Synaptic Plasticity Mimicked Based On An Memristor

Memristor is regarded as the fourth fundamental electrical element besides resistor,capacitor,and inductor.The memristor can be changed with the current flew it and remember the states.As one of the most promising candidates to substitute the conventional computing architecture,neuromorphic circuits has drawn lots of attention from researchers and engineers all over the world.Simulating the behavior of neuron system always faces the challenge on efficiency,two-terminal memory devices have attracted considerable attention because of their simple structure,thus,this thesis pays more attention on the discussion of emulating neuromorphic properties on circuit and device level.The mix of poly(3,4-ethylenedioxythiophene)and poly(styrenesulfonate),denoted as PEDOT:PSS has attracted researchers for its numerous electrical characteristics.This work concentrated on the material PEDOT:PSS,which is similar to biological molecules in electrical performance,and we compared PEDOT:PSS with PVP-doped?CuCl2-doped,illustrating the influence of doping on the resistance.Using Ag/PEDOT:PSS:PVP/Ta memristor to emulate a series of synaptic behaviors and providing an element model in neural network computer.The primary contents are decrisbed as follows:Firstly,we fabricated a series of memristor via electron beam magnetron sputtering and spin coating.The device's potential to mimic synaptic plasticity depends on that the conductance can be continuously adjusted to some extent and the device had rectifier function.Throughdiluted doping ofP VP and doping of CuCl2,the conductance variation of Ag/PEDOT:PSS/Ta structures memristor was changed significantly.The initial conductance was decreased and the maximum conductance was enhanced by doping PVP,the range of conductance variation was enhanced,and enlarged conductance variation about 10 times.The initial conductance and the initial conductance were all increased by doping CuCl2,the range of conductance variation was decreased.PVP is a non-conductive polymer,organic layer conductivity would decrease by doping PVP.And the initial conductance value was reduced,in addition,made the organic layer more loose.Ag ions were more likely to migrate with positive voltage due to the medium effect of Ag ions were smaller,which formed longer Ag conductive filament.And it improved the maximum conductance.PSS decreased and PEDOT configuration changed by doping CuCl2,which improved the middle layer conductivity.The devices conductance increased.At last,three-layered structures of Ag/PEDOT:PSSPVP/Ta memristor was fabricated by spin-coating.By designing suitable pulses,we have successfully emulated a series of synaptic behaviors,including short term plasticity transform long term plasticity,spike rate dependent plasticity(SRDP)and spike timing dependent plasticity(STDP).The relaxation time curve of memory was enhanced greatly by doping PVP and it more accord with human curve of memory.The device had very large change range of conductance that can be recognized easily by external circuits.And the device showed a good ability of consistency.Therefore,the device could be used for large-scale neuromorphic circuits.