Comparative investigation of the vibrational properties of bulk 2H–MoS₂ and its exfoliated nanosheets under high pressure

Abstract

In this paper, we present a comparative study of the vibrational properties of bulk MoS2 and its exfoliated nanosheets under high pressure by resonant Raman spectroscopy. The X‐ray photoelectron spectroscopy measurements demonstrate that the nanosheets made by chemical lithium insertion method are mainly consisted of metallic 1T phase. The wavenumbers of the Ebold2boldg1 and Alg Raman modes for the few layer nanosheets show a linear relationship with pressure which is different from the multilayer MoS2. This phenomenon is due to the differences in their electronic band structure. The systematic research about the 2LA (M) in bulk 2H–MoS2 suggests that the high pressure behaviour of this double resonance Raman mode arises from the pressure‐induced metallization and band gap closure. These difference vibrational properties for few and multilayer MoS2 can be applied for exploring pressure‐modulated advanced devices. Copyright © 2017 John Wiley & Sons, Ltd.

Enhancement of 1T‐MoS2 Superambient Temperature Stability and Hydrogen Evolution Performance by Intercalating a Phenanthroline Monolayer

“…The spectrum of 2H‐MoS 2 shows two main Raman‐active lattice vibrations at 386 (E 1 2g ) and 411 cm −1 (A 1g ), respectively. They are accompanied by the bands expected for resonant 633 nm excitation, including 180 (A 1g ‐LA(M)), 420 (B1u), 454 (2LA(M)), and 467 (A 2u ) cm −1 [36,37] . The presence of 1T‐MoS 2 in the layers of Phen‐MoS 2 is indicated by the appearance of additional modes J 1 , J 2 , and J 3 , typical of 1T‐MoS 2 modification [38,39] at 192, 229 and 289 cm −1 , respectively.…”

Changes in the Raman spectra of monolayer MoS2 upon thermal annealing

“…Molybdenum disulfide (MoS 2 ), one of the transition‐metal dichalcogenides with a layered structure, presents hexagonal (2H‐MoS 2 ) or rhombohedral (3R‐MoS 2 ) symmetry in nature (a third phase, 1T‐MoS 2 , is a metastable metallic material) . Both phases are semiconducting materials.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XII

“…Guo et al reported a comparative investigation of the vibrational properties of bulk 2H ‐MoS 2 and its exfoliated nanosheets under high pressure. The systematic research about the 2LA (M) in bulk 2H ‐MoS 2 suggests that the high‐pressure behavior of this double resonance Raman mode arises from the pressure‐induced metalization and band gap closure . Krylov et al presented a Raman study of HoFe 3 (BO 3 ) 4 at simultaneously high pressure and high temperature that yielded a P–T phase diagram.…”