Thermal mapping of current density in filamentary switching devices

非技术描述：信息在半导体存储器件中的存储和信息在处理单元中的传输是信息处理速度和效率不断提高的两大障碍。解决这些障碍的最有希望的方法之一是使用忆阻器，即具有记忆的电阻。一般认为，电阻变化是由器件材料中离子的再分配引起的。这个项目的重点是回答有关离子运动的驱动力、运动速度和所需温度的基本问题。该项目的第二个目标是发展实验技术来测量偏压下纳米级器件的温度分布。该项目为薄膜和电子设备加工领域的本科生和研究生提供培训机会，并有助于在国民经济的一个重要领域对劳动力进行教育。拓展活动以高中生为目标，鼓励他们从事半导体技术方面的职业。技术描述：项目目标是识别两种类型的电阻开关结构：阈值开关和存储开关的工作机制。这两种器件类型形成一个小直径的导电灯丝，要么是挥发性的，要么是非挥发性的。对于电阻开关中灯丝的形成，提出了两种模型：(1)基于热泳动引起的横向运动；(2)基于氧离子与阳极的垂直运动和交换。所提出的阈值开关的机制包括载流子注入、材料的局部加热、热载流子的产生和二次金属相的成核。卡内基梅隆大学的研究小组将使用扫描热显微镜和扫描焦耳膨胀显微镜测量外加电压下结构中的温度分布，提取灯丝尺寸及其随偏压条件的变化，并通过高角环形暗场和x射线能量色散光谱绘制局部成分变化图。由于温度分布是不同模型的区别特征，因此结果将识别运行机制。该项目的最终目标是建立一个涉及阻力变化的过程的预测和定量模型。研究结果有望成为重要的新电子设备技术的基础，有可能彻底改变非易失性高密度存储器领域。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical description: Storing the information in semiconductor memory devices and transferring it to and from the processing unit are the two major roadblocks in continued increase of information processing speed and efficiency. One of the most promising ways to address these roadblocks is to employ memristors i.e., resistors with memory. It is generally agreed that resistance change is caused by redistribution of ions in the device material. This project is focused on answering fundamental questions concerning the driving forces of ion motion, the speed of motion, and the temperature necessary for it. A secondary goal of the project is the development of experimental technique to measure the temperature distribution in nanoscale devices under bias. The project provides opportunities for training of undergraduate and graduate students in areas of processing of thin films and electronic devices and contributes to education of the workforce in an important area of the national economy. Outreach activities target high school students to encourage them to pursue careers in semiconductor technology.Technical description:The project targets identification of the operating mechanisms in two types of resistive switching structures: threshold and memory switches. Both device types form a small diameter conducting filament that is either volatile or non-volatile. Two models have been proposed for formation of the filament in resistive switches (i) based on lateral motion induced by thermophoresis and (ii) vertical motion and exchange of oxygen ions with the anode. The proposed mechanisms for threshold switches include carrier injection, local heating of the material, creating of hot carriers, and nucleation of a secondary metallic phase. The Carnegie Mellon team is going to use Scanning Thermal Microscopy and Scanning Joule Expansion Microscopy to measure the temperature distribution in structures with applied voltage, extract the filament size, and its changes with biasing conditions and map the local changes of composition by High Angle Annular Dark Field and X-Ray Energy Dispersive Spectroscopy. Since the temperature distribution is the distinguishing characteristics of different models, the results will identify the operating mechanism. The final goal of the project is building a predictive and quantitative model of processes involved the resistance change. Results are expected to form fundamental underpinnings of the important new electronic device technology that potentially can revolutionize the field of non-volatile high-density memories.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.