Interaction between single gold atom and the graphene edge: A study via aberration-corrected transmission electron microscopy

We have developed a spherical aberration corrected transmission electron microscopy(Cs-corrected TEM) technique that allows us to obtain clearer images in real space than everbefore. We applied this technique to titanium oxide, in which light elements such as oxygenare difficult to observe using TEM because of its small cross section and electronicdamage. In the present study, we successfully observed oxygen atoms in rutileTiO2. In addition, this direct observation of oxygen atoms enabled us to study the Magnéli structure(TinO2n−1), which is caused by oxygen vacancies. These vacancies caused an atomic relaxation of thetitanium and oxygen atoms. The relaxed atoms formed a characteristic shear structureof rutile titanium dioxide phase. This shear structure of the Magnéli structure(TinO2n−1) was visualized with a spatial resolution of 0.119 nm. At the same time, the selected areadiffraction (SAD) pattern of the defect structure was obtained. Additional spots wereshown inside the rutile [110] spot. We made structural models of the shear structureand simulated the diffraction pattern and images using a multi-slice simulation.Additional spots in the simulated diffraction patterns accurately reconstructed theexperimental data. We also considered the possibility of the real-space analysis of localstructures using spherical aberration corrected transmission electron microscopy.

Structural and Electronic Properties of BaO/MgO(001)-type Interface Studied via Aberration-corrected Transmission Electron Microscopy and First-principles Calculations

We present a method that allows for a quantitative measurement of the surface self-diffusion on nanostructures, such as nanoparticles, at the atomic scale using aberration-corrected high-resolution transmission electron microscopy (HRTEM). The diffusion coefficient can be estimated by measuring the fluctuation of the atom column occupation at the surface of Au nanoparticles, which is directly observable in temporal sequences of HRTEM images. Both a Au icosahedron and a truncated Au octahedron are investigated, and their diffusion coefficients are found to be in the same order of magnitude, D = 10(-17) to 10(-16) cm(2)/s. It is to be assumed that the measured surface diffusion is affected by the imaging electron beam. This assumption is supported by the observed instability of a (5 × 1) surface reconstruction on a {100} Au facet.

The local coordination structure of metal atoms in single-atom catalysts (SACs) greatly influences their catalytic performance. And for most SACs, single metal atoms were anchored on carbon materials with N or C coordination. However, the rational design of oxygen-containing SACs and analyzing its structure-performance relationship remain challenging. Herein, we used amino-rich compounds to tailor the metatungstate and fix the W atoms and finally obtained the oxygen-containing W-SACs. The structural evolution of tungsten and its coordination atoms were tracked by electrospray ionization high-definition mass spectrometry. Furthermore, aberration-corrected transmission electron microscopy, X-ray absorption fine-structure spectroscopy, and first-principles calculation results revealed that different from the traditional SACs, the WO2N2 moiety (W coordinated with two O atoms and two N atoms) may be the favored structure for W species. This special structure promoted the energy transfer for enhancing singlet oxygen generation. This work presents an efficient way to prepare more high-efficiency SACs by atomic-scale tailoring and structural evolution tracking at the molecular level.

Determining the extent of oxidation in batches of metal nanoparticles is essential to predict the behaviour of the material. Using aberration corrected transmission electron microscopy (TEM) it was possible to detect the formation of an oxide shell, of thickness 3 nm, on the surface of copper nanoparticles. Further analysis showed that this shell actually consists of two layers, both of which were polycrystalline in nature with domains in the size range of 1–2 nm, and having a thickness of 1.5 nm each. Energy dispersive x-ray spectroscopy confirms that the layers arise due to the formation of oxides, but it was not possible to determine their exact nature. Analysis of the intensity variation within images obtained via probe corrected scanning TEM combined with a high angle annular dark field detector indicates that the shell consists of an inner layer of cuprous oxide (Cu2O) and an outer layer of cupric oxide (CuO). This work was complemented by conventional TEM which provided size distribution and revealed that the majority of particles have a core consisting of a single crystal of copper. This demonstrates the ability of TEM to help to determine the oxidation state of nanoparticles and its potential to be applied to a wide range of homogenous and heterogeneous nanoparticles.

