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

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 ( E c) and thickness ( d), also referred to as the Janovec-Kay-Dunn (JKD) law, wherein E c ∝ 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 PbZr 0.2Ti 0.8O 3 exhibit a deviation from JKD scaling wherein a smaller scaling exponent for the evolution of E c 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,more » 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. Altogether, 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.« less
Authors:
ORCiD logo [1] ;  [1] ;  [2] ;  [1] ;  [3] ;  [1] ; ORCiD logo [1] ;  [4] ;  [5] ;  [6] ;  [1] ;  [7] ;  [8] ; ORCiD logo [6]
  1. Univ. of California, Berkeley, CA (United States)
  2. Univ. Andres Bello, Santiago (Chile); Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. Univ. of Science and Technology of China, Hefei (China)
  4. Harbin Institute of Technology, Harbin (China)
  5. Hubei Univ., Wuhan (China)
  6. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  7. Argonne National Lab. (ANL), Argonne, IL (United States)
  8. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kavli Energy NanoScience Institute at Berkeley, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357; AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 12; Journal Issue: 5; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; coercive-field scaling; ferroelectric; size effects; thin film; x-ray diffraction
OSTI Identifier:
1466327

Xu, Ruijuan, Gao, Ran, Reyes-Lillo, Sebastian E., Saremi, Sahar, Dong, Yongqi, Lu, Hongling, Chen, Zuhuang, Lu, Xiaoyan, Qi, Yajun, Hsu, Shang-Lin, Damodaran, Anoop R., Zhou, Hua, Neaton, Jeffrey B., and Martin, Lane W.. Reducing Coercive-Field Scaling in Ferroelectric Thin Films via Orientation Control. United States: N. p., Web. doi:10.1021/acsnano.8b01399.
Xu, Ruijuan, Gao, Ran, Reyes-Lillo, Sebastian E., Saremi, Sahar, Dong, Yongqi, Lu, Hongling, Chen, Zuhuang, Lu, Xiaoyan, Qi, Yajun, Hsu, Shang-Lin, Damodaran, Anoop R., Zhou, Hua, Neaton, Jeffrey B., & Martin, Lane W.. Reducing Coercive-Field Scaling in Ferroelectric Thin Films via Orientation Control. United States. doi:10.1021/acsnano.8b01399.
Xu, Ruijuan, Gao, Ran, Reyes-Lillo, Sebastian E., Saremi, Sahar, Dong, Yongqi, Lu, Hongling, Chen, Zuhuang, Lu, Xiaoyan, Qi, Yajun, Hsu, Shang-Lin, Damodaran, Anoop R., Zhou, Hua, Neaton, Jeffrey B., and Martin, Lane W.. 2018. "Reducing Coercive-Field Scaling in Ferroelectric Thin Films via Orientation Control". United States. doi:10.1021/acsnano.8b01399. https://www.osti.gov/servlets/purl/1466327.
@article{osti_1466327,
title = {Reducing Coercive-Field Scaling in Ferroelectric Thin Films via Orientation Control},
author = {Xu, Ruijuan and Gao, Ran and Reyes-Lillo, Sebastian E. and Saremi, Sahar and Dong, Yongqi and Lu, Hongling and Chen, Zuhuang and Lu, Xiaoyan and Qi, Yajun and Hsu, Shang-Lin and Damodaran, Anoop R. and Zhou, Hua and Neaton, Jeffrey B. and Martin, Lane W.},
abstractNote = {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. Altogether, 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.},
doi = {10.1021/acsnano.8b01399},
journal = {ACS Nano},
number = 5,
volume = 12,
place = {United States},
year = {2018},
month = {4}
}