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A novel focused ion beam (FIB)-based methodology for the preparation of clean and artifact-free specimens on micro-electro-mechanical-system (MEMS)-based chips for in-situ electrical and electro-thermal experiments in a (scanning) transmission electron microscope ((S)TEM) is introduced. Owing to an alternative geometry, the lamellae are attached to a MEMS-based chip directly after the lift-out procedure and afterward further treated or thinned to electron transparency. The quality of produced lamellae on a chip resembles the quality of a classical FIB-prepared sample that is here demonstrated by high-resolution STEM imaging and analytical techniques. Various sample preparation parameters and the performance of in-situ prepared samples have been evaluated through electrical-biasing experiments.

Halide perovskites (HPs) are promising candidates for optoelectronic devices, such as solar cells or light-emitting diodes. Despite recent progress in performance optimization and low-cost manufacturing, their commercialization remains hindered due to structural instabilities. While essential to the development of the technology, the relation between the microscopic properties of HPs and the relevant degradation mechanisms is still not well understood. The sensitivity of HPs toward electron-beam irradiation poses significant challenges for transmission electron microscopy (TEM) investigations of structure and degradation mechanisms at the atomic scale. However, technological advances and the development of direct electron cameras (DECs) have opened up a completely new field of electron microscopy: four-dimensional scanning TEM (4D-STEM). From a 4D-STEM dataset, it is possible to extract not only the intensity signal for any STEM detector geometry but also the phase information of the specimen. This work aims to show the potential of 4D-STEM, in particular, electron exit-wave phase reconstructions via focused probe ptychography as a low-dose and dose-efficient technique to image the atomic structure of beam-sensitive HPs. The damage mechanism under conventional irradiation is described and atomically resolved almost aberration-free phase images of three all-inorganic HPs, CsPbBr3, CsPbIBr2, and CsPbI3, are presented with a resolution down to the aperture-constrained diffraction limit.

We report a software tool for post-correcting the linear and nonlinear image distortions of atomically resolved 3D spectrum imaging as well as 4D diffraction imaging. This tool improves the interpretability of distorted scanning transmission electron microscopy spectrum/diffraction imaging data., Specimen and stage drift as well as scan distortions can lead to a mismatch between true and desired electron probe positions in scanning transmission electron microscopy (STEM) which can result in both linear and nonlinear distortions in the subsequent experimental images. This problem is intensified in STEM spectrum and diffraction imaging techniques owing to the extended dwell times (pixel exposure time) as compared to conventional STEM imaging. As a consequence, these image distortions become more severe in STEM spectrum/diffraction imaging. This becomes visible as expansion, compression and/or shearing of the crystal lattice, and can even prohibit atomic resolution and thus limits the interpretability of the results. Here, we report a software tool for post-correcting the linear and nonlinear image distortions of atomically resolved 3D spectrum imaging as well as 4D diffraction imaging. This tool improves the interpretability of distorted STEM spectrum/diffraction imaging data.

Calcium bodies are specialized organs of terrestrial isopod crustaceans (woodlice) in the family Trichoniscidae. These organs are epithelial sacs that contain an extracellular matrix, mineralized with calcium salts. Recent studies have demonstrated that the mineral content of these organs changes periodically in relation to molt, the process in which crustaceans shed their old exoskeleton and form a new one. During the preparation for molt, minerals are deposited in the calcium bodies and are resorbed during and shortly after molt [1, 2]. As the crustacean exoskeleton contains large amounts of calcium carbonate and calcium phosphate [3], calcium bodies may function as reservoirs that allow woodlice to temporarily deposit minerals from their exoskeleton before molt and mobilize it after molt, when great amounts of calcium are needed for the mineralization of the new exoskeleton.

