Observation of infrared-active modes in Raman scattering from topological insulator nanoplates

Two infrared (IR)-active vibrational modes, observed at 93 and 113cm ¹ in Raman scattering, are evidence of an inversion symmetry breakdown in thin (10nm) nanoplates of topological insulator Bi _2Te3 as-grown on SiO2. Both Raman and IR modes are preserved after typical device fabrication processes. In nanoplates transferred to another SiO2 substrate via contact printing, however, the IR modes are absent, and the Raman spectra are similar to those from bulk samples. The differences between as-grown and transferred nanoplates may result from nanoplate-substrate interactions.