Migration and roughening of Σ3{1 1 2} incoherent twin boundary in an Au nanocrystalline film

High-resolution electron microscopy is used to elucidate the structural transition of {1 1 2} incoherent twin boundaries under a driving force for migration in an Au nanocrystalline film. Initially flat {1 1 2} twin boundaries bounding island and peninsula grains in the film tend to become smoothly curved, corresponding to the atomically-roughened structure, after annealing at an elevated temperature of 300 °C. Previous studies have indicated that the {1 1 2} twin boundaries remain atomically sharp at least at 300 °C, which thus strongly suggests that the boundaries undergo roughening transition by a driving force for migration, a signature of kinetic roughening. [Display omitted] •Migration of {1 1 2} twin boundaries are studied in an Au nanocrystalline film.•Flat {1 1 2} twin boundaries are observed to be curved after annealing at 300 °C.•The observation is attributed to grain-boundary kinetic roughening.