Resolution Electron Microscopy Research Articles

Atomic-level quantitative analysis of electronic functional materials by aberration-corrected STEM

Abstract The stable sub-angstrom resolution of the aberration-corrected scanning transmission electron microscope (AC-STEM) makes it an advanced and practical characterization technique for all materials. Owing to the prosperous advancement in computational technology, specialized software and programs have emerged as potent facilitators across the entirety of electron microscopy characterization process. Utilizing advanced image processing algorithms promotes the rectification of image distortions, concurrently elevating the overall image quality to superior standards. Extracting high-resolution, pixel-level discrete information and converting it into atomic-scale, followed by performing statistical calculations on the physical matters of interest through quantitative analysis, represent an effective strategy to maximize the value of electron microscope images. The efficacious utilization of quantitative analysis of electron microscope images has become a progressively prominent consideration for materials scientists and electron microscopy researchers. This article offers a concise overview of the pivotal procedures in quantitative analysis and summarizes the computational methodologies involved from three perspectives: contrast, lattice and strain, as well as atomic displacements and polarization. It further elaborates on practical applications of these methods in electronic functional materials, notably in piezoelectrics/ferroelectrics and thermoelectrics. It emphasizes the indispensable role of quantitative analysis in fundamental theoretical research, elucidating the structure–property correlations in high-performance systems, and guiding synthesis strategies.

Terahertz control and timing correlations in a transmission electron microscope.

Ultrafast electron microscopy provides a movie-like access to structural dynamics of materials in space and time, but fundamental atomic motions or electron dynamics are, so far, too quick to be resolved. Here, we report the all-optical control, compression, and characterization of electron pulses in a transmission electron microscope by the single optical cycles of laser-generated terahertz light. This concept provides isolated electron pulses and merges the spatial resolution of a transmission electron microscope with the temporal resolution that is offered by a single cycle of laser light. We also report the all-optical control of multi-electron states and find a substantial two-electron and three-electron anticorrelation in the time domain. These results open up the possibility to visualize atomic and electronic motions together with their quantum correlations on fundamental dimensions in space and time.

Scanning Electron Microscopy Imaging of Large DNA Molecules Using a Metal-Free Electro-Stain Composed of DNA-Binding Proteins and Synthetic Polymers.

This paper presents the first scanning electron microscopy (SEM)-based DNA imaging in biological samples. This novel approach incorporates a metal-free electro-stain reagent, formulated by combining DNA-binding proteins and synthetic polymers to enhance the visibility of 2-nm-thick DNA under SEM. Notably, DNA molecules stain with proteins and polymers appear as dark lines under SEM. The resulting DNA images exhibit a thickness of 15.0±4.0nm. As SEM is the primary platform, it integrates seamlessly with various chemically functionalized large surfaces with the aid of microfluidic devices. The approach allows high-resolution imaging of various DNA structures including linear, circular, single-stranded DNA and RNA, originating from nuclear and mitochondrial genomes. Furthermore, quantum dots are successfully visualized as bright labels that are sequence-specifically incorporated into DNA molecules, which highlights the potential for SEM-based optical DNA mapping. In conclusion, DNA imaging using SEM with the novel electro-stain offers electron microscopic resolution with the ease of optical microscopy.

Influence of Composition and Structure on the Optoelectronic Properties of Photocatalytic Bi4NbO8Cl-Bi2GdO4Cl Intergrowths.

