@article{130b775a5bc146ae8fedc08fc47160d9,
title = "Direct Observation of Large Flexoelectric Bending at the Nanoscale in Lanthanide Scandates",
abstract = "There is a growing interest in the flexoelectric effect, since at the nanoscale it is predicted to be very large. However, there have been no direct observations of flexoelectric bending consistent with current theoretical work that implies strains comparable to or exceeding the yield strains of typical materials. Here we show a direct observation of extraordinarily large, two-dimensional reversible bending at the nanoscale in dysprosium scandate due to the converse flexoelectric effect, with similar results for terbium and gadolinium scandate. Within a transmission electron microscope, thin features bend up to 90° with radii of curvature of about 1 μm, corresponding to very large nominal strains. Analysis including independent experimental determination of the flexoelectric coefficient is semiquantitatively consistent with interpreting the results as due to flexoelectricity. These results experimentally demonstrate large flexoelectric bending at the nanoscale.",
keywords = "Flexoelectricity, in situ, lanthanide scandates, transmission electron microscopy",
author = "Pratik Koirala and Mizzi, {Christopher A.} and Marks, {Laurence D.}",
note = "Funding Information: The authors are indebted to Yimei Zhu of Brookhaven National Laboratory and Amanda Petford-Long of Argonne National Laboratory for heroic assistance with extremely hard to handle samples in their low magnetic field transmission electron microscopes. We thank Ryan Paull for the GdScO3 nanoparticles, Tiffany Ly for the KTaO3 nanoparticles, and Tiffany Ly and Zachary Mansley for the secondary electron images. We would also like to thank Oleg Rubel for information on the Berry Phase calculations as well as unreleased versions of the code BerryPI. We thank Fabien Tran and Peter Blaha for discussions on the use of hybrid functionals in the WIEN2k code, as well as James M. Rondinelli, Kenneth R. Poeppelmeier, and Peter W. Voorhees for their scientific input on the materials. Ex situ flexoelectric measurements were made possible using equipment from L. Catherine Brinson and Lincoln J. Lauhon. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under award no. DE-FG02-01ER45945. Funding Information: *E-mail: L-marks@northwestern.edu. ORCID Christopher A. Mizzi: 0000-0002-4209-854X Author Contributions P.K. carried out the electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and reflection electron energy loss spectroscopy measurements and analysis, P.K. and C.M. carried out the ultraviolet photoelectron spectroscopy measurements, and C.M. carried out the ex situ measurements of the flexoelectric coefficient, all under the supervision of L.D.M. L.D.M. carried out the density functional theory calculations. All three authors worked on the manuscript. Funding This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under award no. DE-FG02-01ER45945. Notes The authors declare no competing financial interest. Publisher Copyright: Copyright {\textcopyright} 2018 American Chemical Society.",
year = "2018",
month = jun,
day = "13",
doi = "10.1021/acs.nanolett.8b01126",
language = "English (US)",
volume = "18",
pages = "3850--3856",
journal = "Nano letters",
issn = "1530-6984",
publisher = "American Chemical Society",
number = "6",
}