Density functional theory based interfacial studies of ABO3/SrTiO3 (A = La, Y, Sc, B = Al, Ga) and its relation to polar catastrophe

We have studied the density functional theory of epitaxially strained ABO3 (A = La, Y, Sc, B = Al, Ga) films on SrTiO3 (001) crystals with SrO- and TiO-terminations to investigate polar catastrophe induced by the epitaxial thin film growth. Interfacial polar nature of the strained films depends on the type of cations. While lanthanum based perovskite films produces polarity based on the ionic nature of interfacial atoms, the smaller cations show rather opposite polarities arising from progressive ferroelectric structural distortion acting opposite to the polar nature of cation ions.