Bias-voltage effect on the TiN nanoparticle injection into magnetron sputtered CrN thin films towards nc-TiN/nc-CrN composites

Abstract

The formation of a nanocomposite structure is thermodynamically driven by spinodal decomposition in at least two phases. With respect to the suppression of solid solution formation, artificial nc-TiN/nc-CrN composites were deposited using a novel hybrid-process, in which TiN nanoparticles and CrN thin film were separately synthesized and simultaneously deposited during composite growth. The bias-voltage is known as a crucial deposition parameter concerning the structural and mechanical properties in thin film technology. However, it is still unclear whether an externally injected nanoparticle jet is influenced by the bias-voltage applied to the substrate. In this work, composite thin films were DC sputtered applying bias-voltages of 0 V, -100 V and -200 V in DC mode, as well as -100 V in MF and HiPIMS mode. TEM-investigations reveal the successful embedment of the nanoparticles in the film. Growth defects in the interface between nanoparticle and thin film can be reduced using a pulsed bias-voltage. Based on 2D GI-XRD experiments using synchrotron radiation, a bias-voltage of -200 V DC and -100 V MF enables the reinforcement of a higher nanoparticle content in the thin films. Similar to an increased bias-voltage, the injection of nanoparticles results in a decrease of the crystallite size. In principle, the residual stresses are increased by the nanoparticle embedding, as is the case for an increasing bias-voltage. In the event of a pulsed-bias voltage, however, the residual stresses can be reduced by the embedding of the nanoparticles. The mechanical properties of the CrN thin films can be maintained when nanoparticles are injected.