Synthesis of Ceramic Powders and Surface Films From Laser Heated Gases

Two new processes have been developed that are based on laser heated gases. Both permit unusually precise levels of process control and thereby materials having superior properties.The powder process yields Si, Si₃N₄ and SiC powders that are uniform in size, non-agglomerated, small diameter, spherically shaped and high purity. Manufacturing cost analyses show that sub- micron powders can be made with an energy cost of approximately 2 kWhr/kg and a dollar cost of 2–3.30 $/kg exclusive of the costs of feed materials. This type of process should be capable of producing technically superior, lower cost submicron powders than existing processes.The laser induced chemical vapor deposition process (LICVD) causes reactant gases to be heated by absorbing IR light from a laser beam that passes parallel to the substrate surface. Laser heating permits independent control of gas and substrate temperatures while operating in a conventional thermally activated CVD mode. For hydrogenated amorphous silicon films, this is particularly important because deposition rates are determined by the high gas temperatures and film properties by the low substrate temperatures. Spin density, hydrogen content, electrical conductivity and mobility gap properties show the LICVD process capable of producing very high quality films.