Study On Electrical Regulation And Synaptic Emulation Of Interface Modulated WO_3-x Based Memristor

Building the brain-inspired neuromorphic synaptic device is an important foundation towards the future of artificial intelligence.As an emerging electronic component,memristor with conductance states incrementally modulated,is considered as one of promising candidate for the construction of neuromorphic computing owing to its functional and structural resemblance to the biological synapse.To develop the physical model of new-type memristors is an important foundation for constructing highly stable devices and simulating the cognitive function of synaptic learning.At the same time,metal oxide is one of the important memristor material systems.Herein,a metal/WO3-x interface modulated memristor device is proposed and developed.By using in situ transmission electron microscopy(TEM),the microdynamics of the memristor is visually revealed.In addition,various synaptic plasticity functions are simulated,including short-term and long-term plasticity.Based on the memristor-based system,brain-like visual and auditory cognitive functions are realized..The details are as follows:1.Memristive device construction and emulation of basic synaptic function.(i)We choice amorphous WO3-x thin film as the resistive swiching layer.By studying the basic electrical behavior of different metal top electrodes(Pt,Au,W,Ti)/WO3-x/W sandwich memristor devices,a metal(Pt,Au)/WO3-x Schottky interface memristor suitable for multilevel resistive modulation is developed.(ii)The microscopic ion dynamics processes inside the WO3-x based memristor are directly observed by in-situ TEM with EELS technique,thus revealing the microphysical mechanism model of this kind of interfacial modulated memristor:the electric field drives oxygen ions to migrate and accumulate at the interface of metal(Pt,Au)/WO3-x.After the electric field is removed,oxygen ions spontaneously diffuse.The above oxygen ion dynamics process induces a decrease/increase in the height of the Schottky interfacial barrier,which leads to a decrease/increase in the interfacial resistance.(iii)Since the oxygen ion migration/diffusion process is similar to the Ca²⁺dynamics of biological synapses,the constructed synaptic device successfully and accurately achieved a large number of basic neurosynaptic functions:short-term plasticity function and long-term Plasticity function.2.The realization of visual spatiotemporal learning function.(i)The Triplet spike-time-dependent plasticity(Tri-STDP)is realized based on WO3-x based memristor.A new scheme is proposed for extending the Tri-STDP model towords the generalized Bienenstock-Cooper-Munro(BCM)learning rules.Thus,the Bienenstock-Cooper-Munro(BCM)learning rule of high-order synaptic frequency-based plasticity is successfully simulated using a single memristor.(ii)Based on the BCM mathematical model that is highly consistent with experimental data,we adopt a two-layer neuromorphic feedforward network with 81 presynaptic neurons and 4 postsynaptic neurons as input and output layers.The input signals are four orientation bars with high frequency and low frequency(0°,45°,90°,135°).As a result,the rated based orientation selectivity has been successfully achieved.3.The realization of auditory perception function.(i)Based on the timing-dependent characteristics of WO3-x based memristor,this work designs a memristor-based circuit system suitable for the source azimuth detection,which realizes the sound location function of static sound source.(ii)Based on the frequency-dependent characteristics of WO3-x based memristor and its related Tri-STDP model,a memristor-based circuit system suitable for Doppler velocity measurement is designed to simulate the Doppler frequency-shift effect of human hearing.Furthermore,the velocity of moving sound source is calculated according to the principle of Doppler velocity measurement,thus realizing the function of sound localization of moving sound source.By combining with the above two kinds of memristor-based circuit system,this work builts an artificial auditory perception system based on memristor,which realizes the detection function of the azimuth and velocity of the moving sound source.