SiH₄ on TiSi₂: an investigation of gas adsorption on metal-like compounds

Although titanium disilicide is composed mostly of a nonmetallic element, its electrical conductivity is metal-like. The question therefore arises as to whether the reactivity of TiSi₂ toward gases resembles metals, nonmetals, or some admixture. To investigate this question, the adsorption/desorption kinetics of SiH₄ on polycrystalline TiSi₂ were measured by temperature programmed desorption. SiH₄ interacts strongly with the surface, and only H₂ is observed as a desorption product near 300 K. The kinetics shift from second to first order as the coverage increases above 0.07. There is a crudely Gaussian distribution of desorption energies centered near 19 ± 2 kcal/mol, with a full width at half maximum near 9 kcal/mol. In these and other respects, the behavior of TiSi₂ toward SiH₄ and H₂ mirrors that of typical metals. Coadsorption studies with TiCl₄ further support this conclusion and also give insights into the chemical vapor deposition of TiSi₂ from these two source gases.