LaScO3/SrTiO3: A conducting polar heterointerface of two 3d band insulating perovskites

Abstract

This work reports a quasi-two-dimensional electron gas (q-2DEG) system at the interface of two wideband-gap insulators, (TiO2-terminated) SrTiO3 and LaScO3, with a minimum thickness of 4-unit cell (uc). The highly crystalline and abrupt heterointerface is confirmed with high-resolution electron microscopy. The mixed Ti4+ and Ti3+ valence states (for 4 uc of LaScO3) obtained from the X-ray photoelectron spectroscopy study suggest an intrinsic electronic reconstruction at the interface, leading to a metallic nature. This origin is well supported by density functional theory calculations that reveal an emergence of 3.3 states/eV/spin at the Fermi level for 4 uc in accordance with the polar catastrophe model. The study offers one more perovskite heterostructure, like LaAlO3/SrTiO3, for unraveling the q-2DEG phenomena toward a clear mechanism and futuristic applications.