Low Dimensional Materials/Polymer Nanocomposites Based Flexible Resistive Random Access Memory Device

Flexible resistive random access memory?RRAM?devices have been identified as a promising prospect candidate for the next generation nonvolatile memory in future wearable devices and consumer electronics applications due to their fascinating virtues,such as flexibility,high storage density,high read-write speed,low power consumption and simple structure.Flexible RRAM device has simple configuration of electrode/active layer/electrode sandwich-like structure.The material systems including electrode materials,resistive materials and substrate materials construct RRAM device should be flexible for keeping the device intact and stable under different stress conditions.Until now,resistive materials,such as inorganic materials,organic materials and organic/inorganic nanocomposite have been utilized to fabricate flexible RRAM devices with different properties.Among the resistive materials,low dimensional materials/polymer nanocomposites have emerged as useful electronic materials having integration of advantage characteristics of both of them.In this thesis,we chose low dimensional materials/polymer nanocomposites as the resistive materials and natural organic biomaterials to fabricate a series of flexible RRAM by simple methods.Meanwhile we investigate the resistive switching mechanisms.The main research results are summarized as follows:1.The 1T phase of MoS₂ is introduced into the 2H-MoS₂ nanosheets by two-step hydrothermal synthetic methods,i.e.,1T@2H-MoS₂ nanosheets.The transformation the local lattice of 2H-MoS₂ into 1T phase in the 2H-MoS₂ nanosheets matrix introduces the sulfur vacancies into 1T@2H-MoS₂ nanosheets and increases the concentration of vacancy.These sulfur vacancies act as the trap centers during the resistive switching process and play a decisive role for the resistive switching behaviors.Through analyzing the resistive switching behaviors of Al/2H-MoS₂-PVP/ITO/PET device and Al/1T@2H-MoS₂-PVP/ITO/PET device,we understand that the introduction of sulfur vacancies in the 2H-MoS₂ nanosheets effect the resistive switching behaviors of the memory devices.Al/1T@2H-MoS₂-PVP/ITO/PET device exhibits write once read more times memory effect and the excellent resistive switching prosperities and flexibility.2.The above work has demonstrated that the vacancies distributed in the active layer play an important role in the resistive switching mechanisms.According to this conclusion,we designed the following work.Uniform Co₉Se₈ quantum dots?CSQDs?were successfully synthesized through a facile solvothermal method.The obtained CSQDs with average size of 3.2±0.1 nm and thickness of 1.8±0.2 nm were demonstrated good stability and strong fluorescence under UV light after being easily dispersed in both of N,N-dimethylformamide?DMF?and deionized water.We demonstrated the flexible resistive switching memory device based on the hybridization of CSQDs and polyvinylpyrrolidone?PVP??CSQDs-PVP?.The device with the Al/CSQDs-PVP/Pt/PET structure represented excellent switching parameters such as high ON/OFF current ratio,low operating voltages,good stability,and flexibility.Co₉Se₈ quantum dots dispersing in the active layer act as trap center and determine the resistive switching behavior.3.Based on the above two work,we fabricate Sb nanosheets and Antimonene quantum dots?AQDs?and these nanomaterials act as trap center in the active layer.AQDs can easily disperse in the PVP alcohol solution and the flexible Al/AQDs/Pt/PET devices are obtained.The device exhibits WORM behavior with high ON/OFF current ratio and good stability.After bending for 50times,the ON/OFF ratio and switching voltage retain almost its initial value.These conduction behaviors of ON and OFF state can be explained by the typical trap-controlled SCLC mechanism and filamentary conduction mechanism4.We have introduced different types of trap center in the active layer and observed different resistive switching behaviors.Milk,the common nature organic biomaterials,is utilized as the resistive materials to fabricate the RRAM.The device with the Ag/Milk/Pt/Si structure is demonstrated.The device presents memory and threshold resistive switching behavior by controlling the compliance current in the set process.The compliance current can influence the concentration of the Ag nanoparticle produced by redox reaction in the active layer.This provides a general route for the preparation the protein and metal nanoparticle nanocomposites based RRAM device.