Evidence of shallow bandgap in ultra-thin 1T'-MoTe2 via infrared spectroscopy

Abstract

Although van der Waals (vdW) layered MoS2 shows the phase transformation from the semiconducting 2H-phase to the metallic 1T-phase through chemical lithium intercalation, vdW MoTe2 is thermodynamically reversible between the 2H- and 1T'-phases, and can be further transformed by energetics, laser irradiation, strain or pressure, and electrical doping. Here, thickness- and temperature-dependent optical properties of 1T'-MoTe2 thin films grown by chemical vapor depsition are investigated via Fourier-transformed infrared spectroscopy. An optical gap of 28 +/- 2 meV in a 3-layer (or 2 nm) thick 1T'-MoTe2 is clearly observed at a low temperature region below 50K. No discernible optical bandgap is observed in samples thicker than ~4 nm. The observed thickness-dependent bandgap results agree with the measured dc resistivity data; the thickness-dependent 1T'-MoTe2 clearly demonstrates the metal-semiconductor transition at a crossover below the 2 nm-thick sample.

18 pages, 4 figures

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• 2D materials and van der Waals heterostructures
• Boron nitride substrates for high-quality graphene electronics
• Quantum Spin Hall Effect and Topological Field Effect Transistor in Two-Dimensional Transition Metal Dichalcogenides
• Titanic Magnetoresistance in WTe2
• Discovery of a new type of topological Weyl fermion semimetal state in Mo${}_x$W${}_{1-x}$Te${}_2$

Cited by in corpus (1)

• Nonconventional screening of Coulomb interaction in two-dimensional semiconductors and metals: A comprehensive cRPA study of MX2 (M=Mo, W, Nb, Ta; X=S, Se, Te)