| The structure of LaAlO3 - SrTiO3 interfaces is under intense discussion due to the appearance of metallic conductivity, magnetism and superconductivity. The most important phenomena supposed to be crucial for the observed effects are the polar catastrophe, the formation of oxygen vacancies and the intermixing of La and Sr at the interface. However, at present there is no consensus about the driving force of the unusual properties. Here we apply on and off resonant photoemission to differently prepared LaAlO3 - SrTiO3 interfaces. In particular we study the behavior of the valence band, the Ti 2p, Sr 3d and La 4d lines. Significant differences are found as a function of sample treatment and photon energy. A model of the interface structure is developed. |
|