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Abstract We report a large-angle rocking beam electron diffraction (LARBED) technique for electron diffraction analysis. Diffraction patterns are recorded in a scanning transmission electron microscope (STEM) using a direct electron detector with large dynamical range and fast readout. We use a nanobeam for diffraction and perform the beam double rocking by synchronizing the detector with the STEM scan coils for the recording. Using this approach, large-angle convergent beam electron diffraction (LACBED) patterns of different reflections are obtained simultaneously. By using a nanobeam, instead of a focused beam, the LARBED technique can be applied to beam-sensitive crystals as well as crystals with large unit cells. This paper describes the implementation of LARBED and evaluates the performance using silicon and gadolinium gallium garnet crystals as test samples. We demonstrate that our method provides an effective and robust way for recording LARBED patterns and paves the way for quantitative electron diffraction of large unit cell and beam-sensitive crystals. 

Solution-processable semiconductors hold promise in enabling applications requiring cost-effective electronics at scale but suffer from low performance limited by defects. We show that ordered defect compound semiconductor CuIn₅Se₈, which forms regular defect complexes with defect-pair compensation, can simultaneously achieve high performance and solution processability. CuIn₅Se₈transistors exhibit defect-tolerant, band-like transport supplying an output current above 35 microamperes per micrometer, with a large on/off ratio greater than 10⁶, a small subthreshold swing of 189 ± 21 millivolts per decade, and a high field-effect mobility of 58 ± 10 square centimeters per volt per second, with excellent uniformity and stability, superior to devices built on its less defective parent compound CuInSe₂, analogous binary compound In₂Se₃, and other solution-deposited semiconductors. They can be monolithically integrated with carbon nanotube transistors to form high-speed and low-voltage three-dimensional complementary logic circuits and with micro-light-emitting diodes to realize high-resolution displays. 

We investigate intermittent plasticity in nanopillars of nanocrystalline molybdenum based on in situ transmission electron microscopy observations. By correlating electron imaging results with the measured nanopillar mechanical response, we demonstrate that the intermittent plasticity in nanocrystalline molybdenum is largely caused by dislocation avalanches. Electron imaging further reveals three types of dislocation avalanches, from intragranular to transgranular to cross-granular avalanches. The measured strain bursts resulted from avalanches have similar magnitudes to those reported for the molybdenum single-crystal pillars, while the corresponding flow stress in nanocrystalline molybdenum is greatly enhanced by the small grain size. Statistical analysis also shows that the avalanches behavior has similar characteristic as single crystals in the mean field theory model. Together, our findings here provide critical insights into the deformation mechanisms in a nanostructured body-centered-cubic metal. 

Here, we introduce a novel defect imaging method based on the cepstral analysis of electron diffuse scattering using an Electron Microscope Pixel Array Detector (EMPAD) detector. 

This talk focuses on the principles of 4D-STEM based electron nanodiffraction techniques for defect, strain and short-range ordering analysis using electron diffuse scattering [8, 9]. We review recent progress made in scanning electron nanodiffraction (SEND) data collection, new algorithms based on cepstral analysis, and machine learning based electron DP analysis. These progresses will be highlighted using defect detection, and short-range ordering analysis as application examples. The materials of the study are the medium entropy alloy, CrCoNi, which has exceptional low-temperature mechanical strength and ductility. We will show how SEND helps our understanding of non-random chemical mixing in a CrCoNi alloy, resulting from short-range ordering, behind the mechanical strength in CrCoNi and how these developments provide general opportunities for an atomistic-structure study in advanced alloys.