Electronic structure of an ideal diamond-nickel (001) interface

The rapid improvement in diamond-film growth raises the possibility of constructing diamond-metal interfaces for electronic-device applications. We present calculations of the electronic structure of an idealized, lattice-matched (001) superlattice of diamond and nickel slabs, using both the linear augmented-plane-wave and linear combination of atomic orbitals methods. Eight (001) layers of C were found to be sufficient to allow the diamond valence-band edge to be well defined. For the interface atomic geometry which we have chosen, there is a large density of states at the interface within the bulk diamond band gap whose character is a nonbonding combination of adjacent C ${\mathit{p}}_{\mathit{x}}$,${\mathit{p}}_{\mathit{y}}$ and Ni ${\mathit{d}}_{\mathit{x}\mathit{z}}$,${\mathit{d}}_{\mathit{y}\mathit{z}}$ orbitals, where the interface lies in the x-y plane. The predicted Schottky-barrier height is vanishingly small. The interface electronic structure is analyzed and discussed in detail. Both the high density of interface states and the vanishing barrier height suggest that this geometry may not be optimal. A small or vanishing barrier height would, however, promote Ohmic contacts to p-type diamond.