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Along with the adoption of three-dimensional electron diffraction (3D ED/MicroED) as a mainstream tool for structure determination from sub-micron single crystals, questions about best practices regarding each step along the workflow, from data collection to structure solutions, arise. In this paper, we discuss three particular aspects of a 3D ED/MicroED experiment which, after hundreds of structures solved in Rigaku’s laboratories, we have found to be important to consider carefully. First, for a representative model system of a hydrated compound (trehalose dihydrate), we show that cryo-transfer of the sample into the diffractometer is an effective means to prevent dehydration, while cooling of the sample without cryo-transfer yields a marginal improvement only. Next, we demonstrate for a small (tyrosine) and a large (clarithromycin) organic compound, how a simplified and fast workflow for dynamical diffraction calculations can determine absolute crystal structures with high confidence. Finally, we discuss considerations and trade-offs for choosing an optimal effective crystal-to-detector distance; while a long distance is mandatory for a protein (thaumatin) example, even a small molecule with difficult diffraction behavior (cystine) yields superior results at longer distances than the one used by default.

Abstract Scanning transmission electron microscopy (STEM) has advanced rapidly in the last decade thanks to the ability to correct the major aberrations of the probe-forming lens. Now, atomic-sized beams are routine, even at accelerating voltages as low as 40 kV, allowing knock-on damage to be minimized in beam sensitive materials. The aberration-corrected probes can contain sufficient current for high-quality, simultaneous, imaging and analysis in multiple modes. Atomic positions can be mapped with picometer precision, revealing ferroelectric domain structures, composition can be mapped by energy-dispersive X-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS), and charge transfer can be tracked unit cell by unit cell using the EELS fine structure. Furthermore, dynamics of point defects can be investigated through rapid acquisition of multiple image scans. Today STEM has become an indispensable tool for analytical science at the atomic level, providing a whole new level of insights into the complex interplays that control material properties.

We demonstrate the growth of high quality single phase films of VO2(A, B, and M) on SrTiO3 substrate by controlling the vanadium arrival rate (laser frequency) and oxidation of the V atoms. A phase diagram has been developed (oxygen pressure versus laser frequency) for various phases of VO2 and their electronic properties are investigated. VO2(A) phase is insulating VO2(B) phase is semi-metallic, and VO2(M) phase exhibits a metal-insulator transition, corroborated by photo-electron spectroscopic studies. The ability to control the growth of various polymorphs opens up the possibility for novel (hetero)structures promising new device functionalities.

We studied ZrO2 − La2/3Sr1/3MnO3 pillar–matrix thin films which were found to show anomalous magnetic and electron transport properties. With the application of an aberration-corrected transmission electron microscope, interfacial chemistry, and atomic-arrangement of the system, especially of the pillar–matrix interface were revealed at atomic resolution. Minor amounts of Zr were found to occupy Mn positions within the matrix. The Zr concentration reaches a minimum near the pillar–matrix interface accompanied by oxygen vacancies. La and Mn diffusion into the pillar was revealed at atomic resolution and a concomitant change of the Mn valence state was observed.

3D electron diffraction (3D ED)/Micro electron diffraction (MicroED) has extended the limits of crystallography by enabling the determination of three dimensional molecular structures from sub-μm microcrystals. However, 3D ED/microED measurements using current state-of-the-art electron microscopes require experts in both electron microscopy and crystallography making the method rather difficult for researchers who simply need structures. Here, we present a diffractometer specifically designed for 3D ED/microED and show how it works for determining crystal structures. The newly developed electron diffractometer will provide many researchers with an easy path to structure determination of crystals that are less than 1 μm in size. [ABSTRACT FROM AUTHOR]

In this article, we report the development of a new 200-kV analytical electron microscope equipped with a monochromator with an integrated double Wien-filter system. It enables us to study the electronic structures of materials in detail using electron energy-loss spectroscopy (EELS) analysis at an atomic scale. A highly monochromated and isotropically round electron probe is produced on the specimen plane. The ultimate energy resolutions with 0.1-s acquisition times are measured to be 36 meV at 200 kV and 30 meV at 60 kV. In an EELS mapping experiment performed on SrTiO3 with a monochromated electron probe whose energy resolution is 146 meV, an elemental map exhibits atomic resolution. [ABSTRACT FROM AUTHOR]

We studied ZrO2-La2/3Sr1/3MnO3 pillar--matrix thin films which were found to show anomalous magnetic and electron transport properties. With the application of an aberration-corrected transmission electron microscope, interfacial chemistry, and atomic-arrangement of the system, especially of the pillar--matrix interface were revealed at atomic resolution. Minor amounts of Zr were found to occupy Mn positions within the matrix. The Zr concentration reaches a minimum near the pillar--matrix interface accompanied by oxygen vacancies. La and Mn diffusion into the pillar was revealed at atomic resolution and a concomitant change of the Mn valence state was observed. [ABSTRACT FROM AUTHOR]

We report on the structure of Ag precipitates in aged Al-Ag alloys using transmission electron microscopy and high-angle annular detector darkfield scanning transmission electron microscopy (HAADF-STEM). Irregularly shaped small Ag particles of 1–2 nm dominate the alloy annealed at 140°C for 10 h. These particles are present also within large precipitates (10–50 nm), which are often characterized by their {100} and {110} facets. In addition, atomic-resolution HAADF-STEM images revealed that Ag atoms tend to form {111} planar clusters, which criss-cross a colony of the irregularly shaped small Ag precipitates. [ABSTRACT FROM AUTHOR]