Electronic and structural properties of diamond (001) surfaces terminated by selected transition metals

The presence of adsorbate species on diamond surfaces, even in small concentrations, strongly influences electrical, chemical, and structural properties. Despite the technological significance, coverage of diamond by transition metals has received relatively little attention. In this paper, we present the results of density functional calculations examining up to a monolayer of selected metals (Cu, Ni, Ti, and V) on the (001) diamond surface. We find that addition of carbide forming species (Ti and V) results in significantly higher adsorption energies at all surface coverages relative to those of the non-carbide-forming species. For monolayer coverage by Cu or Ni, and sub-monolayer coverage by Ti and V, we find large, negative electron affinities. We propose that based upon the electron affinities and binding energies, metal-terminated (001) diamond surfaces are promising candidates for electron emission device applications.