In-situ X-ray Scattering Studies of Oxide Epitaxial Growth Kinetics and Dynamics

第一部分： X射线是探测材料的有力工具，由于其短波长和穿透材料而没有强吸收的能力，能够通过衍射测量原子结构。在X射线源中，同步加速器是科学家可用的最亮的光源。该项目采用实时X射线散射来研究金属氧化物的结构和性质，金属氧化物以其显着的电和磁特性而闻名。研究人员的目标是通过仔细研究这些材料的生长过程来揭示它们的全部潜力，特别关注薄膜。薄膜可能会产生显着不同的性质，在散装母体化合物的薄膜衍生。通过在生长过程中不断捕获不断变化的X射线散射模式，该团队可以深入了解晶体层从气相组装时的原子结构。这种理解在创造具有增强或全新特性的创新材料方面至关重要，包括通过晶格中正负离子的移动（铁电效应）存储电荷或在变形下产生电压（压电效应）的能力。这种效应，沿着其他更奇特的效应，可以通过人工制造的薄膜生长来调整，比如那些由两种不同材料交替层组成的薄膜，每层只有几个原子厚。金属氧化物的独特性质在电子存储器、探测器、致动器和能量收集器中找到了应用。除了其科学影响，该项目通过为研究生提供实践培训并让本科生参与尖端研究，在教育和多样性方面发挥着至关重要的作用。第二部分： 本项目探讨了生长过程对金属氧化物薄膜的结构、界面和功能特性的影响的基本问题。超越了实现高质量薄膜的传统目标，重点是揭示独特的生长模式和界面，可能导致性能显着偏离那些观察到的散装母体化合物。该项目集成了铁电薄膜的互补测量，以建立合成，结构表征和所得材料特性之间的反馈回路，从而可以与传统材料的基线特性进行比较。研究计划包括三个主要目标：1）在脉冲激光外延（PLE）中的过程的原位研究，以揭示具有不同表面扩散速率的各个物种对生长的作用，2）调整铁电薄膜的组成以设计畴取向、偏置和开关行为，（3）铁电超晶格中极化和畴结构随薄膜厚度、静电和应变边界条件的动态变化。利用相干X射线散射方法，该项目旨在探索时空相关性，这是不容易通过其他手段，该项目由陶瓷计划和刺激竞争研究的既定计划（EPSCoR）共同资助。该奖项反映了NSF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。

PART 1: NON-TECHNICAL SUMMARYX-rays are a powerful tool for exploring materials, capable of measuring atomic structures through diffraction owing to their short wavelength and their ability to penetrate materials without strong absorption. Synchrotrons, among X-ray sources, stand out as the brightest available to scientists. This project employs real-time X-ray scattering to investigate the structure and properties of metal oxides, known for their remarkable electrical and magnetic properties. The researchers aim to unveil the full potential of these materials by closely studying their growth processes, with a specific focus on thin films. Thin films could give rise to properties significantly different to those in the bulk parent compounds from which the films derive. By continuously capturing an evolving X-ray scattering pattern during growth, the team gains insights into the atomic structure of crystalline layers as they assemble from the vapor phase. This understanding is pivotal in creating innovative materials with enhanced or entirely new properties, including the ability to store an electrical charge via a shift in positive and negative ions in the crystal lattice (ferroelectric effect) or generate electrical voltage under deformation (piezoelectric effect). Such effects, along with other more exotic ones, can be tailored through the growth of artificially produced thin films, such as those with alternating layers of two different materials, each only a few atoms thick. The unique properties of metal oxides find applications in electronic memories, detectors, actuators, and energy harvesters. Beyond its scientific impact, the project plays a crucial role in education and diversity by offering hands-on training to graduate students and involving undergraduates in cutting-edge research. PART 2: TECHNICAL SUMMARY This project explores fundamental questions surrounding the influence of growth processes on the structure, interfaces, and functional properties of metal oxide thin films. Going beyond the conventional goal of achieving high-quality films, the focus is on uncovering unique growth modes and interfaces that could lead to properties significantly divergent from those observed in the bulk parent compounds. The project integrates complementary measurements of ferroelectric films to establish a feedback loop between synthesis, structural characterization, and resulting material properties, allowing for comparisons with baseline properties of conventional materials. The research plan includes three key pursuits: 1) In-situ study of processes in Pulsed Laser Epitaxy (PLE) to unveil the roles of individual species with disparate surface diffusion rates on growth, 2) Tuning the composition of ferroelectric thin films to engineer domain orientation, bias, and switching behavior, and 3) Dynamic exploration of polarization and domain structure in ferroelectric superlattices as a function of thin film thickness and electrostatic and strain boundary conditions. Utilizing coherent X-ray scattering methods, the project aims to probe spatiotemporal correlations that are not readily accessible by other means, thereby contributing significantly to the intellectual depth of the field.This project is jointly funded by Ceramics Program and the Established Program to Stimulate Competitive Research (EPSCoR).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.