Evolution of the band alignment at polar oxide interfaces

First-principles calculations demonstrate the evolution of the band alignment at La(0.7)A(0.3)MnO(3)vertical bar La(1-x)A(x)O vertical bar TiO2 vertical bar SrTiO3(001) heterointerfaces, where A=Ca, Sr, or Ba, as the interfacial A-site composition, La(1-x)A(x), is varied from x=0.5 to x=1.0. This variation leads to a linear change in the SrTiO3 valence-band offset with respect to the Fermi level of the La(0.7)A(0.3)MnO(3) metal electrode and hence to a linear change in the Schottky barrier height at this interface. The effect arises due to electrostatic screening of the polar interface, altering the interfacial dipole and hence the electrostatic potential step at this interface. We find that both the La(0.7)A(0.3)MnO(3) and SrTiO3 layers contribute to screening with both electronic and ionic screening being important for the change in the interface dipole. The results are in agreement with the recent experimental data.