Mixed metal oxyhalides are an exciting class of photocatalysts, capable of the sustainable generation of fuels and remediation of pollutants with solar energy. Bismuth oxyhalides of the types Bi4MO8X (M = Nb and Ta; X = Cl and Br) and Bi2AO4X (A = most lanthanides; X = Cl, Br, and I) have an electronic structure that imparts photostability, as their valence band maxima (VBM) are composed of O 2p orbitals rather than X np orbitals that typify many other bismuth oxyhalides. Here, flux-based synthesis of intergrowth Bi4NbO8Cl-Bi2GdO4Cl is reported, testing the hypothesis that both intergrowth stoichiometry and M identity serve as levers toward tunable optoelectronic properties. X-ray scattering and atomically resolved electron microscopy verify intergrowth formation. Facile manipulation of the Bi4NbO8Cl-to-Bi2GdO4Cl ratio is achieved with the specific ratio influencing both the crystal and electronic structures of the intergrowths. This compositional flexibility and crystal structure engineering can be leveraged for photocatalytic applications, with comparisons to the previously reported Bi4TaO8Cl-Bi2GdO4Cl intergrowth revealing how subtle structural and compositional features can impact photocatalytic materials.

Determination of the point resolution of high-resolution transmission electron microscope using the through-focus technique

From the viewpoint of evaluating the instrumental performance of high-resolution electron microscopy (HREM), the Scherzer condition was investigated using information theory. As a result, the optimum defocus amount Δf can be expressed based on (Csλ)12, and the formula Δf=1.12(Csλ)12 is obtained. Furthermore, a procedure for measuring point resolution using the through-focus technique is developed, and a new method for determining the spherical aberration coefficient using the variance of Δf is introduced in the procedure.

High-Efficiency Coupling of Free Electrons to Sub-λ3 Modal Volume, High-Q Photonic Cavities.

We report on the design, realization, and experimental investigation by spatially resolved monochromated electron energy loss spectroscopy (EELS) of high-quality-factor cavities with modal volumes smaller than λ3, with λ being the free-space wavelength of light. The cavities are based on a slot defect in a 2D photonic crystal slab made up of silicon. They are optimized for high coupling of electrons accelerated to 100 kV to quasi-transverse electrical modes polarized along the slot direction. We studied the cavities in two geometries and took advantage of the deep sub-optical wavelength spatial resolution of the electron microscope and high spectral resolution of the monochromator to comprehensively describe the optical excitations of the slab. The first geometry, for which the cavities have been designed, corresponds to an electron beam traveling along the slot direction. The second consists of the electron beam traveling perpendicular to the slab. In both cases, a large series of modes is identified. The dielectric slot mode energies are measured to be in the 0.8-0.85 eV range, as per design, and surrounded by two bands of dielectric and air modes of the photonic structure. The dielectric even slot modes, to which the cavity mode belongs, are highly coupled to the electrons with up to 3.2% probability of creating a slot photon per incident electron. Although the experimental spectral resolution (around 30 meV) alone does not allow to disentangle cavity photons from other slot photons, the excellent agreement between the experiments and finite-difference time-domain simulations allows us to deduce that among the photons created in the slot, around 30% are stored in the cavity mode. A systematic study of the energy and coupling strength as a function of the photonic band gap parameters permits us to foresee an increase of coupling strength by fine-tuning phase-matching. Our work demonstrates free electron coupling to high-quality-factor cavities with low mode densities and sub-λ3 modal volumes, making it an excellent candidate for applications such as quantum nano-optics with free electrons.

Measuring coefficient of thermal expansion of materials of micrometre size using SEM/FIB microscope with in situ MEMS heating stage.

A new method is proposed to measure the linear coefficient of thermal expansion (CTE) of solid metals and ceramics of micron-sized dimensions. This approach uses a focused ion beam (FIB) to extract and transfer a slab of the sample, typically (15-20) ×10 × (3-5) µm onto a Micro-Electro-Mechanical Systems (MEMS) in situ heating holder inside a scanning electron microscope (SEM). CTE is thereafter calculated by image correlating the change of length (ΔL) between the fiducial marks on the slab as a function of temperature, taking advantage of the temperature calibration of the MEMS heating holder and nanometre resolution of the scanning electron microscope. The CTE results are validated to be consistent with standard copper and silicon. We further demonstrate the method on a graphene platelet reinforced copper composite and a graphite filler phase isolated from a bulk sample, these represent materials that cannot be practically synthesised or isolated at the macro-scale. Errors associated with the measurement are discussed.

