HRTEM and EELS characterization of atomic and electronic structures in Cu/α-Al2O3 interfaces

Interfacial atomic structures of Cu/Al2O3(0 0 0 1) and Cu/Al2O3(112¯0) prepared by the pulsed-laser deposition technique were characterized by high-resolution transmission electron microscopy (HRTEM). It was found that (1 1 1) and (0 0 1) planes of Cu were epitaxially oriented to Al2O3(0 0 0 1) and Al2O3(112¯0) planes, respectively. Chemical bonding states at the interfaces were analysed by electron energy-loss spectroscopy (EELS). In oxygen-K edge energy-loss near-edge structure (O-K ELNES) of the Cu/Al2O3(0 0 0 1) and Cu/Al2O3(112¯0) interfaces, a shoulder peak appeared at the lower energy side of the main peak. This indicates that Cu-O interactions were formed across these Cu/Al2O3 interfaces. In fact, the simulated HRTEM images based on the O-terminated interface models agreed well with the experimental ones. It can be concluded that the O-terminated interfaces were formed in the present Cu/Al2O3 interfaces.