Switchable induced polarization in LaAlO3/SrTiO3 heterostructures

C W Bark; P Sharma; Y Wang; S H Baek; S Lee; S Ryu; C M Folkman; T R Paudel; A Kumar; S V Kalinin; A Sokolov; E Y Tsymbal; M S Rzchowski; A Gruverman; C B Eom

doi:10.1021/nl3001088

Switchable induced polarization in LaAlO3/SrTiO3 heterostructures

Nano Lett. 2012 Apr 11;12(4):1765-71. doi: 10.1021/nl3001088. Epub 2012 Mar 13.

Authors

C W Bark¹, P Sharma, Y Wang, S H Baek, S Lee, S Ryu, C M Folkman, T R Paudel, A Kumar, S V Kalinin, A Sokolov, E Y Tsymbal, M S Rzchowski, A Gruverman, C B Eom

Affiliation

¹ Department of Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin 53706, USA.

PMID: 22400486
DOI: 10.1021/nl3001088

Abstract

Demonstration of a tunable conductivity of the LaAlO(3)/SrTiO(3) interfaces drew significant attention to the development of oxide electronic structures where electronic confinement can be reduced to the nanometer range. While the mechanisms for the conductivity modulation are quite different and include metal-insulator phase transition and surface charge writing, generally it is implied that this effect is a result of electrical modification of the LaAlO(3) surface (either due to electrochemical dissociation of surface adsorbates or free charge deposition) leading to the change in the two-dimensional electron gas (2DEG) density at the LaAlO(3)/SrTiO(3) (LAO/STO) interface. In this paper, using piezoresponse force microscopy we demonstrate a switchable electromechanical response of the LAO overlayer, which we attribute to the motion of oxygen vacancies through the LAO layer thickness. These electrically induced reversible changes in bulk stoichiometry of the LAO layer are a signature of a possible additional mechanism for nanoscale oxide 2DEG control on LAO/STO interfaces.