Deposition of titanium films on complex bowl-shaped workpieces using DCMS and HiPIMS

Abstract

Herein, the deposition of titanium films on complex bowl-shaped workpieces was conducted using direct-current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS) methods, and the differences in the properties of the film deposited using these methods were investigated. Metallic titanium films were deposited on the inner (concave) and outer (convex) surfaces of a bowl-shaped workpiece. The deposition rate, crystal structure, microhardness, and cross-sectional morphology of the titanium films at different deposition angles with respect to the normal vector of the target surface were characterized. Results showed that HiPIMS films exhibited better uniformity in terms of the crystal texture, microhardness, and microstructure than that of DCMS films, for both concave and convex surfaces. The differences between the properties of the HiPIMS and DCMS deposited films can be attributed to the significantly reduced self-shadowing effect in the oblique incidence deposition provided by HiPIMS. The enhanced energetic bombardment of depositing species on the substrate in the ionization-rich HiPIMS plasma facilitates the deposition films with uniform crystal structures and properties. However, a distinct difference in the film deposition rates was observed for the different shapes of the substrates in both deposition techniques. The films deposited on concave surfaces showed better uniformity than that of the films deposited on convex surfaces. This phenomenon can be explained by considering both the effect of the substrate-to-target distance, line of sight and the electric field near the substrate. The results presented in this manuscript are therefore crucial for the coating design of objects with complex shapes when depositing pure metals using DCMS and/or HiPIMS for decorative, tribological, and tool applications.