Observation of Graphite-Like and Diamond-Like Nanostructures in the Raman Spectra of Natural and Synthesized MoS2 Crystals with Small Carbon Additives

Abstract

A comparative study of Raman spectra excited by laser radiation λL = 632.8 nm and 488 nm of natural crystals of 2H-MoS2 and nanocrystallites MoS2 (C) containing 0.5 and 1.0 wt.% Carbon additives. A detailed numerical analysis of the shape of observed D and G bands was performed. The complication of the spectra of graphite-like and diamond-like structures with the appearance of additional spectral components at 1440-1500 cm-1 and 1230-1270 cm-1 as a result of doubling the size of the corresponding elementary quasi-cells are analyzed. It is shown that the frequencies of  D-bands of diamond-like nanostructures 1297 ÷ 1302 cm-1 don’t depend on λL in contrast to the change in the frequencies of the G (k)-bands. A significant effect of 632.8 nm resonant radiation on the electronic states and properties of MoS2 (C) NC was established. The strengthening of the D bands of the diamond-like structure and the ordering of the graphite structure with increasing carbon content in MoS2 (C) nanocrystals have been established. The change of spectral positions of D, G, and G (k) bands at strengthening the degree of disordering of a diamond- and graphite-like structures is considered. The influence of laser radiation on carbon structures is discussed.