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

Das, S and Debnath, K and Chakraborty, B and Singh, A and Grover, S and Muthu, DVS and Waghmare, UV and Sood, AK (2021) Symmetry induced phonon renormalization in few layers of 2H-MoTe2 transistors: Raman and first-principles studies. In: Nanotechnology, 32 (4).

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Official URL: https://dx.doi.org/10.1088/1361-6528/abbfd6


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 E12g and B2g phonon modes exhibit frequency softening and linewidth broadening with hole doping concentration (p) up to �2.3 � 1013/cm2, A1g shows relatively small frequency hardening and linewidth sharpening. The dependence of frequency renormalization of the E12g 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. We present first-principles density functional theory analysis of bilayer MoTe2 that qualitatively captures our observations, and explain that a relatively stronger coupling of holes with E12g or B2g modes as compared with the A1g mode originates from the in-plane orbital character and symmetry of the states at valence band maximum. The contrast between the manifestation of EPC in monolayer MoS2 and those observed here in a few-layered MoTe2 demonstrates the role of the symmetry of phonons and electronic states in determining the EPC in these isostructural systems. © 2021 Institute of Physics Publishing. All rights reserved.

Item Type: Journal Article
Publication: Nanotechnology
Publisher: IOP Publishing Ltd
Additional Information: The copyright of this article belongs to IOP Publishing Ltd
Keywords: Density functional theory; Doping (additives); Field effect transistors; Layered semiconductors; Molybdenum compounds; Phonons, First-principles density functional theory; First-principles study; Linewidth broadening; Number of layers; Orbital character; Phonon coupling; Two Dimensional (2 D); Valence-band maximums, Tellurium compounds
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 03 Feb 2021 06:05
Last Modified: 03 Feb 2021 06:05
URI: http://eprints.iisc.ac.in/id/eprint/67260

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