Three-Dimensional Coherent X-Ray Diffraction Microscopy
Three-Dimensional Coherent X-Ray Diffraction Microscopy
复制标题
三维相干 X 射线衍射显微镜
作者：
I. Robinson;J. Miao
X射线因其显著的穿透能力而被广泛应用于材料的结构分析，至少在大多数材料的粒度的长度尺度上是如此。原则上，这允许对材料的块状属性进行完全的三维表征。与电子显微镜相比，X射线衍射法的主要优点之一是通常可以避免用破坏性的样品制备方法来制作薄片。与电子显微镜相比，X射线衍射的一个主要缺点是它不能产生被研究材料的真实空间图像--根本没有合适的透镜可用。随着透镜的发展，X射线显微镜已经取得了重大进展，通常基于波带片、Kirkpatrick-Baez镜或复合折射透镜。这些技术远远落后于电子光学的发展，特别是在获得高分辨率所需的大倍率方面。在这篇文章中，作者报告了另一种通用成像方法的发展进展，即通过计算方法直接反演衍射图。通过完全避免使用物镜，该技术没有限制分辨率的像差，并且对于样品的辐射损伤可以非常有效。它可以充分利用X射线穿透带来的三维能力。反演步使用基于过采样的计算方法来获得绕射相位问题的一般解。
X-rays have been widely used in the structural analysis of materials because of their significant penetration ability, at least on the length scale of the granularity of most materials. This allows, in principle, for fully three-dimensional characterization of the bulk properties of a material. One of the main advantages of x-ray diffraction over electron microscopy is that destructive sample preparation to create thin sections is often avoidable. A major disadvantage of x-ray diffraction with respect to electron microscopy is its inability to produce real-space images of the materials under investigation—there are simply no suitable lenses available. There has been significant progress in x-ray microscopy associated with the development of lenses, usually based on zone plates, Kirkpatrick–Baez mirrors, or compound refractive lenses. These technologies are far behind the development of electron optics, particularly for the large magnification ratios needed to attain high resolution. In this article, the authors report progress toward the development of an alternative general approach to imaging, the direct inversion of diffraction patterns by computation methods. By avoiding the use of an objective lens altogether, the technique is free from aberrations that limit the resolution, and it can be highly efficient with respect to radiation damage of the samples. It can take full advantage of the three-dimensional capability that comes from the x-ray penetration. The inversion step employs computational methods based on oversampling to obtain a general solution of the diffraction phase problem.