| Due to its unique nonlinear electrical properties,memristor gets wide attention from the scientific community and industry.At present,the memristor has made progress in material selection,preparation technology,mechanism research and function simulation.However,there are many areas worth researching to reduce the economic costs of device fabrication techniques.In this paper,the ZnO memristor were fabricated by all solution-processing to reduce the preparation cost.The good cycle endurance,low power consumption,self-rectifying,self-compliance and forming-free memristor devices of Graphene/ZnO/AZO（aluminum-doped zinc oxide）fabricated by optimizing the preparation process of the thin film.And we studied the conduction mechanism and the transparent property of the device.The research contents and results can be drawn as following:（1）AZO precursors and H+-doped AZO precursors were prepared by using zinc acetate dehydrate,aluminum nitrate nonahydrate,ethanolamine,nitric acid and anhydrous ethanol.The AZO electrode layer was deposited by spin coating.By comparing the different preheated conditions,it is found that the AZO film under the conditions of baking at 250 ℃ for 5 minutes has the most obvious preferred orientation of the C-axis,also the crystallinity is the best and the film resistivity is the lowest.After optimizing the preheated conditions,the effects of annealing temperature and second annealing on the resistivity of AZO film were investigated.The results showed that annealing at 600℃ for 1 hour in the furnace and annealing at 600℃ for 40 minutes in the rapid thermal program,the resistivity of the obtained AZO film has been reduced to the order of 10-1 ohm×cm.And then it has been found that the resistivity of AZO film prepared by high temperature one-time rapid annealing can reach 10-1ohm×cm.In addition,when the AZO film annealed with the ZnO active layer,it was found that the annealing atmosphere of ZnO affected the properties of AZO.Especially annealing in oxygen,Alumina segregation occurred in the AZO film and the conductivity was seriously affected.The effects of H+-doping on the properties of AZO film show that 7at% H+-doping concentration can decrease the resistivity of AZO thin films to the order of 10-3ohm×cm.（2）ZnO precursors were prepared by using zinc acetate dehydrate,ethanolamine and anhydrous ethanol.The ZnO active layer was fabricated on Pt-plated silicon wafer by spin-coating method.Subsequently,the Pt electrode was deposited by electron beam evaporation to form Pt/ZnO（Sol-gel）/Pt memristor.By changing the annealing temperature,annealing atmosphere and sol concentration of ZnO thin film,the resistive switching characteristics of memristor were studied.It is found that there is an important relationship between the high resistance state and the conductivity of ZnO film.When the annealing temperature is increased,the grain size of ZnO film becomes larger,the conductivity of the film becomes better,and the resistance of high-resistance state becomes smaller.Annealing in argon,air or oxygen,with the increase of oxygen concentration in the atmosphere,the intrinsic defects of oxygen vacancies in ZnO films decrease,and the resistance of high-resistance state decreased too.With the increase of sol concentration,the thickness of ZnO thin film increase,the high resistance resistance becomes larger.It can be seen that the change of the high-resistance state resistance directly affects the size of the memristor on/off ratio.With the resistance value of the low-resistance state changes insignificant,the increase of the high-resistance state can improve the on/off ratio of device.（3）A graphene dispersion prepared by using graphite flake powder,acetone and deionized water,and the solution was uniformly dispersed after ultrasonication and centrifugation.Deposited top Graphene electrodes were prepared by vacuum filtration onto porous mixed cellulose ester membranes.Then,the Graphene transferred from the porous mixed cellulose ester membranes onto the target substrate through the substrate transfer technique.It achieves patterning of the electrodes.In the memristor,the AZO top electrode was replaced by a graphene electrode,and it achieved patterning of the electrodes.Comparing the I-V characteristics of the AZO/ZnO/AZO and G/ZnO/AZO memristors prepared by all solution-processing,it was found that the G/ZnO/AZO memristors has stable resistive switching characteristics although the on/off ratio is small,but the operating voltage and power consumption is very small,as well as having self-rectifying effect,which expresses the potential for application in neuronal synapse simulation.It is indicated that the top electrode affects the effective working area of the device,thereby affecting the resistive switching characteristic of memristors.（4）The G/ZnO/AZO memristor with reproducible resistive switching behavior was prepared by all solution-processing after optimizing the preparation technology of the electrode and the active layer.From the SEM cross-sectional image of the device can be found that the interface between each layer is obvious and interfacial connectivity is good,no voids and large defects.And the I-V characteristic curve not only shows forming-free,as well as low power consumption,self-rectifying and self-compliance.After 150 switching cycles,the device still has resistive switching characteristics.It can be seen that the on/off ratio was maintained at approximately 100.Through the logarithmic plots of the I-V curves of the device,we found that the device conform to the space charge limited current conduction mechanism.Afterwards,the substrate of the device was replaced by a thermal oxidation silicon wafer into a quartz glass.The average transmittance of the device was found to reach 46% with good transparency. |
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