Improvement of Microstructure and Mechanical Properties of Hot‐Formed Steel with Ce Addition

In this article, the effect of Ce element on the microstructure and mechanical properties was studied by Ce addition to the hot‐formed steel. Scanning electron microscope and energy dispersive spectrometer (SEM‐EDS) was used to analyze the improvement effect of Ce on inclusions and the effect of inclusions on fracture behavior; Electron back scattering diffractometer (EBSD) was used to analyze the refinement and strengthening effect of Ce on martensitic grains; transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM) was used to analyze the microstructure strengthening effect and microalloying effect of solid solution Ce in hot‐formed steel. Through a systematic analysis of mechanical properties and microstructure, the mechanism of Ce enhances the strength and elongation of hot‐formed steel was clarified. Besides, this work provides a research basis for further improving the safety and machinability of hot‐formed steel.

A Comprehensive Review of Electron Microscopy in Materials Science: Technological Advances and Applications

In nanomaterials and microstructural evolution, electron microscopy has had an important effect on materials investigation. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), Electron Diffraction, Operando Electron Microscopy, and Aberration-Corrected Electron Microscopy offer the investigation on understanding of nanoscale material properties and structure. The present research covers the basics, advantages and disadvantages, and material-related applications of various electron microscopy techniques. TEM is useful for investigating atomic arrangements and imperfections in materials, while SEM offers micro- to nanoscale topographical, morphological, & compositional information. EDS, frequently employed with SEM or TEM, analyzes elements and compounds to determine material compositions. Opando Electron Microscopy allows researchers to observe and assess materials during catalytic reactions and battery charge/discharge cycles. This approach is vital for knowing how dynamic processes influence nanoscale material characteristics and behaviour. Another advanced technique, Aberration-Corrected Electron Microscopy, corrects lens aberrations that interfered with electron microscope resolution. This adjustment enables imaging at sample-limited resolutions, allowing further studies of atomic structures & flaws. These electron microscopy methods significantly improve nanomaterial microstructural evolution understanding. These have enabled extensive study of flaws, transitions between phases, and formation mechanisms, which are essential to producing optimal materials.

Noise-dependent bias in quantitative STEM-EMCD experiments revealed by bootstrapping

Electron magnetic circular dichroism (EMCD) is a powerful technique for estimating element-specific magnetic moments of materials on nanoscale with the potential to reach atomic resolution in transmission electron microscopes. However, the fundamentally weak EMCD signal strength complicates quantification of magnetic moments, as this requires very high precision, especially in the denominator of the sum rules. Here, we employ a statistical resampling technique known as bootstrapping to an experimental EMCD dataset to produce an empirical estimate of the noise-dependent error distribution resulting from application of EMCD sum rules to bcc iron in a 3-beam orientation. We observe clear experimental evidence that noisy EMCD signals preferentially bias the estimation of magnetic moments, further supporting this with error distributions produced by Monte-Carlo simulations. Finally, we propose guidelines for the recognition and minimization of this bias in the estimation of magnetic moments.

Defect mediated magnetism in Pr/TiO2- reduced graphene oxide nanocomposites

Synthesis and characterization of Pr/TiO2 nanoparticles with its reduced graphene oxide nanocomposites by sol-gel and hydrothermal reaction and its magnetic properties is presented. X ray Diffraction and Raman analysis confirms the anatase phase structure in both nanoparticles and composites with Pr doping hindering the crystallite growth. Field Emission Scanning Electron Microscope and High Resolution Transmission Electron Microscope analysis confirm unambiguously the attachment of TiO2 spherical nanoparticles onto the graphene sheets forming an intimate interfacial contact between the particle and sheets enabling electron charge transfers. Difference in surface areas and surface energies give rise to variable emission intensity of the samples. Pr/TiO2 nanocomposites exhibit an increased bandgap values than their nanoparticles. Both Photoluminescence and Electron Paramagnetic Resonance spectroscopy confirm an increase in defect structure with increase of Pr doping. Magnetization studies show weak ferromagnetic ordering for pure TiO2 nanoparticles. The soft magnetic behaviour of the synthesised materials is useful in fabricating memory based devices.

