Influence of temperature on morphological and optical properties of MoS2 layers as grown based on solution processed precursor

A novel liquid phase synthesis of MoS2 thin films has been achieved. Solubility of Molybdenum(V) chloride in appropriate solvent was optimized while having good coating properties essential for thin film formation. Chemical conversion of the deposited Mo-precursor films on silicon/silicon dioxide substrate to MoS2 were obtained by annealing in presence of sulfur. This novel method allows facile upscaling process to large substrates with uniform film thickness down to 4 nm, which are of high interest for future low-cost fabrication of electronic devices. UV-Vis, Raman spectroscopy, and X-ray photoelectron spectroscopy measurements confirm the formation of MoS2 films with a stoichiometric chemical composition of Mo/S ~ 0.47. Furthermore, X-ray diffraction and Transmission electron microscopy measurements revealed formation of polycrystalline films with random grain orientation attributed to the amorphous SiO2 surface of the substrate. Improved crystallinity of deposited films was achieved by increasing the process temperature. Annealing at temperatures above 750 °C increased the uniformity of multilayer films, together with the increase of MoS2 grain size to 100 nm. This simple wet-chemical synthesis approach allows upscaling, controllable film thickness and is suitable for preparation of other transition metal dichalcogenides thin films for applications in the future electronics.