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.-as chemisorbed from the substrate. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.