Three-dimensionality of mobile electrons at X-ray-irradiated LaAlO${}_3$/SrTiO${}_3$ interfaces

Abstract

Effects of X-ray irradiation on the electronic structure of LaAlO${}_3$/SrTiO${}_3$ (LAO/STO) samples, grown at low oxygen pressure and post-annealed ex-situ till recovery of their stoichiometry, were investigated by soft-X-ray ARPES. The irradiation at low sample temperature below ~100K creates oxygen vacancies (VOs) injecting Ti t2g-electrons into the interfacial mobile electron system (MES). At this temperature the oxygen out-diffusion is suppressed, and the VOs are expected to appear mostly in the top STO layer. However, we observe a pronounced three-dimensional (3D) character of the X-ray generated MES in our samples, indicating its large extension into the STO depth, which contrasts to the purely two-dimensional (2D) character of the MES in standard stoichiometric LAO/STO samples. Based on self-interaction-corrected DFT calculations of the MES induced by VOs at the interface and in STO bulk, we discuss possible mechanisms of this puzzling three-dimensionality. They may involve VOs remnant in the deeper STO layers, photoconductivity-induced metallic states as well as more exotic mechanisms such as X-ray induced formation of Frenkel pairs.

References in corpus (10)

• Tailoring the nature and strength of electron-phonon interactions in the SrTiO${}_3$(001) two-dimensional electron liquid
• Polaronic metal state at the LaAlO3/SrTiO3 interface
• Universal Fabrication of Two-Dimensional Electron Systems in Functional Oxides
• Phase separation from electron confinement at oxide interfaces
• Magnetism, spin texture and in-gap states: Atomic specialization at the surface of oxygen-deficient SrTiO${}_3$
• Electron dichotomy on the SrTiO${}_3$ defect surface augmented by many-body effects
• Quantum interference effects of out-of-plane confinement on two-dimensional electron systems in oxides
• $d_{xz/yz}$ Orbital Subband Structures and Chiral Orbital Angular Momentum in the (001) Surface States of SrTiO${}_3$
• Artificial quantum confinement in LAO3/STO heterostructure
• Anisotropy of the infrared-active phonon modes in the mono-domain state of tetragonal SrTiO3 (110)