Enhanced flexoelectricity at reduced dimensions revealed by mechanically tunable quantum tunnelling

Authors

Saikat Das, Institute of Basic Science
Bo Wang, The Pennsylvania State University
Tula R. Paudel, University of Nebraska - LincolnFollow
Sung Min Park, Institute for Basic Science
Evgeny Y. Tsymbal, University of Nebraska-LincolnFollow
Long-Qing Chen, The Pennsylvania State University
Daesu Lee, Pohang University of Science and Technology
Tae Won Noh, Institute for Basic Science

ORCID IDs

Bo Wang

Tula R. Paudel

Daesu Lee

Tae Won Noh

Document Type

Article

Date of this Version

2019

Citation

NATURE COMMUNICATIONS | (2019) 10:537

Comments

© The Author(s) 2019

Open access

https://doi.org/10.1038/s41467-019-08462-0

Abstract

Flexoelectricity is a universal electromechanical coupling effect whereby all dielectric materials polarise in response to strain gradients. In particular, nanoscale flexoelectricity promises exotic phenomena and functions, but reliable characterisation methods are required to unlock its potential. Here, we report anomalous mechanical control of quantum tunnelling that allows for characterising nanoscale flexoelectricity. By applying strain gradients with an atomic force microscope tip, we systematically polarise an ultrathin film of otherwise nonpolar SrTiO₃, and simultaneously measure tunnel current across it. The measured tunnel current exhibits critical behaviour as a function of strain gradients, which manifests large modification of tunnel barrier profiles via flexoelectricity. Further analysis of this critical behaviour reveals significantly enhanced flexocoupling strength in ultrathin SrTiO₃, compared to that in bulk, rendering flexoelectricity more potent at the nanoscale. Our study not only suggests possible applications exploiting dynamic mechanical control of quantum effect, but also paves the way to characterise nanoscale flexoelectricity.