Doping Effect In ZrO₂-based Memristor Based On The First-principles Calculations

Memristor,also known as resistive random access memory(RRAM),is considered as the most promising candidate for the new generation of non-volatile memory due to its advantages of simple structure,fast operation speed,multi-level storage and strong compatibility with CMOS technology.ZrO₂with excellent resistive performance is one of the candidate materials for the memristor resistive layer material,and can be regulated the resistive characteristics by doping.However,the regulation law of doping in ZrO₂is not clear,which easily leads to the blindness of the experiment.The doping effect of ZrO₂-based memristor is studied by using the first-principles calculations,and the underlying reason for the device performance optimization by doping is clarified,which can guide and verify experiments.Firstly,the Au doping effect of ZrO₂-based memristor was investigated.The ZrO₂supercell model with 96 atoms was established with Materials Studio software,and the band structure and density of states for ZrO₂supercell were calculated by CASTEP code module.The results showed that the impurity level appeared in the band gap of Au doped ZrO₂,and the oxygen vacancy defect level was pushed to the bottom of the conduction band,which improved the conductivity of the electrons in ZrO₂.By calculating the oxygen vacancy formation energy and migration barrier energy in ZrO₂,it was found that the oxygen vacancy formation energy and migration barrier energy were effectively reduced by Au doping.After Au doping,more oxygen vacancies were easily formed,and the oxygen vacancies tended to migrate towards Au atoms.The oxygen vacancy cluster of the ZrO₂supercell were further simulated,and the results showed that the oxygen vacancies locally around Au formed an ordered conductive filament,and the electrons could achieve directional transport in the oxygen vacancies.The effect of N doping on the resistive switching performance of ZrO₂-based memristor was investigated.On the one hand,the formation energy and migration barrier energy of V_Oin the ZrO₂supercell were calculated theoretically.The results showed that the formation energy and migration barrier energy of V_Oare significantly reduced after N doping.By calculating the density of state for ZrO₂,it was found that N doping can eliminate the defective state in ZrO₂forbidden band,neutralize the extra V_Oin ZrO₂,and possibly reduce the number of V_Oconductive filaments.On the other hand,it was found that Ti N/N:ZrO₂/Pt device showed stable bipolar resistive switching characteristics,and had smaller operating voltage and larger resistance window,better consistency of resistance parameters,and the multi-level storage characteristics in the experiment.The experimental results can be supported by the theoretical calculation.In summary,the doping effect of Au and N in ZrO₂based memristor were investigated.The results show that doped atoms Au and N can significantly reduce oxygen vacancy formation energy and migration barrier energy,and control the oxygen vacancy to preferentially concentrate around the doped atoms and form conductive filaments.Meanwhile,doped atoms Au and N can also reduce Forming voltage and SET/RESET voltage of devices,which can improve the consistency of device resistance parameters.It provides a reliable theoretical and experimental basis for the research on doping effect of ZrO₂-based memristor.