Preparation Of MoS₂ Thin Films And Study On Their Optical Properties

The molybdenum disulfide?MoS₂?is a representative material of transition metal chalcogenides.Because of its unique photoelectric properties and valley electronics,Mo S 2 has attracted extensive attention in many fields.Compared with traditional semiconductor materials,the thickness of the two-dimensional material is very thin,and it has good flexibility which is beneficial to reduce the size of devices and make flexible electronic devices.MoS₂ has a high carrier mobility and switching ratio.And the ultra-high specific surface area extends the application of MoS₂.Layers of bulk MoS₂ are connected by weak van der Waals force.Bulk MoS₂ is an indirect bandgap semiconductor and the bandgap of bulk MoS₂ is 1.2 e V.MoS₂ can convert to direct bandgap semiconductor when the number of layers reduce.The bandgap of Single layer MoS₂ is 1.85 e V.Due to their tunable band structure,MoS₂ can be used in the field of photodetectors and solar cells.In this paper,we used magnetron sputtering assisted CVD method to prepare layer-controllable MoS₂ thin films.Metal Mo target was used as Mo source and pure S powder was used as S source.Firstly,we used magnetron sputtering to sputter Mo on Si O2/Si substrate.During sputtering process,four parameters were discussed.The samples were tested and characterized by XRD,SEM,EDS and Raman spectroscopy.After samples test,we selected optimal sputtering parameters for preparing monolayer MoS₂ thin films.Subsequently,Si O2/Si substrates sputtered with Mo were placed in a furnace and subjected to a heat vulcanization treatment to prepare MoS₂ thin film.When the sputtering power is 40 W,the sputtering pressure is 0.3 Pa,and the Ar flow rate is 30 sccm,a single-layer MoS₂ thin film can be prepared by magnetron sputtering assisted CVD method.By changing the sputtering time,we can control layer numbers of MoS₂ thin films.After that,the process of preparing MoS₂ thin film by chemical vapor deposition was explored.We discussed four parameters during prepare MoS₂ films,which are the amount of Mo O3,the distance between S and Mo O3,the growth temperature and the growth time.The single crystal MoS₂ can be prepared by using 0.5 mg of Mo O3 and 120 mg of pure S powder,reacting at 780 ? for 20 minutes.Ar maintained a flow rate of 60 sccm during the reaction.We then assisted in the preparation of MoS₂ films by using potassium chloride?KCl?and perylene-3,4,9,10-tetracarboxylic dianhydride?PTCDA?.Large area single crystal MoS₂ can be prepared when we use 3 mg of KCl and 0.1 mg / ml of PTCDA solution,respectively.Finally,on the basis of preparing MoS₂ thin films by chemical vapor deposition,we improved the single-layer MoS₂ photoluminescence intensity by using two methods,which were annealed in air and transferred to Ni O thin films.The mechanism of enhancing photoluminescence by different methods was analyzed.The optimal experimental parameters for improving the photoluminescence of MoS₂ were explored.