Effects of substrate temperature and bias voltage on mechanical and tribological properties of cosputtered (TiZrHfTa)Nx films

Abstract

This study investigated the effects of substrate temperature and bias voltage on the mechanical and tribological properties of cosputtered (TiZrHfTa)N_x films. A substrate temperature ranging from room temperature to 400 °C, and a bias voltage ranging from 0 to −150 V were selected as the sputtering variables. A mixture gas with a nitrogen flow ratio (f_N2 = N₂/[N₂ + Ar]) of 0.2 was used to fabricate nitride films. Nanoindentation and wear tests were conducted to assess the performance of the fabricated (TiZrHfTa)N_x films, which formed a single face-centered cubic structure. Increasing the substrate temperature resulted in grain growth, lattice shrinkage, and nonsignificant improvements in mechanical properties. Applying a bias voltage of −150 V to the substrate increased the hardness of the fabricated film to a peak of 32.7 GPa compared with that of 29.3 GPa for the film prepared in an electronically grounded state. The (Ti_0.24Zr_0.22Hf_0.19Ta_0.35)N_0.66 film prepared at a bias voltage of 0 V and substrate temperature of 400 °C exhibited the optimal combination of mechanical and tribological properties (hardness, 30.0 GPa; elastic modulus, 325 GPa; and wear rate, 1.16 × 10⁻⁵ mm³/Nm).