Performance And Mechanism Based On Polymer Memristor

With the advancement of semiconductor technology nodes,flash memory is facing many technical difficulties.On one hand,due to the high programming voltage,the slow read and write speed(μs)and the large power consumption,special voltage boosting structures(such as charge pumps)are required.On the other hand,von Neumann computing systems involve separate processing and storage units,resulting in slow data movement and the consumption of energy.In addition,as the feature size continues to shrink,it may bring problems that may not be solved,such as process and local heating of the circuit,so it can not meet the requirements of future storage applications for ultra-high density storage.In particular,the recent explosion of datacentric applications related to artificial intelligence has made this problem even more prominent.To deal with these problems,industry and academia have proposed two development ideas for the next generation of non-volatile memory.One is based on the current Flash technology,to improve the technology in response to the emerging problems,hoping to continue to advance on the basis of the existing technology.Another idea is to replace the traditional Flash technology with a brand new nonvolatile memory technology after the Flash reaches the physical limit.At present,redox resistive memory(RRAM or memristor)based on ion participation has the advantages of low power consumption,high switching speed,good retention and high durability,and is considered to be the future non-volatile One of the most promising candidates for storage technology.Especially the device using solid electrolyte thin film metal-ion conductor(also called dielectric layer)-metal(MIM)structure,in which the solid electrolyte(dielectric layer)film is sandwiched between electrochemically active electrodes(Ag,Cu or Al)and inert electrodes(Pt,Au or W).Under the alternating electric field,conductive filaments(metallic conductive channels)are formed and dissolved in the MIM structure to achieve storage.Because its switching mechanism is similar to the inorganic "gap type atomic switch",the nanogap resistance between the active electrode and the inert electrode will change due to the formation and dissolution of the conductive channel,so it can be called "gapless atomic switch").In recent years,some work has proved that solid polymer electrolytes(SPE)can be used as ion conducting media to achieve resistance memory effects in MIM structures.Due to its mechanical flexibility,higher ionic conductivity,compatibility with various substrates,and lower manufacturing costs,SPE can be used as a possible substitute for inorganic dielectric layer materials.In addition,SPE is one of many ionic devices of choice,including organic transistors,ion batteries,memristors,neural computing devices and so on.However,the formation and dissolution of uncontrollable conductive filaments will seriously affect the performance of such devices.On one hand,the current redoxbased ionic devices used as memory have poor consistency in operating parameters.In some devices,volatile and non-volatile operations usually occur simultaneously or alternately.On the other hand,as a brain-like synaptic device that is integrated with storage and computing,the uncontrollable ion migration seriously affects the amount of resistance state that the device can achieve.The structural characteristics of SPE films are believed to play a crucial role in the transport behavior of cations and anions.However,to date,there has been relatively little work to discuss the growth mechanism of conductive filaments in polymer films and the parameter changes during cycling,and these problems are also the key factors hindering the application of memristors.Therefore,it is of great significance for improving the practical application of polymer memristors to further explore the reasons for the poor consistency of ion device parameters and improve them.Based on the above factors,the main research contents of this article are as follows:(1)Explore the factors affecting the large dispersion of the operating parameters of atomic switch-based memristors: by making high ion conductivity planar devices based on polyethylene oxide(PEO),such devices can pass many technical means during the initial formation process It directly captures the microscopic behavior of the nucleation and growth of metal whiskers,and can form filaments and realize the microscopic origin of poor consistency of operating parameters in the performance cycle.In addition,we found that the deposition position of metal atoms is closely related to the crystallinity of the ion transport layer(solid polymer electrolyte).The results provide a reference for the reason why the operating parameters of the ion device are large and discrete,that is,the evolution of the dielectric layer and the metal filament during continuous operation must be considered.This work is of great significance for the commercialization of memristors for future storage and computing technologies.(2)Inhibition of randomness of filament morphology and position in ion migration,filament formation,and repeated cycle testing: treatment of polyvinyl pyrrolidone(PVP)doped conductive polymer to improve the electron and ionic conductivity,thus achieving the growth of the filament in the memristor from the cathode to the anode.Based on the difference in ion and electron mobility and the observation results of the scanning electron microscope,the metal particles formed by the in-situ reduction of metal ions inside the dielectric layer can effectively prevent the formation of uncontrollable metal filaments.This uniform distribution of metal particles in the dielectric layer is similar to co-sputter doping technology,which makes the device excellent performance,such as a small on / reset bias voltage distribution,good retention and durability.Obviously,this method further improves the conduction mechanism of ionic devices and improves the performance of ionic memristive devices.