Preparation And Performance Of Photodetector Based On WS₂ Thin Film

Photodetectors play a key role in pyrotechnics warning,environmental monitoring,video imaging and astronomical research.In order to meet the needs of the rapid development of photoelectric sensors,people are eager to pursue high performance photodetectors with high responsiveness and low dark current.Recently,wide spectrum self-powered detectors provide a new research direction for the development of high performance detectors.Transition metal sulfides have made great progress in photoelectric detection in recent years due to their excellent suitable band gap width and stronger light-matter interaction than graphene.WS₂has higher carrier mobility than other transition metal sulfide materials.However,large-scale production of high-quality WS₂still faces many difficulties.The performance of WS₂-based photodetector needs to be improved urgently.The problems related to the design and pre Paration of large-area high-performance WS₂-based photodetector have not been solved.The following research works were mainly carried out in this Paper:Firstly,the magnetron sputtering deposition of WS₂thin films was studied.The influences of the growth process Parameters(sputtering power,air pressure,annealing temperature,etc.)on the crystal quality and photoelectric properties of WS₂thin films were analyzed.The results show that the optimal sputtering power of WS₂film is 160W and the optimal deposition pressure range is 1.4-1.6 Pa.Then,Ti/WS₂and Cr/WS₂thin films were pre Pared by magnetron co-sputtering.The effects of doping on the properties of the thin films were studied.The samples were characterized by X-ray diffractometer,Raman spectrometer,scanning electron microscope and photo luminescence spectrum.Metal doping into the WS₂lattice imported defects.The film presented features of amorphous and disordered with more impurity levels.Ti/WS₂films are superior to Cr/WS₂films in quality and optical properties.Subsequently,graphene quantum dots and graphene oxide aqueous solution were pre Pared and mixed with WS₂to form heterojunction.The transmission electron microscopy confirmed the size of the graphene quantum dots and the successful recombination of graphene quantum dots with WS₂.The crystal structure and morphology of the two heterojunctions were analyzed by means of atomic force microscopy.It is proved that WS₂/graphene quantum dots have fewer defects and longer carrier life,which is suitable for pre Paring into optoelectronic devices.Finally,the influence of finger s Pacing and size of cross finger electrode on WS₂detector was investigated.Based on WS₂co-sputtering Ti and Cr metals and WS₂/graphene heterojunction,MSM type optoelectronic devices were pre Pared by selecting large fork finger electrode structure with high photoelectric transmission efficiency.The I-V,I-T curves and responsiveness of all devices under white light were tested.The dark current of the devices was also tested.All detectors had wide spectral response.We could operate them at zero bias voltage.Ti/WS₂detector could be used to specify the environment.The maximum responsiveness of WS₂/graphene quantum dots detector was up to 65.48 m A/W and the photo current at 0 V was 2.50×10^-1m A.The mechanism of the wide spectrum detector was also analyzed.