Study On Memristor And Neuro-Synaptic Behaviors Based On Metal Oxide Ferroelectric Thin Films

With the rapid expansion of data information,modern computers based on von Neumann architecture are facing severe challenges,and people’s demand for various information storage is increasing with the rapid development of computer technology.However,the storage speed and storage capacity of traditional memory can not meet the explosive growth of people’s storage demand,so the research on new memory is urgent.In recent years,various research results at home and abroad have shown that memristor（or resistive random access memory）is a candidate for non-volatile memory.The study found that compared with the existing memory,its power consumption is smaller.At the same time,the von Neumann architecture has been broken through because the memristor can simulate the functions of the human brain with both storage and calculation.However,the formation and rupture of conductive filaments inside traditional memristors are extremely unstable,so it is difficult to realistically simulate the function of neural synapses,which hinders the development of memristors in neural synaptic bionics.The study found that the polarization reversal of the ferroelectric thin film of the ferroelectric memristor determines the change of its resistance,It has the characteristics of stable performance,low power consumption and flexible plasticity,which overcomes the shortcomings of traditional memristors.In this paper,the memristors of three kinds of metal oxide ferroelectric thin films are investigated:Firstly,the growth and ferroelectric properties of Bi₂WO₆（BWO）thin films were deeply studied.In addition,the memristor characteristics and resistance variation mechanism of Sm-doped BiFeO₃(Bi_0.9Sm_0.1FeO₃,BSFO)ferroelectric thin film memristor were explored.finally,Al-doped HfO₂（Al:HfO₂,HfAlO）new ferroelectric thin film memristor was fabricated on P⁺-type Si substrate and studied in depth.Its details are as follows:1.Study on BWO ferroelectric thin film memristor:In this paper,the growth conditions of BWO thin films were investigated and the ferroelectricity of BWO thin films was characterized using atomic force microscopy（AFM）and piezoelectric force microscopy（PFM）techniques.Secondly,the electrical performance of the memristor is tested,and the volt-ampere characteristic（IV）curve of the device is obtained,and the high and low resistance retention time of the device can last for 10⁴s,and the high and low resistance ratio(R_OFF/R_ON)of the device can reach 10,showing that good resistance characteristics.Not only that,but also deeply studied the memristive performance of BWO ferroelectric memristor and simulated the learning performance of brain synapses,which provides a worthy reference for further research.2.Study on BSFO ferroelectric thin-film memristor:This study demonstrates ferroelectric resistive switching behavior in a BSFO heterostructure with Pd top electrode and LSMO bottom electrode.Secondly,the electrical performance of the memristor was tested,and the current contrast ratio of the BSFO ferroelectric thin film memristor was read in the IV curve of about10,and the BSFO ferroelectric thin film memristor successfully simulated the key characteristics of biological synapses.The work function of the electrode material and the formation of the interfacial Schottky barrier are proved to be important for realizing remarkable resistive switching.This study demonstrates that BSFO artificial synapses support various long-term plasticity functions and are promising for future nonvolatile memory applications.3.Study on HfAlO ferroelectric thin-film memristor:This work is to fabricate and study a memristor with 6.5%Al-doped HfO₂（HfAlO）ferroelectric thin film grown on a P+-type Si substrate,and then obtain the typical IV of the memristor by testing the electrical properties of the device.curve,the R_OFF/R_ON of the device can reach 10.The turn-on voltage of the device is mainly concentrated at 1.3 V.The turn-off voltage of the device is mainly concentrated at-2.1V.The IV curve can be repeated for 70 cyclic scans,showing good repeatability and uniformity.In addition,we also studied the effect of modulation on the conductance of the device under different parameter pulses.In addition,we studied and explored the biomimetic behavior of the device on the synaptic learning behavior.The findings lay the foundation for future research on new types of memory and brain-like chips.