Structural distortion and charge redistribution in SrTiO3 (111) polar surfaces

Abstract The structural and electronic properties of the SrTiO 3 (111) polar surfaces are studied using first-principles calculations. The structural distortions for Ti termination are larger than that for SrO 3 termination. A negative charge density of −0.55e is concentrated at the surface of Ti termination, which may explain the recent finding of two-dimensional electron gas exits at the SrTiO 3 (111) surface. A positive charge density of 0.64e is accumulated at the surface of SrO 3 termination. The nonstoichiometric TiO and SrO 2 terminations are also considered. Oxygen octahedrons tilt to the opposite direction in the adjacent cells along the stacking direction. TiO and SrO 2 terminated slabs are both insulating with surface charge modified relatively small. The surface energies for all the SrTiO 3 (001), (011) and (111) surfaces are calculated to compare the surface stability.