Residual stress and strains of highly textured ZrN films examined by x-ray diffraction methods

ZrN films of very strong (100) fibre texture on the substrates of stainless steel and tool steel were obtained by using a reactive DC magnetron sputtering technique. The residual strains along various directions in the as-deposited films were measured using an x-ray diffraction method. The results show that the variations of strains with the direction in the films deposited on both substrates do not follow that predicted for an isotropic medium. Instead, the strain variations are close to that of a single crystal. The residual stresses derived from the measured strains on the basis of the anisotropic elasticity are about 4 GPa in compression. A simple calculation indicates that the thermal stresses imposed by the substrates are relatively small. Therefore, the residual stresses in these films are mainly due to the mutual impingement of grains and the growth defects developed during the deposition process. The strong texture in the present films also results in smaller strain distributions compared with that in similar films of milder texture.