Comparison of Interfacial Chemistry at Cu/α-Alumina and Cu/γ-Alumina Interfaces

Abstract Different alumina polymorphs (alpha, gamma and a transient phase) are formed in a copper matrix by oxidation of (Cu, Al) at 900°C, at an oxygen activity of aO2 = 10−13. Spatially resolved electron energy loss spectroscopy is used to determine bonding and electronic structure at the different interfaces. Compared to adjacent bulk phases, at the interfaces, the near edge fine structures are modified. Cu L2,3 shows an increased intensity compared to metallic copper and a chemical shift to higher energy. The size of both varies for the different interfaces, smallest chemical shift and highest L2,3 intensity are observed at {111} γ-alumina//{111}Cu interfaces, while larger chemical shift and smaller L2,3 intensities are found for α-alumina/Cu interfaces in the order of {112¯0}α-alumina//{100}Cu, {0001}α-alumina//{001}Cu, {112¯3}α-alumina//Cu. In the interfacial OK edge, an additional pre-edge intensity is observed. For γ-alumina//Cu, it appears as a clear pre-peak, indicating hybridization with strong...