<b><i>Ab initio</i></b>calculations of the atomic and electronic structure of clean and hydrogenated diamond (110) surfaces

We present ab initio local-density-functional calculations of the electronic structure of clean and hydrogenated diamond (110) surfaces. The clean surface relaxes to a structure where the chains in the first two planes are straightened so that the interatomic distances are shortened and the bond angles are increased. Upon relaxation the surface remains flat and no dimerization occurs. The dangling bonds lead to surface states within the bulk gap. The surface is metallic, but with a very low density of states at the Fermi level. After the deposition of a monolayer of hydrogen, which saturates all dangling bonds, the surface relaxes back to an almost bulk-terminated structure. The occupied surface states are removed from the gap and the surface becomes semiconducting. We also compare the C(110) surface with the other two low-index diamond surfaces.