基于氧化锌薄膜的阻变极性研究

发布时间：2018-05-15 05:31

本文选题：阻变存储器 + 单极性阻变　；参考：《湘潭大学》2014年硕士论文

【摘要】：依赖于高速度、大容量、低功耗非挥发性存储器的信息技术正快速的发展。Flash存储是当前的主流，具有很高的容量，但速度慢并且逐渐接近尺寸可伸缩性的物理极限。为了未来信息存储的需要，新兴的非挥发性存储，如相变存储器(PRAM)、铁电存储器(FRAM)、磁变存储器(MRAM)及阻变存储器(RRAM)最近几年得到广泛的研究。在这些候选者中，阻变存储器具有出色的优点，如高响应速度、长保持性、多值存储和低功耗，以及更好的伸缩性和与传统的CMOS工艺相兼容；被认为是下一代非挥发性存储器的最佳候选者。许多的过渡金属氧化物，如ZnO、TiO2、ZrO2、MnO2、和NiO等具有可重复的阻变特性，其中，氧化锌被广泛的探索，，是因为其具有组份简单、清晰的转变特性、低的转变电压、较高的开关比值且通过不同的掺杂可调节其电学特性。本论文选择氧化锌阻变存储器为研究对象，利用溶胶-凝胶(Sol-Gel)法来制备不同掺杂的ZnO薄膜器件，主要探索了不同的器件结构和测试条件对其阻变极性的影响，具体工作内容概括如下： 1.采用不同的顶电极(Pt or Ag)，Metal/La-doped ZnO/Pt三明治结构被构造，单极性阻变行为和双极性阻变行为分别在Pt/La-doped ZnO/Pt和Ag/La-doped ZnO/Pt结构器件中获得。比起不掺杂的氧化锌器件(Pt/ZnO/Pt和Ag/ZnO/Pt)，镧掺杂的器件具有良好的阻变均一性，如狭窄分布的阻变参数、更高的开关比、更好的保持性和急剧的转变特性。进一步地我们制备了Pt/La-doped ZnO/ZnO or SrTiO3/Pt结构器件，其中ZnO和SrTiO3作为缓冲层，并且发现不同的阻变行为依赖于不同的缓冲层。稳定的单极和双极阻变行为可分别在具有ZnO和SrTiO3缓冲层的结构器件中展现。相比Pt/ZnLaO/Pt结构器件，通过嵌入缓冲层，器件展现出更加良好的阻变特性； 2.单极和双极模式的共存现象也在钒掺杂的氧化锌器件中观察到，在第一次电压扫描的过程两种模式可分别在不同的限制电流下被激活，0.1mA的限制电流下器件展现出可重复的双极阻变行为，10mA的限制电流下呈现出单极阻变行为；两种阻变模式之间的转变是可逆的，值得注意的是在这样的转变中可实现三种逻辑状态； 3.单极和双极模式的共存也在Pt/Zn0.99Zr0.01O/Pt结构器件中观察到，激活(Forming)过程之后，器件具有单极阻变行为，在Reset过程中若同向扫描测试器件呈现出单极阻变行为，若反向测试时则为双极阻变行为；对于双极性阻变模式，通过施加不同的限制电流或者不同的扫描电压范围可在器件的低、高阻态分别实现可控的多态阻值，类似的结果也在亚微米结构器件中被发现(200ns的脉冲测试下各个阻态分别可重复104次)。
[Abstract]:Information technology, which relies on high speed, large capacity, low power and non-volatile memory, is developing rapidly. Flash memory is the mainstream, with high capacity, but slow speed and approaching the physical limit of dimensional scalability. In order to meet the needs of future information storage, new non-volatile memory, such as phase change memory (PRAM), ferroelectric memory (FRAM), magnetic variable memory (MRAM) and resistive memory (RRAM), have been extensively studied in recent years. Among these candidates, resistive memory has excellent advantages, such as high response speed, long retention, multi-value storage and low power consumption, better scalability and compatibility with traditional CMOS processes; It is considered to be the best candidate for next generation non-volatile memory. Many transition metal oxides, such as ZnOOTiO2O2ZrO2MnO2and NiO, have repeatable resistance properties, among which zinc oxide has been extensively explored because of its simple composition, clear transition characteristics, low transition voltage, etc. The electrical properties can be adjusted with higher switching ratio and different doping. In this paper, zinc oxide resistive memory is chosen as the research object, and different doped ZnO thin film devices are fabricated by sol-gel method. The effects of different device structures and test conditions on the resistance polarity are mainly explored. Specific work can be summarized as follows: 1. Different top electrode Pt or Agna / Metal- / La-doped ZnO/Pt sandwich structures were constructed, and unipolar and bipolar resistive behaviors were obtained in Pt/La-doped ZnO/Pt and Ag/La-doped ZnO/Pt structures, respectively. Compared with undoped zinc oxide devices such as Pt / ZnO / Pt and Ag / ZnO / PT, lanthanum doped devices have good resistance uniformity, such as narrow distribution of resistive parameters, higher switching ratio, better retention and sharp transition characteristics. Furthermore, we have fabricated Pt/La-doped ZnO/ZnO or SrTiO3/Pt devices with ZnO and SrTiO3 as buffer layers, and it is found that different resistive behaviors depend on different buffer layers. Stable monopole and bipolar resistive behaviors can be demonstrated in structures with ZnO and SrTiO3 buffer layers, respectively. Compared with Pt/ZnLaO/Pt devices, the devices exhibit better resistive characteristics by embedding the buffer layer. 2. The coexistence of unipolar and bipolar modes is also observed in vanadium doped zinc oxide devices. In the process of the first voltage scan, the two modes can be activated under different limiting currents, respectively, and the devices exhibit repeatable bipolar resistive behavior at the limiting current of 0.1mA. The devices exhibit unipolar resistive behavior under the limited current of 10mA. The transition between the two resistance modes is reversible, and it is worth noting that three logical states can be realized in such a transition. 3. The coexistence of unipolar and bipolar modes is also observed in Pt/Zn0.99Zr0.01O/Pt structure devices. After activating the forming process, the devices exhibit unipolar resistive behavior, and the unipolar resistive behavior is observed in the Reset process if the device is tested in the same direction. For the bipolar resistance mode, the controllable polymorphic resistance can be achieved in the low and high resistance states by applying different limiting current or different scanning voltage range. Similar results have also been found in sub-micron devices with pulse measurements of 200 ns, each resistive state can be repeated 104 times respectively.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TP333;O484.4

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