Raman spectroscopic investigations of epitaxial BiFeO₃ thin films on rare earth scandate substrates

Abstract

BiFeO 3 epitaxial thin films fabricated by pulsed laser deposition on different scandate substrates were investigated by means of Raman spectroscopy. We observed periodic changes in Raman position, full width at half maximum and intensity for some phonon modes as a function of the azimuthal angle ϕ. Further analysis revealed the possibility to assign the so far controversial discussed Raman modes at low wavenumbers (<250 cm À1 ) through rotational Raman measurements at different azimuthal angles, which show high sensitivity to the aforementioned parameters. Furthermore, the ferroelectric/ferroelastic domain structure shown by piezo-response force microscopy investigations of the samples was confirmed. Our results are supported by symmetry-based calculations including the analysis of Raman scattering geometry as well as the dielectric function of BiFeO 3 in the infrared range. Figure 7. (a) Raman spectra for the BiFeO 3 /DyScO 3 thin film with one Lorentzian mode in the range of 100-140 cm À1 . The experimental behaviour of Raman intensity, wavenumber and FWHM of this mode in relation to the azimuthal angle ϕ as well as the calculated behaviour (red dashed lines) is presented in (b), (c) and (d), respectively. Where the mode shows maxima for the wavenumber, minima in full width at half maximum can be detected and vice versa.Raman investigations of epitaxial BiFeO 3 thin films

Titanium doping of BiFeO3 ceramics and identification of minor phases by Raman spectroscopy

“…). For the BiFeO 3 phase, the Raman active modes were tentatively assigned according to the theoretical calculations recently published by Talkengerg et al As it can be observed, the spectra of both powders show bands corresponding to both the Bi 25 FeO 39 and Bi 2 Fe 4 O 9 secondary phases, together with those belonging to the BiFeO 3 . It is worth to mention that the presence of the Bi 2 Fe 4 O 9 phase in the BFTO powder was neither detected by XRD nor by the TEM analysis, probably due to its low proportion.…”

“…Definitely, this enhanced capacity for the detection of minor byproducts may help in avoiding misleading conclusions (and discrepancies) on the functional response of this multiferroic system. ) observed in the experimental spectra of the BFO and BFTO powders (assignation to the BiFeO 3 modes or to the Bi 2 Fe 4 O 9 mullitetype and the Bi 25 FeO 39 sillenite-type secondary phases as explained in the text) and the calculated Raman wavenumbers for the BiFeO 3 modes from literature [27] Mode BFO BFTO Raman shift Calculated [27]…”

“…However, inconsistencies among the different published researches on this topic are concurrently noticed. In particular, the assignment of the Raman modes has been controversially discussed . Experimental and theoretical studies, which are still going on, will undoubtedly allow a better correlation between the Raman modes and the BFO structure.…”

“…In particular, the assignment of the Raman modes has been controversially discussed. [24][25][26][27][28][29][30] Experimental and theoretical studies, which are still going on, will undoubtedly allow a better correlation between the Raman modes and the BFO structure.…”

Recent advances in linear and non‐linear Raman spectroscopy. Part X

“…performed Raman spectroscopic investigations of epitaxial BiFeO 3 thin films on rare earth scandate substrates. Their results were supported by symmetry‐based calculations including the analysis of Raman scattering geometry as well as the dielectric function of BiFeO 3 in the IR range …”