SYNTHESIS AND CHARACTERIZATION OF ULTRAFINE SI POWDERS FROM LASER-INDUCED SIH4 GAS REACTIONS

Ultrafine silicon powders with a mean particle diameter of 20-200 nm a nd a mean crystallite diameter of 18-37 nm were synthesized from high purity SiH4 by laser induced gas phase reactions. The Si powders have been characterized by TEM, XPS, FTIR, XRD and BET techniques, and the effects of processing variables including SiH4 flow rate, laser power, cell pressure and the Ar/SiH4 ratio on the formation of the Si powder s have been studied. Results showed that the powders consisted of mono dispersed spherical particles, and agglomerated particles; both types of particles have polycrystalline structure, which resulted from the i nterparticle collision growth during the formation of the powders. The nonagglomerated spherical particles with a small size were favored to form with a lower laser power and higher Ar/SiH4 ratios. The Si powde rs have O-Si-H surface configuration due to oxidation when exposed to air.