Atomic-resolution spectroscopic imaging of oxide interfaces

Perovskite oxides show a rich variety of electronic phases in bulk. The prospect of combining these phases at the atomic scale has fueled the interest in oxide heterostructures. The existence of interfaces can, however, greatly affect the macroscopic properties of these structures, leading on the one hand to exotic new phases stabilized at the interface or on the other hand to the degradation of bulk-like properties. With recent advances in electron microscopy the composition and bonding at such buried interfaces can now be imaged with atomic resolution. The bonding information is obtained from the near-edge fine-structure of core-level electron energy loss spectra. Here, we discuss the near-edge fine-structure focusing on the O-K and transition metal L2,3 edges which are of particular importance for the family of perovskite oxides. Spectroscopic imaging of a vanadate/titanate heterostructure demonstrates the capability of the technique to characterize atomic-scale interdiffusion at interfaces. Resolution limits in spectroscopic imaging due to inelastic delocalization effects are discussed.