Two-dimensional tungsten disulfide(WS2),as a semiconductor material with unique layer-dependent electronic and optoelectronic characteristics,demonstrates a promising application prospect in the field of optoelectronic devices.The fabrication of wafer-scale monolayer WS2 films is currently a critical challenge that propels their application in advanced transistors and integrated circuits.Chemical vapor deposition(CVD)is a feasible technique for fabricating large-area,high-quality monolayer WS2 films,yet the complexity of its growth process results in low growth efficiency and inconsistent film quality of WS2.In order to guide experimental efforts to diminish grain boundaries in WS2,thereby improving film quality to enhance electronic performance and mechanical stability,this study investigates the nucleation mechanisms of WS2 during CVD growth through first-principles theoretical calculations.By considering chemical potential as a crucial variable,we analyze the growth energy curves of WS2 under diverse experimental conditions.Our findings demonstrate that modulating the temperature or pressure of the tungsten and sulfur precursors can decisively influence the nucleation rate of WS2.Notably,the nucleation rate reaches a peak at a tungsten source temperature of 1250 K,while an increase in sulfur source temperature or a decrease in pressure can suppress the nucleation rate,thereby enhancing the crystallinity and uniformity of monolayer WS2.These insights not only furnish a robust theoretical foundation for experimentally fine-tuning the nucleation rate as needed but also provide strategic guidance for optimizing experimental parameters to refine the crystallinity and uniformity of monolayer WS2 films.Such advancements are expected to accelerate the deployment of WS2 materials in a range of high-performance electronic devices,marking a significant stride in the field of materials science and industrial applications.
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