Electronic structure of scandium nitride with nitrogen and scandium deficits

The effect of the stoichiometry on the lattice parameter, cohesive energy, bulk modulus and electronic structure of scandium nitride is studied by first-principles total energy computations. The calculations were made within the native spatial group of ScN (Fm3m) defining a doubled super cell using six of the available Wyckoff positions. In these position, it is possible to set the 32 N and 32 Sc atoms and can be used to make eight stoichiometric points in the Sc–N compositional range. The results show significant trends. For low nitrogen contents the material preserve its metallic character. At 1:1 ratio our calculations shows a semi-metallic character. However, for high nitrogen content there is a band gap of about 1 eV from the top of the valence band to the bottom of conduction band. However the gap is about 2 eV measured from the Fermi-level to the bottom of conduction band. That means that the material behaves as a heavily doped p-type semiconductor, with empty tail states extended 1 eV within the prohibited band.