Research On The Fabrication And Properties Of Memristor Based On Tungsten Oxide Heterojunction

At present,the mainstream electronic computing system uses the von Neumann architecture which separates storage and computation.However,growing the trend of miniaturization of electronic components and pursuit of promoting calculate power puts forward an increasing requirements to the higher integration of the device.As the size of transistors is gradually approaching its physical limit,it is an inevitable choice to explore non-von Neumann architecture devices with integrated memory and computing functions for the further development of electronic technology in the post-Moore law era.As a new non-volatile memory device,memristor,which could realize resistance switching and memorizing between high resistance state and low resistance state,is considered as one of popular candidate for the next generation of electronic devices with integrated memorizing and computing functions.A variety of materials with resistive properties have been explored and used to build memristor.Among these material,metal oxide semiconductor is one of the most promising memristor materials for industrial application because of its easy regulation,mature process,extensive research and non-toxicity.In this thesis,two kinds of metal oxide semiconductor materials,tungsten oxide and zirconium oxide,have been used to construct memristor with different structures by magnetron sputtering,which is a traditional physical deposition method.The main achievements are shown as follows:1.The basic theory and carrier transport model of memristor were studied,and the device preparation and fabrication were carried out based on the theoretical model.Herein,WO_Xwas deposited by radio frequency(RF)magnetron sputtering serving as the dielectric layer between indium tin oxide(ITO)and Ag electrode to fabricate memory cells.After that,the memristor was annealed in air.The annealing temperature was kept constant at 300℃,and the annealing time was controlled as 60min,100 min,180 min and 300 min,respectively.The electrical properties of the constructed memristor were tested and found to be significantly affected by the annealing treatment.Some of the device exhibited a stable coexistence of bipolar resistive switching(RS)and negative differential resistance(NDR)behaviors at room temperature,which showed the potential of further development of multifunctional electric device.2.The carrier transport model of the device had been established,and the influence of annealing on the memristive performance of the device and the root cause of the influence were also studied.Through further fitting and analysis of the I-V curves,the transport process of carriers inside the device was determined,and this process was affected by the traps existing in the dielectric.The trap level in each device was obtained by calculation and deduction,and its variation law was summarized.The devices with different annealing are characterized by XRD,Raman and other test methods.The results reveal that the root of the change of trap level is the formation and strengthening of W-O bond.This trend matches the performance change trend of the device.3.The Ag/WO_X/Zr O_X/ITO double-dielectric-layer memristor was prepared by magnetron sputtering based on the common heterojunction structure in electronic devices.Then,the two treatment methods of co-annealing of the double dielectric layer and single annealing of the lower layer had been compared,and the temperature was changed to further explore the effect of annealing treatment on the heterojunction memristor.Two kinds of annealing parameters,300℃100 min and 550℃240 min respectively,were used to obtain double-dielectric-layer memristor with different properties.By further fitting and analyzing of the I-V curve,the carrier transport model in the device was determined.A model of the influence of heterojunction memristor interface defects on RS performance has been proposed.The results show that the co-annealing at an appropriate temperature can eliminate the lattice mismatch and interface states at the interface of the heterojunction,thereby effectively improving the stability of the memristor.