Morphological and kinetics study of initial-stage oxidation of copper and copper alloy by in situ TEM.

摘要

Fundamental understanding of metal and alloy oxidation is of significant importance to a wide range of applications. Using In situ Transmission Electron Microscopy (TEM) incorporated with environmental capabilities, initial stages of Cu and Cu alloy oxidation have been investigated to bridge the information gap between the knowledge obtained from surface science methods and that of traditional oxidation theories of bulk oxide growth.;Real time TEM observations as well as ex-situ AFM, STEM characterization are employed to study the initial stages of Cu and Cu-Au/Pt oxidation from oxygen chemisorption induced surface reconstruction to oxide island nucleation and growth. Surface conditions of Cu have a dramatic effect on the nucleation density and growth rate of oxide islands and increasing oxygen partial pressure results in the orientation transition from epitaxial to non-epitaxial growth of Cu2O on Cu surface. The morphologies and kinetics of oxide islands formed on Cu-Au and Cu-Pt surface have a sensitive dependence on the oxidation temperature. These morphologies and kinetics can be attributed to the surface diffusion of oxygen on metal surface and the segregation of nonoxidizable element (Au, Pt). Atomic scale oxidation is also investigated by high resolution environmental TEM including metastable surface reconstructions reflecting the kinetic hindrance toward the bulk oxide formation and the observation of step-edge induced oxide growth showing the dominate source of Cu adatom for the growth of surface Cu2O are surface steps. In conclusion, the morphologies and kinetics of oxide islands on Cu and Cu alloy surface can be controlled by oxidation temperature and oxygen pressure as well as alloying metal. The atomic scale oxidation shed light to the initial interaction of oxygen and Cu surface to understand the surface related properties.