Dissolvable Crossbar Memristors

As the fourth kind of passive device with resistance,capacitance and inductance,memristor has both information storage and logic operation functions,and has great research potential in big data storage and analogue neural network.Transient electronic device refers to an emerging electronic device whose physical shape and function can partly disappear or completely disappear immediately after the specified function is completed,triggered by external stimuli.In this paper,we combine the memristor with transient electronics to study the soluble transient memristor.The memristor with Cu/a-Si/W cross-bar structure was prepared by using copper?Cu?as the top electrode,amorphous silicon?a-Si?as the middle layer and tungsten?W?as the bottom electrode,to clarify the resistance property,resistance change mechanism,and the dissolvability.First,soluble electrodes,interlayer and substrate materials used for memristors were studied.It has been found that Cu,the metal material with excellent electrical conductivity,has good dissolubility and can be used as the active electrode of conductive filament type memristors.The dissolution mechanism of Cu has been analyzed by X-ray photoelectron spectroscopy?XPS?.a-Si,which is compatible with the semiconductor process,has been chosen as the memristor interlayer material.And polyvinyl alcohol?PVA?has been selected as the substrate material and their solubility was?has been?analyzed,respectively.Cu/a-Si/W memristor has been prepared on Si/SiO₂ substrate and the resistance property and mechanismhave been performed.Influence of the preparation method of the interlayer,thickness of the middle layer,and thickness of the bottom electrode on the performance of device has been analyzed.The memristor with Cu?80 nm?/a-Si?30nm?/W?60 nm?cross structure has been determined.Ratio of the high resistance state?HRS?versus low resistance state?LRS?of the device is greater than 40.The device can be used 10² times or even more,Resistance of HRS and LRS can remain in that state over 10⁴ seconds,exhibiting the nonvolability.The experimental verification has confirmed that this device has the function of simulating synaptic enhancement,synaptic inhibition and enhancement of the synapses such as pulse enhancement.Combined with the results of temperature change test,formation and fracture of the conductive filaments have been identified as the resistance change mechanism.The properties of Cu/a-Si/W devices on PVA substrates have also been declared.Influence of the thickness of the bottom electrode on the performance of the device was analyzed and the structure of Cu?80 nm?/a-Si?30 nm?/W?100 nm?was determined.The structure of the device can be cycled more than 20 times with HRS and LRS ratio greater than 5,and the SET voltage(V_SET)and RESET voltage(V_RESET)can be relatively stable in the 0.5V range,with switching characteristics.The devices on the PVA substrate can simulate synaptic enhancement,synaptic inhibition and pulse enhancement properties under pulsed stimulation and dissolve out within 6 min of deionized water with good solubility.In addition,the method of memristor transfer was also studied.The device is transferred from the Si/SiO₂ substrate to the flexible substrate PVA by means of a water-assist method using a heat release tape.The transferred device was placed in deionized water and dissolved within 200 s.