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电子与光子材料（EPM）和陶瓷（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：由于波长短，x射线可以通过衍射测量小到原子尺寸的结构，并且由于不被强烈吸收，x射线可以到达材料内部。同步加速器是科学家所能获得的最亮的x射线源。在这个项目中，实时x射线散射用于研究晶体金属氧化物薄膜在一个为同步加速器源定制的特殊薄膜沉积室中的生长。生长表面的x射线散射模式作为时间函数的电影用于了解晶体层从气相组装时的原子结构，这对于寻求创造具有改进或新颖性能的新材料具有重要的见解。有用特性的例子包括通过晶格中正离子和负离子的相对位移来存储电荷的能力（铁电效应），或者在变形时产生电压（压电效应）。这些效应和其他一些更奇特的效应可以通过人工制造的薄膜（例如，两种不同材料的交替层，每层只有几个原子厚）的生长来潜在地改变。由于其新颖的特性，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，致动器和能量收集器。该项目在一个高度跨学科的领域培养研究生，并向本科生介绍x射线科学和薄膜沉积技术。技术细节：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备，对脉冲激光沉积薄膜生长过程中由氧化物材料组成的表面、界面和多层的演变进行现场时间分辨x射线散射研究。钙钛矿氧化物表现出各种复杂的结构扭曲和相关的功能特性，这些特性也可以通过非平衡结构的生长而连续调节。然而，通过外延薄膜和多层膜的生长来实现合成结构目前涉及一个耗时的试错方法，这极大地限制了新材料和新器件的进展速度。原位同步加速器x射线散射提供了在几秒钟内生成互反空间图的能力。这些图在单个快照中提供了平面内外晶格参数、极性畴结构、表面粗糙度和表面终止的实时演化信息，从而提供了生长过程变量与所得原子结构之间关系的关键反馈。该项目还关注与碰撞诱导的能量过程在促进平面界面形成中的作用相关的基本问题，以及如何控制这些过程以产生改进的材料。特定的原子尺度机制正在被测试，使用原位x射线散射来跟踪氧化薄膜在沉积过程中表面的动力学。该项目还为研究生提供了一个令人兴奋的可能性，使他们能够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涉及大学-国家实验室合作的跨学科项目的机会。