DFT modelling of SrO(SrTiO3)n Ruddlesden-Popper surfaces

Strontium titanate (SrTiO3) is an oxide crystallizing with cubic perovskite-type of structure that exhibits a high tunability of dielectric, electric, mechanical and optical properties by means of defects. Apart from dopants, also intrinsic oxygen vacancies or ordered stacking faults, e.g. Ruddlesden-Popper (RP) phases SrO(SrTiO3)n, may influence these properties.
We have investigated the surface energy, relaxation and electronic properties of such RP surfaces up to n = 3 in comparison to ’pure’ SrTiO3 by means of density-functional theory for ⟨ 001⟩ and ⟨ 100⟩ directions and with all possible perfect crystal terminations. We find a significant influence of the surface-near SrO-OSr stacking fault on surface energies and rumpling. Migrating surface states decrease the band gap of TiO2 terminations but all terminations show insulating character. A detailed discussion of surface-near relaxations will be presented.