铁酸铋异质结阻变特性与机制研究
发布时间：2018-09-06 08:14
【摘要】：多铁性铁酸铋(BiFeO3,简称BFO)材料是目前唯一在室温同时具有铁电和铁磁性的多铁性材料,具有优异的铁电和磁电耦合特性,在新型非挥发性存储器件、多功能传感器件、自旋电子器件、光伏器件等领域具有广阔的应用前景。铁酸铋基阻变存储器件结合了铁电存储器和阻变存储器的优点,通过铁电极化的反转调控界面势垒和载流子输运特性,以此来实现高低阻态切换,而非缺陷调控阻变行为,显示出独特的优势。本论文围绕铁酸铋基阻变结构,构筑了铁酸铋/金属和铁酸铋/半导体两种异质结阻变结构,对铁酸铋薄膜和器件制备技术及阻变电学行为进行了研究,深入探讨了异质结构的阻变机制、物理模型及主要调控因素。论文首先采用溶胶-凝胶法和脉冲激光沉积法在单晶硅和钛酸锶衬底上成功制备出具有良好铁电性的高质量铁酸铋薄膜,通过引入氧化物缓冲层、化学掺杂、以及控制氧压与沉积温度等减少薄膜缺陷与漏电路径,获得了致密、均匀、铁电性能好、漏电流密度低的铁酸铋薄膜。同时,对铁酸铋进行双金属离子掺杂,获得了具有一定铁磁性的铁酸铋材料;并采用无磁性镁元素掺杂制备铁酸铋纳米结构提升其磁性,获得了铁磁性与顺磁性共存的铁酸铋纳米结构。设计并制备了Au/BFO/SRO异质结阻变结构,在无需电成型操作下,获得了具有自限流特性且可靠性高的双极性阻变行为。设计并实现了对铁酸铋电阻状态的有效调控,通过设置不同的扫描电压、外加限流、扫描模式等方法获得多个有效的存储状态,证明其具有多值存储能力。从电极材料、铁电极化、材料缺陷等分析了铁酸铋材料的阻变机制,结合其电学行为及对温度与测试氛围依赖性的结果,证明铁电极化调控界面势垒及载流子输运特性的阻变机制,并揭示了铁电极化反转与氧空位的迁移在铁酸铋阻变行为中的竞争机制,获得了影响铁酸铋阻变特性的关键因素。此外,根据此阻变模型,对自限流特性及多值行为进行了解释。设计并制备了BFO/ZnO异质结阻变结构,获得了双稳高低阻态切换特性及二极管整流效应。研究了薄膜厚度及铁电材料的化学掺杂对异质结阻变效应的影响,建立并完善了BFO/ZnO异质结阻变物理模型,通过极化效应调控界面载流子耗尽或积累态,并将铁电极化引入异质结能带结构中,推导出铁酸铋与氧化锌的界面势垒,获得了铁电极化调控异质结阻变特性的方法及关键影响因素。
[Abstract]:Polyferric bismuth ferrate (BiFeO3,) is the only ferroelectric and ferromagnetic material at room temperature. It has excellent ferroelectric and magnetoelectric coupling properties. It is widely used in novel non-volatile memory devices and multifunctional sensing devices. Spin electronic devices, photovoltaic devices and other fields have a broad application prospects. Bismuth ferrite based resistive memory device combines the advantages of ferroelectric memory and resistive memory, and realizes the high and low resistance state switching, not the defect regulating the resistive behavior, through the inversion control interface barrier and carrier transport characteristics of iron electrode. Show unique advantages. In this thesis, two kinds of heterojunction structures, bismuth ferrate / metal and bismuth ferrate / semiconductor, are constructed around the structure of bismuth ferrate. The fabrication technology and the electrical resistance behavior of bismuth ferrate films and devices are studied. The resistance mechanism, physical model and main regulation factors of heterostructure are discussed. In this paper, high quality bismuth ferrite thin films with good ferroelectric properties were prepared on monocrystalline silicon and strontium titanate substrates by sol-gel method and pulsed laser deposition. By controlling the oxygen pressure and deposition temperature to reduce the defect and leakage path, dense, uniform, good ferroelectric properties and low leakage current density of bismuth ferrite thin films were obtained. At the same time, bismuth ferrate was doped by bimetallic ions to obtain bismuth ferrate material with certain ferromagnetism, and bismuth ferrate nanostructure was prepared by non-magnetic magnesium doping to enhance its magnetic properties. The ferromagnetic and paramagnetic bismuth ferrate nanostructures were obtained. The Au/BFO/SRO heterojunction resistive structure is designed and fabricated. The bipolar resistive behavior with self-limiting characteristics and high reliability is obtained without electroforming operation. The effective control of the state of bismuth ferrate resistance is designed and realized. By setting different scanning voltage, external current limiting, scanning mode and so on, several effective storage states are obtained, and it is proved that it has multi-value storage ability. The resistance mechanism of bismuth ferrate material was analyzed from the aspects of electrode material, iron electrode and material defect. The results of electrical behavior and dependence of temperature and test atmosphere on the resistance mechanism of bismuth ferrate material were analyzed. The resistance mechanism of interface barrier and carrier transport characteristics regulated by iron electrode is proved. The competitive mechanism of iron electrode inversion and oxygen vacancy migration in the resistance behavior of bismuth ferrate is revealed. The key factors affecting the resistance of bismuth ferrate are obtained. In addition, based on the resistive model, the self-limiting characteristics and multi-value behavior are explained. The BFO/ZnO heterojunction resistive structure is designed and fabricated. The bistable high and low resistive switching characteristics and diode rectifying effect are obtained. The effects of film thickness and chemical doping of ferroelectric materials on the heterojunction resistance were studied. The physical model of BFO/ZnO heterojunction resistance was established and improved. The interface carrier depletion or accumulation state was regulated by polarization effect. The interface barrier between bismuth ferrate and zinc oxide was deduced by introducing iron electrode into the heterojunction energy band structure. The method of controlling the resistance of heterojunction by iron electrode and the key influencing factors were obtained.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ135.32;TP333
