Preparation And Resistive Switching Properties Of Cu_xS Thin Films1

With the explosive growth of data,mobile phones,computers and other electronic products have put forward higher requirements on the information processing and storage capacity of integrated circuit chips.Therefore,it is urgent to develop a nonvolatile memory which can store and process a large amount of data.Memristor is considered to be one of the most competitive next generation information processing units due to its simple structure,low energy consumption,fast response time and high integration.Researchers have made remarkable progress in the fields of nonvolatile memory,logic operations,and synaptic simulation by developing new memristor materials,new structures,and applying electrical,optical and other stimulus signals.However,there are still many problems to be solved before large-scale integrated applications.At present,the selection of materials and the corresponding preparation process are not yet mature,and the resistance mechanism of different materials is not clear enough.In view of the above considerations,this paper focuses on the topic of"preparation of Cu_xS films and their memristor properties".It mainly includes the following two aspects:Firstly,in order to optimize the ion migration path in the Al/Cu_xS/Cu memristor dielectric layer,Cu_xS nanosheet films perpendicular to the substrate were prepared by anodic oxidation to facilitate the orderly formation of conductive wires.The results show that the Al/Cu_xS/Cu series memristor exhibits the coexistence of resistance behavior(RS)and negative differential resistance(NDR).The operating voltage is less than 0.3 V,the resistance performance is stable,the retention time is more than 10⁴s,and the device is still stable after 120 cycles.On this basis,the mechanism of the repeatable coexistence of RS effect and NDR phenomenon is discussed in detail.The results show that the space charge limited current(SCLC)mechanism and the conduction wire mechanism formed by the migration of copper ions co-dominate the change of memristor resistance value in the dielectric layer of Cu_xS.Meanwhile,the Schottky potential barrier at the interface between Cu_xS and copper is the cause of NDR.This work provides a new way to optimize the performance of nonvolatile memory with various physical properties in the future.Secondly,Cu₂S thin films were prepared by pulsed laser deposition and chemical vapor deposition,and finally the Cu/Cu₂S/p-Si nanostructured memristor was formed.The morphology,composition and optical properties of Cu₂S films were characterized by scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)and UV-Vis NIR spectrophotometer.The results show that the Cu₂S films prepared by the two-step method are composed of polycrystalline nanoparticles and distributed uniformly in a large area.I-V cycle test shows that the memristor operating voltage is 3V.Under the irradiation of xenon lamp,the current of the device increases about 5 times compared with that in the dark condition,that is,the photogenerated carriers will reduce the Schottky barrier and lead to the change of the resistance mechanism of the device,which is of reference value for exploring the multi-channel response of the Cu₂S-based memristor.