Grain growth stagnation in solid state thin films: A phase-field study

Abstract

Grain boundary grooving significantly affects the grain growth behavior in a polycrystalline thin film with columnar grain structure by partial or complete pinning of moving grain boundaries. Theoretically, it can be shown that the stagnation of grain growth can occur for certain combinations of grain size and film thickness, for which grain boundaries cannot escape from the groove root. However, in real systems, grooves attached with the grain boundaries can migrate along with the moving grain boundaries. The possibility for stagnation arises when a groove behaves like a notch fixed at the surface. Such a condition can arise if the surface diffusivity is sufficiently reduced after stable groove formation using surface treatment. In the present study, grain growth in a solid-state thin film is investigated using a three-dimensional phase-field method that allows grains of a solid phase to be in equilibrium with a vapor phase at a constant temperature. The model captures the essential physics of surface diffusion-controlled thermal grooving and its interaction with a moving grain boundary. From the phase-field simulations, three possible interactions between the grain boundary and the groove are identified: stagnation of grain boundary, grain boundary-groove detachment, and coupled movement of the groove and the grain boundary.