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Title: Mechanism of polarization switching in wurtzite-structured zinc oxide thin films

Abstract

The properties of a potentially new class of ferroelectric materials based on wurtzite-structured ZnO thin films are examined using the first-principles calculations. Theoretical P-E hysteresis loops were calculated using the fixed-D method for both unstrained and (biaxially) strained single crystals. Ferroelectric polarization switching in ZnO (S.G. P6{sub 3}mc) is shown to occur via an intermediate non-polar structure with centrosymmetric P6{sub 3}/mmc symmetry by displacement of cations relative to anions in the long-axis direction. The calculated coercive electric field (E{sub c}) for polarization switching was estimated to be 7.2 MV/cm for defect-free monocrystalline ZnO. During switching, the short- and long-axis lattice parameters expand and contract, respectively. The large structural distortion required for switching may explain why ferroelectricity in this compound has not been reported experimentally for pure ZnO. Applying an epitaxial tensile strain parallel to the basal plane is shown to be effective in lowering E{sub c} during polarization, with a 5% biaxial expansion resulting in a decrease of E{sub c} to 3.5 MV/cm. Comparison with calculated values for conventional ferroelectric materials suggests that the ferroelectric polarization switching of wurtzite-structured ZnO may be achievable by preparing high-quality ZnO thin films with suitable strain levels and low defect concentrations.

Authors:
; ; ; ;  [1]; ; ;  [2]
  1. Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587 (Japan)
  2. Materials and Structures Laboratory, Tokyo Institute Technology, Yokohama 226-8503 (Japan)
Publication Date:
OSTI Identifier:
22594296
Resource Type:
Journal Article
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 109; Journal Issue: 10; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0003-6951
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANIONS; CATIONS; COMPARATIVE EVALUATIONS; DEFECTS; ELECTRIC FIELDS; EPITAXY; FERROELECTRIC MATERIALS; HCP LATTICES; LATTICE PARAMETERS; MONOCRYSTALS; POLARIZATION; STRAINS; SYMMETRY; THIN FILMS; ZINC OXIDES

Citation Formats

Konishi, Ayako, Ogawa, Takafumi, Fisher, Craig A. J., Kuwabara, Akihide, Moriwake, Hiroki, E-mail: moriwake@jfcc.or.jp, Shimizu, Takao, Yasui, Shintaro, and Itoh, Mitsuru. Mechanism of polarization switching in wurtzite-structured zinc oxide thin films. United States: N. p., 2016. Web. doi:10.1063/1.4962440.
Konishi, Ayako, Ogawa, Takafumi, Fisher, Craig A. J., Kuwabara, Akihide, Moriwake, Hiroki, E-mail: moriwake@jfcc.or.jp, Shimizu, Takao, Yasui, Shintaro, & Itoh, Mitsuru. Mechanism of polarization switching in wurtzite-structured zinc oxide thin films. United States. doi:10.1063/1.4962440.
Konishi, Ayako, Ogawa, Takafumi, Fisher, Craig A. J., Kuwabara, Akihide, Moriwake, Hiroki, E-mail: moriwake@jfcc.or.jp, Shimizu, Takao, Yasui, Shintaro, and Itoh, Mitsuru. Mon . "Mechanism of polarization switching in wurtzite-structured zinc oxide thin films". United States. doi:10.1063/1.4962440.
@article{osti_22594296,
title = {Mechanism of polarization switching in wurtzite-structured zinc oxide thin films},
author = {Konishi, Ayako and Ogawa, Takafumi and Fisher, Craig A. J. and Kuwabara, Akihide and Moriwake, Hiroki, E-mail: moriwake@jfcc.or.jp and Shimizu, Takao and Yasui, Shintaro and Itoh, Mitsuru},
abstractNote = {The properties of a potentially new class of ferroelectric materials based on wurtzite-structured ZnO thin films are examined using the first-principles calculations. Theoretical P-E hysteresis loops were calculated using the fixed-D method for both unstrained and (biaxially) strained single crystals. Ferroelectric polarization switching in ZnO (S.G. P6{sub 3}mc) is shown to occur via an intermediate non-polar structure with centrosymmetric P6{sub 3}/mmc symmetry by displacement of cations relative to anions in the long-axis direction. The calculated coercive electric field (E{sub c}) for polarization switching was estimated to be 7.2 MV/cm for defect-free monocrystalline ZnO. During switching, the short- and long-axis lattice parameters expand and contract, respectively. The large structural distortion required for switching may explain why ferroelectricity in this compound has not been reported experimentally for pure ZnO. Applying an epitaxial tensile strain parallel to the basal plane is shown to be effective in lowering E{sub c} during polarization, with a 5% biaxial expansion resulting in a decrease of E{sub c} to 3.5 MV/cm. Comparison with calculated values for conventional ferroelectric materials suggests that the ferroelectric polarization switching of wurtzite-structured ZnO may be achievable by preparing high-quality ZnO thin films with suitable strain levels and low defect concentrations.},
doi = {10.1063/1.4962440},
journal = {Applied Physics Letters},
issn = {0003-6951},
number = 10,
volume = 109,
place = {United States},
year = {2016},
month = {9}
}