Reducing Coercive-Field Scaling in Ferroelectric Thin Films via Orientation Control

Ruijuan Xu, Ran Gao, Sebastian E. Reyes-Lillo, Sahar Saremi, Yongqi Dong, Hongling Lu, Zuhuang Chen, Xiaoyan Lu, Yajun Qi, Shang Lin Hsu, Anoop R. Damodaran, Hua Zhou, Jeffrey B. Neaton, Lane W. Martin

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

The desire for low-power/voltage operation of devices is driving renewed interest in understanding scaling effects in ferroelectric thin films. As the dimensions of ferroelectrics are reduced, the properties can vary dramatically, including the robust scaling relationship between coercive field (Ec) and thickness (d), also referred to as the Janovec-Kay-Dunn (JKD) law, wherein Ec ? d-2/3. Here, we report that whereas (001)-oriented heterostructures follow JKD scaling across the thicknesses range of 20-330 nm, (111)-oriented heterostructures of the canonical tetragonal ferroelectric PbZr0.2Ti0.8O3 exhibit a deviation from JKD scaling wherein a smaller scaling exponent for the evolution of Ec is observed in films of thickness ≤ 165 nm. X-ray diffraction reveals that whereas (001)-oriented heterostructures remain tetragonal for all thicknesses, (111)-oriented heterostructures exhibit a transition from tetragonal-to-monoclinic symmetry in films of thickness ≤ 165 nm as a result of the compressive strain. First-principles calculations suggest that this symmetry change contributes to the deviation from the expected scaling, as the monoclinic phase has a lower energy barrier for switching. This structural evolution also gives rise to changes in the c/a lattice parameter ratio, wherein this ratio increases and decreases in (001)- and (111)-oriented heterostructures, respectively, as the films are made thinner. In (111)-oriented heterostructures, this reduced tetragonality drives a reduction of the remanent polarization and, therefore, a reduction of the domain-wall energy and overall energy barrier to switching, which further exacerbates the deviation from the expected scaling. Overall, this work demonstrates a route toward reducing coercive fields in ferroelectric thin films and provides a possible mechanism to understand the deviation from JKD scaling.

Original languageEnglish (US)
Pages (from-to)4736-4743
Number of pages8
JournalACS nano
Volume12
Issue number5
DOIs
StatePublished - May 22 2018
Externally publishedYes

Bibliographical note

Funding Information:
R.X. acknowledges support from the National Science Foundation under grant DMR-1708615. R.G. acknowledges support from the National Science Foundation under grant OISE-1545907. S.E.R.-L. acknowledges partial support from the Molecular Foundry (supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy) and the Laboratory Directed Research and Development Program at the Lawrence Berkeley National Laboratory under contract number DE-AC02-05-CH11231. S.S. acknowledges support from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under award number DE-SC-0012375 for development of ferroelectric thin films. H.L. acknowledges support from the National Science Foundation under grant DMR-1608938. Y.Q. acknowledges support from the National Science Foundation of China under grant 51472078. Z.C. and A.R.D. acknowledge partial support from the Army Research Office under grant W911NF-14-1-0104 and from Intel Corp. X.L. acknowledges the National Science Foundation of China under grant 11372002. S.L.H. acknowledges support from the National Science Foundation under the MRSEC program DMR-1420620. J.B.N. and L.W.M. acknowledge that this work was in-part funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, under contract no. DE-AC02-05-CH11231: Materials Project Program KC23MP for the development of novel materials. This research used resources of the Advanced Photon Source, a U.S.

Funding Information:
R.X. acknowledges support from the National Science Foundation under grant DMR-1708615. R.G. acknowledges support from the National Science Foundation under grant OISE-1545907. S.E.R.-L. acknowledges partial support from the Molecular Foundry (supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy) and the Laboratory Directed Research and Development Program at the Lawrence Berkeley National Laboratory under contract number DE-AC02-05-CH11231. S.S. acknowledges support from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under award number DE-SC-0012375 for development of ferroelectric thin films. H.L. acknowledges support from the National Science Foundation under grant DMR-1608938. Y.Q. acknowledges support from the National Science Foundation of China under grant 51472078. Z.C. and A.R.D. acknowledge partial support from the Army Research Office under grant W911NF-14-1-0104 and from Intel Corp. X.L. acknowledges the National Science Foundation of China under grant 11372002. S.L.H. acknowledges support from the National Science Foundation under the MRSEC program DMR-1420620. J.B.N. and L.W.M. acknowledge that this work was in-part funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences Materials Sciences and Engineering Division, under contract no. DE-AC02-05-CH11231: Materials Project Program KC23MP for the development of novel materials. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory, under contract no. DE-AC02-06CH11357.

Funding Information:
Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory, under contract no. DE-AC02-06CH11357.

Publisher Copyright:
© 2018 American Chemical Society.

Keywords

  • X-ray diffraction
  • coercive-field scaling
  • ferroelectric
  • size effects
  • thin film

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