Origin of a Tetragonal BiFeO3 Phase with a Giant c/a Ratio on SrTiO3 Substrates

Authors

  • Huajun Liu,

    1. Department of Materials Science and Engineering, National University of Singapore, Singapore 117574, Singapore
    2. Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Singapore 117602, Singapore
    Search for more papers by this author
  • Ping Yang,

    1. Singapore Synchrotron Light Source National University of Singapore, 5 Research Link, 117603, Singapore
    Search for more papers by this author
  • Kui Yao,

    1. Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Singapore 117602, Singapore
    Search for more papers by this author
  • Khuong Phuong Ong,

    1. Institute of High Performance Computing, 1 Fusionopolis Way,# 16-16 Connexis, Singapore 138632, Singapore
    Search for more papers by this author
  • Ping Wu,

    1. Institute of High Performance Computing, 1 Fusionopolis Way,# 16-16 Connexis, Singapore 138632, Singapore
    Current affiliation:
    1. Singapore University of Technology and Design, 20 Dover Drive, Singapore 138682, Singapore
    Search for more papers by this author
  • John Wang

    Corresponding author
    1. Department of Materials Science and Engineering, National University of Singapore, Singapore 117574, Singapore
    • Department of Materials Science and Engineering, National University of Singapore, Singapore 117574, Singapore.
    Search for more papers by this author

Abstract

A tetragonal BiFeO3 phase with giant c/a of approximately 1.25 has been of great interest recently as it potentially possesses a giant polarization and much enhanced electromechanical response. This super-tetragonal phase is known to be a stable phase only under high compressive strains of above approximately 4.5%, according to first principle calculations. However, in previous work, this super-tetragonal BiFeO3 phase was obtained in films deposited at high growth rate on SrTiO3 substrates with compressive strain of only around 1.5%. By detailed structure analysis using high resolution synchrotron X-ray diffraction, atomic force microscopy, and transmission electron microscopy, the parasitic β-Bi2O3 phase is identified as the origin inducing the formation of super-tetragonal BiFeO3 phase on SrTiO3 substrates. In addition, ab initio calculations also confirm that this super-tetragonal phase is more stable than monoclinic phase when Bi2O3 is present. Using Bi2O3 as a buffer layer, an alternative route, not involving strain engineering, is proposed to stabilize this promising super-tetragonal BiFeO3 phase at low growth rates.

Ancillary