Anisotropic optical properties of rhombohedral and tetragonal thin film BiFeO3 phases

Daniel Schmidt, Lu You, Xiao Chi, Junling Wang, and Andrivo Rusydi
Phys. Rev. B 92, 075310 – Published 25 August 2015

Abstract

The anisotropic optical properties of multiferroic BiFeO3 thin films have been determined with Mueller matrix ellipsometry at room temperature. The full dielectric tensors of tetragonal-like and rhombohedral-like BiFeO3 phases epitaxially grown on LaAlO3 and SrTiO3 single crystal substrates, respectively, within the spectral range of 0.6 and 6.5 eV are reported. Strain-driven anisotropy changes and transition shifts are observed as well as evidence of sub-band gap many-particle excitations are found. The transition shifts, mostly to higher energies for the highly strained tetragonal-like BiFeO3 phase on LaAlO3, are indicative of band structure differences. Additionally, optical modeling, confirmed by piezoelectric force microscopy studies, revealed that the average polarization direction of bivariant BiFeO3 on LaAlO3 is not parallel to the crystallographic [001] direction but tilted by about 7. Spectral weight analyses reveal phase-dependent differences, underlining that theoretical calculations of optical spectra need further improvement to appropriately account for electronic and excitonic correlations to fully understand multiferroic BiFeO3.

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  • Received 27 July 2015
  • Revised 12 August 2015

DOI:https://doi.org/10.1103/PhysRevB.92.075310

©2015 American Physical Society

Authors & Affiliations

Daniel Schmidt1,*, Lu You2, Xiao Chi1, Junling Wang2, and Andrivo Rusydi1,3,†

  • 1Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore
  • 2School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
  • 3NUSNNI-Nanocore, Department of Physics, National University of Singapore, 2 Science Drive, Singapore 117551, Singapore

  • *schmidt@huskers.unl.edu
  • phyandri@nus.edu.sg

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Vol. 92, Iss. 7 — 15 August 2015

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