Preparation Of Large Area MoS₂ And Mo_xW_1-xS₂ Alloy Film By Chemical Vapor Deposition

As a typical two-dimensional material,transition metal chalcogenides are widely used in the preparation of ultra-thin electrons or micro devices because of their excellent optical,electrical,and mechanical properties.At present,there have been a lot of studies on the properties,preparation methods,and applications of transition metal chalcogenides.However,in order to achieve high-volume,high-quality controlled growth,the preparation process is still undergoing a continuous improvement.This paper will mainly focus on optimizing growth conditions,growing large areas of molybdenum disulfide and MoxW1-xS2 alloy.1.Graphene quantum dots were prepared by pyrolysis of citric acid.The fluorescence,UV-visible absorption spectrum and particle size were analyzed.2.The single-zone atmospheric tube furnace was used for growth.The graphene quantum dots solution was diluted to different concentrations.MoS2 grown after the substrate was pretreated.The analysis of the experimental results showed that the graphene quantum dot solution promoted the large-area growth of molybdenum disulfide.In the graphene quantum dot solution concentration of 1.5mg/ml,a large-area continuous film-forming sample can be prepared.At present,a single layer of molybdenum disulfide having uniform thickness of about 500 ?m can be obtained at a normal pressure of 700 ?.3.Since transition metal chalcogenides have a bandgap of 1 to 2 eV,the preparation of a ternary alloy can achieve continuous adjustment of the band gap.Using the same CVD system under atmospheric pressure,MoO3 and WO3 sublimed by heat and reacted with sulfur to form a ternary MoxW1-xS2 alloy.The influence of the distance between the tungsten source and molybdenum source and the heating temperature in the central area on the growth of samples was studied.WO3 has a higher melting point and sublimation temperature.There are few alloy samples produced under normal pressure.In order to better control the reaction,an evacuation system was added to the original CVD system.The effect of low pressure conditions on alloy growth was studied.Under the condition,the sample in the alloy is more easily deposited,and the alloy can grow at a relatively low temperature.