Calibration of High-Resolution X-Ray Tomography With Atomic Force Microscopy.
Calibration of High-Resolution X-Ray Tomography With Atomic Force Microscopy.
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DOI：
10.6028/jres.105.067
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发表时间：
2000-11
影响因子：
1.5
通讯作者：
Fu J
中科院分区：
文献类型：
--
作者：
Kalukin AR;Winn B;Wang Y;Jacobsen C;Levine ZH;Fu J
对于薄膜的二维X射线成像，扫描透射式X射线显微镜(STXM)技术近年来已经获得了特征尺寸为40 nm的图像。然而，在科学文献中还没有描述在该尺度上使用STXM数据产生的三维断层图像的校准，并且校准过程具有在更大尺度上进行的X射线断层扫描所未遇到的新问题。例如，在X射线微层析成像中，人们总是可以选择在物体的一段上使用光学成像来验证X射线投影测量；另一方面，在STXM中，样品特征太小，无法通过光学波长的光来分辨。这一事实意味着必须依靠更高分辨率的程序来进行校准，例如原子力显微镜(AFM)。然而，这种程序通常依赖于对样品进行高度破坏性的切片，并且很难解释，因为它们提供的是表面信息而不是深度信息。在这篇文章中，描述了一种校准过程，克服了这些限制，实现了STXM断层图像与AFM图像和同一对象的扫描电子显微镜图像的校准。用扫描透射式X射线显微镜在同步加速器上对Ge星形图案进行成像。19个200×200像素的高分辨率投影图像被层析重建为三维图像。二维图像中小到40 nm的特征和三维重建中小到80 nm的特征被分辨出来。基于原子力显微镜、扫描电子显微镜、X射线透射率和断层重建的横向长度尺度在10纳米内一致。在样品中心，由投影图像计算的图形厚度为(51±15)nm对(80±52)nm，其中不确定度以两个标准差的水平评估。
For two-dimensional x-ray imaging of thin films, the technique of scanning transmission x-ray microscopy (STXM) has achieved images with feature sizes as small as 40 nm in recent years. However, calibration of three-dimensional tomographic images that are produced with STXM data at this scale has not yet been described in the scientific literature, and the calibration procedure has novel problems that have not been encountered by x-ray tomography carried out at a larger scale. In x-ray microtomography, for example, one always has the option of using optical imaging on a section of the object to verify the x-ray projection measurements; with STXM, on the other hand, the sample features are too small to be resolved by light at optical wavelengths. This fact implies that one must rely on procedures with higher resolution, such as atomic force microscopy (AFM), for the calibration. Such procedures, however, generally depend on a highly destructive sectioning of the sample, and are difficult to interpret because they give surface information rather than depth information. In this article, a procedure for calibration is described that overcomes these limitations and achieves a calibration of an STXM tomography image with an AFM image and a scanning electron microscopy image of the same object. A Ge star-shaped pattern was imaged at a synchrotron with a scanning transmission x-ray microscope. Nineteen high-resolution projection images of 200 × 200 pixels were tomographically reconstructed into a three-dimensional image. Features in two-dimensional images as small as 40 nm and features as small as 80 nm in the three-dimensional reconstruction were resolved. Transverse length scales based on atomic force microscopy, scanning electron microscopy, x-ray transmission and tomographic reconstruction agreed to within 10 nm. Toward the center of the sample, the pattern thickness calculated from projection images was (51 ± 15) nm vs (80 ± 52) nm for tomographic reconstruction, where the uncertainties are evaluated at the level of two standard deviations.