Pressure-Induced Metallization of Molybdenum Disulfide

Abstract

X-ray diffraction, Raman spectroscopy, and electrical conductivity measurements of molybdenum disulfide MoS(2) are performed at pressures up to 81 GPa in diamond anvil cells. Above 20 GPa, we find discontinuous changes in Raman spectra and x-ray diffraction patterns which provide evidence for isostructural phase transition from 2H(c) to 2H(a) modification through layer sliding previously predicted theoretically. This first-order transition, which is completed around 40 GPa, is characterized by a collapse in the c-lattice parameter and volume and also by changes in interlayer bonding. After the phase transition completion, MoS(2) becomes metallic. The reversibility of the phase transition is identified from all these techniques.

Structural characteristic correlated to the electronic band gap inMoS2

“…1(a)]. Our XRD data show no structural transition at pressures up to 25 GPa, which is consistent with the reported high pressure XRD results [3][4][5]. We performed Rietveld refinement to obtain detailed structural characteristics from the measured high quality XRD patterns [ Fig [3].…”

“…For example, the bulk MoS 2 , an indirect gap semiconductor, shows a pressure-induced metallization and structural phase transition from 2Hc to 2Ha [3][4][5]. When exfoliated to monolayer, the band gap evolves to a direct band gap [6][7][8].…”

Phonon and Raman scattering of two-dimensional transition metal dichalcogenides from monolayer, multilayer to bulk material

“…Recently, both X-ray diffraction and Raman spectroscopy of ML (at ∼19 GPa) and bulk MoS 2 (between 20 and 30 GPa) under high pressure confirmed the above transitions. 99,120,148 Fig . 18(a) shows the Raman spectra of bulk MoS 2 at various pressures up to 57 GPa in both compression (denoted by c) and decompression (denoted by d) runs.…”

Vibrational spectrum renormalization by enforced coupling across the van der Waals gap betweenMoS2andWS2Fan1, Zhu2, Ke3 et al. 2015Phys. Rev. B321221View full textAdd to dashboardCite

“…In bulk or multilayer materials, their Raman active modes are found to stiffen with increasing pressure applied. [10][11][12] However, as the materials studied are composed of a stack of identical layers (hence homo-multilayers), it is not possible to distinguish the vibrational modes from individual monolayers. In this work, we apply high pressure to hetero-bilayers composed of a MoS 2 monolayer stacked on a WS 2 monolayer, and demonstrate that a dimensional crossover, similar to that observed in electronic band structure renormalization, occurs also in the lattice vibrational structure of the system.…”

“…For instance, with the application of high hydrostatic pressures at 10 ~ 20 GPa, an insulator-metal phase transition with a rapid drop in resistivity has been observed in bulk MoS 2 . [10][11][12] These studies all focus on normalization of the electronic structure with artificially tuned interlayer coupling. It is less clear how the vibrational structure of the system responds to modulation of the interlayer coupling.…”