Dual-functional etchants that simultaneously demineralize and stabilize dentin render collagen resistant to degradation for resin bonding.

To develop dual-functional etchants that could demineralize and stabilize dentin collagen simultaneously, and to assess the effects of these etchants on collagen crosslinking, biostability and resin bonding properties under clinically relevant conditions. Dual-functional etchants were prepared by mixing 56% glycolic acid and 17% phosphoric acid and adding 1% of theaflavins (TF) or proanthocyanidins from grape seed extract (GSE). The etchant without crosslinker was used as control. The prepared human dentin specimens were treated with the 3 etchants for 30s and analyzed for chemical interaction using Fourier transform infrared spectroscopy and resistance of the demineralized layer to collagenase degradation using electron microscopy (EM). Resin-dentin interfacial bonding properties were evaluated after 24h and after 10,000 thermocycling through microtensile bond strength (μTBS), nanoleakage and matrix metalloproteinases (MMPs) activity via in situ zymography. Statistical analysis was done using ANOVA and post- hoc Tuckey's test. Compared to control, TF and GSE dual-functional etchants were able to demineralize dentin, induce collagen crosslinking and protect the demineralized layer from collagenase degradation within 30s. High resolution EM images showed better protection with TF etchant compared to GSE. There was a significant reduction in μTBS and an increase in nanoleakage and MMPs activity in control after thermocycling (p<0.05) while these changes weren't seen in dual-functional etchants. Dual-functional etchants, especially TF containing, provide collagen protection against degradation and result in stable μTBS and less nanoleakage and MMPs activity under clinically relevant conditions.

Atomic-scale imaging of electron sensitive zeolites with aberration corrected transmission electron microscopy

The spatial resolution of transmission electron microscopes (TEMs) and scanning transmission electron microscopes (STEMs) has been drastically improved by introducing aberration correction. However, observable range in electron sensitive zeolites are still limited due to electron irradiation damages. Nevertheless, atomic resolution imaging of some zeolites is currently being realized by various developments in electron microscopic hardware, such as high sensitivity cameras. On the other hand, surveying the status of TEM and STEM imaging is very important for further progress in the structural analysis of zeolites. Here, we demonstrate and compare the high-resolution imaging of zeolites with several kinds of imaging modes.

In Situ Nanoindentation at Elevated Humidities

AbstractNanoindentation is one of the most widespread methods to measure the mechanical performance of complex materials systems. As it allows for local characterization of composite architectures with sub‐micron spatial features and a large range of properties, nanoindentation is commonly used to measure the properties of biological materials. In situ nanoindentation, a further development of the approach, is a powerful tool for the analysis of plastic deformation and failure of materials. Here, samples can be mechanically manipulated using the indenter, while their behavior is monitored with the resolution of a scanning electron microscope (SEM). Indeed, numerous studies demonstrate the potential of this approach for studying the most fundamental material characteristics. However, so far, these measurements are performed in high‐vacuum conditions inherent to the conventional electron microscopy method, which are irrelevant when studying biological structures that evolved to perform in hydrated conditions. In this work, the ability to conduct nanoindentation experiments under controlled humidity and temperature inside an environmental SEM is developed. This technique has the potential to become crucial for materials design and characterization in many domains where humidity has a significant impact on performance. These include organic/polymer systems, microelectronic and optoelectronic devices, materials for catalysis, batteries, and many more.

