First-principles study of surface charging in LaAlO sub(3) / SrTiO sub(3) heterostructures

The two-dimensional electron gas (2DEG) observed at the interface between LaAlO sub(3) (LAO) and SrTiO sub(3) (STO) is known to be very sensitive to the proximity of the LaAlO sub(3) surface and the conditions to which the surface is exposed. We use first-principles calculations to study surface reconstructions on LAO films, taking into account that the LAO surface can be charged. The results for the charged surfaces and for the coupling between the surface and the 2DEG enable us to account not only for the behavior of the 2DEG as a function of thickness of the LAO layer, but simultaneously determine the stable terminations and reconstructions on the LAO surface under a variety of conditions.