Crystal Growth at the Nanoscale: New Phenomena Revealed by In situ X-ray Scattering

纳米级晶体生长：原位 X 射线散射揭示的新现象

• 批准号: 0706278
• 负责人: Paul Miceli
• 金额: $ 32.28万
• 依托单位: University of Missouri-Columbia
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-07-01 至 2011-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0706278&HistoricalAwards=false
• 关键词: Crystal; Growth; Nanoscale; New; Phenomena

Non-Technical AbstractWith new device technologies moving towards significantly smaller length-scales, the need for fundamental science to explore how atoms move and arrange themselves on surfaces is becoming imperative for understanding how materials grow. Although there has been significant recent progress towards understanding some of the mechanisms that dictate atomic assemblies on surfaces, the role of defects (meaning atoms that do not occupy expected positions) has been overlooked. Because defects can be initially incorporated at the surface and then become buried below it, conventional experimental tools which are sensitive only to the surface cannot see the defects. In addition, very small crystals (nanocrystals) are subject to new forces (quantum-mechanical forces) that have not been previously considered in theories of crystal growth. This individual investigator award will utilize a beam of x-rays from the Advanced Photon Source, which is the brightest source of x-rays in the United States, to probe, both, the surface and the subsurface structure as atoms are deposited onto a surface. It is expected that these experimental studies will lead to essential new insight to growth mechanisms and, thus, provide a comprehensive framework for understanding how materials grow at surfaces. The project will train and mentor graduate students and postdoctoral researchers as well as undergraduate students. The research activities at the Advanced Photon Source will enhance their educational experience while they will become part of a national resource of future scientists who can utilize these new state-of-the-art facilities.Technical AbstractThe main thrust of the project investigates new atomic-scale mechanisms that strongly affect the growth and evolution of nanocrystals and epitaxial films. Particular emphasis is given to elusive subsurface phenomena, which are uniquely addressed by in situ x-ray scattering. Experiments will be performed on simple "model" systems that lead to clear interpretations and the establishment of fundamental concepts. The subsurface sensitivity of in situ x-ray scattering enables new insight and solutions to problems that have eluded other surface sensitive techniques. It will be learned, at the atomic-scale, how defects become incorporated into a film, how these affect the subsequent growth once incorporated, and how defects relate to the evolving surface morphology. The new results will provide the foundation and a "stepping stone" for investigating more complex systems. These studies will also reveal how interfaces influence the growth of epitaxial nanocrystals and how the small crystal size is manifested in its growth kinetics. Exploring and exposing the novel growth kinetics of quantum size effect nanocrystals is expected to lead to a new conceptual framework for understanding these systems. The project will utilize the in situ surface scattering facility developed by the PI at the Advanced Photon Source (APS), where the high brightness of the x-ray source and the instrument design provide new capabilities that enable these studies. Because the project addresses fundamental issues that help understand how to manipulate nanomaterials, these studies will broadly impact emerging technologies that have important societal benefits such as computer, communication and medical technologies. Education and research are extensively integrated into the project, as it involves graduate students, postdocs and undergraduates. State-of-the-art infrastructure at the APS offers excellent training opportunities for students and postdocs.

随着新的设备技术朝着显著更小的长度尺度发展，探索原子如何在表面上移动和排列的基础科学的需求对于理解材料如何生长变得至关重要。 虽然最近在理解一些决定表面上原子组装的机制方面取得了重大进展，但缺陷（即未占据预期位置的原子）的作用一直被忽视。 由于缺陷最初可以在表面处结合，然后被埋在其下方，因此仅对表面敏感的常规实验工具无法看到缺陷。 此外，非常小的晶体（纳米晶体）受到以前在晶体生长理论中没有考虑过的新的力（量子力学力）的影响。 这项个人研究奖将利用先进光子源的X射线束，这是美国最亮的X射线源，探测原子沉积在表面上时的表面和次表面结构。 预计这些实验研究将导致对生长机制的重要新见解，从而为理解材料如何在表面生长提供全面的框架。 该项目将培训和指导研究生和博士后研究人员以及本科生。 在先进的光子源的研究活动将提高他们的教育经验，而他们将成为未来的科学家谁可以利用这些新的国家的最先进的facilities. Technical AbstractThe项目的主要推力国家资源的一部分调查新的原子尺度的机制，强烈影响纳米晶体和外延膜的生长和演变。 特别强调的是难以捉摸的地下现象，这是唯一解决的原位X射线散射。 实验将在简单的“模型”系统上进行，这些系统将导致清晰的解释和基本概念的建立。 原位X射线散射的次表面敏感性使人们能够对其他表面敏感技术所无法解决的问题有新的认识和解决方案。 它将学习，在原子尺度上，缺陷如何成为纳入一个电影，这些如何影响随后的增长，一旦纳入，以及如何缺陷涉及到不断变化的表面形态。 新的结果将为研究更复杂的系统提供基础和“垫脚石”。 这些研究还将揭示界面如何影响外延纳米晶体的生长以及小晶体尺寸如何在其生长动力学中表现出来。 探索和揭示量子尺寸效应纳米晶体的新生长动力学有望为理解这些系统提供一个新的概念框架。 该项目将利用PI在高级光子源（APS）开发的原位表面散射设施，其中X射线源的高亮度和仪器设计提供了实现这些研究的新功能。由于该项目解决了有助于理解如何操纵纳米材料的基本问题，这些研究将广泛影响具有重要社会效益的新兴技术，如计算机，通信和医疗技术。 教育和研究被广泛融入该项目，因为它涉及研究生，博士后和本科生。 APS最先进的基础设施为学生和博士后提供了极好的培训机会。