Interface‐Induced Polarization in SrTiO₃‐LaCrO₃ Superlattices

Abstract

Epitaxial interfaces and superlattices comprised of polar and non‐polar perovskite oxides have generated considerable interest because they possess a range of desirable properties for functional devices. In this work, emergent polarization in superlattices of SrTiO3 (STO) and LaCrO3 (LCO) is demonstrated. By controlling the interfaces between polar LCO and non‐polar STO, polarization is induced throughout the STO layers of the superlattice. Using X‐ray absorption near‐edge spectroscopy and aberration‐corrected scanning transmission electron microscopy displacements of the Ti cations off‐center within TiO6 octahedra along the superlattice growth direction are measured. This distortion gives rise to built‐in potential gradients within the STO and LCO layers, as measured by in situ X‐ray photoelectron spectroscopy. Density functional theory models explain the mechanisms underlying this behavior, revealing the existence of both an intrinsic polar distortion and a built‐in electric field, which are due to alternately positively and negatively charged interfaces in the superlattice. This study paves the way for controllable polarization for carrier separation in multilayer materials and highlights the crucial role that interface structure plays in governing such behavior.

Probing surfaces and interfaces in complex oxide films via in situ X-ray photoelectron spectroscopy

“…This enabled the extraction of the band alignment across the entire 15-unit-cell structure through careful modeling of the core-level peak positions as a function of incoming angle, producing good agreement with DFT models [136,137].…”

Metal Oxide Nanocomposites: A Perspective from Strain, Defect, and Interface

“…For instance, elastic strain engineering is one of the most interesting approaches to tune physical properties . Other approaches to manipulate the functional properties of thin films include chemical doping, interface engineering, octahedral rotation, epitaxial stabilization, polarization doping, and dimensional confinement . By carefully selecting substrates and/or buffer layers, different strain states can be achieved in materials in thin film form.…”

Effect of intrinsic point defects on ferroelectric polarization behavior of SrTiO3

“…In past years it has been revealed that ferroelectric polarization is not exclusive to polar materials and can be induced throughout the nonferroelectric layer of the heterostructure by combining a nonferroelectric oxide such as SrTiO 3 with a ferroelectric oxide, e.g., BaTiO 3 [7], or even with another nonferroelectric oxide, e.g., LaCrO 3 [8]. Moreover, the emergence of net ferroelectric polarization was recently demonstrated for nanometer-thick films of SrTiO 3 [9] where this effect was attributed to electrically induced alignment of polar nanoregions that can naturally form because of the presence of intrinsic defects in SrTiO 3 crystals.…”