Low temperature deposition of functional thin films on insulating substrates enabled by selective ion acceleration...

Ionized physical vapor deposition techniques, such as high-power impulse magnetron sputtering (HiPIMS), are gaining popularity but face challenges for deposition on insulating materials, where applying negative potentials for ion acceleration is difficult. While radio frequency biasing works on insulators, it risks film damage from energetic process gas ions. Here, we present Synchronized Floating Potential HiPIMS (SFP-HiPIMS), which exploits the substrate's transient negative floating potential during HiPIMS discharges. By timing the ion arrival with this negative potential, selective metal-ion acceleration can be achieved, improving adatom mobility while minimizing energetic Ar⁺ bombardment. As proof-of-concept, we deposit Al_0.88Sc_0.12N thin films on various insulating substrates. SFP-HiPIMS improves the films' crystallinity, texture and residual stress, and also enables epitaxial growth on c-cut sapphire at temperatures as low as 100 °C. SFP-HiPIMS provides a solution for a long-standing challenge in physical vapor deposition, which works for many different materials and integrates readily with standard deposition equipment.