The mechanism of initial de-wetting and detachment of thin Au films on YSZ

Thin Au layers on single crystal Y2O3-doped ZrO2 (YSZ) de-wet from the substrate during thermal annealing in the solid state, and form small crystalline particles. Voids in the film nucleate at the metal–ceramic interface, and then grow to form pinholes in the film. Thus void nucleation at the metal–ceramic interface was identified to be the mechanism for solid-state de-wetting, rather than grain boundary grooving at the free surface of the film. Eventually, complete de-wetting occurs via solid-state diffusion, driven by minimization of the surface and interface energies of the system. In parallel to the de-wetting process, bubbles form in the film, driven by compressive thermal stresses and by the pressure exerted by gas chemisorbed from the substrate.