Adsorption of hydrogen on the (001) surface of diamond

The electron-energy structure, total, and local densities of states of the clean (001)-(1×1),π-bonded symmetric dimer (001)-(2×1), monohydride (001)-(2×1):H, and dihydride (001)-(1×1):2H surface structures of diamond are investigated utilizing the self-consistent tight-binding method. The total-energy minimization method has been used to determine the equilibrium geometry of the (001) diamond surface. Clean (001)-(1×1) and π-bonded symmetric-dimer (001)-(2×1) surfaces are characterized by sharp dangling bonds near the middle of the gap. Adsorption of H completely removes surface states from the gap in the dihydride phase. In the dihydride phase, hydrogen-induced bonding surface states occur near the top of the valence band and at the bottom of the conduction band, resulting in an enhancement of the surface conductivity due to the adsorption of hydrogen. In the monohydride (001)-(2×1):H symmetric-dimer phase the bonidng surface states occur in the range around the top of the valence band and near the middle of the gap. The results obtained are discussed and compared with experimental data available in the literature.