An Ultrafast Direct Electron Camera for 4D STEM

Using 4D STEM to Probe Mesoscale Order in Molecular Glass Films Prepared by Physical Vapor Deposition

“…These results demonstrate the value of 4D STEM with a high-speed camera like the Direct Electron Celeritas, which enables a high degree of control over electron dose and spatial sampling . The Celeritas runs at up to ∼86000 fps and has high gain and low noise for single-electron sensitivity . With a 0.6 pA probe, an exposure time of 8 ms (125 fps) is sufficient to record enough signal, depositing a dose of ∼100 e – /Å 2 , which allows a small probe step (∼2 nm) for improved spatial resolution and lets us map larger regions on the sample without significant sample drift during the acquisition time.…”

“…Here, we use an ultrafast, high-sensitivity direct electron detector to study the mesoscale orientational order in thin films of a phenanthroperylene ester from the scattering signal from the stacking of molecules via π-bonding. We achieve results uninfluenced by beam damage at ∼3 nm resolution, which is sufficient to image orientation domains as small as 10 nm, even for the subtle, diffuse scattering features from a glass.…”

Robust Atomic-Resolution Imaging of Lithium in Battery Materials by Center-of-Mass Scanning Transmission Electron Microscopy

“…While segmented detectors allow rapid data acquisition, current state-of-the-art pixelated detectors operate fast enough to produce high-quality data and offer many advantages critical for producing reliable images, such as allowing the true CoM to be measured, significantly simplifying the experimental setup since no precise beam–detector alignment is required and providing the flexibility to optimize results by adjusting parameters such as collection angle in postprocessing. In addition, the next generation of pixelated detectors is currently under development and will allow even more rapid data acquisition. − The analysis of pixelated detector data is also relatively straightforward (see the Supporting Information) and thus will eventually allow on-the-fly data processing by taking advantage of rapidly developing open-source computational methods. , Finally, a detector that enables the CoM to be directly measured without recording a diffraction pattern has also recently been developed and enables measurements at speeds comparable to segmented detectors . While this type of detector provides a good compromise between pixelated and segmented detectors, pixelated detectors provide the most flexibility, for example allowing conventional STEM images to be simultaneously reconstructed from the data, and their acquisition speeds are increasing rapidly, − as mentioned above.…”

“…In addition, the next generation of pixelated detectors is currently under development and will allow even more rapid data acquisition. − The analysis of pixelated detector data is also relatively straightforward (see the Supporting Information) and thus will eventually allow on-the-fly data processing by taking advantage of rapidly developing open-source computational methods. , Finally, a detector that enables the CoM to be directly measured without recording a diffraction pattern has also recently been developed and enables measurements at speeds comparable to segmented detectors . While this type of detector provides a good compromise between pixelated and segmented detectors, pixelated detectors provide the most flexibility, for example allowing conventional STEM images to be simultaneously reconstructed from the data, and their acquisition speeds are increasing rapidly, − as mentioned above. For these reasons, we focus here on DPC measured using a pixelated detector, or CoM-STEM.…”

4D STEM with an Ultrafast Camera Reveals Mesoscale Structure in Anisotropic Molecular Glass Thin Films

“…(We find that they sustain only ~100 e -/Å 2 at 200 kV before losing orientational order.) Studying this material at low dose is made possible by a new, ultrafast direct electron detection camera [7] operated at 0.125 ms per diffraction pattern for these experiments, and a 0.1 nm step size between probe positions, with a 0.6 pA, 2 nm diameter probe. The resulting 4D STEM datasets can be several TBs, so analysis required significant extensions to data analysis libraries like pyXEM and Hyperspy [8].…”