Dynamics of Chemisorption/Scattering of Atomic Hydrogen on Partially Covered Si(111) Surfaces

摘要

The chemisorption and scattering of atomic hydrogen from fully and partially covered Si111) surfaces have been investigated using classical trajectory methods. Beam experiments were simulated for hydrogen atoms which had initial translational energy of 0.126 eV and three different azimuthal angles incident on a Si(111) surface. The effects of the surface with five different degrees of hydrogen-atom coverage were examined. The potential-energy surface used in this study is expressed as the sum of a lattice potential, a lattice-adatom interaction potential, and a repulsive adatom-adatom potential. The lattice-adatom interaction potential function accurately describes two binding sites on the Si(111) surface, a top binding site and an interstitial or open binding site. Presence of the interstitial or open site affects approach of hydrogen atoms to the surface by deflection of the trajectory from the target impact point. Direct scattering, exchange scattering, direct chemisorption, and chemisorption with exchange were observed. Indirect scattering via an absorbed state and hydrogen-atom migration on the surface were also observed. The probability of each process is dependent upon incidence angle and the degree of hydrogen-atom coverage present. Reprints. (mjm)