Metastable porosity in thin polycrystalline films

We demonstrate that grain boundary pores at the thin film–substrate interface do not shrink when their initial size exceeds certain threshold value. This critical size depends on the interface energies, the elastic moduli of the film material, the film thickness and the grain size. For thin metal films on ceramic substrates, the threshold pore size is in the range of few nanometers. We demonstrate that these metastable pores may provide preferential nucleation sites for the holes during solid-state dewetting of the films.