Abstract
Abstract The Laser Chemical Vapour Precipitation (L-CVP) of Si3N4 powders from mixtures of halogenated silanes and NH3 has been studied. The reactant gases were mixed at varying position in the laser beam, thus preventing low temperature reactions. The Si3N4 was collected and separated from the waste product, NH4Cl, by electrostatic precipitation. A major problem in utilizing SiHCl3 and SiCl4 is their poor absorption of radiation from CO2-lasers. SF6 and SiF4 have been explored for possible use as an inert sensitizer. Silicon can be prepared from SiH2Cl2 without the use of a sensitizer. The diameter of the Si3N4 particles is typically between 15nm and 110nm dependent on the process conditions.
