SIH4 ON TISI2 - AN INVESTIGATION OF GAS-ADSORPTION ON METAL-LIKE COMPOUNDS

Although titanium disilicide is composed mostly of a nonmetallic eleme nt, its electrical conductivity is metal-like. The question therefore arises as to whether the reactivity of TiSi2 toward gases resembles me tals, nonmetals, or some admixture. To investigate this question, the adsorption/desorption kinetics of SiH4 on polycrystalline TiSi2 were m easured by temperature programmed desorption. SiH4 interacts strongly with the surface, and only H-2 is observed as a desorption product nea r 300 K. The kinetics shift from second to first order as the coverage increases above 0.07. There is a crudely Gaussian distribution of des orption energies centered near 19 +/- 2 kcal/mol, with a full width at half maximum near 9 kcal/mol. In these and other respects, the behavi or of TiSi2 toward SiH4, and H-2 mirrors that of typical metals. Coads orption studies with TiCl4 further support this conclusion and also gi ve insights into the chemical vapor deposition of TiSi2 from these two source gases.