Semiconductor-metal transition in semiconducting bilayer sheets of transition-metal dichalcogenides

Abstract

Using first-principles calculations we show that the band gap of bilayer sheets of semiconducting transition metal dichalcogenides (TMDs) can be reduced smoothly by applying vertical compressive pressure. These materials undergo a universal reversible semiconductor to metal (S-M) transition at a critical pressure. S-M transition is attributed to lifting the degeneracy of the bands at fermi level caused by inter-layer interactions via charge transfer from metal to chalcogens. The S-M transition can be reproduced even after incorporating the band gap corrections using hybrid functionals and GW method. The ability to tune the band gap of TMDs in a controlled fashion over a wide range of energy, opens-up possibility for its usage in a range of applications.

Pressure-induced semiconducting to metallic transition in multilayered molybdenum disulphide

“…In agreement with prior theoretical studies 18,19,46 , our theoretically predicted band gap is found to depend inversely on pressure and that the critical pressure for the electronic phase transition is predicted to scale down for multilayered films from B16% normal compressive strain to B11% for bilayer MoS 2 ( Supplementary Fig. 8).…”

“…Hybrid Heyd-Scuseria-Ernzerhof 42 functional and DFT with many-body perturbation theory in the GW approximation 43 are among the few methods to correctly predict the band gap of TMDs; however, these methods are computationally very expensive. Nevertheless, our previous study for bilayer MoS 2 has shown that the overall nature of the variation in the E g and the band structure with pressure are independent of the functional used 18 and that the PBE functional gives reasonably accurate results, justifying the use of the PBE/GGA methods for this work. With the increase in pressure, the degeneracy in the bands of the unstrained structure is lifted due to the enhanced interlayer interaction.…”

“…Furthermore, previous theoretical studies have suggested that an iso-structural semiconducting to metallic (S-M) transition in multilayered MoS 2 can be induced by pressure or strain [18][19][20] . Despite the broad interest in this phenomenon in layered nanomaterials, previous experimental results only reported a limited reduction in the electrical resistance 17,[21][22][23] with no clear evidence for the pressureinduced S-M transition.…”

Two-dimensional inorganic analogues of graphene: transition metal dichalcogenides

“…For instance, the indirect-band gap of bilayer TMDCs can be driven to zero at an electric field of 2-3 Vnm −1 applied perpendicular to the layers, allowing for larger band gap tuneability than that in graphene [65]. Under strain, the band gap of mono-and bi-layer MoS 2 decreases and the material undergoes an insulator-to-metal transition [66][67][68][69]. Chemical stimuli can also modulate the band gap.…”

Highly anisotropic electronic transport properties of monolayer and bilayer phosphorene from first principles

“…3 Their band gaps, ranging approximately 1.0-2.5 eV, are normally at the K point in the Brillouin zone when direct. 3,4 Theoretical calculations predict intrinsic monolayer mobilities in the range of 25-410 cm 2 /Vs (electron) and 90-540 cm 2 /Vs (hole) for MX 2 , where M=Mo,W and X=S,Se. [5][6][7] Experimentally reported values are substantially smaller with the highest around 250 cm 2 /Vs (p-type).…”