Research On Preparation And Characteristics Of SrCoO_x Thin Film Memristive Devices

Due to the characteristics of high defect migration speed and low defect migration barrier,perovskite transition metal oxide materials have great research space in the field of high-performance memory devices.The perovskite structure of Sr Co O_x（SCO_x）can undergo a reversible topological phase transition without changing the lattice framework by adjusting the oxygen content.From the low-resistance ABO₃ perovskite oxide system to the high-resistance ABO_2.5 brownmillerite oxide system,SCO_x system has the advantages of clear resistance change mechanism,good retention,and good device uniformity.It has shown application potential in the field of non-volatile resistance random access memory.However,it is usually difficult to obtain single-phase Sr Co O_x films in experiments.How to adjust the preparation process conditions to regulate the oxygen content of the Sr Co O_xfilm and precisely adjust the resistance state of the Sr Co O_x mixed-phase film is very important.In this paper,pulsed laser deposition technology is used to fabricate SCO_x thin film devices based on two different bottom electrodes,Nb:Sr Ti O₃ and Sr Ru O₃.With the help of microscopic characterization methods such as Atomic Force Microscope,Scanning Electrical Microscope,X-ray Diffraction,X-ray Photoelectron Spectroscopy,the functional films prepared under different deposition temperatures and different oxygen partial pressures were analyzed.A semiconductor characteristic analyzer was used to conduct electrical performance tests on the devices.It is found that the deposition temperature and oxygen partial pressure have an important influence on the microstructure and resistive performance of the SCO_x film.It is found that different deposition temperatures and oxygen partial pressures can significantly change the microstructure of SCO_x films and affect resistive performance.The SCO_x thin-film memristor prepared with a deposition temperature of 700～750 ^oC and an oxygen partial pressure in the range of 3～7 Pa can realize repeated erasing and writing,which has good high and low resistance state stability and low power consumption.The ratio of device switching can reach 245.SCO_x memristive devices mainly include ohmic conduction mechanism and space charge limited current conduction mechanism.Since the bottom electrode and the SCO_xfunctional layer form a Schottky barrier,the SCO_x thin film memristive device will also exhibit a Schottky thermal charge emission mechanism under the action of a high operating voltage.The electrothermal coupling simulation model based on Sr Ru O₃/SCO_x/Au structure is established by using the multi physical finite element simulation software COMSOL.The changes of oxygen vacancy concentration,potential and temperature during resistance change process were analyzed.The devices with different electrode material parameters were analyzed in detail.It is found that the bottom electrode with low conductivity and thermal conductivity tends to accumulate heat inside the SCO_x memristive device,and the migration and reconstruction of oxygen vacancies occur closer to the electrode,thereby reducing the operating voltage of the device,which is consistent with the experimental results.Increasing the cut-off voltage of the reset process can obtain a multi-resistance window,which increases the possibility of the SCO_x device achieving multi-resistance states.