Characterization and study of reduction and sulfurization processing in phase transition from molybdenum oxide (MoO2) to molybdenum disulfide (MoS2) chalcogenide semiconductor nanoparticles prepared by one-stage chemical reduction method

In this research, molybdenum disulfide (MoS2) nanoparticles were prepared by chemical reduction method using MoO3 and thiourea as a precursor. The physical properties of the synthesized MoO2-MoS2 nanoparticles annealed at different temperatures of 200, 300, 750 degrees C have been investigated, before and after exposure to sulfur vapor. The nanostructure of nanoparticles has been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM) analyses and UV-Vis spectrophotometer. The X-ray diffraction analysis showed the formation of MoS2 single phase at annealing temperature of 750 degrees C in the presence of sulfur vapor. The Raman spectrum of the nanoparticles revealed that the formation of MoS2 at 750 degrees C after annealing in sulfur vapor. The values of band gap were obtained in the range of 3.64-3.17 eV and 3.47-1.95 eV for MoS2 nanoparticles before and after exposure to sulfur vapor, respectively. According to SEM images, the grain size decreases with increasing annealing temperature up to 750 degrees C. Also, nanoplate-nanoparticles of MoS2 are formed at annealing temperature of 200-750 degrees C. The TEM images of MoS2 nanoparticles at Ta = 750 degrees C confirm that the nanoparticles have a homogeneous distribution with a hexagonal structure. The FTIR spectra of the MoS2 nanoparticles showed the peaks at about 467 cm(-1) belong to the characteristic bands of Mo-S.