Study On Hydrothermal Preparation Of MoS₂ And Its Effect On The Performance Of Resistance Random Access Memory ?RRAM?

Resistance Random Access Memory?RRAM?plays an important role in our life.In order to satisfy the requirements of small size,high storage density,fast storage speed,long service life and low power consumption of RRAM,using molybdenum disulfide?MoS₂?as resistance material in the preparation of RRAM is one of the hotspots of current research.MoS₂ is a transition metal sulfide with sandwich-like layered structure in hexagonal crystal system,and application of MoS₂film as a resistive layer material in RRAM,which can make RRAM have excellent storage performance.Compared with other methods,hydrothermal preparation has the advantages of lower reaction temperature,no harmful solvent and high yield.In the preparation of MoS₂ films,the selection of solvent,the control of thickness and the method of film formation have always been the technical difficulties,which hinder the application of MoS₂ resistance materials in RRAM.Based on this,this paper mainly made the following research:Firstly,MoS₂ materials were synthesized by hydrothermal method under different conditions.The effects of reaction time,temperature and pH on the structure and properties of MoS₂ were investigated.The results show that the best reaction optimum condition is 24 h,230?,pH=2.The morphology of MoS₂ is regular and the yield of MoS₂ is 93%.The main performance of MoS₂ is a diameter of 500 nm flower-like microspheres,which composed of sheet structures of 5nm.The thermal decomposition temperature is 200?,and the remaining amount is 30%after the high temperature of 800?,which shows good thermal stability.Secondly,using ethanol and isopropanol as solvent,MoS₂ suspension was prepared by ball milling and ultrasonic method.The effects of different solvents and methods on MoS₂ suspension were studied.The experimental results show that the solvent has no effect on MoS₂ suspension.The dispersion of MoS₂ suspension is better when the ball milling time is 36 h and the ultrasonic time is 8 h.The MoS₂ film was prepared by spin coating method,and its thickness was measured and discussed.The results show that the higher the rotating speed is,the lower the MoS₂suspension concentration is,the thinner the film is.The film is formed by spin coating at low speed,the surface is smoother and the film is more uniform.The film uniformity of MoS₂suspension with the ratio of?1:13?at 5000 rpm is better than that of other rotating speeds.Thirdly,ITO/MoS₂/Al,Cu/MoS₂/Al and flexible transferable Cu/MoS₂/Al devices were fabricated.The switching characteristics,switching resistance ratio,cycle characteristics and switching mechanism were further analyzed.The results show that the nano-switching devices can achieve ON-OFF at a little energy consumption external voltage of 2 V.The switching resistance ratio and cycle characteristics of RRAM devices are related to the limiting current:the switching resistance ratio reaches 10⁴ without limiting current,with a large storage window and poor cycle times.After adding the limiting current,the cycle performance is improved and the cycle times are about 900 times.The double logarithmic I-V curve shows that the switching ON-OFF of ITO/MoS₂/Al resistance random RRAM devices are mainly affected by Space Charge Limited Current mechanism?SCLC?,while Cu/MoS₂/Al devices are combined by SCLC and conductive filament mechanism.After transferring Cu/MoS₂/Al devices to flexible substrates of eggs,apples,skin,the switching ON-OFF of RRAM devices can still be realized,showing good storage performance.