Abstract
The resonance Raman scattering for geometries Y(YX)Z and Y(ZX)Z at temperature 10 K and infrared reflection spectra in E∥a and E∥b polarizations at 300 K were investigated. The number of Aa (Ba) and Au (Bu) symmetry vibrational modes observed experimentally and calculated theoretically agree better in this case than when TlGa2Se4 crystals belong to D2h symmetry group. The emission of resonance Raman scattering and excitonic levels luminescence spectra overlap. The lines in resonance Raman spectra were identified as a combination of optical phonons in Brillouin zone center.
Highlights
TlGaSe2 crystals are triple thallium chalcogenides with a layered structure [1, 2]
Raman scattering spectra of TlGaSe2 crystals were measured on double high-aperture spectrometers DFS-32 with linear dispersion of 5 Å/mm and relative aperture of 1 : 5 and resonance Raman scattering spectra on spectrometer SDL1 with dispersion of 7 Å/mm and relative aperture of 1 : 2
It was shown that the amount of modes in Raman scattering and IR reflection spectra measured at 10 K is half the expected according to group theory calculations
Summary
TlGaSe2 crystals are triple thallium chalcogenides with a layered structure [1, 2]. One of these crystals features is the strong anisotropy of physical characteristics due to the specificity of the crystals lattice [1,2,3]. Reflection spectra for the 50–4000 cm−1 region were studied and polar vibrational modes LO and TO and their parameters were determined. Such crystals had an effect of switching of current-voltage and acoustooptic characteristics [13,14,15].
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