In this in situ study, details of the coalescence of Pt nanoparticles encapsulated within carbon nanotubes are investigated whilst under electron irradiation in aberration corrected transmission electron microscopy.

Abstract: Contrast transfer function (CTF) is a vital function in transmission electron microscopy (TEM). It expresses to what extent amplitudes converted from the phase changes of the diffracted waves contribute to the TEM image, including the effects of lens aberrations. Simulation is very helpful to understand the application of the function thoroughly. In this work, we develop the CTFscope as a component in the Landyne software suite, to calculate the CTF with temporal and spatial dumping envelopes for conventional TEM and to extend it to various aberrations (up to fifth order) for aberration-corrected (AC)-TEM. It also includes effects on the CTF and imaging due to the objective aperture and image drift for tutorial purposes. The CTFscope has a user-friendly graphical interface for simulation, visualization, saving, and loading of the microscopy conditions and results. It can be used to explore instrumental performance information due to optical aberrations, effects on the resolution of a TEM and AC-TEM, and for teaching electron microscopy courses.

Transmission electron microscopy (TEM) has hit a significant milestone of sub-angstrom resolution. On one hand, electron microscopists and materials scientists are enjoying the highest TEM spatial resolution ever attainable; on the other hand, study of materials in a steady state is hard to meet the increasing demand in new application fields such as nanocatalysts, nanocrystal growth, nanoelectronics, nanosensors, and nanomechanics in which size effect and structural or property responses to stimuli from the surrounding environment are key information to learn. Special attention is thus paid to in-situ TEM. A great deal of effort in developing and improving electron microscopes and specimen holders have resulted in unprecedented progresses in attaining insight into materials in dynamic environments. In many ways, transmission electron microscopes are now functionalized as workstations or nanoscale labs rather than just imaging tools. In this chapter, various types of in-situ TEM technologies are introduced accompanied by application examples. In parallel to the sub-angstrom breakthrough made by the aberration-corrected TEM, atomic resolution is now emphasized in advanced in-situ TEM, advancement on this aspect will be discussed together with other important notes and further challenges.

Quasi‐one‐dimensional III‐V semiconducting nanowires attract enormous attention owing to their physical properties such as tunable direct bandgap, high surface to volume ratio, high carrier mobility, tunable structures. Hence they have potential application in next generation electronics, sensors, photonics and photovoltaics. Understanding the details such as, atomic scale structure, local chemical stoichiometry and defects in a sub nanometer scale are inevitable when nanowires are intended for devices. A systematic interfacial investigation on molecular beam epitaxy grown III‐V based nanowires such as InAs, GaAs, [1] in general and in particular, heterostructure nanowires of axially grown Ga x In 1_x As‐InAs and InAs‐InAsSb will be presented. [2] In this work, atomic scale structural interfaces and interfacial chemical composition are analyzed using advanced aberration corrected transmission electron microscopy. Atomic resolution high angle annular dark field scanning transmission electron microscopy (HAADF‐STEM) and high resolution energy dispersive x‐ray spectroscopy techniques are predominatly used for characterizing the grown nanowires. Our work demonstrates on tailoring the growth, periodicities and the stoichiometry of III‐V nanowire heterostructure containing single/multiple electronic barriers involving In,Ga,As and Sb. We aim to provide understanding on the growth of dissimilar interfaces in heterostructure nanowire (see fig 1). In the InAs‐InAsSb heterostructure wires, [1] our work demonstrates the quality of the misfit strained interface in terms of structural abruptness and chemical homogeneity.

