Electronic structure of Nb2N and NbN thin films

The electronic structure of the hexagonal beta-Nb2N, hexagonal delta(')-NbN, and cubic delta-NbN thin films have been investigated by x-ray photoemission spectroscopy. Calculated density of states for these phases are also presented and used in the interpretation of the experimental valence band spectra. The experimental energy distribution curves are consistent with the calculated densities of states. Comparing hexagonal to cubic phases, both beta-Nb2N and delta(')-NbN are more covalent than the cubic phase NbN. Prominent covalent bonding in hexagonal beta-Nb2N and delta(')-NbN nitrides can be related with the higher hardness values as compared to that of the cubic phase. This study discloses relevant observations important for both the technological applications and fundamental properties. (c) 2006 American Institute of Physics.