CAREER: Towards rational design and control of oxygen migration in oxide thin films for nano-ionic technologies

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。信息存储和数据处理传统上依赖于在不同材料之间来回移动电子。相比之下，一些新兴技术依赖于将氧离子移进移出薄材料，通过改变材料的化学性质来改变它们的特性，比如电阻或磁性。后一种方法的预期优势包括更高的能源效率、更长的信息存储寿命，以及支持量子计算等新计算方法的能力。然而，准确测量极薄薄膜中的氧扩散仍然具有挑战性，并且在我们理解不同材料如何阻碍或促进小长度尺度上氧离子运动的能力方面造成瓶颈。这个CAREER项目由材料研究部的陶瓷项目支持，通过开发一种新的测量技术来解决这一瓶颈，该技术可以精确测量通过不同薄膜堆叠的氧迁移，并从中提取有关每层及其之间界面产生的氧迁移障碍的信息。然后，这些知识可以用于设计基于离子运动的技术，其精度与今天基于硅的电子产品相同。此外，该计划的教育推广部分创建了低成本的活动工具包和免费培训视频，以帮助K-12教师向学生介绍材料科学概念，并教他们一些关键的电子设备。这些工具包由免费的在线视频提供支持，这些视频强化了活动概念，并将它们与正在进行的研究联系起来。这样的经历有助于培养一批热情的年轻科学家，他们对材料科学原理有初步的了解，并知道如何利用这些知识创造更环保的技术。控制薄膜异质结构中的纳米级氧迁移对于利用在下一代信息技术中发现的强相关氧化物材料中的独特功能特性非常重要。作为改善氧化膜中离子迁移控制的一步，这个由材料研究部陶瓷项目支持的CAREER项目，在纳米级离子扩散领域创造了新的测量能力和知识。具体来说，该程序开发了一种新的原位散射方法来量化氧浓度分布，并从不同的异质结构几何形状中提取定量扩散系数和活化能。将这种方法与薄膜工程技术相结合，可以隔离异质结构设计元素（例如，应变、层厚度、层堆叠）之间的单个结构-性质关系，以及它们对钙钛矿原型结构中氧迁移的影响。通过将这些空间分辨散射研究与温度相关的阻抗光谱相结合，这项工作提供了对在各种异质结构设计和温度制度下工作的主动扩散机制的见解。与这些研究工作相结合的是一项教育计划，该计划创建并分发旨在支持州学习标准的电子材料活动工具包，并由外行观众视频数据库提供支持，这些视频将每个活动的核心思想与正在进行的研究联系起来。参与该项目的研究生将在电子材料合成、最先进的表征方法以及与各种受众的科学交流方面获得经验。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).PART 1: NON-TECHNICAL SUMMARYInformation storage and data processing has traditionally relied on moving electrons back and forth between different materials. In contrast, several emerging technologies rely on moving oxygen ions in and out of thin materials to change their properties, like electrical resistance or magnetism, by changing the materials chemistry. The expected advantages of this latter approach include greater energy efficiency, longer information storage lifetimes, and the ability to support new computing approaches like quantum computing. However, accurately measuring oxygen diffusion in very thin films remains challenging and creates a bottleneck in our ability to understand how different materials hinder or facilitate oxygen ion movement at small length scales. This CAREER project, supported by the Ceramics program in the Division of Materials Research, addresses this bottleneck by developing a new measurement technique to accurately measure oxygen migration through stacks of different thin films and from that extract information about the barrier to oxygen migration created by each layer and the interfaces between them. This knowledge can then be used to design technologies based on ion motion with the same precision that enables silicon-based electronics today. In addition, the educational outreach component of this program creates low-cost activity kits and free training videos to help K-12 teachers introduce students to materials science concepts and teach them about several key electronic devices. These kits are supported by free online videos that reinforce the activity concepts and connect them to ongoing research. Such experiences help create a pipeline of enthusiastic young scientists with an early knowledge of materials science principles and how they can be used to create greener technologies. PART 2: TECHNICAL SUMMARY Controlling nanoscale oxygen migration in thin film heterostructures is important to harnessing the unique functional properties found in strongly correlated oxide materials for the next generation of information technologies. As a step towards improved ionic migration control in oxide films, this CAREER project, supported by the Ceramics program in the Division of Materials Research, creates new measurement capabilities and knowledge in the field of nanoscale ion diffusion. Specifically, this program develops a new in-situ scattering approach to quantify oxygen concentration profiles and extract quantitative diffusion coefficients and activation energies from different heterostructure geometries. Combining this approach with thin film engineering techniques enables the isolation of individual structure-property relationships between elements of the heterostructure design (e.g., strain, layer thickness, layer stacking) and their effect on oxygen migration in prototypical perovskite structures. By coupling these spatially resolved scattering studies with temperature-dependent impedance spectroscopy, this work provides insight into the active diffusion mechanism(s) operative in various heterostructure designs and temperature regimes. In conjunction with these research efforts is an educational plan that creates and distributes electronic materials activity kits designed to support state learning standards and are themselves supported by a database of lay-audience videos connecting core ideas from each activity to ongoing research. Graduate students engaged with the project gain experience in electronic materials synthesis, state-of-the-art characterization methodologies, and scientific communication to a variety of audiences.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.