THE STABLE CONFIGURATIONS FOR OXYGEN-CHEMISORPTION ON THE DIAMOND (100) AND (111) SURFACES

The structures resulting from oxygen chemisorption onto the diamond (100) and (111) ideal and reconstructed surfaces have been extensively studied using the SLAB-MINDO molecular orbital method. For the C(100) surface, we find that the lowest energy configuration for monolayer chemisorption is a 1 x 1 on-top structure whilst that for half-monolayer chemisorption is a 2 x 1 dimer bridge site topology. For the C(111) surface, both the single-bond cleavage and triple-bond cleavage surfaces have been studied. Bridge site molecular oxygen chemisorption parallel to the surface is found to be responsible for monolayer oxygen coverage on the single dangling bond C(111) surface. For half-monolayer coverage, chemisorption of atomic oxygen onto the bridge sites of the 2 x 1 pi-bonded chain model reconstructed surface is the preferred mechanism. Molecular oxygen is found to be directly dissociative on the triple dangling bond C(111) surface. The lowest energy monolayer configuration on the triple-bond cleavage surface is found to be a tilted on-top model of the single chain reconstructed surface whilst a half-monolayer exposure prefers the bridge sites of the surface single chains. Both the monolayer and half-monolayer minimum energy configurations are found to retain the 2 x 1 topology of the clean C(111) surface. These results are compared with previous studies of oxygen chemisorption onto the Si(100) and (111) surfaces.