Effects of substrate temperature on properties of NbNx films grown on Nb by pulsed laser deposition

NbNx films were deposited on Nb substrate using pulsed laser deposition. The effects of substrate deposition temperature, from room temperature to 950 °C, on the preferred orientation, phase, and surface properties of NbNx films were studied by X-ray diffraction, atomic force microscopy, and electron probe micro analyzer. We find that the substrate temperature is a critical factor in determining the phase of the NbNx films. For a substrate temperature up to 450 °C the film showed poor crystalline quality. With temperature increase the film became textured and for a substrate temperature of 650−850 °C, mix of cubic δ-NbN and hexagonal phases (β-Nb2N + δ′-NbN) were formed. Films with a mainly β-Nb2N hexagonal phase were obtained at deposition temperature above 850 °C. The c/a ratio of β-Nb2N hexagonal shows an increase with increased nitrogen content. The surface roughness of the NbNx films increased as the temperature was raised from 450 to 850 °C.