Researches On Resistance Switching Characteristics Of Al₂O₃ Multilayer Films And Phase Analysis Of BaTiO₃

The 21st century is an era of information.In recent years,people's demand for better data storage performance and stronger data processing capacity of memorizer has been increasing,which has prompted continuous improvement and innovation of semiconductor integrated processes and technologies and accelerated the research progress of the next generation of memory devices to break the limits of Moore's law.The devices based on the resistance effect have excellent data storage and processing capacity as well as good ductility and compatibility,and are expected to be the next generation of memory devices.Perovskite oxide BaTiO₃ is a typical ferroelectric material with good ferroelectric,piezoelectric and resistance switching properties.The studies show that BaTiO₃ has a potential application prospect in photoelectric effect because of its large electro-optical coefficient.BiFeO₃,which belongs to the perovskite family,is a kind of single-phase multiferroic material with ferroelectric and antiferromagnetic properties at room temperature.In this article,BaTiO₃,ITO/Al₂O₃/BiFeO₃/Ag and Si/Pt/Al₂O₃/BiFeO₃/ITO thin films of high quality were sputtered by ultrahigh vacuum magnetron sputtering equipment.The performance of the devices can be adjusted by controlling the appropriate growth conditions and then changing the conditions such as annealing temperature,thickness of each component films and different contact interface.The main content is as follows:?1?BTO films were prepared at different annealing temperatures,and their I-V curves were tested by Keithley2400.The device currents increased under light conditions,and the maximum photocurrent of the samples was obtained under annealing condition of 600?.In this experiment,the BaTiO₃ thin films were characterized and phase analyzed by scanning electron microscope?SEM?,energy dispersive X-ray spectrometry?EDX?and X-ray diffraction analysis?XRD?.EDX analysis showed that annealing would change the stoichiometric ratio of BTO,and XRD also proved that Ba₂TiO₄ phase would appear in BTO films at a lower annealing temperature.XRD patterns showed that the diffraction peaks of samples annealed at higher temperature are slightly shifted in the direction of higher diffraction Angle,which may be because annealing changes the crystal variable stress of thin films.We used Scherrer's formula and Williamson-Hall analysis to discuss the crystal formation in BTO films.The results showed that the annealing process could greatly change the phase structure of BTO.?2?Three groups of ITO/BiFeO₃/Al₂O₃/Ag multilayer structures with different thickness of Al₂O₃ film layer were prepared by magnetron sputtering.All multilayer films exhibit the characteristics of bipolar resistive switching?RS?.With the variation of the thickness of Al₂O₃ films,the switching behaviors of the memory devices change.Compared with other devices,the device with a 5nm thick Al₂O₃ layer is forming-free,and its maximum resistance ratio is about 30.There is an obvious switching window in the negative bias region,and at a low reading voltage??-0.5V?,the device with the thinnest Al₂O₃ film exhibits a distinguishable high-low resistance state.It's interesting that,during the continuous cyclic voltage scanning,three types of I-V curves appear randomly and alternately in the sample with Al₂O₃ of 5nm,which is rarely reported in the literatures.In this paper,we propose the dual mechanism of the virtual cathode growth dominated by Ag ions and the formation and rupture of conductive filaments?CFs?contributed by Joule heating-assisted oxygen vacancies migration.This model successfully explains the reasons for the coexistence and conversion of three kinds of curves in the memory device with a 5nm thick Al₂O₃ film,and also explains the different switching behaviors in the three groups of samples.?3?Si/Pt/Al₂O₃/BiFeO₃/ITO devices with Al₂O₃ layer of 5nm were prepared on[Si/Pt]substrate,and the influence of light on their resistance switch characteristics was investigated.The experiments showed that the devices under both dark and light conditions have multistage switching phenomenon.There were negative differential resistance?NDR?effect in the devices when no light was added,and the device current increased and the NDR effect disappeared under light condition,indicating that the light energy can regulate the photoelectric properties and switching effect of the devices.