Doping-Mediated Lattice Engineering of Monolayer ReS₂ for Modulating In-Plane Anisotropy of Optical and Transport Properties

Abstract

ReS 2 exhibits strong anisotropic optical and electrical responses originating from the asymmetric lattice. Here, we show that the anisotropy of monolayer (1L) ReS 2 in optical scattering and electrical transport can be practically erased by lattice engineering via lithium (Li) treatment. Scanning transmission electron microscopy revealed that significant strain is induced in the lattice of Li-treated 1L-ReS 2 , due to high-density electron doping and the resultant formation of continuous tiling of nanodomains with randomly rotating orientations of 60°, which produced a nearly isotropic response of polarized Raman scattering and absorption of Li-treated 1L-ReS 2 . With Li treatment, the in-plane conductance of 1L-ReS 2 increased by an order of magnitude, and its angle dependence became negligible. Our result that the asymmetric phase was converted into the isotropic phase by electron injection could significantly expand the optoelectronic applications of polymorphic two-dimensional transition metal dichalcogenides.

Analyzing Anisotropy in 2D Rhenium Disulfide Using Dichromatic Polarized Reflectance

“…Peak X 1 (1) and X 2 (1) are the ground state of the two direct excitons corresponding to the recombination emission of excitons along and perpendicular to the Re-Re chain in the ReS 2 crystal. [57] Peak X 1/2 (2) and peak X 1/2 (3) are attributed to a nonthermalized hot PL process from the hydrogenic Rydberg series of X 1 and X 2 . [58] The low-symmetry parallelogram feature of Re 4 clusters results in a large-size ReS 2 unit cell consisting of 12 atoms, giving rise to 36 phonon modes (18 A g modes and 18 A u modes).…”

“…Anisotropy in 2D materials provides an additional degree of freedom for one to explore new exciting device concepts and functionalities, [1][2][3][4][5][6][7] such as polarization-sensitive photodetectors [8] and nanoelectromechanical systems with unique resonant responses. [1,9] Utilizing their anisotropic electrical, [10] optical, [11,12] mechanical, [5,13] and thermal properties, [14,15] one can design atomically thin devices such as modulators, polarizers, thermoelectrics, plasmonic devices, and nanoelectromechanical devices.…”

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Among anisotropic 2D materials, rhenium disulfide (ReS 2 ) is unique due to its highly asymmetric structure. [28][29][30][31][32] Its distorted 1T crystal structure has only triclinic symmetry, that is, no symmetry except a center of inversion, [2,28,33,34] and thus is expected to exhibit strongly anisotropic properties. Furthermore, ReS 2 has a number of remarkable features: i) it has a rich Raman spectrum (18 Raman-active modes); ii) relative intensity of its Raman peaks exhibits strong polarization-dependence; iii) it shows much better material stability for most measurements [35] compared with some other anisotropic 2D materials (such as black P, [36,37] WTe 2 , [38] and MoTe 2 [39] ).

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“…) is obtained. Here, R M was calculated using Equation(2) with measured values from Step 1, I′ BM was measured in Step 2, and I B was measured in Step 3. The laser power was carefully chosen to avoid sample damage, which is 1.2 mW for the 532 nm laser, and 0.45 mW for the 633 nm laser.…”

Scalable-doped Nanoporous 1T″ ReSe2 via a General Surface Co-Alloy Strategy

“…ReX 2 (X = S, Se), as a member of Group VII-TMDs, possesses a thermodynamically stable semiconducting phase with 1T′ and 1T″ structures, depending on the coordination modes between the Re metal and chalcogen atoms. − Compared to thermodynamically stable 1T′ phase ReX 2 , 1T″ phase ReX 2 shows superior performance for energy conversion and storage due to the low charge transfer resistance of the high conductivity. − Although the phase-engineered syntheses of 1T″ ReX 2 from the 1T′ phase have been developed via the hydrothermal reaction, , high pressure, and chemical exfoliation, the as-produced 1T″ ReX 2 domains are quite low, which limits the practical applications of ReX 2 . ,,, Interestingly, introducing strain by substitution doping into TMDs can directly alter the intrinsic interatomic distances and electron density, − thus creating an energy-favorable environment for bonding electrons, which may be a robust strategy for realizing the inherent properties and the structure transformation of metastable 1T″-phase Group VII TMDs.…”