Deposition of Ti[sbnd]Zr alloy films using Ti and Zr dual-cathode high-power impulse magnetron co-sputtering

Abstract

In this study, titanium–zirconium binary alloy films were deposited using heterogeneous dual-cathode high-power impulse magnetron sputtering with a closed magnetron field. For both Ti and Zr cathodes, the discharge voltage pulses were synchronized with an equal pulse width. In addition, we investigated the effects of the average discharge power ratios of the two cathode materials, deposition pressure, and substrate bias voltage on the mechanical strength and microstructure of the deposited films. The results revealed that the film composition could be controlled by the average power ratio of the two cathodes at a constant deposition pressure; however, the deposition rate of each element varied with the deposition pressure. At a constant average power ratio at the two cathodes, the Zr content in the films decreased with decreasing the deposition pressure. Decreasing the deposition pressure can smoothen the film surface, but the dependence of the film composition on two cathode powers also changes. An adequate enhancement of the negative substrate bias can further increase the film hardness and reduce the film elastic modulus, yielding only a moderate loss in the film deposition rate and marginal variations in the film composition. However, the magnitudes of the increase in hardness and the decrease in elastic modulus brought by enhancing negative substrate bias varies with the film composition, and will be minimized when the atomic fractions of Ti and Zr are near equal. Notably, with adjusting the negative substrate bias, adding Zr can change the film hardness from 4.8 to 10.6 GPa, and the film elastic modulus from 100 to 162 GPa. Overall, the advantageous mechanical and structural properties of the TiZr alloy films deposited using HiPIMS might be useful in tools, biomedical devices, wearable equipment applications.