Microstructure and modifications of Cu/Al2O3 interfaces

A combined approach of high-resolution transmission electron microscopy and electron energy-loss near-edge structure studies was employed to determine the atomic structure and bonding mechanisms at Cu/Al2O3 interfaces in depe ndence on the alpha -Al2O3 substrate orientation. The investigated specimen s were prepared by molecular beam epitaxy using ultrahigh vacuum conditions , which led to atomically abrupt interfaces. The results show that intermet allic Cu-Al bonds occur at the investigated Cu/(11 (2) over bar0)Al2O3 inte rface, while ionic-covalent bonding contributions are observed at the Cu/(0 001)Al2O3 interface. The interfacial microstructure of diffusion-bonded Cu/ (0001)Al2O3 samples was changed by annealing treatments under various oxyge n partial pressures. Annealing resulted in the formation of a CuAlO2 reacti on phase at the interface between Cu and Al2O3.