Coherent Surface X-ray Diffraction

9876610Robinson在这个项目中，一种称为相干X射线衍射（CXD）的新技术将得到进一步发展，并应用于表面和界面的研究。 CXD作为静态结构的探针在一个非常精细的长度尺度上的潜在应用将首先被追求。 这些实验将使用来自阿贡国家实验室先进光子源（APS）的波荡器辐射。 CXD的时间依赖对应物，称为X射线光子相关光谱（XPCS）将被应用于通过分子束和化学气相沉积方法在Si和Ge表面生长的研究，以了解生长不稳定性如何导致生长材料中的缺陷。 这项工作的总体目标是通过测量简单的二维系统，如畴结构PMN和GeSi的静态散斑来促进对相干衍射过程的理解。一个长期的目标是调查的热波动的表面平衡的XPCS方法，以获得更好的定量了解的一般热力学原理，支配的表面的行为。 最近发明的一种称为相干X射线衍射的方法被发现在表面和界面的研究中有重要的应用。 该方法是非常敏感的硅晶片的粗糙度在一个非常精细的规模。 提出了一种新的数学方法，从实验数据中得到表面形貌或埋置界面的图像，其分辨率超过一个有用的长度尺度。 这种成像方法可以取代目前通过扫描触针方法成像表面形貌的实践。 探索性研究将在阿贡国家实验室的先进光源上进行，并将为表面研究的灵敏度建立新的基准。 除了提高对相干X射线衍射方法本身的理解外，这项研究的结果将对半导体和纳米结构的未来技术产生重要影响。 这项研究将为研究生和博士后研究人员提供培训，这将是在21世纪世纪的未来几十年非常重要的技术领域。

9876610RobinsonIn this project a new technique called Coherent X-ray diffraction (CXD) will be further developed and applied to the study of surfaces and interfaces. Potential applications of CXD as a probe of static structure on a very fine length scale will be pursued first. The experiments will use the undulator radiation from the Advanced Photon Source (APS) at the Argonne National Laboratory. The time dependent counterpart of CXD, called X-ray Photon Correlation Spectroscopy (XPCS) will be applied to the study of growth at surfaces of Si and Ge by molecular-beam and chemical-vapor deposition methods in order to understand how growth instabilities arise that lead to defects in the grown material. The overall goals of the work are to advance the understanding of the coherent diffraction process by measuring static speckle from simple two dimensional systems, such as domain structures PMN and GeSi. A long term goal is the investigation of thermal fluctuations of surfaces in equilibrium with the XPCS method in order to obtain a better quantitative understanding of the general thermodynamic principles that govern the behavior of surfaces. %%% A recently invented method called Coherent X-ray Diffraction was found to have important applications to the study of surfaces and interfaces. The method is very sensitive to the roughness of silicon wafers on an extremely fine scale. A new mathematical method was developed to yield from the experimental data the image of the surface topography, or of a buried interface, with a resolution over a useful length scale. This imaging method may supercede the current practice of imaging the surface topography by scanning stylus methods. The exploratory research will be performed on the Advanced Light Source of the Argonne National Laboratory and will establish a new benchmark for the sensitivity for surface studies. In addition to improving the understanding of the coherent X-ray diffraction method itself, the results of this research will have important bearings on the future technology of semiconductors and nano-structures. This research will provide training to graduate students and postdoctoral research associates in an area of technology which will be of great importance during the next several decades of the 21st Century.***