Influence of fabrication parameters on crystallization, microstructure, and surface composition of NbN thin films deposited by rf magnetron sputtering

In this work NbN thin films have been grown by magnetron rf sputtering of a δ-NbN (99.99%) target. In particular, the influence of certain fabrication parameters (substrate temperature, power supplied to the target or additional N2 flux in the preparation chamber) on the crystallization, microstructure, and surface composition of the deposited films have been studied. The films have been characterized by X-ray diffraction (XRD) at grazing angle in the θ–2θ configuration, scanning electron microscopy (SEM), wavelength dispersive spectrometry (WDS), and X-ray photoelectron spectroscopy (XPS). XRD results show that films grown at a substrate temperature of 573 K and a power supply applied to the target of 300 W present the same crystalline structure of the target while films grown at these temperature and power supply conditions plus the additional presence of N2 during fabrication, grow highly textured along the plane (200). SEM results indicate that the films present columnar growth and a high homogeneity. WDS analysis shows that films grown at 573 K and 300 W are stoichiometric. XPS shows a complex surface composition of the films most external 5 nm, indicating the presence of niobium nitride (NbNx), niobium oxy-nitride (NbNxOy), and niobium oxide (Nb2O5).