Electronic structure of the Mott insulator LaVO3 in a quantum well geometry

We used x-ray photoemission spectroscopy to investigate the electronic structure of one to five unit cell thick layers of the Mott insulator LaVO3 embedded in LaAlO3. By limiting the upper layer of LaAlO3 to three unit cells, the underlying LaVO3 could be probed. The V 2p core-level spectra had both V3+ and V4+ components, and above two unit cell thick LaVO3, the structures exhibited spectra similar to bulk samples. The atomically flat surfaces enabled the study of the emission angle dependence, which indicates that the V4+ is localized to the topmost layer. These results demonstrate the potential for probing interface electronic structure in oxide ultrathin films by surface spectroscopy.