Raman Scattering Characterization of Mo_xW_1-xS₂Layered Mixed Crystals

Abstract

A series of MoxW1−xS2 (0 ≤ x ≤ 1) layered mixed crystals was grown by the chemical vapor transport method. A systematic study of these crystals was then conducted using the Raman scattering measurements. The peaks of the two dominant first-order Raman-active modes, A1g and E 1 2g , and of several second-order bands are observed from 150 cm −1 to 500 cm −1 . The peaks corresponding to A1g mode show one-mode type behavior, whereas the peaks of E 1 2g mode demonstrate two-mode type behavior for the entire series. These results can be explained by the atomic displacements of each mode. For A1g mode, only S atoms vibrate, thereby resulting in a one-mode type behavior for the mixed crystals. For E 1 2g mode, metal and S atoms vibrate. The mass difference in the vibrating Mo and W cations causes the two-mode type behavior of E 1 2g mode. In addition, the largest asymmetry and broadening of A1g mode for Mo0.5W0.5S2 is attributed to random alloy scattering.

Lanthanide near-infrared emission and energy transfer in layered WS2/MoS2 heterostructure

“…Fig. 4a [32]. The Raman characteristic is similar with the previous result in the WS 2 / MoS 2 layered heterostructure [33].…”

Theoretical study of Raman scattering in MoS2xSe2(1 − x) layered alloys

“…In addition, the observation of the largest asymmetry and broadening of A 1g band in Mo 0.5 W 0.5 S 2 has been attributed to a random alloy scattering. Similar results were obtained by Sigiro [47] for Mo x W 1 − x S 2 alloys, where the A 1g mode was shown to be connected with the movement of S atoms normally to the layer and practically not changed in the spectrum. In contrast, the E 1 2g band, which is connected with the movements of all atoms in the unit cell of layer, demonstrates more complicated dependence on x.…”

“…All these statements agree with the experimental observations reported elsewhere. [14][15][16]20,29,37,47] The simulation of theoretical dependencies of the Raman spectra of layered alloys allows to estimate the value of parameters of the intralayer and interlayer interactions. When simulating for different intralayer modes (A 1g or E 1 2g ), these parameters were selected for the best fitting of the experimental spectra obtained in the work by Li et al [16] Figure 4 shows the modeling of Raman spectra for the A 1g and E 1 2g modes versus x in MoS 2x Se 2(1 − x) alloy.…”