Controlled manipulation of materials on the atomic scale is a continuing challenge in physics and material science. Doping of two‐dimensional (2D) materials via low energy ion implantation could open possibilities for fabrication of nanometre‐scale patterned devices, as well as for functionalization compatible with large‐scale integrated semiconductor technology. High resolution imaging and spectroscopic analysis of these electronic dopants at the atomic scale is fundamental for understanding sites, retention, bonding and resulting effects on Fermi level shifts. This has been made achievable with the advent of aberration corrected transmission electron microscopy (TEM) and scanning TEM, as well as low‐loss electron energy loss spectroscopy (EELS). We show for the first time directly that 2Ds can be doped via ion implantation. Retention is in good agreement with predictions from calculation‐based literature values [1], as are initial results of the sites of dopants and their influence on the band structure of surrounding atoms. We present results of N‐ and B‐implantation in graphene [2,3] as well as current progress with ion‐implantation in TMDCs.

Hydrogenation of Mg nanofilms catalyzed by size-selected Pd nanoparticles: Observation of localized MgH2 nanodomains

High-resolution transmission electron microscopy is often used to characterize grain boundaries, but it is usually limited to special high symmetry boundaries with a high density of coincident sites. For these ‘special’ boundaries, both crystals can be brought into a low-index zone-axis with the boundary plane parallel to the incident electron beam. In this case the atomistic structure of the boundary can be solved, which is not possible for other, more general grain boundaries. In the present study, general grain boundaries in SrTiO3 were analyzed using aberration-corrected transmission electron microscopy and scanning transmission electron microscopy. These boundaries included at least one type of disconnection (i.e., defects that can have a step and/or a dislocation component). Since the dislocation component of disconnections along general grain boundaries cannot be fully resolved using the methods currently available, a plane matching approach was used to compare disconnections at different boundaries. Using this approach, the dislocation component of the disconnections was partially characterized and was found to have an edge component mainly parallel to {100} and {110}, close to normal to the macroscopic grain boundary plane. The step component of the disconnections was found to be aligned mainly parallel to the same crystallographic planes ({100} and {110}).

Multimodal in-situ experiments are the wave of the future, as this approach will permit multispectral data collection and analysis during real-time nanoscale observation. In contrast, the evolution of technique development in the electron microscopy field has generally trended toward specialization and subsequent bifurcation into more and more niche instruments, creating a challenge for reintegration and backward compatibility for in-situ experiments on state-of-the-art microscopes. We do not believe this to be a requirement in the field; therefore, we propose an adaptive instrument that is designed to allow nearly simultaneous collection of data from aberration-corrected transmission electron microscopy (TEM), probe-corrected scanning transmission electron microscopy, ultrafast TEM, and dynamic TEM with a flexible in-situ testing chamber, where the entire instrument can be modified as future technologies are developed. The value would be to obtain a holistic understanding of the underlying physics and chemistry of the process-structure–property relationships in materials exposed to controlled extreme environments. Such a tool would permit the ability to explore, in-situ, the active reaction mechanisms in a controlled manner emulating those of real-world applications with nanometer and nanosecond resolution. If such a powerful tool is developed, it has the potential to revolutionize our materials understanding of nanoscale mechanisms and transients.Graphical

The exotic internal structure of polar topologies in multiferroic materials offers a rich landscape for materials science research. As the spatial scale of these entities is often subatomic in nature, aberration-corrected transmission electron microscopy (TEM) is the ideal characterization technique. Software to quantify and visualize the slight shifts in atomic placement within unit cells is of paramount importance due to the now routine acquisition of images at such resolution. In the previous ~decade since the commercialization of aberration-corrected TEM, many research groups have written their own code to visualize these polar entities. More recently, open-access Python packages have been developed for the purpose of TEM atomic position quantification. Building on these packages, we introduce the TEMUL Toolkit: a Python package for analysis and visualization of atomic resolution images. Here, we focus specifically on the TopoTEM module of the toolkit where we show an easy to follow, streamlined version of calculating the atomic displacements relative to the surrounding lattice and thus plotting polarization. We hope this toolkit will benefit the rapidly expanding field of topology-based nano-electronic and quantum materials research, and we invite the electron microscopy community to contribute to this open-access project.

Nanodomains and nanometer-scale disorder in multiferroic bismuth ferrite single crystals