Observation of atomic diffusion at twin-modified grain boundaries in copper

Abstract

Grain boundaries affect the migration of atoms and electrons in polycrystalline solids, thus influencing many of the mechanical and electrical properties. By introducing nanometer- scale twin defects into copper grains, we show that we can change the grain- boundary structure and atomic- diffusion behavior along the boundary. Using in situ ultrahigh- vacuum and high- resolution transmission electron microscopy, we observed electromigration- induced atomic diffusion in the twin- modified grain boundaries. The triple point where a twin boundary meets a grain boundary was found to slow down grain- boundary and surface electromigration by one order of magnitude. We propose that this occurs because of the incubation time of nucleation of a new step at the triple points. The long incubation time slows down the overall rate of atomic transport.