THE CHEMISORPTION BEHAVIOR OF OXYGEN ON THE SI(100) SURFACE

Starting from the 2 × 1 reconstruction the chemisorption of oxygen on the Si(100) surface has been studied extensively by the ASED-MO method. While molecular oxygen adsorption on the reconstructed 2 × 1 surface prefers the dimer-bridge site, dissociation follows immediately with the Si(100)2 × 1 structure reverting back to the ideal unreconstructed surface so that the dissociated oxygen atoms occupy the dimer-bridge sites of a 1 × 1 oxygen superlattice. Further molecular oxygen chemisorption is found to favor the non-dimer-bridge sites as a peroxy bridge model. At elevated temperatures the oxygen molecules are able to overcome the corresponding energy barrier to chemisorb on the short-dimer-bridge sites (between the first layer and second layer silicon atoms). Molecular chemisorption is found to be a precursor to the chemisorption of atomic oxygen onto the short-bridge sites and coexists with atomic chemisorption under certain conditions. Chemisorption at the short-bridge sites can only occur, however, after occupation of the dimer-bridge sites by oxygens. © 1990.