Polarization Dependent Raman Active Modes Study of the Mo(subscript 1-x)W(subscript x)S2 Mixed Layered Crystals

Dumitru O. Dumcenco ； Yu-Chen Su ； Yi-Ping Wang ； Kuei-Yu Chen ； Ying-Sheng Huang ； Ching-Hwa Ho ； Kwong-Kau Tiong

《Chinese Journal of Physics》 49卷1期 (2011/02) Pp. 270-277

並列摘要

A systematic study of a series of Mo(subscript 1-x)W(subscript x)S2 mixed-layered crystals with 0≤x≤1 grown by the chemical vapor transport method was conducted by using Raman scattering measurements. The composition of the samples was determined by X-ray photoelectron spectroscopy. Measurements in the basal plane revealed two dominant first-order Raman-active modes A(subscript 1g) and E(superscript 1 subscript 2g) as well as several second-order modes in the range of 250-450 cm^(-1). The E(subscript 1g) mode was observed in the edge plane of thick samples. For all the Mo(subscript 1-x)W(subscript x)S2 samples, the peaks corresponding to the A(subscript 1g) mode showed one-mode behavior, whereas the peaks corresponding to the (superscript 1 subscript 2g) mode exhibited two-mode behavior. These results can be explained on the basis of the atomic displacements for each mode. In the case of the A(subscript 1g) mode, only sulfur atoms vibrate, and this results in the one-mode behavior. In contrast, in the case of the E(superscript 1 subscript 2g) mode, metal atoms and sulfur atoms vibrate together, and the resulting mass difference between the vibrating Mo and W cations results in the two-mode behavior of the peaks corresponding to the (superscript 1 subscript 2g) mode.