was numerically analyzed. When a substrate was moved away from the plasma, gas-phase polymerization increased the contribution of oligomer radicals to film deposition. In addition, the contribution of silylene radicals became lower compared with that of silyl radicals. As a result of the trade-off between these two effects, an optimal plasma-substrate distance, where a high-quality a-Si:H film was obtained, appeared. Dilution of feed silane with hydrogen effectively reduced gas-phase polymerization and enhanced the generation of hydrogen radicals that create silyl radicals selectively through a reaction with silane. Improvement of the film quality as a result of plasma-substrate separation and hydrogen dilution was thus explained by the change in the composition of film precursors.

Fluid flow and heat transfer in a rotating cylindrical container with a counterrotating disk at the fluid surface are numerically investigated. The effects of disk rotation and of Prandtl numbers on the fluid flow and heat transfer in the container are discussed. Flow and temperature fields are obtained for various rotational Reynolds numbers of the disk and for Prandtl numbers of the fluid. Nusselt numbers on the walls are calculated for the temperature fields and are compared with available experimental data. © 1999 Scripta Technica, Heat Trans Asian Res, 28(3): 172–182, 1999