Dewetting upside-down: two-sided solid state dewetting of thin gold film on soft KBr substrate

We deposited a 30 nm-thick Au film on single crystalline KBr substrate and studied the solid state dewetting behavior of the film at a temperature of 350 degrees C. At this temperature, the ions of the KBr compound exhibit significant mobility along the Au-KBr interface, which affects the morphology and kinetics of the solid state dewetting. We performed statistical morphology analysis of the Au-KBr interface by selectively dissolving the KBr substrate after the dewetting heat treatments and subsequent atomic force microscopy imaging of the "upside-down" oriented Au film. We demonstrated that atomic mobility at the interface leads to embedding of the partially dewetted Au film into the KBr substrate. We proposed a quantitative model of the shape evolution of a disc-shaped Au particle on the KBr substrate under the condition of finite interface mobility of the substrate species. The model predictions were consistent with the experimentally observed sinking rates of Au nanostructures.