Experimental And Numerical Study Of ZnO Resistive Switching Memory

With the rapid development of information technology,such as mobile terminals,cloud computing and big data,the demand of high-performance electronics is becoming more and more urgent.As a hinder of the progress of electronics,new type high-performance memories have attracted plenty of attention all over the world.Resistive switching memory has enough potential to replace flash memory,which dominates the market recently,for its high storage density,fast program/erase speed,non-volatility and so on.However,flash still dominates the market because the mechanism of resistive switching memory still remains unclear.In this thesis,we study the mechanism of ZnO resistive switching memory by numerical simulation to provide a effective way to control the electrical properties.First,the effect of synthesis parameters on the electrical properties was studied to obtain a high-performance Al/ZnO/p~+-Si resistive switching memory.According to characterization results,the synthesized ZnO has a wurtzite structure and the conductive filaments in ZnO films consist of oxygen vacancies.Then,linear fitting of the current-voltage(I-V)characteristics show that the high resistance state(HRS)and the low resistance state(LRS)are dominated by Poole-Frenkel(P-F)effect current and space charge limited current(SCLC),respectively.With the modification of oxygen vacancy concentration,simulated I-V characteristics fit well with experimental data,which indicates that resistive switching is led by the change of oxygen vacancy concentration and this effect is realized by electron emission and capture of oxygen vacancy.Finally,percolation theory is used to calculate the quantitative relationship of oxygen vacancy concentration and the conductivity of ZnO film.With the consideration of point effect of conductive filaments(CFs),a universal percolation model is proposed,which describes both HRS and LRS.This model not only successfully forecast the effect of memory size on electrical properties,but also directly shows the growth process of CFs.Moreover,it indicates that the mechanism of resistive switching memory can be divided into two levels:voltage-oxygen vacancy and oxygen vacancy-current.