Influence of nitrogen content on the structural, electrical and mechanical properties of CrNx thin films

CrNx films were prepared using 20 kHz medium magnetron frequency magnetron sputtering in order to analyze the structural and mechanical features regarding to N2 content variations. XRD diffraction patterns reveal that only Cr phase with strong [1 1 1] orientation is observed for 0% nitrogen contents, the mixed Cr2N and Cr phases appear at 20% nitrogen content, while for 40% N2 content, no crystal structure feature is seen, indicating that an amorphous phase is generated. Further increasing the nitrogen content to 60% or above, only CrN phase appeared. SEM image shows a columnar-type structure lying in the transition zone between T and I zones of Thornton Model for the films. The critical load (Lc) are 23 and 14 g for the Cr films and CrNx (x > 0) films, respectively. The Cr film (0% N2 content) shows a low friction coefficient against the steel ball, but much higher against the Si3N4 ball. The friction coefficient of the CrNx films is lower in the range of nitrogen content from 20 and 40%, and then reached about 0.7, no obvious changes was observed with the N2 content further increasing.