Electrochemical ferroelectric switching: Origin of polarization reversal in ultrathin films

N. C. Bristowe, Massimiliano Stengel, P. B. Littlewood, J. M. Pruneda, and Emilio Artacho
Phys. Rev. B 85, 024106 – Published 9 January 2012

Abstract

Against expectations, robust switchable ferroelectricity has been recently observed in ultrathin (1 nm) ferroelectric films exposed to air [V. Garcia et al., Nature (London) 460, 81 (2009)]. Based on first-principles calculations, we show that the system does not polarize unless charged defects or adsorbates form at the surface. We propose electrochemical processes as the most likely origin of this charge. The ferroelectric polarization of the film adapts to the external ionic charge generated on its surface by redox processes when poling the film. This, in turn, alters the band alignment at the bottom electrode interface, explaining the observed tunneling electroresistance. Our conclusions are supported by energetics calculated for varied electrochemical scenarios.

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  • Received 22 December 2011

DOI:https://doi.org/10.1103/PhysRevB.85.024106

©2012 American Physical Society

Authors & Affiliations

N. C. Bristowe1,2, Massimiliano Stengel3,4, P. B. Littlewood1,5, J. M. Pruneda6, and Emilio Artacho2

  • 1Theory of Condensed Matter, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
  • 2Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, United Kingdom
  • 3ICREA – Institució Catalana de Recerca i Estudis Avançats, E-08010 Barcelona, Spain
  • 4Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, E-08193 Bellaterra, Spain
  • 5Physical Sciences and Engineering, Argonne National Laboratory, Argonne, Illinois 60439, USA
  • 6Centre d’Investigación en Nanociéncia i Nanotecnologia (CSIC-ICN), Campus UAB, E-08193 Bellaterra, Spain

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Issue

Vol. 85, Iss. 2 — 1 January 2012

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