Switchable Induced Polarization\nin LaAlO₃/SrTiO₃ Heterostructures

Abstract

Demonstration of a tunable conductivity of the LaAlO₃/SrTiO₃ interfaces drew significant attention to\nthe development\nof oxide electronic structures where electronic confinement can be\nreduced to the nanometer range. While the mechanisms for the conductivity\nmodulation are quite different and include metal–insulator\nphase transition and surface charge writing, generally it is implied\nthat this effect is a result of electrical modification of the LaAlO₃ surface (either due to electrochemical dissociation of surface\nadsorbates or free charge deposition) leading to the change in the\ntwo-dimensional electron gas (2DEG) density at the LaAlO₃/SrTiO₃ (LAO/STO) interface. In this paper, using piezoresponse\nforce microscopy we demonstrate a switchable electromechanical response\nof the LAO overlayer, which we attribute to the motion of oxygen vacancies\nthrough the LAO layer thickness. These electrically induced reversible\nchanges in bulk stoichiometry of the LAO layer are a signature of\na possible additional mechanism for nanoscale oxide 2DEG control on\nLAO/STO interfaces.