[Abstract]:Polyferric bismuth ferrate (BiFeO3,) is the only ferroelectric and ferromagnetic material at room temperature. It has excellent ferroelectric and magnetoelectric coupling properties. It is widely used in novel non-volatile memory devices and multifunctional sensing devices. Spin electronic devices, photovoltaic devices and other fields have a broad application prospects. Bismuth ferrite based resistive memory device combines the advantages of ferroelectric memory and resistive memory, and realizes the high and low resistance state switching, not the defect regulating the resistive behavior, through the inversion control interface barrier and carrier transport characteristics of iron electrode. Show unique advantages. In this thesis, two kinds of heterojunction structures, bismuth ferrate / metal and bismuth ferrate / semiconductor, are constructed around the structure of bismuth ferrate. The fabrication technology and the electrical resistance behavior of bismuth ferrate films and devices are studied. The resistance mechanism, physical model and main regulation factors of heterostructure are discussed. In this paper, high quality bismuth ferrite thin films with good ferroelectric properties were prepared on monocrystalline silicon and strontium titanate substrates by sol-gel method and pulsed laser deposition. By controlling the oxygen pressure and deposition temperature to reduce the defect and leakage path, dense, uniform, good ferroelectric properties and low leakage current density of bismuth ferrite thin films were obtained. At the same time, bismuth ferrate was doped by bimetallic ions to obtain bismuth ferrate material with certain ferromagnetism, and bismuth ferrate nanostructure was prepared by non-magnetic magnesium doping to enhance its magnetic properties. The ferromagnetic and paramagnetic bismuth ferrate nanostructures were obtained. The Au/BFO/SRO heterojunction resistive structure is designed and fabricated. The bipolar resistive behavior with self-limiting characteristics and high reliability is obtained without electroforming operation. The effective control of the state of bismuth ferrate resistance is designed and realized. By setting different scanning voltage, external current limiting, scanning mode and so on, several effective storage states are obtained, and it is proved that it has multi-value storage ability. The resistance mechanism of bismuth ferrate material was analyzed from the aspects of electrode material, iron electrode and material defect. The results of electrical behavior and dependence of temperature and test atmosphere on the resistance mechanism of bismuth ferrate material were analyzed. The resistance mechanism of interface barrier and carrier transport characteristics regulated by iron electrode is proved. The competitive mechanism of iron electrode inversion and oxygen vacancy migration in the resistance behavior of bismuth ferrate is revealed. The key factors affecting the resistance of bismuth ferrate are obtained. In addition, based on the resistive model, the self-limiting characteristics and multi-value behavior are explained. The BFO/ZnO heterojunction resistive structure is designed and fabricated. The bistable high and low resistive switching characteristics and diode rectifying effect are obtained. The effects of film thickness and chemical doping of ferroelectric materials on the heterojunction resistance were studied. The physical model of BFO/ZnO heterojunction resistance was established and improved. The interface carrier depletion or accumulation state was regulated by polarization effect. The interface barrier between bismuth ferrate and zinc oxide was deduced by introducing iron electrode into the heterojunction energy band structure. The method of controlling the resistance of heterojunction by iron electrode and the key influencing factors were obtained.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ135.32;TP333
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