On the Morphology and Optical Properties of Molybdenum Disulfide Nanostructures from a Monomolecular Layer to a Fractal-Like Substructure

摘要

The impact of layer thickness on the morphology and optical properties of MoS2 nanostructures, including monomolecular layers, formed by the carrier-gas-assisted transport of sulfur vapor to the hot zone of a reactor containing metallic molybdenum and subsequent deposition on mica (muscovite) substrates is investigated. Molybdenum disulfide nanostructures of different thicknesses grown at different temperatures of gas-transport synthesis are studied by atomic-force microscopy, optical absorption spectroscopy, and Raman spectroscopy. It is found that synthesis at temperatures of 525-600 degrees C makes it possible to obtain monomolecular MoS2 layers containing trigonal domains and featuring direct-gap optical transitions at 1.84eV with the formation of excitons at room temperature. Fractal-type MoS2 substructures are obtained for the first time. The frequencies of intralayer and interlayer vibrational modes E1/2g and A(1g), respectively, in their Raman spectra (377.5 and 403.8 cm(-1), respectively) differ both from the corresponding values for a monomolecular layer and the known frequencies for bulk samples. The frequency of the E1/2g intralayer mode in these samples (377.5 cm(-1)) is the lowest of all previously reported.