Temperature-dependent Raman Spectroscopy of Doped and Undoped Topological Insulators*

Topological insulators, materials whose bulk interior is insulating but have an unusual two dimensional electronic state at the surface, represent a new class of quantum materials now being intensively investigated. The objective of this work was to study how the introduction of magnetic dopants affect the Raman response of topological insulator thin films in terms of spectral peak position and linewidth. We performed temperature dependent Raman spectroscopy on 8nm thick doped and undoped samples of capped Bi₂Te₃ thin films grown by molecular beam epitaxy_. The dopants used were Cr and V at 2% and 4% replacement of Bi. We describe the effect of this doping on the position, and full width at half maximum of the observed thin film spectra. From the analysis of the temperature dependent Raman response, we suggest that this behaviour can be understood in terms of doping-induced strain. This study revealed information about the lattice dynamical properties of Bi₂Te₃; in particular, how these properties evolve with the manipulation of metallic and transition metallic atoms in the topological insulator lattice.