Conductive Polymer-based Resistive Memory Materials And Device Fabrication

With the explosive growth of information and the vigorous development of information technology,the performance requirements of storage materials and storage devices are also increasing.Polymer resistive memory materials have become one of the candidates for the next generation of new memory materials and devices due to their advantages of low cost,easy structure adjustment,large-area preparation and flexible substrate.However,the wide band gap of the polymer requires higher energy to activate the electron transition from the HOMO level to the LUMO level,resulting in a high threshold voltage and high energy consumption of the polymer resistive memory.The conductive polymer molecular chain contains a large number of conjugated structures,with wide energy band and high work function,which is beneficial to the hole injection of ITO layer into the resistive active layer,and reduces the threshold voltage and energy consumption of the polymer resistive memory.Therefore,this paper designs a variety of composite resistive memory materials based on conductive polyaniline or aniline oligomers,and uses them as active layers to prepare sandwich-type resistive memory with ITO as the bottom electrode and AL as the top electrode.The structure and resistive storage properties of materials were studied.The storage mechanism of the corresponding materials was discussed by combining quantum chemical calculations and I-V fitting curves.The main contents of this paper are as follows:(1)Preparation of polyaniline&hyperbranched polyimide and memory.Hyperbranched polyimide(MN-6FHBPI)was prepared by polycondensation of melamine and 6FDA,and reacted with sulfosalicylic acid doped polyaniline(SPANI)to obtain grafted polymer MN-6FHBPI/SPANI.The structure and photoelectric properties of the polymer were tested by FT-IR,UV-vis,Electrochemical workstation and AFM.The results show that the polymer prepare successfully and have good photoelectric properties.The polymer resistive memory devices(ITO/Polymer/Al)were prepared by MN-6FHBPI,SPANI,MN-6FHBPI/SPANI and SPANI+MN-6FHBPI,respectively.MN-6FHBPI,SPANI,MN-6FHBPI/SPANI and SPANI+MN-6FHBPI are assembly as polymeric resistive memory devices(ITO/polymer/Al)to study their storage performance.The four memory devices exhibit different storage characteristics.Among them,ITO/(SPANI+MN-6FHBPI)/Al has a higher switching current ratio of 10~4 and a lower threshold voltage of+0.99V,and the surface roughness is lower.The I-V fitting curve shows that the memory conforms to the Schottky emission model in the high resistance state and conforms to the ohmic current law in the low resistance state.It can be seen that inserting SPANI between the resistive active layer and the electrode helps to improve the performance of the memory.It is a simple method for preparing low threshold voltage resistive memory.(2)Preparation of aniline oligomer-polyimide active materials and memory.Intermediates were synthesized from N-phenyl-p-phenylenediamine with 6FDA,BPADA and BTDA,respectively.Three kinds of polyimides(6FDA-PI,BPADA-PI,BTDA-PI)containing aniline oligomer structure were obtained by the reaction of intermediates with p-phenylenediamine.The molecular structure and photoelectric properties of the polymer were characterized by FT-IR,UV-vis and TGA.The results show that the polymer was successfully prepared and have good photoelectric properties and thermal stability.Polymer resistive memory devices were prepared by using three polyimides as resistive active materials,and their storage properties were studied.The threshold voltages of these three memory devices are all less than+1V,and ITO/6FDA-PI/Al and ITO/BTDA-PI/Al are non-volatile,while ITO/BPADA-PI/Al is volatile.The analysis of quantum chemical calculation results is related to the electron-withdrawing ability and dipole moment in the polymer chain structure.(3)PANI/PTCA material and memory PANI/PTCA composites were prepared by in-situ polymerization of aniline monomer on PTCA by chemical oxidation method.The molecular structure and photoelectric properties of the composites were analyzed by FT-IR,XRD and UV-vis.These composites were used to prepare polymer resistive memory devices respectively.The I-V and I-t test results show that the threshold voltage of ITO/PANI/PTCA/Al is lower than that of ITO/SPANI/Al in the second chapter.Among them,the storage performance of PANI/PTCA3 is better,the on/off current ratio of the device is 10~4,the threshold voltage is 1.8V,and the stability of high impedance state and low impedance is better.Through the analysis of I-V fitting curve,it can be concluded that the storage mechanism of ITO/PANI/PTCA/Al is the charge transfer between PTCA and PANI to form the high resistance state of the device into a low resistance state,which conforms to the space charge limiting current mechanism.