4D Scanning Transmission Ultrafast Electron Microscopy: Single-Particle Imaging and Spectroscopy

We report the development of 4D scanning transmission ultrafast electron microscopy (ST-UEM). The method was demonstrated in the imaging of silver nanowires and gold nanoparticles. For the wire, the mechanical motion and shape morphological dynamics were imaged, and from the images we obtained the resonance frequency and the dephasing time of the motion. Moreover, we demonstrate here the simultaneous acquisition of dark-field images and electron energy loss spectra from a single gold nanoparticle, which is not possible with conventional methods. The local probing capabilities of ST-UEM open new avenues for probing dynamic processes, from single isolated to embedded nanostructures, without being affected by the heterogeneous processes of ensemble-averaged dynamics. Such methodology promises to have wide-ranging applications in materials science and in single-particle biological imaging

Electron Energy Loss Spectroscopy Signal Processing Tool for Materials Research

Allowing scientists to analyze materials’ structure and chemistry at an atomic level, the electron microscope has become a vital tool in materials engineering. Due to the inherent nature of signals (inelastic electrons or X-ray) having a low signal-to-noise ratio, processing the signal collected with an electron microscope is frequently required and uses sophisticated computer code. The software written to do this can be very difficult to learn and use. To make these tools more easily accessible to new users, we will create a simple user interface and host it online. Using the Rappture development tool, a menu driven graphical user interface was created for the HyperSpy software package allowing all software commands to be handled automatically. Choosing the Rappture development tool means the interface will also be easily updated to include new functionality as HyperSpy evolves. When completed, this interface will be made available online via the NanoHUB server at Purdue University. This will help scientists analyze materials in a uniform and repeatable manner using a readily available and easy to learn interface

Development of Electron Microscopy Analysis and Simulation tools for nanoHUB

Electron microscopy has a crucial role in the field of materials science and structural biology. Although electron microscopy gives lots of important results and findings, some additional simulations and image processing/reconstruction is required to get more information from the data that are collected from the experiments. For this purpose, researchers are using IMOD1 and QSTEM2 for electron microscopy analysis and simulation. IMOD is a set of programs used for tomographic reconstruction and 3D visualization and QSTEM is used for quantitative simulations of TEM and STEM images. However, IMOD and QSTEM are hard to install or use for beginners who are not familiar with computational skills. To overcome this issue, we have developed “Online IMOD and STEM tools” to allow users to perform microscopy analysis and simulation with ease. We applied several ways to launch or combine tools. Based on the original source codes of the software, we used the graphical interface builder Rappture to build a new interface to launch several tools. Also, we used the nanowhim window manager to combine and organize tools. The online version of IMOD and QSTEM will enable researchers from all over the world to use IMOD and QSTEM programs directly and easily on the nanoHUB website

Introduction of Rare-Earth Oxide Nanoparticles in CNT-Based Nanocomposites for Improved Detection of Underlying CNT Network

17 USC 105 interim-entered record; under review.The article of record as published may be found at https://doi.org/10.3390/nano11092168Epoxy resins for adhesive and structural applications are widely employed by various industries. The introduction of high aspect ratio nanometric conductive fillers, i.e., carbon nanotubes, are well studied and are known to improve the electrical properties of the bulk material by orders of magnitude. This improved electrical conductivity has made carbon nanotube-based nanocomposites an attractive material for applications where their weight savings are at a premium. However, the analytical methods for validating carbon nanotube (CNT) nanofiller dispersion and for assuring that the properties they induce extend to the entire volume are destructive and inhibited by poor resolution between matrix and tube bundles. Herein, rare-earth oxide nanoparticles are synthesized on CNT walls for the purpose of increasing the contrast between their network and the surrounding matrix when studied by imaging techniques, alleviating these issues. The adherence of the synthesized nanoparticles to the CNT walls is documented via transmission electron microscopy. The crystalline phases generated during the various fabrication steps are determined using X-ray diffraction. Deep ultraviolet-induced fluorescence of the Eu:Y2 O3 -CNT nanostructures is verified. The impacts to nanocomposite electrical properties resulting from dopant introduction are characterized. The scanning electron microscopy imaging of CNT pulp and nanocomposites fabricated from untreated CNTs and Eu:Y2O3-CNTs are compared, resulting in improved contrast and detection of CNT bundles. The micro-CT scans of composites with similar results are presented for discussion.U.S. Government affiliation is unstated in article text

