Si Gao, Fucai Zhang, AI Kirkland, Xiaoqing Pan, Peng Wang，“Electron Ptychography: From 2D to 3D Reconstructions”，Microscopy and Microanalysis 23 (S1), 346-347（2017）

【原文】

Electron Ptychography: From 2D to 3D Reconstructions

ABSTRACT

Transmission electron microscopy (TEM) is a powerful tool for material science characterisation due to its high spatial resolution. Coherent diffraction imaging (CDI) [1] is a "lensless" method that forms an image of an object by solving the phase problem from a single diffraction pattern with an iterative phasing algorithm. This approach can, in principle, overcome the current image resolution limiting factors and ultimately achieve wavelength-limited resolution. However, conventional CDI experiments require isolated samples and a priori knowledge about the sample shape or extent. Maiden and Rodenburg suggested an extended ptychographical iterative engine (ePIE), which does not need this prior information and overcomes many of the other issues of CDI, such as convergence stagnation and limited field of view. Recently, two-dimensional (2D) ptychographical reconstructions at atomic lateral resolution [2] have been achieved using ePIE [3] on a CeO2 nanoparticle. However, when the sample becomes thicker, the multiplicative assumption of electron-sample interaction becomes invalid causing the ptychographical reconstruction to breakdown. To overcome this limitation, Maiden et al. incorporated the well-known multiple slice solution to multiple scattering into the ePIE algorithm (3PIE) [4]. In this approach the sample is split into axial sections, to produce 3D optically sectioned images of the sample. This 3D multiple-section reconstruction of ptychography has been successfully demonstrated with both light [4] and X-ray [5] optics recently. However, this method is still a challenge for use with the electrons.