Dopant Distribution, Motion, and Electrochemical Transfer in Resistive Switching Heterostructures

技术：基于氧化物的异质结构（金属-氧化物-金属）中的电阻切换自 1960 年代以来就已为人所知，并且最近（自 2000 年以来）经历了商业和科学兴趣的爆炸式增长，特别是对于非易失性电阻变化随机存取存储器。电阻切换可以定义为材料或异质结构能够在至少两个随时间稳定的电阻值之间可逆地变化（在电刺激下）的过程。 大多数为解释电阻开关而提出的竞争机制都是定性的，并且只有间接的观察支持。然而，它们几乎都涉及通过离子运动在氧化物层中重新分布掺杂剂。该项目将以定量方式询问金属-氧化物-金属异质结构中的电势和氧分布，以量化氧化物内和金属-氧化物界面上的氧运动，并开发一个预测计算模型，捕获三个维度的切换过程的动力学方面。 所述综合研究和教育计划旨在理解、设计和生产适用于数据存储和逻辑器件的纳米级电阻开关。将研究异质结构内均匀离子重新分布可以定量表征并最终针对电阻切换进行优化的假设的测试。为此，该研究将确定卡内基梅隆大学设计和制造的附近氧气的分布，测量氧气交换率，并量化金属氧化物结和氧化物异质结附近的电势。将使用各种表征方法，包括二次离子质谱、电子全息术、扫描开尔文探针显微镜、扫描电化学显微镜、基于电容的方法和空间分辨二次离子质谱来询问离子的重新分布和转移。将开发一个多维连续级计算模型，描述电阻开关中的电化学转移和离子重新分布，该模型将通过适合未来应用的纳米级电阻开关金属-氧化物-金属器件的测试进行验证。非技术：该项目将为新型超高密度数据存储器件和可重构逻辑技术的器件设计和性能提供基础基础，从而产生广泛的社会影响。研究活动将影响多元化博士群体的教育。本科生通过：实验室和计算研究、高级选修课和二年级实验室模块。新的选修课程题为“缺陷相互作用：实现先进功能材料和设备”，将提供具体示例，说明缺陷相互作用（例如忆阻器界面附近/跨界面的点缺陷运动）如何充当先进设备的推动者，包括电阻开关、电池、燃料电池和高功率电子设备。实验室模块将在二年级核心材料科学课程“材料缺陷”中实施。它将向学生演示点缺陷在电化学材料中的行为方式。最后，PI 将在国际研究会议上组织电阻开关研究研讨会。

Technical: Resistive switching in oxide-based heterostructures (metal-oxide-metal) has been known since the 1960's and has experienced a recent (since 2000) explosion of commercial and scientific interest, particularly for nonvolatile resistance-change random access memories.Resistive switching can be defined as the process in which a material or heterostructure is able to reversibly change (under electrical stimulation) between at least two resistance values that are stable with time. Most of the competing mechanisms proposed to explain resistive switching are qualitative and have only indirect observational support. However, they nearly all involve the redistribution of dopants in the oxide layer through ion motion. The project will interrogate in a quantitative fashion the electrical potential and oxygen distribution in metal-oxide-metal heterostructures, to quantify the oxygen motion within the oxide and across the metal-oxide interface, and develop a predictive computational model that captures the kinetic aspects of the switching process in three dimensions. The integrated research and education program described aims to understand, design, and produce nanoscale resistive switches appropriate for data storage and logic devices. Testing of the hypotheses that uniform ion redistribution within a heterostructure can be quantitatively characterized and ultimately optimized for resistive switching will be studied. To do so the research will determine the distribution of oxygen near, measure the oxygen exchange rates across, and quantify the electrical potential near metal-oxide junctions and oxide heterojunctions, designed and fabricated at Carnegie Mellon. A variety of characterization methods, including secondary ion mass spectroscopy, electron holography, scanning Kelvin probe microscopy, scanning electrochemical microscopy, capacitance-based methods, and spatially resolved secondary ion mass spectroscopy to interrogate ion redistribution and transfer will be used. A multi-dimensional continuum level computational model will be developed that describes the electrochemical transfer and ion redistribution in the resistive switch, which will be verified by testing of nanoscale resistive switching metal-oxide-metal devices, appropriate for future applications.Non-Technical: This project will have a broad societal impact by providing the fundamental underpinnings to device design and performance in novel ultra-high density data storage devices and reconfigurable logic technologies. The research activities will impact the education of a diverse group of Ph.D. and Undergraduate students through: laboratory and computational research, an advanced elective course, and a sophomore-level laboratory module. The new elective course, entitled 'Defect Interactions: Enabling Advanced Functional Materials and Devices,' will provide concrete examples of how defect interactions (such point defect motion near / across interfaces in memristors) act as enablers in advanced devices, including resistive switches, batteries, fuel cells, and high power electronics. A laboratory module will be implemented in the sophomore level core materials science course 'Defects in Materials.' It will demonstrate to students how point defects behave in electrochemical materials. Finally, the PIs will organize a research symposium on resistive switching at an international research conference.