Characterization of Thin-Film Copper Using in Situ Environmental Transmission Electron Microscopy

Corrosion costs the U.S.A. a few percent of its GNP annually. Atomic scale characterization offers detailed dynamics of corrosion for fundamental understanding. We prepared thin-films (~70 nm) of copper, a model metal system, on single crystal NaCl substrates using e-beam evaporation. We performed in situ reduction/oxidation of Cu within a Hitachi H9500 environmental transmission electron microscope. The Cu films were annealed in hydrogen gas to remove the native oxide and to create clean copper facets, and then exposed to oxygen gas at 250°C. We noticed facet-dependent differences at the early stages of Cu-oxide growth in situ, where the relative oxidation rates by facet varied such that (100) < (110) < (111). These results can be used to guide future work on how to control corrosion by manipulating the crystal planes and surface defects used in corrosion-protection applications including municipal water transport, turbine blades, and integrated circuits.