Increasing interest in three-dimensional nanostructures adds impetus to electron microscopy techniques capable of imaging at or below the nanoscale in three dimensions. We present a reconstruction algorithm that takes as input a focal series of four-dimensional scanning transmission electron microscopy (4D-STEM) data. We apply the approach to a lead iridate, Pb$_2$Ir$_2$O$_7$, and yttrium-stabilized zirconia, Y$_{0.095}$Zr$_{0.905}$O$_2$, heterostructure from data acquired with the specimen in a single plan-view orientation, with the epitaxial layers stacked along the beam direction. We demonstrate that Pb–Ir atomic columns are visible in the uppermost layers of the reconstructed volume. We compare this approach to the alternative techniques of depth sectioning using differential phase contrast scanning transmission electron microscopy (DPC-STEM) and multislice ptychographic reconstruction.

4D-STEM, in which the 2D diffraction plane is captured for each 2D scan position in the scanning transmission electron microscope (STEM) using a pixelated detector, is complementing, and increasingly replacing existing imaging approaches. However, at present the speed of those detectors, although having drastically improved in the recent years, is still 100 to 1,000 times slower than the current PMT technology operators are used to. Regrettably, this means environmental scanning-distortion often limits the overall performance of the recorded 4D data. Here, we present an extension of existing STEM distortion correction techniques for the treatment of 4D data series. Although applicable to 4D data in general, we use electron ptychography and electric-field mapping as model cases and demonstrate an improvement in spatial fidelity, signal-to-noise ratio (SNR), phase precision, and spatial resolution.

Mineralized dental tissues and dental pulp were characterized using advanced analytical transmission electron microscopy (TEM) methods. Quantitative X-ray energy dispersive spectroscopy was employed to determine the Ca/P and Mg/P concentration ratios. Significantly lower Ca/P concentration ratios were measured in peritubular dentine compared to intertubular dentine, which is accompanied by higher and variable Mg/P concentration ratios. There is strong evidence that magnesium is partially substituting calcium in the hydroxyapatite structure. Electron energy-loss near-edge structures (ELNES) of C-K and O-K from enamel and dentine are noticeably different. We observe a strong influence of beam damage on mineralized dental tissues and dental pulp, causing changes of the composition and consequently also differences in the ELNES. In this article, the importance of TEM sample preparation and specimen damage through electron irradiation is demonstrated.

We report on the sub-electron-volt-sub-angstrom microscope (SESAM), a high-resolution 200-kV FEG-TEM equipped with a monochromator and an in-column MANDOLINE filter. We report on recent results obtained with this instrument, demonstrating its performance (e.g., 87-meV energy resolution at 10-s exposure time, or a transmissivity of the energy filter of T1 eV = 11,000 nm2). New opportunities to do unique experiments that may advance the frontiers of microscopy in areas such as energy-filtered TEM, spectroscopy, energy-filtered electron diffraction and spectroscopic profiling are also discussed.

Amorphous 1–2-nm-wide intergranular films in ceramics dictate many of their properties. The detailed investigation of structure and chemistry of these films pushes the limits of today's transmission electron microscopy. We report on the reconstruction of the one-dimensional potential profile across the film from an experimentally acquired tilt series of energy-filtered electron diffraction patterns. Along with the potential profile, the specimen thickness, film orientation with respect to the grain lattice and specimen surface, and the absolute specimen orientation with respect to the laboratory frame of reference are retrieved.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.