Hexagonal nitride coatings:: electronic and mechanical properties of V2N, Cr2N and δ-MoN

The electronic structure of hexagonal V2N, Cr2N and delta-MoN thin film nitrides, deposited by rf magnetron sputtering, have been investigated by X-ray photoemission spectroscopy. The binding energy values and the shape of the core level peaks are representative of the chemical bonding between the elements, and thus related to the mechanical properties. Comparing hexagonal and fee structures, both V2N and Cr2N are more covalent than the cubic phases VN and CrN. In the case of molybdenum nitrides, the fee and the hexagonal close-packed (hcp) structures exhibit comparable covalency level. The prominent covalent bonding in hexagonal Cr2N and V2N nitrides can be related with their higher hardness values compared to that of the fcc phases. (C) 1998 Elsevier Science S.A. All rights reserved.