Origin of the two-dimensional electron gas at the interface of NdGaO 3 /SrTiO 3

Abstract Density functional theory within the generalized gradient approximation is employed to investigate the two-dimensional electron gas (2DEG) at the interface of NdGaO 3 /SrTiO 3 (0 0 1) heterostructure. For the superlattice model, the 2DEG originates from the Ti d xy electrons, which are transferred from the NdGaO 3 side. However, the interface of the thin film model exhibits insulated properties. In order to investigate the different properties of the two models, it is noted that large polar distortion in the NdGaO 3 side occurs in the thin film model comparing to the superlattice model, and the built-in electric field is screened by the large distortion, and result in preventing the electron transfer from the NdGaO 3 side to Ti d xy orbitals. For the thin film model, the surface layer of NdGaO 3 is the energy favor position of oxygen vacancy, which results in the rotation of the oxygen octahedrons. The 2DEG is induced by the balance between the distortion by the surface and the oxygen octahedrons rotation by the oxygen vacancy.