The Study Of Transparent And Flexible Resistive Memory Devices Based On Co Doped BaTiO₃ Film

With the advent of the era of big data and information explosion,people's requirements for information processing speed and information storage capacity are also gradually increasing.Although Flash storage technology is still the mainstream storage technology,it has gradually failed to meet the needs of information processing and preservation.That is to say,the development of new non-volatile storage technology is imminent.As the promising candidate for the next-generation nonvolatile memory,the resistive-switching random access memory offers various technological advantages,such as simple device configuration,fast operation speed,high endurance,excellent scalability,small size,and low-power consumption.With the development of AIo T(Artificial Intelligence and Internet of Things)and wearable devices,new electronic devices are also required to be more compact,flexible and transparent.As an important part of electronic devices,memory devices also need to be transparent and flexible.Therefore,research on transparent and flexible non-volatile resistive memory devices has become very necessary.Nowadays,enterprises and universities have made a detailed study on resistive memory,but there are still some inevitable issues,such as the mechanism of resistive switching and the selection of resistive materials,which is unfavorable for the development of resistive memory.So in this dissertation,mica/SrRuO₃/BaTi_0.95Co_0.05O₃/Au and mica/Ag-ITO/BaTi_0.95Co_0.05O₃/Ag/ITO memory devices were prepared.The breakage mechanism in bending process is explained.The resistive switching mechanism and resistive change model based on the perovskite resistive storage material(BaTi_0.95Co_0.05O₃)were demonstrated.Meanwhile,the stability of devices in the flat state,bending state,variable illumination and different temperature are also studied.The research content of this dissertation is as follows:(1)Study on bending properties and storage properties of semi-transparent and flexible mica/SrRuO₃/BaTi_0.95Co_0.05O₃/Au resistive memory.Perovskite ceramics and single crystals are commonly hard and brittle due to their small maximum elastic strain.Here,large-scale BaTi_0.95Co_0.05O₃ film with a SrRuO₃ buffered layer on a 10?m thick mica substrate is prepared,the BaTi_0.95Co_0.05O₃ film preferentially grown along the[110]direction.Mica/SrRuO₃/BaTi_0.95Co_0.05O₃ is flexible with a small bending radius of 2.2mm and semi-transparent for visible light at wavelengths of 500nm-800nm.After growing the Au top electrode,the mica/SrRuO₃/BaTi_0.95Co_0.05O₃/Au resistive memory shows bipolar resistive switching characteristic with±17V operating voltage.The On/Off ratio of this memory is up to50.By analyzing the materials used in the memory and related experiments,we verify that the resistive mechanism of the memory belongs to the valence change mechanism,and its conductive model belongs to the conductive filament model dominated by oxygen vacancies.The resistive-switching properties show no obvious changes after the 2.2-mm-radius bending memory being written/erased for 360000 cycles or after the memory being bend to 3mm radius for 10000 times.Most importantly,the memory works properly at 25°C-180°C or after being annealed at 500°C.The memory satisfies the practical application of flexible resistive memory.(2)Study on heat resisting,transparent and flexible Ag-ITO film.As one of the most universal transparent conductive films in the industry,ITO is not suitable for flexible electronic devices due to its poor resistance to mechanical fatigue.In this dissertation,the growth of Ag doped ITO film at high temperature has successfully improved the shortcomings of ITO film,such as poor mechanical bending resistance and poor high temperature stability.The Ag-ITO film with an Ag doping amount of 2.7wt%has the best performance.If the Ag doping amount is too small,the film will be broken during the bending process;if the Ag amount is too large,the Ag element will precipitate at the grain boundary.The transparency of 2.7wt%Ag doped ITO film is up to 80%for visible light at wavelengths of 400nm-800nm.The square resistance is stabilized at 20?/?before and after bending 10000 times with the bending radius of 3mm.The square resistance of the film also remains stable during the temperature-changing process or annealing from 25°C to 600°C.By testing and analysis,it can be shown that 2.7wt%Ag-ITO is a good high temperature resistant flexible transparent conductive film.(3)Study on bending properties and storage properties of transparent and flexible mica/Ag-ITO/BaTi_0.95Co_0.05O₃/Ag/ITO resistive memory.Combined with the previous research content in this dissertation,the direct preparation of transparent and flexible inorganic perovskite thin film resistive memory device was reported.The transparence of mica/Ag-ITO/BaTi_0.95Co_0.05O₃/Ag/ITO memory is up to 75%in the visible light range between 400nm-800nm.The memory shows unipolar switching characteristic.The operating voltage is below2V because of the thickness reduction of BaTi_0.95Co_0.05O₃.Through the fitting of the I-V curve and the electrode material,it can be explained that the resistive mechanism of the memory belongs to the electrochemical metallization,and the conductive model belongs to the conductive model dominated by the Ag element.The memory can switch between high resistance state and low resistance state with 50ns pulse voltage.Either high resistance state or low resistance state remains stable even after the 14400 cycles'dynamic bending test with the minimum radius of 3mm.In addition,the testing of the array samples and the testing of the conductive atomic force for the microdomains also explain to some extent potential of the memory for high-density storage.In summary,this dissertation describes the properties of mica/SrRuO₃/BaTi_0.95Co_0.05O₃/Au and mica/Ag-ITO/BaTi_0.95Co_0.05O₃/Ag/ITO resistive memory devices under conditions of flatness,bending,illumination and temperature change.The bipolar and unipolar resistive switching mechanism and resistive change model were demonstrated.In addition,a high performance Ag-ITO transparent flexible conductive film was prepared.Hoping that these results will help the development of new transparent and flexible resistive memory.