Two-dimensional electron systems in perovskite oxide heterostructures: Role of the polarity-induced substitutional defects

Abstract

The discovery of a two-dimensional electron system (2DES) at the interfaces of perovskite oxides such as LaAlO3 and SrTiO3 has motivated enormous efforts in engineering interfacial functionalities with this type of oxide heterostructures. However, its fundamental origins are still not understood, e.g. the microscopic mechanisms of coexisting interface conductivity and magnetism. Here we report a comprehensive spectroscopic investigation of the depth profile of 2DES-relevant Ti 3d interface carriers using depth- and element-specific techniques, standing-wave excited photoemission and resonant inelastic scattering. We found that one type of Ti 3d interface carriers, which give rise to the 2DES are located within 3 unit cells from the n-type interface in the SrTiO3 layer. Unexpectedly, another type of interface carriers, which are polarity-induced Ti-on-Al antisite defects, reside in the first 3 unit cells of the opposing LaAlO3 layer (~10 Å). Our findings provide a microscopic picture of how the localized and mobile Ti 3d interface carriers distribute across the interface and suggest that the 2DES and 2D magnetism at the LaAlO3/SrTiO3 interface have disparate explanations as originating from different types of interface carriers.

arXiv comment28 pages, 4 figures; Supplemental Materials 19 pages

References in corpus (23)

• Magnetic effects at the interface between nonmagnetic oxides
• Why Some Interfaces Cannot be Sharp
• Unveiling a two-dimensional electron gas with universal subbands at the surface of SrTiO3
• High Mobility in LaAlO3/SrTiO3 Heterostructures: Origin, Dimensionality and Perspectives
• Mapping the Spatial Distribution of Charge Carriers in LaAlO3/SrTiO3 Heterostructures
• Orbital reconstruction and two-dimensional electron gas at the LaAlO3/SrTiO3 interface
• A polarity-induced defect mechanism for conductivity and magnetism at polar-nonpolar oxide interfaces
• Profiling the interface electron gas of LaAlO3/SrTiO3 heterostructures by hard X-ray photoelectron spectroscopy
• The Galaxies Beamline at SOLEIL Synchrotron: Inelastic X-ray Scattering and Photoelectron Spectroscopy in the Hard X-ray Range
• Polaronic metal state at the LaAlO3/SrTiO3 interface
• Direct k-space mapping of the electronic structure in an oxide-oxide interface
• Polarity-induced oxygen vacancies at LaAlO3|SrTiO3 interfaces
• Parallel electron-hole bilayer conductivity from electronic interface reconstruction
• Defect engineering in oxide heterostructures by enhanced oxygen surface exchange
• Localized vs. delocalized character of charge carriers in LaAlO3/ SrTiO3 superlattices
• Real-space mapping of electronic orbitals
• Interface properties and built-in potential profile of a LaCrO${}_3$/SrTiO${}_3$ superlattice determined by standing-wave excited photoemission spectroscopy
• Electronic phase separation at LaAlO3/SrTiO3 interfaces tunable by oxygen deficiency
• Evolution of the SrTiO${}_3$ surface electronic state as a function of LaAlO${}_3$ overlayer thickness
• The Conducting Channel at the LaAlO${}_3$/SrTiO${}_3$ Interface
• Raman and fluorescence contributions to resonant inelastic soft x-ray scattering on LaAlO${}_3$/SrTiO${}_3$ heterostructures
• Hard x-ray standing-wave photoemission insights into the structure of an epitaxial Fe/MgO multilayer magnetic tunnel junction
• Depth-resolved resonant inelastic x-ray scattering at a superconductor/half-metallic ferromagnet interface through standing-wave excitation

Cited by in corpus (3)

• High resolution depth profiling using near-total-reflection hard X-ray photoelectron spectroscopy
• Emergent phenomena at oxide interfaces studied with standing-wave photoelectron spectroscopy
• Probing the polar-nonpolar oxide interfaces using resonant x-ray standing wave techniques