Atomic-scale imaging of interfacial polarization in cuprate-titanate heterostructures

Abstract

The interfaces in oxide heterostructures that bring novel physical phenomena and functionalities have attracted great attention in fundamental research and device applications. For uncovering structure–property relationships of oxide heterostructures, direct evidence of the atomic-scale structure of heterointerfaces is highly desired. Here, we report on studying the structure of interfaces between YBa2Cu3O7-δ thin films and SrTiO3 substrates by means of aberration-corrected ultrahigh-resolution electron microscopy. Employing advanced imaging and spectroscopic techniques, shifts of atoms at the interface away from the regular lattice sites are measured, leading to the interfacial polarity. The local polarization induced by the atomic shifts directs toward the cuprate films and is estimated to be about 36.1 μC/cm2. The observed interfacial polar layer is understood by the special atomic configuration across the interface, which could modulate the electrical properties in superconducting devices that are based on the ferroelectric/superconductor heterosystems.