The cluster approach in the study of atomic and molecular chemisorption on silicon

Abstract

Ab initio and MNDO methods have been used in the framework of the cluster model for a systematic study of the chemisorption of atoms and molecules on low-index silicon surfaces. Chemisorption of hydrogen and halogen atoms occurs preferentially at on-top positions for the (111) surface, but (except hydrogen) at bridge positions on the (100) surface. Chemisorption of other species (O, OH, S, SH, H 2 O, H 2 S) always occurs at bridge positions. When large adsorbates are involved, high coordination sites become to assume an increasing importance, although the binding energy at the preferred site generally decreases with the dimensions of the adsorbate.