Photoelectrochemical, optical and magnetic properties of magnetite nanoparticles

AbstractMagnetite magnetic nanoparticles are prepared using olive leaf extract as a green reducing and stabilizing agents. After reaction the product is heated up to get rid of the organic compounds and get pure magnetite nanoparticles. Differential scanning calorimetry is used to study the phase transformation as a function of heating temperature. Scanning electron microscope and high resolution transmission electron microscope show spherical and crystallized nanoparticles with a size of 5 nm. X‐ray diffraction and Raman and x‐ray photoelectron spectroscopy indicate the formation of Magnetite phase with high cristallinity and purity. The synthesized Magnetite nanoparticles are semiconductors with gap energy around 2 eV. Observed by transmission electron microscope graphite rods with stacked carbon disks are decorated with the prepared nanoparticles and show enhanced photocurrent. The vibrating sample magnetometer measurements indicate that the prepared Magnetite nanoparticles have superparamagnetic behavior. These results are very promising for clinical and water splitting applications.

Synthesis of Ag−/Graphene Aerogel Composite for Removal of Methyl Orange

AbstractIn this study, silver‐titanium dioxide/graphene aerogel (Ag−TiO2/GA−ATG) was synthesized via chemical reduction using ethylene diamine (EDA). The effects of reductant doses on the formation of the three‐dimensional structure and the photocatalytic degradation efficiency of ATG were evaluated with five different volumes (20, 30, 40, 50, and 60 μL), corresponding to the ATG1, ATG2, ATG3, and ATG4, respectively. The results showed that 40 μL of EDA was the suitable condition for the formation of ATG three‐dimensional structure. Characterizations revealed that ATG3 was successfully synthesized with distinctive peaks of Ag and TiO2 in the X‐ray diffraction patterns whilst scanning electron microscope and high resolution transmission electron microscope images showed a porous structure, silver nanoparticles and TiO2 with an average size of 10–25 nm were uniformly distributed on the graphene surface. Furthermore, ATG3 possessed the highest photocatalytic capability to deteriorate methyl orange with an efficiency of up to 99.53 % with a catalyst dose of 0.3 mg/mL, superior compared to those of TiO2 and TiO2/GA. The radicals scavenging experiments elucidated ⋅ to majorly contribute to the photodegradation process. Moreover, ATG3 showed high recyclability, which retains 80 % of yield even after 10 cycles. Those findings proved that ATG has high potential in the environmental remediation field.

Acinar micromechanics in health and lung injury: what we have learned from quantitative morphology.

Within the pulmonary acini ventilation and blood perfusion are brought together on a huge surface area separated by a very thin blood-gas barrier of tissue components to allow efficient gas exchange. During ventilation pulmonary acini are cyclically subjected to deformations which become manifest in changes of the dimensions of both alveolar and ductal airspaces as well as the interalveolar septa, composed of a dense capillary network and the delicate tissue layer forming the blood-gas barrier. These ventilation-related changes are referred to as micromechanics. In lung diseases, abnormalities in acinar micromechanics can be linked with injurious stresses and strains acting on the blood-gas barrier. The mechanisms by which interalveolar septa and the blood-gas barrier adapt to an increase in alveolar volume have been suggested to include unfolding, stretching, or changes in shape other than stretching and unfolding. Folding results in the formation of pleats in which alveolar epithelium is not exposed to air and parts of the blood-gas barrier are folded on each other. The opening of a collapsed alveolus (recruitment) can be considered as an extreme variant of septal wall unfolding. Alveolar recruitment can be detected with imaging techniques which achieve light microscopic resolution. Unfolding of pleats and stretching of the blood-gas barrier, however, require electron microscopic resolution to identify the basement membrane. While stretching results in an increase of the area of the basement membrane, unfolding of pleats and shape changes do not. Real time visualization of these processes, however, is currently not possible. In this review we provide an overview of septal wall micromechanics with focus on unfolding/folding as well as stretching. At the same time we provide a state-of-the-art design-based stereology methodology to quantify microarchitecture of alveoli and interalveolar septa based on different imaging techniques and design-based stereology.

