s Study of Thermal Conductivity in Two-dimensional Bi2Te3 from Micro- Raman Spectroscopy

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.