Spatially localized electronic states at the LaAlO3/TiO2 interface: mapping of a 2D electron gas

Perovskite heterostructures play an increasingly important role in optoelectronics applications, such as solar cells, LEDs and photo detectors [1]. The combination of two different semiconducting materials often leads to drastic changes of the electrical, magnetic or optical properties in the vicinity of the interface. Thus, full characterization of the localized electronic states is of utmost importance. We approach this goal with a combined ab-initio and experimental study of the electronic states localized at the LaAlO3/TiO2 interface.
The material of interest is a heterostructure consisting of the cubic perovskite LaAlO3 and TiO2 in anatase phase. Bulk anatase is typically a semiconductor with a few eV wide direct band gap. In combination with LaAlO3, however, unoccupied states appear directly above the Fermi energy for 2-3 TiO2 layers closest to the interface. When a small energy window is chosen for imaging, similar to elemental mapping albeit with a window of 0.5 eV or even smaller, the localized electronic states can be mapped in real space [2]. We compare the experimental results to inelastic channeling simulations of a Ti-La terminated interface based on [3].