Anisotropic optical properties of rhombohedral and tetragonal thin film BiFeO${}_3$ phases

Abstract

The anisotropic optical properties of multiferroic BiFeO${}_3$ thin films have been determined with Mueller matrix ellipsometry at room-temperature. The full dielectric tensors of tetragonal-like and rhombohedral-like BiFeO${}_3$ phases epitaxially grown on LaAlO${}_3$ and SrTiO${}_3$ 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 BiFeO${}_3$ phase on LaAlO${}_3$, are indicative of band structure differences. Additionally, optical modelling, confirmed by piezoelectric force microscopy studies, revealed that the average polarization direction of bivariant BiFeO${}_3$ on LaAlO${}_3$ is not parallel to the crystallographic [001] direction but tilted by about $7^{\circ }$. 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 BiFeO${}_3$.

7 pages, 5 figures

References in corpus (6)

• First-principles study of spontaneous polarization in multiferroic BiFeO${}_3$
• The beta Phase of Multiferroic Bismuth Ferrite and its beta-gamma Metal-Insulator Transition
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• Linear and Nonlinear Optical constants of BiFeO_3
• Effect of epitaxial strain on ferroelectric polarization in multiferroic BiFeO3 films
• Nanoscale domains in strained epitaxial BiFeO3 thin Films on LaSrAlO4 Substrate

Cited by in corpus (7)

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• Electronic correlation determining correlated plasmons in Sb-doped Bi${}_2$Se${}_3$
• Investigation of electronic energy levels in a weak ferromagnetic oxygen-deficient BiFeO2.85 thick film using absorption and X ray photoelectron spectroscopic studies
• Understanding electronic excited states in BiFeO${}_3$ via ab initio calculations and symmetry analysis
• Temperature-dependent generalized ellipsometry of the metal-insulator phase transition in low-symmetry charge-transfer salts
• Crossover between bulk and interface photovoltaic mechanisms in ferroelectric vertical heterostructure