Effect of N2 flow rates on the structure and hardness of nanocrystalline CrZrN thin films prepared by reactive DC magnetron co-sputtering

This work successfully investigated the effect of N2 gas flow rates on the structure and hardness of chromium zirconium nitride (CrZrN) thin films. The CrZrN films were deposited on silicon wafers using a reactive DC unbalance-magnetron co-sputtering process with N2 flow rates ranging from 4 to 10 sccm. The crystal structure was investigated using grazing-incidence X-ray diffraction (GI-XRD). Field-emission scanning electron microscopy (FE-SEM) was used to examine the included material's microstructure, surface morphology, and thickness. The elemental composition was determined using energy dispersive spectroscopy (EDS). The hardness was measured using the nanoindentation method in depth-controlled mode. The results reveal that the as-deposited films were formed as a nanocrystalline (Cr,Zr)N solid solution with small crystal sizes less than 10 nm. Increasing the N2 flow rate altered the preferred orientation growth behavior by decreasing the 2θ-values and increasing the lattice constants. The thickness decreased from 569 nm to 410 nm as the N2 flow rate increased, due to target poisoning. The elemental composition of the as-deposited films was affected by changes in the N2 flow rates. The N content increased with higher N2 flow rates, while the Cr and Zr contents decreased. The surface morphology of the films changed as the N2 flow rate increased, due to the reduction in ion-bombardment energy, leading to a decrease in substrate temperature. The as-deposited films consisted of tiny grains, which grew larger with increasing N2 flow rates. Cross-sectional analysis showed that the films exhibited a compact columnar structure. The hardness of CrZrN films in this study ranged from 13.1 to 13.8 GPa at various N2 flow rates.