Solid-state dewetting of thin Au films on oxidized surface of biomedical TiAlV alloy

Recent applications of solid-state dewetting for the functionalization of medical implants raise the question of the thin film dewetting kinetics on surfaces with natural roughness. In this work, we studied the initial stages of solid-state dewetting of thin nanocrystalline gold (Au) films deposited on an oxidized surface of a biomedical titanium-aluminum-vanadium (Ti-6Al-4V) alloy. The interrupted annealing technique was employed to study the evolution of holes in the film and film flattening. While a high number of dewetting holes was formed in the film at the early stages of dewetting at the temperature of 300°C, the nanoporous but continuous film morphology remained stable even after prolonged anneals at higher temperature of 500°C. We developed models describing Au thin film dewetting on surfaces with typical topographical features of oxidized Ti-6Al-4V. These models considered the Au diffusion along the grain boundaries as a controlling factor of the film flattening. The stabilization of nanoporous film structure was attributed to the slowdown of the dewetting holes expansion at the sharp edges of the substrate. Our work demonstrates that solid state dewetting of thin metal films deposited on the rough surface of oxidized metal can be utilized for producing continuous nanoporous metal coatings.