Raman Spectra of Monolayer, Few-Layer, and Bulk ReSe₂: An Anisotropic Layered Semiconductor

Abstract

Rhenium diselenide (ReSe2) is a layered indirect gap semiconductor for which micromechanical cleavage can produce monolayers consisting of a plane of rhenium atoms with selenium atoms above and below. ReSe2 is unusual among the transition-metal dichalcogenides in having a low symmetry; it is triclinic, with four formula units per unit cell, and has the bulk space group P1̅. Experimental studies of Raman scattering in monolayer, few-layer, and bulk ReSe2 show a rich spectrum consisting of up to 16 of the 18 expected lines with good signal strength, pronounced in-plane anisotropy of the intensities, and no evidence of degradation of the sample during typical measurements. No changes in the frequencies of the Raman bands with layer thickness down to one monolayer are observed, but significant changes in relative intensity of the bands allow the determination of crystal orientation and of monolayer regions. Supporting theory includes calculations of the electronic band structure and Brillouin zone center phonon modes of bulk and monolayer ReSe2 as well as the Raman tensors determining the scattering intensity of each mode. It is found that, as for other transition-metal dichalcogenides, Raman scattering provides a powerful diagnostic tool for studying layer thickness and also layer orientation in few-layer ReSe2.

Highly Efficient Infrared Photodetection in a Gate‐Controllable Van der Waals Heterojunction with Staggered Bandgap Alignment

“…In the ReS 2 region, the Raman peaks observed at 152 and 212 cm −1 are related to the E 2g ‐like and A 1g ‐like phonon modes, respectively 36. The two peaks with high signal intensities in the ReSe 2 Raman spectrum (at 125 and 158 cm −1 ) indicate E g ‐like and A g ‐like Raman peaks 37. The Raman spectrum of the overlapped ReS 2 /ReSe 2 region contained all peaks related to the vibration modes of both ReS 2 and ReSe 2 .…”

Electronic and Optoelectronic Applications Based on 2D Novel Anisotropic Transition Metal Dichalcogenides

“…The strongest modes are present between 120 and 240 cm −1 in unpolarized Raman spectrum for a ReS 2 monolayer 57. Experimentally, Wolverson et al found that the ReSe 2 Raman modes occupy the frequency range from 100 to 300 cm −1 and are densely spaced, with the exception of a gap at ≈140 cm −1 (Figure 3e) 97…”

Quasiparticle band gaps, excitonic effects, and anisotropic optical properties of the monolayer distorted1Tdiamond-chain structuresReS2andReSe2Zhong1, Gao2, Shi3 et al. 2015Phys. Rev. B13911860View full textAdd to dashboardCite

“…Unlike hexagonal TMDCs, ReX 2 (X= S, Se) crystallizes in a distorted 1-T diamond-chain structure with the triclinic symmetry, as a result of charge decoupling from an extra valence electron of Re atoms [18][19][20] . This structural distortion leads to a much weaker interlayer coupling.…”

“…Such a vanishing interlayer coupling in ReX 2 structures enables probing 2D-like systems without the need of monolayer or few layers, overcoming the challenge of preparing large-area, single-crystal monolayers 18 . Furthermore, the structure distortion of 1T-ReX 2 makes it exhibit unique anisotropic optical, electrical, and mechanical properties 18,20 , with considerable interests for various applications in polarization controller, liquid crystal displays, 3D visualization techniques, (bio)dermatology, and in optical quantum computers 21,22 .…”