Four-Dimensional Scanning Transmission Electron Microscopy (4D-STEM): From Scanning Nanodiffraction to Ptychography and Beyond

Abstract

Scanning transmission electron microscopy (STEM) is widely used for imaging, diffraction, and spectroscopy of materials down to atomic resolution. Recent advances in detector technology and computational methods have enabled many experiments that record a full image of the STEM probe for many probe positions, either in diffraction space or real space. In this paper, we review the use of these four-dimensional STEM experiments for virtual diffraction imaging, phase, orientation and strain mapping, measurements of medium-range order, thickness and tilt of samples, and phase contrast imaging methods, including differential phase contrast, ptychography, and others.

Patterned probes for high precision 4D-STEM bragg measurements

“…In scanning transmission electron microscopy (STEM), a converged electron probe is rastered across the sample, and some of the scattered electrons (usually those scattered incoherently by thermal diffuse scattering) are measured to assign a value to each pixel [11]. Modern electron detector technology allows the full scattering pattern at each STEM probe position to be recorded, an experiment referred to as four-dimensional scanning transmission electron microscopy (4D-STEM) [12]. This method, also referred to as scanning electron nanodiffraction (SEND) or nanobeam electron diffraction (NBED), has been used in analyses of crystal orientation [13][14][15], local ordering of glassy states [16], sample thickness [17,18], and other analyses as described in a recent review [12].…”

Serial protein crystallography in an electron microscope

“…It is moreover not only limited to proteins but encompasses all nanocrystalline compounds, such as pharmaceuticals 47,48 or porous materials 23,49,50 . Augmenting parallel-beam crystallography with coherent scanning diffraction techniques such as coherent nano-area diffraction, convergent-beam diffraction or low-dose ptychography might be a viable way to obtain Bragg reflection phase information 51,52 . Finally, integrating the serial acquisition approach with emerging methods of in-situ and time-resolved electron microscopy 53,54 may open up avenues for structural dynamics studies on beam-sensitive systems.…”

Functional Materials Under Stress: In Situ TEM Observations of Structural Evolution

“…4D-STEM is a diffraction based technique that has the potential to combine high spatial resolution (∼1nm) with a large field of view (∼1µm) [42,43,45] . To acquire a 4D-STEM dataset, one needs to work in the STEM mode, where the electron probe scans through the area of interest and the diffraction pattern is recorded at each scanning position.…”

“…Therefore, atomic-scale features and defects can be directly observed during in-situ STEM experiments [40,41] . As an emerging data-intensive STEM technique, nano-beam electron diffraction (NBED, also called 4D-STEM) combines the benefits of a finelyfocused electron probe and the information-rich diffraction patterns [42][43][44][45] . Direct electron detector (DED) cameras can operate at thousands of frames per second, enabling time-resolved in-situ 4D-STEM experiments [46][47][48][49][50][51] , from which multi-modal characterization can be extracted from a single experimental dataset.…”

“…Direct electron detector (DED) cameras can operate at thousands of frames per second, enabling time-resolved in-situ 4D-STEM experiments [46][47][48][49][50][51] , from which multi-modal characterization can be extracted from a single experimental dataset. Examples include orientation mapping [44,45] , strain evolution [52,53] , and local structural ordering [50] . As in-situ nanomechanical testing is usually conducted irreversibly, the multi-channel nature of 4D-STEM is essential to capture more of the information during dynamic processes.…”