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.

Noble metallic nanoparticles with unique plasmonic properties are useful in a variety of applications including bio-imaging, sensing, cancer therapy, etc. The properties of metallic nanoparticles can be tuned in multiple ways, among which laser welding is a highly efficient method. In this study, laser-induced inter-welding of Ag–Au nanoparticle (NP) dimers was investigated using in situ transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). For the first time, the welding process was directly visualized. The structural and compositional evolution of Ag–Au dimers was studied in detail, and several typical nanostructures formed during the welding process, including two types of core–shell structures, were discovered. Based on these observations, we proposed a complete mechanism explaining how welding proceeds under the influence of a laser. Finite difference time domain (FDTD) simulations demonstrated that the plasmonic properties of welded Ag–Au dimers were different from those of pure Au–Au or Ag–Ag dimers and can be tuned by forming shells, alloying or changing the size ratio of Ag and Au NPs.

Understanding the structural stability of nanomaterials such as nanowires is imperative for their practical applications. Here, using single-shot ultrafast transmission electron microscopy, we captured the Plateau-Rayleigh instability behavior of silver nanowires decomposing into silver nanoparticles upon laser irradiation on nanosecond time scales. We found that this dynamic process can be accelerated by a factor of 10 through increasing the peak laser fluence from 6.03 to 14.60 mJ/cm². Moreover, by comparing the laser fluence required to initiate the Plateau-Rayleigh instability in silver nanowires on carbon and Formvar membranes, it was found that the main driving force for the Plateau-Rayleigh instability in this study was substrate heating. Finite element analysis and molecular dynamics simulations are also applied to estimate the temperature jump of the nanowires and atomistic behavior, respectively. In addition, the complex motions of silver nanowires under laser irradiation were systematically investigated by combining the results of ultrafast transmission electron microscopy with scanning electron microscopy characterizations and were determined to be related to nanowire-membrane interactions or pre-existing stresses on the nanowires, which in turn demonstrated the potential of ultrafast transmission electron microscopy for the characterization of nanomaterials and devices under extreme conditions.

In situ laser heating with transmission electron microscopy (ILH‐TEM) is utilized as a neoteric method to probe the thermal behavior and stability of metal‐ (Pt, Au‐) metal oxide (Fe₃O₄) heterodimer (HD) nanoparticles. Two different supporting membrane types are used for the laser heating: pure‐carbon and silicon‐nitride, requiring different amounts of laser power to induce morphological changes. Diffraction pattern analysis and scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) are utilized to analyze reduction of the iron oxide under laser heating, which has differing effects depending on the support film heating mode and the heterodimer particle. A unique wetting behavior of Pt and Au onto Fe₃O₄ is observed in both heterodimers of Au and Pt. However, this wetting behavior is found to be partially reversible only in the case of the Au‐Fe₃O₄ HD system, whereas for the Pt‐Fe₃O₄ HD system, this wetting process was found to be irreversible under the applied experimental conditions. This observation of a novel wetting behavior has future implications for understanding the performance of oxide supported metal nanoparticles in high temperature applications, such as catalysis.

Epoxy 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:Y₂O₃-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.