Voiding of thin films on substrates is an important issue both for the production and the reliability of many devices and (nanotechnological) applications, like coatings for anticorrosion, wear protection, magnetic or optical properties, and decorative purposes. It is commonly accepted that grain boundary grooving plays a crucial role in the voiding process. However, in this Comment it is shown that grain boundary grooving without grain growth will usually not lead to a voiding of the film. Instead each grain develops a convex equilibrium surface that connects the neighboring grain boundaries. As the driving force for surface diffusion vanishes in this state, any further evolution based on surface diffusion stops. Often voiding does not occur, as the depth of the grooves in this state is usually smaller than the film thickness. However, it is also shown, on the basis of the same arguments, that the combination of grain growth and grain boundary grooving will eventually lead to voiding independently of the film thickness.

• Received 7 June 2012

DOI:https://doi.org/10.1103/PhysRevB.87.037401