Study On Preparation Technology And Performances Of Single-Layer MoS₂ By CVD

In recent years,two-dimensional layered nanomaterials have attracted widespread attention from researchers due to their excellent structural stability and unique photoelectric properties.As the most typical two-dimensional transition metal sulfide,molybdenum disulfide has stable crystal structure and chemical properties,and has high carrier mobility and good electrical properties,which not only breaks the limitations of graphene‘s zero band gap,but also the band gap can be adjusted with the number of layers,and the thin films with different number of layers have different fluorescence characteristics.Therefore,the preparation of MoS₂films and the application of devices such as photodetectors,sensors and transistors based on MoS₂films have become hot research topics.This paper focuses on the preparation technology of single-layer MoS₂films by CVD?Chemical vapor deposition?.The effects of reaction condition on film quality were investigated by Scanning electron microscope,Optical microscope,Raman,Photoluminescence and Atomic force microscope,and also the preparation technology of MoS₂photodetector with the thin film as channel material,as well as the photoelectric characteristics of photodetector under different test conditions were studied.Main research results are as follows:?1?The influence laws of reaction temperature,MoO₃powder dosage,carrier gas flow rate,substrate placement distance,placement mode and substrate types on the quality and size of MoS₂crystal film were obtained.It was found that when the reaction temperature is 810?,the molybdenum source dosage is 0.01 g,the gas flow rate is 70 sccm,and the sapphire substrate inclines upward about 20°and be placed 9 cm downstream of the molybdenum source,a single layer MoS₂crystal film with regular morphology,good surface quality and side length of about100?m can be produced.?2?The preparation technology of single-layer MoS₂crystal film photodetector was studied.It was found that when the photodetector was prepared with one step,and with the growing substrate as the device substrate,a large number of MoS₂crystal films were easily wasted,and the MoS₂crystal films were easily worn during operation.The two step method is to prepare the electrodes of photodetectors on the new substrate by using the two processes of photolithography masking and hard masking,and then the film grown on the substrate was positioned and transferred to the new device substrate to prepare the photodetector,but the metal electrode prepared by the hard masking process was easy to fall off from the substrate surface,causing the damage to the device,while,if the photodetector electrode was prepared by photoetching masking method,and then the film grown on the substrate was transferred to new device substrate by positioning transfer method,the device structure was firm,and a large number of MoS₂crystal films could be precisely positioned on the electrode surface.?3?The optical responsivity of single-layer MoS₂film photodetectors with different optical power,field bias and incident wavelength were obtained.It was found that the optical responsivity decreased with the increase of luminous power,and gradually increased with the increase of outfield bias.In the range of wavelength of 405?650 nm,the optical responsivity decreased with the increase of wavelength.All of the above conditions have a regulatory effect on can regulate the photoelectric performance of the device,and the switch ratio is about 10⁵.The results show that the optical responsivity is 0.13 A/w at the luminous power is 10^-6W,the wavelength is 405 nm and the bias voltage is 9 V.