Symmetry induced phonon renormalization in few layers of 2H-MoTe2 transistors: Raman and first-principles studies

Understanding of electron–phonon coupling (EPC) in two-dimensional (2D) materials manifesting as phonon renormalization is essential to their possible applications in nanoelectronics. Here we report in situ Raman measurements of electrochemically top-gated 2, 3 and 7 layered 2H-MoTe2 channel based field-effect transistors. While the ${{\rm{E}}}_{2g}^{1}$ and B2g phonon modes exhibit frequency softening and linewidth broadening with hole doping concentration (p) up to ~2.3 × 10^13/cm^2, A1g shows relatively small frequency hardening and linewidth sharpening. The dependence of frequency renormalization of the ${{\rm{E}}}_{2g}^{1}$ mode on the number of layers in these 2D crystals confirms that hole doping occurs primarily in the top two layers, in agreement with recent predictions.

DOI: https://doi.org/10.1088/1361-6528/abbfd6

(*Subhadip Das, Koyendrila Debnath, Biswanath Chakraborty, Shivani Grover, D V S Muthu, U V Waghmare, and A K Sood are the other authors of this paper.)