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

x射线是探索材料的有力工具，由于其波长短，并且能够穿透材料而没有强吸收，因此能够通过衍射测量原子结构。在x射线源中，同步加速器是最亮的。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能，金属氧化物以其卓越的电和磁性能而闻名。研究人员的目标是通过密切研究这些材料的生长过程，特别是薄膜，来揭示这些材料的全部潜力。薄膜可以产生明显不同的性质，这些性质是由薄膜产生的大块母体化合物产生的。通过不断捕捉生长过程中不断变化的x射线散射模式，研究小组深入了解了晶体层从气相组装时的原子结构。这种理解对于创造具有增强或全新性能的创新材料至关重要，包括通过晶格中正离子和负离子的移动（铁电效应）存储电荷的能力，或在变形时产生电压（压电效应）。这样的效果，以及其他更奇特的效果，可以通过人工制造的薄膜的生长来定制，比如两种不同材料的交替层，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得到了应用。除了科学影响之外，该项目还为研究生提供实践培训，并让本科生参与前沿研究，在教育和多样性方面发挥着至关重要的作用。本项目探讨了围绕生长过程对金属氧化物薄膜结构、界面和功能特性的影响的基本问题。超越了获得高质量薄膜的传统目标，重点是发现独特的生长模式和界面，这些模式和界面可能导致与大块母体化合物中观察到的性质显著不同。该项目整合了铁电薄膜的互补测量，在合成、结构表征和所得材料特性之间建立反馈回路，允许与传统材料的基线特性进行比较。研究计划包括三个重点：1)原位研究脉冲激光外延（PLE）过程，揭示具有不同表面扩散速率的单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、偏压和开关行为；3)动态探索铁电超晶格中极化和畴结构作为薄膜厚度、静电和应变边界条件的函数。利用相干x射线散射方法，该项目旨在探测其他方法难以获得的时空相关性，从而为该领域的智力深度做出重大贡献。该项目由陶瓷项目和促进竞争研究的既定项目（EPSCoR）共同资助。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。

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.