Ultra-Inclined Nanocolumnar ZnO Films Sputtered Using a Novel Masking Configuration Providing Controlled and Restricted Oblique Angle Deposition for Enhanced Sensing Platforms

Abstract

Oblique angle deposition (OAD) of inclined thin films is mainly performed using electron beam evaporation due to its accurate point source control over the incoming evaporated flux angle α, leading to thin films with a nanocolumnar inclination angle β. However, the utilization of magnetron sputtering (MS) with an extended source for OAD is not extensively studied and reported. This work presents a thorough analysis of ZnO inclined thin films deposited by a novel restricted DC-reactive MS-OAD technique. OAD-inclined films are deposited at α ranged 60°-88°, where incoming flux is restricted using a patented masking configuration enabling tunable control of deposited nanocolumn angular range. The described technique provides accurate control over the resulting β (99.5% reproducibility), allowing demonstrated β_max of 47.3°, close to theoretical limits predicted for ZnO. The approach discussed here probes enhanced control of β comparable to that observed in evaporation, however using an extended source, resulting in high-quality reproducible nanocolumnar-inclined films. The mentioned improvements result from the exploration of operational parameters such as magnetron power, working pressure, and chamber temperature, as well as the design of the restricting configuration and substrate holders and their influence on the resulting inclined thin film crystallinity, and morphology.