Growth Control And Photoelectric Properties Measurement Of Molybdenum Disulfide Thin Films

The main work of this paper is the preparation of molybdenum disulfide?MoS₂?by chemical vapor deposition?CVD?.These include the controlled synthesis of single crystal MoS₂ nanosheets and the preparation of centimeter continuous films.The properties of the MoS₂ film photodetector were tested and the effect of film crystallization on the performance was analyzed.By adjusting some parameters such as gas flow,growth temperature,growth time and number of precursors during the growth process,we found a CVD preparation condition suitable for the growth of single crystal large area MoS₂nanosheets.In order to grow a continuous MoS₂ film,the growth process is again improved.A 1*1 cm continuous monolayer molybdenum disulfide film was successfully fabricated on a SiO₂/Si substrate.Under the characterization of Optical Microscopy,Atomic Force Microscopy and Raman Spectroscopy,we have demonstrated that the films obtained have a high degree of monolayer uniformity.A simple photodetector device was fabricated by plating a Cu electrode on the MoS₂ film.The light detection performance was tested by the 660/532/450 nm laser.It was found that the optical responsivity decreased with the increase of optical power,which indicate that the monolayer molybdenum disulfide detector is more sensitive to capturing weak light.In addition,it was found that under the excitation of 660 nm laser,the photoconductivity of the film with lower crystallinity decreased which shows negative photoconductivity?NPC?,but the photocurrent was slightly improved in the film with high crystallinity.At the end of the paper,the relationship between crystallinity and photoconductivity is discussed.It is preliminarily concluded that the bound excitons in the forbidden band have a competitive relationship with the influence of free excitons on the carriers in the conduction band.