STABILITY, RECONSTRUCTION, AND ELECTRONIC-PROPERTIES OF DIAMOND (100)AND (111) SURFACES

Results of scanning-tunneling-microscopy (STM) and molecular-dynamics (MD) annealing studies based on quantum-mechanically derived interatom ic forces using a semiempirical density-functional approach are combin ed for analyzing diamond surface structures. Experimentally obtained S TM images of diamond (100) and (111) faces on polycrystalline films re veal (1X1),(root 3X root 3)R30 degrees, and possible (2X1) structures. The (100) faces show stable (2X1) reconstruction with dimer formation . Surface structures with and without adsorbed hydrogen are determined and their stability is obtained by MD simulated annealing techniques. The bulklike and (root 3X root 3) R30 degrees structures; as they are observed on grown (111) facets, are attributed to the two different s ingle atomic (111) layers, which support growth mechanisms, in which t he two alternating single atomic layers grow in turn and not simultane ously. The equilibrium surface modifications which have been realized are electronically characterized by investigating the local electronic density of states at selected surface atoms. This information is comp ared and related to the features seen in the STM images.