Localized and delocalized Ti 3d carriers in LaAlO3/SrTiO3 superlattices revealed by resonant inelastic x-ray scattering

The important source of interface conductivity in LaAlO3/SrTiO3 heterostructures, the Ti 3d carriers, is probed with resonant inelastic x-ray scattering at the Ti 2p(3/2) edge of epitaxially grown superlattices. We reveal unambiguously the generation of both localized and delocalized Ti 3d carriers as a result of the built-up heterointerface. Furthermore, we determine that the interface Ti3+O6 octahedra are orthorhombically distorted and quantify the crystal-field splitting energies. We argue that for as-grown superlattices, both types of Ti 3d carriers originate mainly from oxygen vacancies, whereas for fully oxidized samples they result from electronic reconstruction.