Deformation behavior of metallic glass thin films

We report room-temperature deformation behavior of damage-free metallic glass films characterized by nanoindentation and atomic force microscopy. The glass films with thicknesses ranging from 5 μm down to ∼60 nm plastically deform by shear bands when subjected to both spherical and sharp Berkovich indenters. Importantly, we found that gallium contamination from focus ion beam (FIB) milling significantly suppresses shear band formation, indicating that the absence of shear bands in FIB milled samples may be caused by gallium irradiation damage, rather than sample size effect. Finite element simulation reveals that a high stress gradient at the film/substrate interface promotes the plastic deformation of the thin films but does not give rise to significant strain inhomogeneity.