Grain Boundary-Induced Plasticity During Thin Film Buckling

The effect of grain boundaries (GB) on the buckling of an Al thin film delaminated from its substrate is investigated by means of molecular dynamics simulations at finite temperature. It is evidenced that the GB localizes the plasticity and deeply modifies the profile of the buckled thin film through the formation of a vertical fold at the location of the initial GB. Several plasticity mechanisms have been also described such as the development of extrinsic faults or the formation of uncommon C’D and CD’ dislocations. In this context, the folding angle and plastic strain in the film have been analyzed through a careful counting of the emerging dislocations at the film surfaces. The buckling profile of the film has been then analytically determined in the framework of the Föppl–von Karman’s (FvK) theory of thin plates and successfully compared with the simulated ones. The modifications of the film pattern in light of the different plastic (dislocations) and elastic (buckling) phenomena are finally discussed.