Surface and Interface Chemistry of Epitaxial BST Films and Pt/BST Interfaces

Perovskite-structure metal titanate thin films are being investigated as dielectric materials for a broad range of capacitor applications such as tunable microwave devices. However, the near surface chemistry of metal titanate thin films, and interfaces of such films coated with metals, remains poorly understood even though interface effects are known to have a strong influence on the electrical properties of perovskite-structure metal titanate thin film based capacitors. In this study, the surface and interface chemistry of epitaxially grown BST films and Pt/epi-BST interfaces has been investigated using nanoscale characterization techniques including angle resolved X-ray photoelectron spectroscopy, high resolution transmission electron microscopy, and electron energy loss spectroscopy. In this proceedings, we report on the near surface composition of epitaxially grown BST films as determined by angle resolved photoelectron spectroscopy and discuss the implications of the observed cation concentration ratios on surface core-level shifts of Ba and Sr observed in photoemission of BST thin films.