Resistive Switching In Transparent Metal Oxides And Its I-V Characteristics At Low Resistance State

As one of the most promising nonvolatile storage technologies exhibiting fast write/read speed,good scalability and compatibility with conventional CMOS fabrication process,resistive random access memory(RRAM)has attracted many attentions from industries and academic communities in recent years.Shrinking its physical dimensions to meet requirements of three-dimensional(3D)integration is an inevitable choice.However,3D-RRAM would face fluctuations in switching parameters due to it thermal stability,power and crosstalk.The conduction mechanism in device is coordinate with defects and the interface status,so that device performance will be changed with it.In previous study rare refer to use double layer to improve device thermal stability.In addition,plasma treatment is an effective way to modulation defects which could improve device performance,but scarcely reported for plasma treat to adjust interface characteristic.Therefore,in this work,we study the effects of stacked HfO_x/ZnO layers on resistive switching properties.Additionally,argon-plasma treatment was applied to the HfO_x/ZnO interface to investigate the modification on resistive switching.The mechanism of the modification was also studied.HfO_x and ZnO have transmittance of 80%in visible range with band gaps of 5.73 eV and 3.35 eV respectively.Both HfO_x and ZnO RRAMs exhibit bipolar resistive switching with poor thermal stability and operation currents in mA.The conduction at low resistance state(LRS)is ascribed to filament-assisted Ohm conduction,while the conduction in the high resistance state(HRS)is dominated by space-charge-limited mechanism(SCLC).A ZnO layer was then attached to the HfO_x to form a RRAM with Ti/HfO_x/ZnO/ITO structure in order to improve the performance of HfOX based RRAMs.Compared with its single layer counterpart,double-layer(DL)degrades the operation current from mA to μA.The HRS conduction of the stacked HfO_x/ZnO was dominated by Schottky emission conduction,while the conduction in the LRS is dominated by Poole-Frenkel emission mechanism.Schottky barrier at the HfO_x/ZnO interface increases with the temperature rise to stabilize its operation current at～2μA at 180℃,The activation energy for the diffusion of oxygen vacancies(～1.65eV)in the DL-RRAM is also increased to ensure 85 ℃ data retention extended from 159 hours(single layer RRAM)to 10 years.Furthermore,argon-plasma treatment introduce oxygen vacancies at the HfO_x/ZnO interface to influence barrier height.The current could thus be tunable and the embedded self-rectification is also enable.