4D-STEM Ptychography for Electron-Beam-Sensitive Materials

Abstract

Recent advances in high-speed pixelated electron detectors have substantially facilitated the implementation of four-dimensional scanning transmission electron microscopy (4D-STEM). A critical application of 4D-STEM is electron ptychography, which reveals the atomic structure of a specimen by reconstructing its transmission function from redundant convergent-beam electron diffraction patterns. Although 4D-STEM ptychography offers many advantages over conventional imaging modes, this emerging technique has not been fully applied to materials highly sensitive to electron beams. In this Outlook, we introduce the fundamentals of 4D-STEM ptychography, focusing on data collection and processing methods, and present the current applications of 4D-STEM ptychography in various materials. Next, we discuss the potential advantages of imaging electron-beam-sensitive materials using 4D-STEM ptychography and explore its feasibility by performing simulations and experiments on a zeolite material. The preliminary results demonstrate that, at the low electron dose required to preserve the zeolite structure, 4D-STEM ptychography can reliably provide higher resolution and greater tolerance to the specimen thickness and probe defocus as compared to existing imaging techniques. In the final section, we discuss the challenges and possible strategies to further reduce the electron dose for 4D-STEM ptychography. If successful, it will be a game-changer for imaging extremely sensitive materials, such as metal−organic frameworks, hybrid halide perovskites, and supramolecular crystals.

Measuring and Manipulating Defect-induced Micro-electronic Fields at Metal-Support Interface

“…The center of mass (COM) was calculated according to the entire diffraction pattern of 4D datasets (Fig. S9) (44). COM contained the information of the shift in the center of the diffraction intensity at each point of the electron prob, covering the circle area with diameter of 0.6 Å.…”

Applications of Transmission Electron Microscopy in Phase Engineering of Nanomaterials

“…The 4D data set essentially captures all information carried by the transmitted electrons about the electron–matter interactions. An important application of 4D-STEM is electron ptychography, which reveals the structure of a specimen by reconstructing its transmission function from redundant convergent-beam electron diffraction (CBED) patterns in the 4D-STEM data set. ,− The reconstruction can be accomplished by using either iterative or noniterative algorithms. , …”

“…40,173−176 The reconstruction can be accomplished by using either iterative or noniterative algorithms. 175,177 Compared with conventional (S)TEM imaging modes, electron ptychography utilizing 4D-STEM data (referred to as 4D-STEM ptychography) offers several notable advantages. First, it can incorporate the multislice method and implement corrections for sample orientation, drift, scan instability, and other imperfections in the iterative reconstruction algorithm, leading to greater tolerance for specimen thickness and imaging conditions.…”

Three-dimensional inhomogeneity of zeolite structure and composition revealed by electron ptychography

“…Here, we demonstrate that electron ptychography (21)(22)(23)(24)(25)(26) can address these problems and achieve subangstrom resolution to resolve individual O atomic columns in various zeolites with specimen thicknesses up to ~40 nm, which has not been reported with other directimaging techniques. Electron ptychography is a coherent diffractive imaging method that uses a series of convergent-beam electron diffraction patterns, commonly referred to as four-dimensional STEM (4D-STEM) data, to generate high-resolution images.…”