Interface band engineering in LaAlO₃/SrTiO₃ heterostructures

Novel two-dimensional electron systems at the interfaces of oxide heterostructures, as e.g. at the LaAlO₃/SrTiO₃ (LAO/STO) heterointerface, recently have attracted much attention. A key requirement for future applications is the controllability of the electronic interface properties. We show that these properties can be controlled in LAO/STO by the oxygen vacancy (V₀) concentration which can in turn be adjusted during photoemission experiments by means of synchrotron light irradiation and simultaneous oxygen dosing. In detail, the V₀ concentration determines the density of mobile and trapped charge carriers as well as the band bending and alignment at the interface. We systematically investigate these properties on (001) and (111) oriented LAO/STO heterostructures with controlled V₀ concentrations by depth profiling the film and substrate core levels by means of angle-dependent hard X-ray photoelectron spectroscopy, while resonant soft X-ray photoemission is used to probe the interfacial valence band states.