Abstract

Background: Topological insulator (TI), Bi₂Te₃ is a new class of quantum materials. Having ultralow dissipation surface states, TIs hold great promise toward different potential applications. Micro-Raman spectroscopy is a conventional and non-destructive technique, which has been widely used to characterize the structural and electronic properties of thermoelectric materials.

Objective: The objective of this study is to review power dependent and temperature dependent Raman spectra of B₂Te₃ nanoflakes on SiO₂/Si substrate to estimate the temperature coefficient and thermal conductivity of these flakes for possible application of this material in thermoelectrics.

Methods: Bi₂Te₃ flakes of different thicknesses were mechanically exfoliated from high-quality bulk Bi₂Te₃ crystal using scotch tape on 300 nm SiO₂/ Si substrates. The power dependent and temperature dependent Raman spectra were acquired with the help of HORIBA LabRAM confocal micro- Raman system in a backscattering geometry.

Results: The observed power dependent and temperature dependent Raman spectra of Bi₂Te₃ nanoflakes follow the same trend as discussed in various pieces of literature. From temperature coefficient and power coefficient values, the in-plane thermal conductivity has been estimated, which is found to be in the order of 102 W/m-K. The enhancement in the thermal conductivity suggests that the underlying substrate significantly affects the heat dissipation of the Bi₂Te₃ flake based on the coupling strength with Bi₂Te₃.

Conclusion: This work provides a good platform to understand the role of the substrate on the thermal conductivity of exfoliated Bi₂Te₃ nanoflakes and this study can be extended to other substrates.

Keywords: Topological insulators, thermal conductivity, temperature coefficient, power coefficient, micro-Raman, figure ofmerit.

Graphical Abstract