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 °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 β-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.