Terrestrial isopods from the group Trichoniscidae accumulate calcium in specialized organs, known as the calcium bodies. These consist of two pairs of epithelial sacs located alongside the digestive system. These organs contain various forms of calcium and constantly present bacteria. To elucidate their origin and role, we analyzed the bacteria of the calcium bodies in the cave-dwelling isopod Titanethes albus and the epigean species Hyloniscus riparius, by microscopy, histochemistry, energy dispersive X-ray spectrometry, 16S rRNA analysis and in situ hybridization. The calcium bodies of both species comprise numerous and diverse bacterial communities consisting of known soil bacteria. Despite their diversity, these bacteria share the polyphosphate-accumulation ability. We present the model of phosphorous dynamics in the calcium bodies during the molting cycle and potentially beneficial utilization of the symbiotic phosphate by the host in cyclic regeneration of the cuticle. Although not fully understood, this unique symbiosis represents the first evidence of polyphosphate-accumulating bacterial symbionts in the tissue of a terrestrial animal.

Breaking the time-reversal symmetry (TRS) in three-dimensional (3D) topological insulators (TIs) is essential for unlocking exotic physical states and exploring potential device application. Doping of the prototypical 3D-TI Bi2Te3 with transition metal ions can lead to ferromagnetic ordering at low temperatures. Here we report the study of incorporation of dysprosium (Dy) into Bi2Te3 with the intent to achieve higher ferromagnetic ordering temperatures and higher magnetic moments.

The investigation of surface plasmon excitations has recently become a field of research due to their high potential to be applicable in sensors, information technologies, cancer research etc. These coherent delocalized electron oscillations are common at metal-dielectric interfaces. However, they also exist in highly doped semiconductors, conducting oxide system or graphene, i.e. in many other systems with high carrier mobility. This poses the question whether such resonances can also be observed at the insulator interfaces.

When a plane wave, whether a photon, electron or neutron, passes through a transparent object, the exit wave provides information about the object’s internal structure, refractive index, electric and magnetic fields within and near the specimen plus many other signals, depending on the type of radiation. The ability to detect the full exit wavefunction instead of only the intensity allows for numerical correction of the aberrations of the imaging system. Unfortunately, the phase information of a wave is lost when it hits a detector. Retrieving phase information with high reliability and sensitivity is a key challenge in many fields of optics. Gabor’s 1948 holography experiments with electrons showed the potential for reconstructing the complete wavefunction for the first time. Since then, many complementary approaches have been developed in different branches of optics, each with its own problems . In this study, we describe an approach for measuring the full exit wavefunction, which combines two different holography methods to overcome the deficiencies of each technique alone. We combine in-line electron holography (using a setup similar to Gabor’s first experiment) to recover high spatial frequency information with an off-axis setup that allows low spatial frequency information to be recovered. The synergistic combination of these two complimentary techniques is achieved by using the off-axis information as an initial guess for the in-line reconstruction algorithm, which then iteratively recovers the phase information. Figure 1 shows an outline of the procedure, which is followed during the reconstruction of the phase by the hybrid method. Initial experiments have been carried out successfully with electrons in a study of iron-carbon core-shell and gold nanoparticles. Figure 2 shows examples of the phase and amplitude that were obtained from several iron-carbon core-shell nanoparticles, even under suboptimal experimental conditions.

Reconstruction of the complex-valued wave function that gives rise to the probability density of fast electrons in transmission electron microscopy (TEM) seems, at first glance, to be a solved problem. However, it is still challenging when considered more closely. In conventional TEM experiments, only the intensity (i.e., the square of the amplitude) of the wave function can be measured. Direct information about the phase of the wave, which carries information about electrostatic and magnetic fields that the electron has passed through, is lost during detection. In order to recover the phase information, it is necessary to interfere the electron wave function with a reference wave, in order to create an interference pattern. Denis Gabor introduced an approach that could be used to solve this problem 66 years ago [1]. In Gabor s original setup, which is the pioneering scheme for in-line holography, the wave that has been scattered by the specimen (the object wave) interferes with a reference wave propagated along the same axis. Using laser light, Leith and Upatnieks [2] showed that separation of the axes of propagation of the reference and object waves could be used to solve the twin-image problem. Mollenstedt later translated this idea back to electron microscopy, creating the field of off-axis electron holography [3,4].

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