A Comparative Study of Gallium-, Xenon-, and Helium-Focused Ion Beams for the Milling of GaN

The milling profiles of single-crystal gallium nitride (GaN) when subjected to focused ion beams (FIBs) using gallium (Ga), xenon (Xe), and helium (He) ion sources were investigated. An experimental analysis via annular dark-field scanning transmission electron microscopy (ADF-STEM) and high-resolution transmission electron microscopy (HRTEM) revealed that Ga-FIB milling yields trenches with higher aspect ratios compared to Xe-FIB milling for the selected ion beam parameters (30 kV, 42 pA), while He-FIB induces local lattice disorder. Molecular dynamics (MD) simulations were employed to investigate the milling process, confirming that probe size critically influences trench aspect ratios. Interestingly, the MD simulations also showed that Xe-FIB generates higher aspect ratios than Ga-FIB with the same probe size, indicating that Xe-FIB could also be an effective option for nanoscale patterning. Atomic defects such as vacancies and interstitials in GaN from He-FIB milling were suggested by the MD simulations, supporting the lattice disorder observed via HRTEM. This combined experimental and simulation approach has enhanced our understanding of FIB milling dynamics and will benefit the fabrication of nanostructures via the FIB technique

Direct Visualization of Aluminum Particle Wetting on Carbon Using In Situ Laser Heating TEM

The fundamental understanding of aluminum particle wetting is critical for many industrial and military applications, such as nanocomposites, surface coatings, and explosives. In this study, the wetting behavior of aluminum particles on carbon is directly visualized using an in situ laser heating transmission electron microscope (ILH-TEM). Morphological, structural, and chemical analyses of the reaction products formed after laser irradiation of the aluminum–carbon system are characterized ex situ by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) using imaging, diffraction, and electron energy loss spectroscopy (EELS). Different stages of the wetting were captured for ex situ analysis by exposing the samples to a varying number of laser pulses. Additionally, molecular dynamics (MD) simulations were carried out using a reactive force field (ReaxFF) to obtain an atomistic perspective of the aluminum–carbon interactions. The results show that dissolution and reaction occur during the wetting process and the spreading front advancement results from the reaction between aluminum and carbon at the triple line. The complete mechanism of aluminum wetting is discussed in detail, i.e., the impact of laser heating, breakdown of the passivation layer, and interaction of aluminum and carbon, resulting in wetting enhancement

Direct Visualization of Aluminum Particle Wetting on Carbon Using In Situ Laser Heating TEM

The fundamental understanding of aluminum particle wetting is critical for many industrial and military applications, such as nanocomposites, surface coatings, and explosives. In this study, the wetting behavior of aluminum particles on carbon is directly visualized using an in situ laser heating transmission electron microscope (ILH-TEM). Morphological, structural, and chemical analyses of the reaction products formed after laser irradiation of the aluminum–carbon system are characterized ex situ by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) using imaging, diffraction, and electron energy loss spectroscopy (EELS). Different stages of the wetting were captured for ex situ analysis by exposing the samples to a varying number of laser pulses. Additionally, molecular dynamics (MD) simulations were carried out using a reactive force field (ReaxFF) to obtain an atomistic perspective of the aluminum–carbon interactions. The results show that dissolution and reaction occur during the wetting process and the spreading front advancement results from the reaction between aluminum and carbon at the triple line. The complete mechanism of aluminum wetting is discussed in detail, i.e., the impact of laser heating, breakdown of the passivation layer, and interaction of aluminum and carbon, resulting in wetting enhancement