SrTiO3(0 0 1)∣LaAlO3(0 0 1) multilayers: A density-functional investigation

SrTiO3(0 0 1)∣LaAlO3(0 0 1) (STO∣LAO) multilayers were investigated by density-functional band structure calculations. The lattice constant parallel to the interface equals roughly the average of the two constituents (3.81 Å). The system contains two interface terminations: (I) SrO(0 0 1)∣AlO2(0 0 1) with a spacing of 1.92 Å as in STO and (II) TiO2(0 0 1)∣LaO(0 0 1) with a spacing of 1.89 Å as in LAO. Additional displacements of the metal atoms close to the boundaries lead to rumplings of up to 0.06 Å. A stoichiometric model is electronically neutral and insulating. Model systems with only termination I exhibit spatially localised holes in the O-based valence band; in systems with termination II the additional electron occupies the Ti-based conduction band. The strongly anisotropic dielectric constants obtained from linear response calculations show that the interface chemistry allows a fine tuning of perovskite multilayers.