Effects of deposition temperature and bilayer thickness on the mechanical properties of AlN/TiN multilayer thin films

By controlling the thickness of individual layers (20–70 nm) and substrate temperature (∼50–800 °C), a number of AlN/TiN multilayer films were grown in a reactive magnetron sputtering on the Si(100) and WC–Co substrates. The films were characterized using grazing incidence X-ray diffraction (XRD), nanoindentation, and cross-sectional electron microscopy [transmission electron microscopy (TEM) and HRTEM]. The measured hardnesses of multilayer films were found to be always higher than the rule of mixture, but the magnitude of hardness enhancement was found to be dependant on the bilayer thickness and deposition temperature. The obtained results are discussed in terms of interface-related phenomena, as well as structural modifications, that occur within the individual layers of TiN and AlN, i.e., change of grain size, transition of preferred orientation from (111) to (200), localized epitaxial growth between TiN and AlN crystallites, and development of biaxial residual stresses.