Resistance Switching And Transient Performance Of Memristors Prepared From MgO Thin Films

Memristor is a new electronic device with the function of information storage and logic operation,which has important research value in such aspects as non-traditional computer and analog neural network.Transient electronic device can be controlled to dissolve or disappear under certain conditions.Transient memristor combines the characteristics of these two devices,which have irreplaceable value in application.Magnesium oxide（MgO）thin film is of high dielectric constant and good insulation,and it can dissolve in water,which can be used as the resistance switching layer in memristor.In this thesis,memristors based on MgO thin films were prepared,and the resistance switching characteristics and transient performances of which are mainly studied.The MgO thin films were fabricated by electron-beam evaporation method,and the influences of substrate temperature,deposition rate and deposition time on MgO film were studied.The MgO thin film prepared under 25℃is of multiple crystalline state.With the increasing of substrate temperature,the film surface roughness increases,as well as the refractive index n and extinction coefficient k,while thickness decreases.At the deposition rate of 1?/s,film possesses the smallest surface roughness,the largest n and the largest density.Film thickness is proportional to the deposition time.When deposition time longer,film thickness is larger,so as n,while k is nearly constant.The process parameters for the preparation of MgO thin film are substrate temperature of25℃,deposition rate of 1?/s,deposition time of 100s,the thickness of 10 nm,and the substrate of Si/SiO₂.The Ni（80nm）/MgO（10nm）/Ni（80nm）point electrode structure memristor were prepared through mask,the resistance switching characteristics of which were studied.Founding that the device does not need electric forming process with the SET voltage of about 0.8V and RESET voltage of about-0.6V.The device has good cycling stability,with the ratio of high and low resistance state resistance greater than 10² in the process of 100 cycles.The device is nonvolatile,with high and low resistance state resistance holding greater than 10⁴s.Two kinds of resistance mechanisms exist in Ni/MgO/Ni memristor,the conductive filament mechanism and the space charge limited current mechanism.In low resistance state when the current is proportional to the voltage,matches conductive filament mechanism;In high impedance state when the current and voltage is piecewise linear relationship,matches the space charge limited current mechanism.Under the condition of low temperature,high resistance of the device state resistance varies with temperature in line with the characteristics of insulators,while low resistance state resistance increases with temperature rise,in line with the metal properties,which further proof that the presence of two kinds of resistance mechanism in memristor.The transient performance of memristor also be studied.Using the method of natural air drying film-forming fibroin membrane（FM）substrate and poly vinyl alcohol（PVA）substrate were prepared,and memristors were prepared on which.Found that 10nm MgO thin film can dissolve in water in 60 min,as well as the Ni,Fe,W electrodes.The memristors of Ni/MgO/Ni,W/MgO/Ni,and W/MgO/Fe prepared on Si/SiO₂,FM and PVA substrate all can be dissolved in water,indicating them are transient memristors.