Figure 2

Micro-Raman spectra of Bi₂Te₃ on semiconducting (a) Si and (b) GaAs substrates; TERS spectra of Bi₂Te₃ on semiconducting (c) Si and (d) GaAs substrates. Modes P3 and P4 are related to small stoichiometry variations within the area probed by the laser spot. Mode P5 is usually observed only in Raman spectra of 1–2 QL thick layers¹¹.