Mechanism Of Resistive Switching Effect In NiO Films

Recently,requirements for the memory with large capacity and microscale increase as the global informationization is developing rapidly.Therefore,the Resistive Random Access Memory(RRAM),which is based on the resistive switching(RS)effect and is one of the most promising candidates for the next-generation nonvolatile memories,has drawn enormous attention from both academic and industrial communities due to its excellent device properties,including simply structure,high density,low cost and high endurance.So far,diverse mechanisms have been proposed to explain the observed RS effect,and among them the formation/rupture of conducting filaments model is one of the most mainstream models,which not only involves unique physics but also shows rich and interesting phenomena.However,the evolution mechanism and process of conducting filaments of the conducting filament model,especially the thermochemical mechanism(TCM),remains unclear,including the migration of ions,the size of filaments and the location of filament rupture.These critical questions are undoubtedly significant barriers to their applications for RRAM and artificial neural networks.In addition,the combination of RS effect and magnetoresistance(MR)behavior can provide evidence to reveal the mechanism of RS effect and benefit the development of multifunctional devices,which is of great scientific significance and potential application prospect.In this context,we chose the NiO film,which is the model material for TCM effect,as the research object,and investigated the evolution mechanism of conducting filaments by use of the observation of MR behaviors and impedance spectroscopy as follows.We fabricated Au/NiO/Pt capacitor structure using pulsed laser deposition(PLD)and magnetron sputtering.We observed rich and interesting MR behaviors in the NiO film with different resistance states,including the normal and anomalous anisotropic magnetoresistance and tunneling magnetoresistance,which provide new insights into the filaments.Our experimental results combining with the first-principles calculation reveal the microscopic evolution mechanism of conducting filaments,on basis of which we proposed an evolution model of filaments during the RESET process in the NiO film.Furthermore,this work provides a referable way to uncover the nature of conducting filament in other TCM systems,and is significant for developing nanoscale multifunctional devices.In addition,we obseved the impedance spectroscopy characteristics of the NiO film with different resistance states,from which we obtained the equivalent circuits and conducting regions corresponding to different resistance values.We extracted the component resistance(R)and capacitance(C)values through the fitting of semicircle,which can provide convincing evidence for the gradual evolution process of multiple filaments during the RESET process.Moreover,this work futher demonstrate the impedance spectroscopy is a highly powerful technique used to investigate the mechanism of RS effect.