The Resistive Switching Properties And Device Applications Based On Doping Composite Oxide Thin Films

The resistive switching characteristics have been investigated in many semiconductors and sulators when exerting an extral changeable bias on them. And it is able to prepare a resistance random access memory (RRAM) with its advantages including simple structure, high-density integration, small size, fast switching speed and so on, which offer the most promising application opportunities to replace si-flash memories. In this thesis, the Co doped BaTiO3thin films are prepared on Pt(111)/Ti/SiO2/Si substrates by Sol-gel method; Then the metal top electrodes were prepared by evaporation method and testing the electric properties of the samples, in further to explore the resistive behaviors and conductve mechanisms and offer reliable data for the application of RRAM. The details of experiments and results including:(1) The eight-wise BRS behavior is found to be realized not requiring the electro forming process in the Au/BaTii.xCoxO3/Pt, the operate voltage is in the range of-1V to+1V, and the ON/OFF ratio is increased with the increase of Co doping concentration, its more than106when the Co doping concentration is5%, better than other perovskite films The results implied that the Co ions acceptor doping effect the concentration of oxygen vacancies and control the BRS behaviors.(2) According to the conclusion of Co ions acceptor doping effect the concentration of oxygen vacancies, we prepared BaTiO3/Co:BaTiO3/BaTiO3trilayers; Electric-field induced transition of bipolar resistive switching behavior to complementary resistive switching behavior has been demonstrated in the Au/BaTiO3/Co:BaTiO3/BaTiO3/Pt device due to the depletion of oxygen vacancies in BaTiO3layer and interface effects. The operating current is small with10-6A; Furthermore, the operating current of the CRS devices significantly reduced10"7A by decreasing the doped layer.(3) Resistive switching behaviors have been investigated in the Au/BaTiO3/NiO/Pt neoteric device by serially stacking the two elements with different switching types, and the schematic diagrams of different stages of the cooperative process are discussed. The coexistence of CRS and URS are mainly ascribed to the co-effect of electric field and Joule heating mechanism; Compared with BaTiO3/Co:BaTiO3/BaTiO3trilayers, the operating voltage are reduced with a range of-4V to+4V.(4) Nonliear resistive switching behaviors have been investigated in Al/Co:BaTiO3/Pt and Al/BaTiO3/Co:BaTiO3/Pt devices, and both the operating current and the operating current are reduced. Whearas the volatile resistive switching is obtained in Al/Co:BaTiO3/Pt.The results further impied that the ON/OFF ratio can be enhanced by controlling acceptor doping into the n-type semiconductor, which is generally beneficial to easily read the memory states in the periphery circuit; Otherwise, the CRS behaviors are obtained by controlling the doping concentration and interface effect. One of the cells in CRS will always be in high resistance state (HRS), i.e. OFF state at low voltage so the sneak current can be effectively suppressed; Furthermore, CRS behaviors and bipolar nonliear resistive switching behaviors are investigated, which had lower operating voltage and operating current and reduced power consumption.