Raman spectroscopy of a few layers of bismuth telluride nanoplatelets.

We can shape the electronic and phonon properties of Bi ₂ Te ₃ crystals via the variation of the number of layers. Here, we report a Raman study with the aid of first-principles calculations on few-layered Bi ₂ Te ₃ systems ranging from 5 to 24 nm layer thickness using 1.92, 2.41 and 2.54 eV excitation energies. We examine how the frequency position, intensity and lineshape of the main Raman modes (A ¹ _1g , E ² _g , and A ² _1g ) behave by the variation of the layer thickness and excitation energy. We observed a frequency dispersion on the number of layers of the main modes, indicating changes in the inter- and intra-layers interaction. A resonant Raman condition is reached for all modes for samples with 11 and 18 nm thickness because of van Hove singularities at the electronic density of states. Also, the Breit-Wigner-Fano line shape of the A ² _1g mode shows an increase of electron-phonon coupling for thick layers. These results suggest a relevant influence of numbers of layers on the Raman scattering mechanics in Bi ₂ Te ₃ systems.
Competing Interests: The authors declare no competing financial interest.
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