Optical second-harmonic investigations of H2 and D2 adsorption on Si (100) 2 × 1: the surface temperature dependence of the sticking coefficient

Optical second-harmonic generation has been used to determine the sticking probability for dissociative adsorption of H2 and D2 on Si(100)2× 1 as a function of surface temperature. The initial sticking coefficient increases from 10−8 at 550 K to 10−5 at 1000K. It shows an activated behaviour as a function of the surface temperature with an activation energy of 0.70 ± 0.1 eV for Hz and 0.75 ± 0.1 eV for D2. The results demonstrate that lattice distortions play a significantly stronger role in the adsorption process than would be expected solely from the tilting of Si-Si dimers.