\textbf{Raman spectroscopy of exfoliated few-layered n-type Bi}$_{\mathrm{\mathbf{2}}}$\textbf{Te}$_{\mathrm{\mathbf{3}}}$

A novel chemical-exfoliation spark-plasma-sintering (CE-SPS) process was applied to enhance the thermoelectric figure of merit and compatibility factor of few-layered n-type Bi$_{\mathrm{2}}$Te$_{\mathrm{3}}$. New vibrational modes were observed in the micro-Raman spectra of the few-layered Bi$_{\mathrm{2}}$Te$_{\mathrm{3}}$ samples, which are absent in the bulk. Here we focus on the emergence of the new intermediate and high-frequency Raman modes and their dependence on the layer thickness. A detailed Raman study probing the origin of these exfoliation induced defect modes will be presented.