Effect of film thickness on the structure and properties of nanocrystalline ZrN thin films produced by ion plating

Nanocrystalline ZrN thin films were successfully deposited on Si (100) and AISI 316 stainless steel (316SS) substrates using a hollow cathode discharge ion plating (HCD-IP) method. The objective of this study was to investigate the effect of film thickness on the composition, structure and mechanical properties of the ZrN films. The results showed that (111) was the dominant preferred orientation. The effect of the film thickness was significant on the N/Zr ratio, roughness, grain size and electrical resistivity. The packing factor was only slightly varied with film thickness; and the thinnest specimen, at a ZrN thickness of 160 nm, reached a quite high packing factor of 0.8. Nanoindentation data indicated that hardness of the films was not related to the film texture or residual stress. Since the grain sizes of ZrN films were less than 20 nm, the dislocation pileup or Hall-Petch hardening was not expected to active. The deformation mechanisms of the nanocrystalline ZrN films may be due to grain rotation or grain boundary sliding, instead of a dislocation slip mechanism. The residual stresses of all ZrN films were compressive, and did not vary with film thickness. The residual stress of the ZrN films deposited on Si is lower than that on AISI 316 stainless steel. This may be due to the differences in electrical conductivities and thermal expansion coefficients between Si and 316 stainless steel.