Structure, shape and composition are the basic parameters responsible for properties of nanoscale materials, distinguishing them from their bulk counterparts. To reveal these in three dimensions at the nanoscale, electron tomography is a powerful tool. Advancing electron tomography to atomic resolution in an aberration-corrected transmission electron microscope remains challenging and has been demonstrated only a few times using strong constraints or extensive filtering. Here we demonstrate atomic resolution electron tomography on silver/gold core/shell nanoclusters grown in superfluid helium nanodroplets. We reveal morphology and composition of a cluster identifying gold- and silver-rich regions in three dimensions and we estimate atomic positions without using any prior information and with minimal filtering. The ability to get full three-dimensional information down to the atomic scale allows understanding the growth and deposition process of the nanoclusters and demonstrates an approach that may be generally applicable to all types of nanoscale materials.

We report on the formation of one-dimensional Au/Ag core-shell nanostructures in superfluid helium nanodroplets $\left({\mathrm{He}}_N\right)$ and their subsequent surface deposition under soft landing conditions. In vortex charged ${\mathrm{He}}_N$, dopant atoms and clusters prefer to agglomerate along vortex cores, which serve as personal cryo-templates for each nanowire. A sequential pickup scheme enables the fabrication of Au/Ag structures with either Au as core and Ag as shell or vice versa. The core-shell structure is in both cases shown by energy-dispersive x-ray spectroscopy (EDX) in a scanning transmission electron microscope (STEM). The inherent spatial resolution and element sensitivity of this method allows a direct observation of the two different phases. High resolution STEM studies elucidate morphological details of the Au/Ag nanostructures and, together with the EDX analysis, indicate that the nanowires are formed in a multicenter aggregation process.

Ag nanowires with diameters below 6 nm are grown within vortex containing superfluid helium nanodroplets and deposited onto a heatable substrate at cryogenic temperatures. The experimental setup allows an unbiased investigation of the inherent stability of pristine silver nanowires, which is virtually impossible with other methods due to chemical processes or templates involved in standard production routes. We demonstrate by experiment and by adaption of a theoretical model that initially continuous wires disintegrate into chains of spheres. This phenomenon is well described by a Rayleigh-like breakup mechanism when the substrate is heated to room temperature. Our findings clarify the recent discussions on the cause of the observed segmented patterns, where a breakup during deposition [Gomez et al., Phys. Rev. Lett., 2012, 108, 155302] or mechanisms intrinsic to the helium droplet mediated growth process [Spence et al., Phys. Chem. Chem. Phys., 2014, 16, 6903] have been proposed. The experimental setup confirms the validity of previous suggestions derived from bulk superfluid helium experiments [Gordon et al., Phys. Chem. Chem. Phys., 2014, 16, 25229] for the helium droplet system, and further allows a much more accurate determination of the breakup temperature.

Lithium iron phosphate (LiFePO₄, LFP) serves as a crucial active material in Li‐ion batteries due to its excellent cycle life, safety, eco‐friendliness, and high‐rate performance. Nonetheless, debates persist regarding the atomic‐level mechanisms underlying the electrochemical lithium insertion/extraction process and associated phase transitions. A profound clarity on the fundamental lithium storage mechanisms within LFP is achieved through meticulous scanning transmission electron microscopy (STEM) and selected area electron diffraction (SAED) imaging. This study shows systematical tracking of lithium ions within their respective channels and unveils the phase distribution within individual LFP crystallites not only quantitatively but also at unprecedented atomic‐level resolution. Incontrovertible evidence of the co‐existence of segregated yet only partially lithiated Li_xFePO₄ regions in electrochemically delithiated LFP crystals are provided using correlative electron microscopic methods and data analysis. Remarkably, by directly tracing ion transport within lithium channels a diffusion coefficient range (10⁻¹³–10⁻¹⁵ cm²s⁻¹) for correlated lithium ion motion in LFP is estimated and Funke's ion transport jump relaxation model is validated experimentally for the first time. These findings significantly advance the understanding of olivine‐type materials, offering invaluable insights for designing superior battery materials.

Micrometer sized helium droplets provide an extraordinary environment for the growth of nanoparticles. The method promises great potential for the preparation of core-shell particles as well as one-dimensional nanostructures, which agglomerate along quantum vortices, without involving solvents, ligands, or additives. Using a new apparatus, which enables us to record mass spectra of heavy dopant clusters (>10⁴ amu) and to produce samples for transmission electron microscopy simultaneously, we synthesize bare and bimetallic nanoparticles consisting of various materials (Au, Ni, Cr, and Ag). We present a systematical study of the growth process of clusters and nanoparticles inside the helium droplets, which can be described with a simple theoretical model.