Study On Resistive Switching Of TiO₂/ZnO Thin Film Based On Stretchable Electrode

Resistive random access memory(RRAM)has received a great of attention for non-volatile memory application due to its simple structure,high storage density and small in size.Meanwhile,the requirement of high flexibility has been required to realise ductility with the development of wearable device.It is well-known that the functional layer plays a key role on the memory device performance.So,it is important to study the effect of mechanical properties on the micro-structure of functional layer.Previous mechanical tests would cause the functional layer to be squeezed by substrate under bending and twisting test.Moreover,the delamination would be easily caused due to the different elastic molues of functional layer and electrodes,which could interfere the analysis of active layer resistive properties.Among all the mechanical tests,tensile test is an effective method to promise device sustain one single direction force.However,there are few reports about the effect of tension tests on the nanocomposite film resistive switching.In this article,we fabricate Argentum nanowires(AgNWs)/Polydimethylsiloxane(PDMS)flexible electrode and nanoparticles,including TiO₂ and ZnO.The excellent sample was obtained by changing composite method and micro structure.The effect of mechanical peoperties on the device resistive properties and charge transport was studied by the First Principles and ABAQUS.Firstly,we fabricate TiO₂ nanoparticle by hydrothermal method and spin-coat the nanoparticle film on the AgNWs/PDMS flexible electrode.The effect of film layers on the device reistive switching was studied and results show that the ON/OFF ratio is about(?2719)when the TiO₂ film layer is 3.The reason may be that too many layers can introduce more defects in the functional layer,which can block the charge transport and reduce the formation of conduction filaments.However,so few layers can reduce the effective thickness of active layers,increasing the current in the high resistance state(HRS).To investigate the effect of tension on the TiO₂ nanoparticle film,upon stretching 100 times,the ON/OFF ratio decrease above 49.7%,set voltage increase from 0.8V to 1.8V,which are due to that GaIn electrode permeate into film by the tunneling crack and reduce the effective thickness of active layer.The charge transport mechanism corresponds to the space charge limite conduction(SCLC)under different stretching timesSecondly,we fabricated ZnO nanoparticle by sol-gol method and n-n ZnO-TiO₂ layered composite film device.The effect of hydrothermal temperature and thickness of film on the device resistive switching was studied.The results show that the ON/OFF ratio was about 2652 when the hydrothermal temperature of ZnO is 160? and ZnO film layers are 2.The charge transport mechanism corresponds to the space charge limite conduction(SCLC).The Firet Princple results show that,compared with the TiO₂ nanoparticle film,the n-n ZnO-TiO₂ layered film can increase the density of charge carrier,leading to the higher current in the HRS and lower ON/OFF ratio.To further study the effect of stretching on the resistive properties of active layer,we investigate the ON/OFF ratio and set voltage after stretching.The results show that when stretching 200 times,ON/OFF ration decrease nearly 63.2%,Vset is about 2.3V.Upon device stretching 300 times,the device is broke down.The reason maybe that tunneling crack block the formation of tree-condition oxygen vacancy fialments.Finally,we fabricate TiO₂-ZnO nanocomposite film and investigate the effect of composite ratio and active layer thickness on the device resistive switching.The results show that the ON/OFF ratio is higheat(?1789)when the composite ratio is 2:1,and Vset is 0.6V.With the increase of ZnO composite ratio,the ON/OFF ratio decrease because the difference of grain size would cause low matched-degree between ZnO and TiO₂.The interface of nanoparticles could formate block layer to hinder electron migration,leading to a lower current in the LRS.We select the excellent sample and study stretching effect on the resistive switching.The results show that the ON/OFF ratio is about 812 under stretching 300 times.Upon stretching 400 times,the ON/OFF ratio is about 80,which indicates that device is nearly broke down.The SEM images and Finite Element Analysis show that the main fatigue fracture includes micro-crack and tunneling cracks,which hinder the electron migrations between nanoparticles and block the conduction fialments.The current in the LRS decrease,which weaken the switching performance.