Quantum confinement in transition metal oxide quantum wells

Abstract

We report on the quantum confinement in SrTiO 3 (STO) quantum wells (QWs) grown by molecular beam epitaxy. The QW structure consists of LaAlO 3 (LAO) and STO layers grown on LAO substrate. Structures with different QW thicknesses ranging from two to ten unit cells were grown and characterized. Optical properties (complex dielectric function) were measured by spectroscopic ellipsometry in the range of 1.0 eV-6.0 eV at room temperature. We observed that the absorption edge was blue-shifted by approximately 0.39 eV as the STO quantum well thickness was reduced to two unit cells. This demonstrates that the energy level of the first sub-band can be controlled by the QW thickness in a complex oxide material.