Ab initio calculations of PbTiO3/SrTiO3 (001) heterostructures

We performed ab initio calculations for the PbTiO3/SrTiO3 (001) heterostructures. For both PbO and TiO2-terminations of the PbTiO3 (001) thin film, augmented on the SrTiO3 (001) substrate, the magnitudes of atomic relaxations Δz increases as a function of the number of augmented monolayers. For both terminations of the augmented PbTiO3 (001) nanothin film, all upper, third and fifth monolayers are displaced inwards (Δz is negative), whereas all second, fourth and sixth monolayers are displaced outwards (Δz is positive). The B3PW calculated PbTiO3/SrTiO3 (001) heterostructure band gaps, independently from the number of augmented layers, are always smaller than the PbTiO3 and SrTiO3 bulk band gaps. For both PbO and TiO2-terminated PbTiO3/SrTiO3(001) heterostructures, their band gaps are reduced due to the increased number of PbTiO3 (001) monolayers. The band gaps of PbO-terminated augmented PbTiO3 (001) films are always larger than those for TiO2-terminated PbTiO3 (001) thin films. The only exception is the case of 7-layer PbO-terminated and 8-layer TiO2-terminated augmented PbTiO3 (001) thin films, where their band gaps both are equal to 2.99 eV. For each monolayer of the SrTiO3 (001) substrate, charge magnitudes always are more than several times larger, than for each monolayer in the augmented PbTiO3 (001) thin film. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)