Real-time X-ray Scattering Studies of Oxide Epitaxial Growth

氧化物外延生长的实时 X 射线散射研究

• 批准号: 1506930
• 负责人: Randall Headrick
• 金额: $ 48万
• 依托单位: University of Vermont & State Agricultural College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1506930&HistoricalAwards=false
• 关键词: Real; time; ray; Scattering; Studies

This project is jointly funded by the Electronic and Photonic Materials (EPM) and Ceramic (CER) Programs in the Division of Materials Research. NON-TECHNICAL DESCRIPTION: X-rays are an enormously powerful tool for the study of materials: they can measure structures down to atomic dimensions using diffraction because of their short wavelength, and they can reach inside materials because they are not strongly absorbed. Synchrotrons are the brightest sources of X-rays available to scientists. In this project, real-time X-ray scattering is used to study the growth of crystalline metal oxide thin films in a special film deposition chamber customized for installation at a synchrotron source. A movie of the X-ray scattering pattern from the growing surface as a function of time is used to learn about the atomic structure of the crystalline layers as they assemble from the vapor phase, which yields important insights in the quest to create new materials with improved or novel properties. Examples of useful properties include the ability to store an electrical charge via a relative shift of positive and negative ions in the crystal lattice (ferroelectric effect), or to produce an electrical voltage when deformed (piezoelectric effect). These effects, and several other more exotic effects can potentially be modified through growth of artificially-produced thin films (e.g., with alternating layers of two different materials, each only a few atoms thick). Due to their novel properties, metal oxides are significant in a number of applications, including electronic memories, detectors, actuators and energy harvesters. This project provides graduate student training in a highly interdisciplinary area, and it introduces undergraduate students to X-ray science and thin film deposition technology.TECHNICAL DETAILS: This project utilizes a new world-class synchrotron facility at Brookhaven National Laboratory (NSLS II) to carry out in situ time-resolved X-ray scattering studies of the evolution of surfaces, interfaces, and multilayers composed of oxide materials during thin film growth by pulsed laser deposition. Perovskite oxides exhibit an extraordinary variety of complex structural distortions and associated functional properties, which may also be continuously tunable through growth of non-equilibrium structures. However, realizing synthetic structures through the growth of epitaxial thin films and multilayers currently involves a time-consuming trial and error approach, which greatly limits the pace of progress towards new materials and devices. In situ synchrotron X-ray scattering provides the capability to generate reciprocal space maps in a matter of seconds. These maps provides real time information on the evolution of both in and out of plane lattice parameters, polar domain structure, surface roughness and surface termination, in a single snapshot, thus providing critical feedback on the relationship between growth process variables and the resulting atomic structure. This project also focuses on fundamental issues related to the role of impact-induced energetic processes in promoting the formation of planar interfaces, and how such processes can be controlled to produce improved materials. Specific atomic-scale mechanisms are being tested using in situ X-ray scattering to follow the dynamics of surfaces of oxide thin films during deposition. This project also provides an exciting possibility for graduate students to gain expertise in both thin film growth and characterization of materials by advanced methods, and for undergraduate students to participate in an interdisciplinary project involving university-national laboratory collaborations.

该项目由材料研究部的电子和光子材料（Electronic and Photonic Materials，简称EMPs）和陶瓷（Ceramic，简称CER）项目共同资助。非技术描述：X射线是研究材料的一种非常强大的工具：由于其波长短，它们可以使用衍射测量原子尺寸的结构，并且由于它们没有强烈吸收，它们可以到达材料内部。同步加速器是科学家可用的最亮的X射线源。在这个项目中，实时X射线散射被用来研究在一个特殊的薄膜沉积室安装在同步辐射源定制的结晶金属氧化物薄膜的生长。来自生长表面的X射线散射图案作为时间的函数的电影用于了解晶体层从气相组装时的原子结构，这在寻求创造具有改进或新颖特性的新材料方面产生了重要的见解。有用的性质的实例包括经由晶格中的正离子和负离子的相对移位来存储电荷的能力（铁电效应），或者当变形时产生电压的能力（压电效应）。这些效应和其他几种更奇特的效应可以通过人工产生的薄膜的生长（例如，具有两种不同材料的交替层，每种材料只有几个原子厚）。由于其新颖的性质，金属氧化物在许多应用中具有重要意义，包括电子存储器，探测器，致动器和能量采集器。该项目提供了一个高度跨学科领域的研究生培训，并向本科生介绍了X射线科学和薄膜沉积技术。该项目利用布鲁克海文国家实验室（NSLS II）的一个新的世界级同步加速器设施，对表面、界面、以及在通过脉冲激光沉积的薄膜生长期间由氧化物材料构成的多层。过氧化氢氧化物表现出非常多样的复杂结构扭曲和相关的功能特性，这也可以通过非平衡结构的生长来连续调节。然而，通过外延薄膜和多层膜的生长实现合成结构目前涉及耗时的试错方法，这极大地限制了新材料和器件的进展速度。原位同步加速器X射线散射提供了在几秒钟内生成倒易空间图的能力。这些地图提供了真实的时间信息的演变和平面晶格参数，极性域结构，表面粗糙度和表面终止，在一个单一的快照，从而提供关键的反馈之间的关系生长过程变量和所得的原子结构。该项目还侧重于与撞击引起的高能过程在促进平面界面形成方面的作用有关的基本问题，以及如何控制这些过程以生产改进的材料。正在使用原位X射线散射测试特定的原子尺度机制，以跟踪沉积过程中氧化物薄膜表面的动态变化。该项目还为研究生提供了一个令人兴奋的可能性，通过先进的方法获得薄膜生长和材料表征方面的专业知识，并为本科生提供了参与大学-国家实验室合作的跨学科项目的机会。