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Thickness dependent transition from the 1T� to Weyl semimetal phase in ultrathin MoTe2: Electrical transport, noise and Raman studies

Kuiri, M and Das, S and Muthu, DVS and Das, A and Sood, AK (2020) Thickness dependent transition from the 1T� to Weyl semimetal phase in ultrathin MoTe2: Electrical transport, noise and Raman studies. In: Nanoscale, 12 (15). pp. 8371-8378.

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Abstract

Bulk 1T�-MoTe2 shows a structural phase transition from the 1T� to Weyl semimetallic (WSM) Td phase at �240 K. This phase transition and transport properties in the two phases have not been investigated on ultra-thin crystals. Here we report electrical transport, 1/f noise and Raman studies on ultra-thin 1T�-MoTe2 (�5 to 16 nm thick) field-effect transistor (FETs) devices as a function of temperature. The electrical resistivities for a thickness of 16 nm and 11 nm show maxima at temperatures of 208 K and 178 K, respectively, making a transition from the semiconducting to semi-metallic phase, hitherto not observed in bulk samples. Raman frequencies and linewidths for an 11 nm thick crystal show a change around 178 K, attributed to the additional contribution to the phonon self-energy due to the enhanced electron-phonon interaction in the WSM phase. Furthermore, the resistivity at low temperature shows an upturn below 20 K along with the maximum in the power spectral density of the low frequency 1/f noise. The latter rules out the metal-insulator transition (MIT) being responsible for the upturn of resistivity below 20 K. The low temperature resistivity follows � � 1/T, changing to � � T with increasing temperature supports electron-electron interaction physics at electron-hole symmetric Weyl nodes below 20 K. These observations will pave the way to unravel the properties of the WSM state in layered ultra-thin van der Waals materials. © 2020 The Royal Society of Chemistry.

Item Type: Journal Article
Publication: Nanoscale
Publisher: Royal Society of Chemistry
Additional Information: Copyright for this article Royal Society of Chemistry
Keywords: Crystals; Electric field effects; Electron-electron interactions; Electron-phonon interactions; Electrons; Field effect transistors; Metal insulator boundaries; Semiconductor insulator boundaries; Spectral density; Temperature; Van der Waals forces, Electrical transport; Field effect transistor (FETs); Increasing temperatures; Low temperature resistivity; Raman frequencies; Structural phase transition; Thickness-dependent transition; Ultra-thin crystals, Metal insulator transition
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 08 Apr 2021 10:59
Last Modified: 08 Apr 2021 10:59
URI: http://eprints.iisc.ac.in/id/eprint/65281

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