Adsorption kinetics and surface unrelaxation in H:GaAs(110) studied by time-of-flight scattering and recoiling spectrometry

Time-of-flight scattering and recoiling spectrometry is used to study the chemisorption of II on a GaAs(110) surface. Monitoring of the neutral plus ion intensify for both the H direct recoils and the Ne and Ar backscattered projectiles as a function of the H exposure, the surface temperature, and the incident direction of the projectiles gives information about the substrate unrelaxation and its dependence on the adsorption kinetics. It is found that the adsorption proceeds with a sticking coefficient that decreases strongly with the coverage. at low exposures, the unrelaxed fraction of the surface increases linearly with the coverage. For coverages of the order of one monolayer there is an important fraction of the surface that remains relaxed as in the clean surface. The I-I recoil intensity is almost independent of the crystallographic sample orientation, suggesting that an important fraction of the H atoms are not adsorbed in well ordered sites. (C) 1999 Elsevier Science B.V. All rights reserved.