LASER-INDUCED CHEMICAL VAPOR-DEPOSITION OF TITANIUM DIBORIDE

This paper describes the pyrolytic deposition process of titanium diboride on mullite and on alumina by the hydrogen reduction of TiCl4 and BCl3. The great influence of the hydrogen on the growth rate and on the morphology is discussed. The deposition process resulted in a reaction rate limited regime and a diffusion rate limited regime, each with its characteristic morphology. The origin of the observed morphology in the diffusion limited regime is, in the case of alumina substrates, thermal diffusion limitation, and in the case of mullite substrates mass diffusion limitation as well. Photolytic enhancement may more than double the growth rate.