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Electron backscatter diffraction (EBSD) is a powerful characterization technique which allows the study of microstructure, grain size, and orientation as well as strain of a crystallographic sample. In addition, the technique can be used for phase analysis. A mirror-flat sample surface is required for this analysis technique and different polishing approaches have been used over the years. A commonly used approach is the focused ion beam (FIB) polishing. Unfortunately, artefacts that can be easily induced by Ga FIB polishing approaches are seldom published. This work aims to provide a better understanding of the underlying causes for artefact formation and to assess if the helium ion microscope is better suited to achieve the required mirror-flat sample surface when operating the ion source with Ne instead of He. Copper was chosen as a test material and polished using Ga and Ne ions with different ion energies as well as incident angles. The results show that crystal structure alterations and, in some instances, phase transformation of Cu to Cu 3 Ga occurred when polishing with Ga ions. Polishing with high-energy Ne ions at a glancing angle maintains the crystal structure and significantly improves indexing in EBSD measurements. By milling down to a depth equaling the depth of the interaction volume, a steady-state condition of ion impurity concentration and number of induced defects is reached. The EBSD measurements and Monte Carlo simulations indicate that when this steady-state condition is reached more quickly, which can be achieved using high-energy Ne ions at a glancing incidence, then the overall damage to the specimen is reduced.

Exposed to ionizing radiation, nanomaterials often undergo unusual transformations compared to their bulk form. However, atomic-level mechanisms of such transformations are largely unknown. This work visualizes and quantifies nanopore shrinkage in nanoporous alumina subjected to low-energy ion beams in a helium ion microscope. Mass transport in porous alumina is thus simultaneously induced and imaged with nanoscale precision, thereby relating nanoscale interactions to mesoscopic deformations. The interplay between chemical bonds, disorders, and ionization-induced transformations is analyzed. It is found that irradiation-induced diffusion is responsible for mass transport and that the ionization affects mobility of diffusive entities. The extraordinary room temperature superplasticity of the normally brittle alumina is discovered. These findings enable the effective manipulation of chemical bonds and structural order by nanoscale ion-matter interactions to produce mesoscopic structures with nanometer precision, such as ultra-high density arrays of sub-10-nm pores with or without the accompanying controlled plastic deformations. When nanomaterials are exposed to ionizing radiation, they often sustain mesoscopic changes not seen in their bulk form. Here, the authors use a helium ion microscope to induce and examine transformations in nanoporous alumina, drawing connections between atomic structure and nano- and microscale behavior in materials under irradiation.

Ion beam-induced heat damage in thermally low conductive specimens such as biological samples is gaining increased interest within the scientific community. This is partly due to the increased use of FIB-SEMs in biology as well as the development of complex materials, such as polymers, which need to be analyzed. The work presented here looks at the physics behind the ion beam–sample interactions and the effect of the incident ion energy (set by the acceleration voltage) on inducing increases in sample temperature and potential heat damage in thermally low conductive materials such as polymers and biological samples. The ion beam-induced heat for different ion beam currents at low acceleration voltages is calculated using Fourier’s law of heat transfer, finite element simulations, and numerical modelling results and compared to experiments. The results indicate that with lower accelerator voltages, higher ion beam currents in the nanoampere range can be used to pattern or image soft material and non-resin-embedded biological samples with increased milling speed but reduced heat damage.

A dark-field scanning transmission ion microscopy detector was designed for the helium ion microscope. The detection principle is based on a secondary electron conversion holder with an exchangeable aperture strip allowing its acceptance angle to be tuned from 3 to 98 mrad. The contrast mechanism and performance were investigated using freestanding nanometer-thin carbon membranes. The results demonstrate that the detector can be optimized either for most efficient signal collection or for maximum image contrast. The designed setup allows for the imaging of thin low-density materials that otherwise provide little signal or contrast and for a clear end-point detection in the fabrication of nanopores. In addition, the detector is able to determine the thickness of membranes with sub-nanometer precision by quantitatively evaluating the image signal and comparing the results with Monte Carlo simulations. The thickness determined by the dark-field transmission detector is compared to X-ray photoelectron spectroscopy and energy-filtered transmission electron microscopy measurements.

Nanoparticle syntheses utilizing biomimetic approaches have advanced in recent years. Polypeptides, with their ability to influence inorganic crystal growth, are a topic of great interest. Their effect on the particle formation has not been completely understood yet. Here we report a bioinspired synthesis of cobalt ferrite nanoparticles carried out in vitro under mild conditions using a short, synthetic polypeptide c25-mms6. The influence of c25-mms6 on the nanoparticle formation was investigated by comparing the particles synthesized with the polypeptide to particles synthesized under equivalent conditions without c25-mms6. A separation into D small,av  = 10 nm small, superparamagnetic spheres and D big,av  = 48 nm disc-like single-domain particles was observed. Non-stoichiometric cobalt ferrite particles with a shape-dependent stoichiometry were produced in the polypeptide-free synthesis. Stoichiometric D small,av  = 10 nm CoFe 2 O 4 spheres and D big,av  = 60–70 nm  Co 2 FeO 4 ferromagnetic discs were obtained in the polypeptide-enhanced synthesis. The results indicate that the polypeptide acts as a catalyst during the multistep biomineralization process and allows the formation of stoichiometric phases which cannot be synthesized at room temperature using conventional bottom-up syntheses.