AtomAI framework for deep learning analysis of image and spectroscopy data in electron and scanning probe microscopy

AtomAI is an open-source software package bridging instrument-specific Python libraries, deep learning, and simulation tools into a single ecosystem. AtomAI allows direct applications of the deep convolutional neural networks for atomic and mesoscopic image segmentation converting image and spectroscopy data into class-based local descriptors for downstream tasks such as statistical and graph analysis. For atomically-resolved imaging data, the output is types and positions of atomic species, with an option for subsequent refinement. AtomAI further allows the implementation of a broad range of image and spectrum analysis functions, including invariant variational autoencoders (VAEs). The latter consists of VAEs with rotational and (optionally) translational invariance for unsupervised and class-conditioned disentanglement of categorical and continuous data representations. In addition, AtomAI provides utilities for mapping structure-property relationships via im2spec and spec2im type of encoder-decoder models. Finally, AtomAI allows seamless connection to the first principles modeling with a Python interface, including molecular dynamics and density functional theory calculations on the inferred atomic position. While the majority of applications to date were based on atomically resolved electron microscopy, the flexibility of AtomAI allows straightforward extension towards the analysis of mesoscopic imaging data once the labels and feature identification workflows are established/available. The source code and example notebooks are available at https://github.com/pycroscopy/atomai.

Reconstructing neural circuits using multiresolution correlated light and electron microscopy.

Correlated light and electron microscopy (CLEM) can be used to combine functional and molecular characterizations of neurons with detailed anatomical maps of their synaptic organization. Here we describe a multiresolution approach to CLEM (mrCLEM) that efficiently targets electron microscopy (EM) imaging to optically characterized cells while maintaining optimal tissue preparation for high-throughput EM reconstruction. This approach hinges on the ease with which arrays of sections collected on a solid substrate can be repeatedly imaged at different scales using scanning electron microscopy. We match this multiresolution EM imaging with multiresolution confocal mapping of the aldehyde-fixed tissue. Features visible in lower resolution EM correspond well to features visible in densely labeled optical maps of fixed tissue. Iterative feature matching, starting with gross anatomical correspondences and ending with subcellular structure, can then be used to target high-resolution EM image acquisition and annotation to cells of interest. To demonstrate this technique and range of images used to link live optical imaging to EM reconstructions, we provide a walkthrough of a mouse retinal light to EM experiment as well as some examples from mouse brain slices.

High-Resolution Electron Tomography of Ultrathin Boerdijk-Coxeter-Bernal Nanowire Enabled by Superthin Metal Surface Coating.

The rapid advancement of transmission electron microscopy has resulted in revolutions in a variety of fields, including physics, chemistry, and materials science. With single-atom resolution, 3D information of each atom in nanoparticles is revealed, while 4D electron tomography is shown to capture the atomic structural kinetics in metal nanoparticles after phase transformation. Quantitative measurements of physical and chemical properties such as chemical coordination, defects, dislocation, and local strain have been made. However, due to the incompatibility of high dose rate with other ultrathin morphologies, such as nanowires, atomic electron tomography has been primarily limited to quasi-spherical nanoparticles. Herein, the 3D atomic structure of a complex core-shell nanowire composed of an ultrathin Boerdijk-Coxeter-Bernal (BCB) core nanowire and a noble metal thin layer shell deposited on the BCB nanowire surface is discovered. Furthermore, it is demonstrated that a new superthin noble metal layer deposition on an ultrathin BCB nanowire could mitigate electron beam damage using an in situ transmission electron microscope and atomic resolution electron tomography. The colloidal coating method developed for electron tomography can be broadly applied to protect the ultrathin nanomaterials from electron beam damage, benefiting both the advanced material characterizations and enabling fundamental in situ mechanistic studies.