Study of strain effect on in-plane polarization in epitaxial BiFeO3 thin films using planar electrodes

Zuhuang Chen, Xi Zou, Wei Ren, Lu You, Chuanwei Huang, Yurong Yang, Ping Yang, Junling Wang, Thirumany Sritharan, L. Bellaiche, and Lang Chen
Phys. Rev. B 86, 235125 – Published 17 December 2012
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Abstract

Epitaxial strain plays an important role in determining physical properties of perovskite ferroelectric oxide thin films because of the inherent coupling between the strain and the polarization. However, it is very challenging to directly measure properties such as polarization in ultrathin strained films, using traditional sandwich capacitor devices, because of high leakage current. Hence, a planar electrode device with different crystallographical orientations between electrodes, which is able to measure the polarization response with different electric field orientation, is used successfully in this work to directly measure the in-plane polarization–electric-field (P-E) hysteresis loops in fully strained thin films. We used BiFeO3 (BFO) as a model system and measured in-plane P-E loops not only in the rhombohedral-like (R-like) BFO thin films but also in largely strained BFO films exhibiting the pure tetragonal-like (T-like) phase. The exact magnitude and direction of the spontaneous polarization vector of the T-like phase is deduced thanks to the collection of in-plane polarization components along different orientations. It is also shown that the polarization vector in the R-like phase of BiFeO3 is constrained to lie within the (11¯0) plane and rotates from the [111] towards the [001] pseudocubic direction when the compressive strain is increased from zero. At high misfit strains such as 4.4%, the pure T-like phase is obtained and its polarization vector is constrained to lie in the (010) plane with a significantly large in-plane component, ∼44 μC/cm2. First-principles calculations are carried out in parallel, and provide a good agreement with the experimental results.

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  • Received 15 October 2012

DOI:https://doi.org/10.1103/PhysRevB.86.235125

©2012 American Physical Society

Authors & Affiliations

Zuhuang Chen1,*, Xi Zou1, Wei Ren2,3, Lu You1, Chuanwei Huang1, Yurong Yang2,4, Ping Yang5, Junling Wang1, Thirumany Sritharan1, L. Bellaiche2, and Lang Chen1,†

  • 1School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
  • 2Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA
  • 3Department of Physics, Shanghai University, 99 Shangda Road, Shanghai 200444, China
  • 4Physics Department, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
  • 5Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, Singapore 117603, Singapore

  • *glory8508@gmail.com
  • langchen@ntu.edu.sg

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Issue

Vol. 86, Iss. 23 — 15 December 2012

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