Structural, electronic, and mechanical properties of niobium nitride prepared by thermal diffusion in nitrogen

Niobium nitride (NbNx) was prepared by heating Nb sample in a nitrogen atmosphere (133 Pa) at a temperature of 900 degrees C. The structural, electronic, nanomechanical and surface properties of the deposited layers have been determined as a function of processing time. The results suggested that the niobium nitride was crystalline in the single phase of hexagonal beta-Nb2N and the nitrogen-to-niobium ratio was found to be in the range of 0.67 +/- 0.03 to 0.74 +/- 0.03. Longer processing times resulted in layers with higher nitrogen-to-niobium ratios. The mean grain size of these nitrides was about 18 nm. The valence band photoemission and calculated density of state spectra characterized by two peaks were associated with N 2p-Nb 4d hybridization. X-ray photoemission spectra of Nb 3p and 3d core levels revealed a strong interaction with nitrogen along with binding energy shift. As the processing time was increased, the film growth continued with consistent improvement in hardness and modulus. (C) 2013 Elsevier B.V. All rights reserved.