Synthesis of silane and silicon in a non-equilibrium plasma jet. Fifth quarterly report, June 21, 1977--October 31, 1977

The objective of this program is to determine the feasibility of using a non-equilibrium hydrogen plasma jet as a chemical synthesis tool in helping to meet the objectives of the JPL Low-Cost Silicon Solar Array Project. Reactions of hydrogen atoms (produced by a glow discharge and expanded through a nozzle) with chlorosilanes are being studied. During this period, previous results were evaluated and four possible processes identified for further study: (1) production of polycrystalline silicon photovoltaic surfaces, (2) production of SiHCl/sub 3/ from SiCl/sub 4/, (3) production of SiH/sub 4/ from SiHCl/sub 3/, and (4) purification of SiCl/sub 4/ by metal impurity nucleation. Estimates, based on homogeneous and wall recombination rates, indicate that the hydrogen atom concentration far downstream of the nozzle at the liquid nitrogen traps is less than 20% of its original value. This could account for the low yields, about 10% of SiCl/sub 4/ converted to SiHCl/sub 3/ collected in the traps, but does not explain the failure to observe reactions of SiCl/sub 4/ in the gas phase. In situ mass spectrometric measurements using SiHCl/sub 3/ indicated about 30% SiHCl/sub 3/ consumption; SiH/sub 4/ was qualitatively identified as a gas-phase product. Previous difficulties with the mass spectrometer have been corrected and these questions can now be addressed more accurately. The most striking result was the recognition that the strongly adhering silicon films, amorphous or polycrystalline, produced in the studies could be the basis for preparing a photovoltaic surface directly; this process has potential advantages over other vapor deposition processes