DIRECT OBSERVATION OF THE MOSAIC STRUCTURE OF THERMAL OXIDE-FILMS ON COPPER

The structure of thermal oxide films on copper has been investigated b y optical microscopy, SEM and TEM of the stripped films and ultramicro tomed sections. High resolution transmission electron microscopy of th e ultramicrotomed sections of the oxide film and the attached metal su bstrate revealed the mosaic structure of the oxide clearly at atomic-s cale resolution for the first time. Thus, the correlation between the oxidation rate anisotropy and the anisotropy of the extent of paths fo r easy diffusion in the oxide has been confirmed. Further, examination of the oxide by XPS and EPMA has also shown the presence of CuO near the surface regions of the oxide, along with Cu2O constituting the bul k of the oxide even for the oxidation times shorter than about 10 min at 178-degrees-C.