Electron Energy-Loss Near-Edge Structure Studies of a Cu/(11-20)?-Al2O3 Interface

Abstract

Electron energy-loss near-edge structure (ELNES) studies were employed to determine the bonding mechanisms and electronic structure of a Cu/(1120)α-Al 2 O 3 interface prepared by molecular beam epitaxy. The existence of an interfacial ELNES component at the Al-L 2,3 edge reveals that the Al atoms participate in the bonding and change their local coordination compared to bulk Al 2 O 3 . At the interfacial O-K ELNES some pre-edge intensity appears, indicating the presence of deep-level O-2p states hybridised with Cu-3d and/or Al-3p states. The interfacial Cu-L 2,3 ELNES shows a chemical shift of the edge onset to higher energy-loss values and the existence of unoccupied Cu-3d states. The shape and edge onset are similar to the Cu-L 2,3 edge measured in an intermetallic CuAl 2 compound. Image simulations of the experimental high-resolution transmission electron microscopic images were carried out assuming Cu-Al bonds at the Cu/(1120)Al 2 O 3 interface as found by the ELNES studies. The derived structural model for the atomistic arrangement at the interface contains a mixed monolayer of Cu and Al atoms that exhibits a projected bonding distance of (0.15 ± 0.02) nm to the first O-layer of the Al 2 O 3 substrate.