The effect of oxygen vacancies on the properties of polar and nonpolar (0 0 1) LaAlO3/SrTiO3 heterostructures

By using first-principles calculations, we investigated the influence of oxygen vacancy (Vo) on the (001) LaAlO3/SrTiO3 (LAO/STO) heterostructures. Our results show that the effect of Vo on the properties of LAO/STO depends on the polarity of the system. In the polar LAO films Vo screens the internal electric field, which hinders the formation of two-dimensional electronic gas at the interface. Vo cannot reduce the critical thickness of the insulator-to-metal transition although it provides excess electrons. By contrast, in the nonpolar LAO films the metallic states are always maintained regardless of the position of Vo, but Vo causes electronic reconstruction near the Fermi level, and the distribution of conductive electrons differs greatly from the Vo-free case.