Synthesis and structure of molybdenum diselenide nanosheets produced from MoO3 and Se powders

Abstract In this paper, we report on the synthesis of molybdenum diselenide (MoSe2) nanosheets produced by hot filament chemical vapor deposition using the admixture of molybdenum trioxide (MoO3) and selenium (Se) powders. The results of field emission electron scanning microscope, transmission electron microscope, micro-Raman spectroscope and X-ray photoelectron spectroscope indicate that the MoSe2 nanosheets are well synthesized when the mixing mass ratios of Se to MoO3 powders are 5 and 10, which are lower than the ratios of Se to MoO3 powders reported elsewhere. However, other nanomaterials made of Se or molybdenum oxide are formed if the mixing ratios of 20 and 2. Based on the theory related to gas transport process, the formation of different nanomaterials in different mixing ratios is studied. The formation of MoSe2 nanosheets under relatively low ratios results from the increase of collision probability of MoO3 molecules with Se atoms due to the prolonged residence time of MoO3 molecules in gas environment. Furthermore, the photoluminescence (PL) properties of the synthesized nanomaterials appear to be different from the reported results. The excited PL bands of the MoSe2 specimens have a blue shift of ∼19 nm, which is due to the bandgap expansion caused by the residual stress in the MoSe2 nanosheets. These outcomes are environment-benign, enable structural control of MoSe2 nanosheets and facilitate the development of optoelectronic devices incorporating MoSe2-based materials.