忆阻器材料特性的第一性原理研究

发布时间：2018-07-02 22:39

本文选题：忆阻机理 + 材料模拟CuOx　；参考：《华中科技大学》2012年硕士论文

【摘要】：随着人们每天处理的信息量呈现出爆炸式增长，传统的存储器正面临前所未有的高速度、大容量及多样化需求的严峻挑战。忆阻器的出现给予了人们新的思路和曙光。忆阻器与传统的存储器相比，以其更高的速度、更大容量、低功耗等存储特性有望成为下一代信息存储器件。此外，，以其独特的非线性电路特性和电荷记忆特性有望实现储存与计算的融合、制备具有神经元突触功能的认知器件以及逻辑运算等。正是这些优点，使国内外科研机构和半导体厂商都视忆阻器为下一代新型电子智能存储器件。当前国内外对忆阻器的材料、器件及其应用等方面进行了一系列的研究。然而忆阻器的纳米尺度电输运机制的不确定，导致的忆阻器机理的认识存在严重的分歧，直接制约了忆阻器的研发与应用。根据忆阻材料特性，构建器件模型，采用理论计算探讨非线性阻变特性并不是很多。本研究基于密度泛函理论和能带结构理论，使用第一性原理和非平衡格林函数方法，提出一种忆阻材料模拟方案，并使用AtomistixToolKit（ATK）软件对忆阻材料进行电子特性计算模拟，分析忆阻材料纳米尺度下的电子输运机制，探讨忆阻器的非线性阻变机理。根据提出的忆阻材料模拟方案，分别对CuOx忆阻材料和硫系化合物忆阻材料进行计算模拟，构建Ag电极-CuOx和Ag电极-Ge2Sb2Te5双电极系统模型。进一步使用模型，利用ATK软件分别对Ag电极-CuOx和Ag电极-Ge2Sb2Te5两个双电极忆阻系统，进行忆阻材料电子特性计算模拟，结合计算模拟结果分析忆阻材料非线性电阻特性。除此之外，分别对CuOx忆阻材料的CuO和CuOx两种不同的双电极系统的I-V特性进行计算模拟，通过计算数据来分析CuOx忆阻器纳米尺度电子输运机理是由于电极与功能层的接触在电压的作用下由于边界迁移效应使得界面接触由欧姆接触逐渐改变为非欧姆接触。第三，对Ge2Sb2Te5忆阻材料进行Ag电极-Ge2Sb2Te5晶态与非晶态双电极系统I-V特性进行计算模拟，通过计算模拟得出Ge2Sb2Te5忆阻材料机理，由于存在Ge2Sb2Te5忆阻材料大量的空位，在发生缺陷效应下，以及Ag电极也渗透和掺杂在Ge2Sb2Te5空位中使得Ge2Sb2Te5忆阻材料呈现忆阻特性。本研究的忆阻器材料计算模拟方法和结论，为研究忆阻材料的机理提供了新的思路和重要理论参考。
[Abstract]:With the explosive growth of the amount of information that people process every day, the traditional memory is facing the severe challenge of unprecedented high speed, large capacity and diversified demand. The appearance of amnesia gives people a new way of thinking and dawn. Compared with the traditional memory, the memory device is expected to become the next generation information storage device with its higher speed, larger capacity and lower power consumption. In addition, because of its unique characteristics of nonlinear circuits and charge-memory, it is expected to realize the fusion of storage and computation, the fabrication of cognitive devices with synaptic function of neurons, and the logical operation. It is these advantages that make both domestic and foreign scientific research institutions and semiconductor manufacturers view amnesia as the next generation of electronic intelligent memory devices. At present, a series of research on materials, devices and applications of the resistive devices have been carried out at home and abroad. However, the uncertainty of nano-scale electrical transport mechanism leads to serious differences in the understanding of the mechanism, which directly restricts the research and development and application of the device. According to the characteristics of the resistive material, the device model is constructed, and the nonlinear resistance characteristics are not discussed by theoretical calculation. Based on density functional theory (DFT) and band structure theory (DFT) and using the first-principles and non-equilibrium Green's function method, this paper presents a simulation scheme for the memory materials, and uses Atomistix ToolKit (ATK) software to simulate the electronic properties of the materials. The mechanism of electron transport at nanometer scale is analyzed and the nonlinear resistance mechanism of the resistor is discussed. According to the proposed simulation scheme, the CuOx memristor and sulfur compound mnemonic material were calculated and simulated, respectively, and the model of Ag electrode -CuOx and Ag electrode -Ge2Sb2Te5 double electrode system was constructed. Further more, using ATK software to simulate the electronic characteristics of the two double electrode memory systems, Ag electrode -CuOx and Ag electrode -GE _ 2Sb _ 2TE _ 5, and to analyze the nonlinear resistance characteristics of the materials by combining the simulation results. In addition, the I-V characteristics of CuO and CuOx two-electrode systems are calculated and simulated respectively. The mechanism of nanoscale electron transport of CuOx amnesia is analyzed by calculating data. The interface contact is changed from ohmic contact to non-ohmic contact because of the contact between electrode and functional layer under the effect of voltage because of the boundary migration effect. Thirdly, the I-V characteristics of GE _ 2SB _ 2TE _ 5 crystal and amorphous two-electrode system are calculated and simulated. The mechanism of GE _ 2Sb _ 2TE _ 5 memory material is obtained by calculation and simulation. Due to the existence of a large number of vacancies in GE _ 2Sb _ 2TE _ 5 memristor material, the defect effect occurs. The Ag electrode also permeated and doped in the GE _ 2SB _ 2TE _ 5 vacancy, which made the GE _ 2SB _ 2TE _ 5 memristor exhibit the characteristics of amnesia. The method and conclusion of the material calculation and simulation in this paper provide a new way of thinking and important theoretical reference for studying the mechanism of the resistive material.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TP333

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