Preparation of high‐quality ultrathin transmission electron microscopy specimens of a nanocrystalline metallic powder

Abstract

This article explores the achievable transmission electron microscopy specimen thickness and quality by using three different preparation methods in the case of a high-strength nanocrystalline Cu-Nb powder alloy. Low specimen thickness is essential for spatially resolved analyses of the grains in nanocrystalline materials. We have found that single-sided as well as double-sided low-angle Ar ion milling of the Cu-Nb powders embedded into epoxy resin produced wedge-shaped particles of very low thickness (<10 nm) near the edge. By means of a modified focused ion beam lift-out technique generating holes in the lamella interior large micrometer-sized electron-transparent regions were obtained. However, this lamella displayed a higher thickness at the rim of ≥30 nm. Limiting factors for the observed thicknesses are discussed including ion damage depths, backscattering, and surface roughness, which depend on ion type, energy, current density, and specimen motion. Finally, sections cut by ultramicrotomy at low stroke rate and low set thickness offered vast, several tens of square micrometers uniformly thin regions of ∼10-nm minimum thickness. As major drawbacks, we have detected a thin coating on the sections consisting of epoxy deployed as the embedding material and considerable nanoscale thickness variations.

Effect of Eu‐doping and grain boundary plane on complexion transitions in MgAl2O4

“…All annealed samples were polished to facilitate electron microscopy characterization. Thin specimens for scanning transmission electron microscopy (STEM) were prepared via a focused ion beam (FIB) lift‐out technique using an FEI Scios instrument 16 . Final milling steps using 900 eV Ar‐ion bean were conducted to remove FIB damage using a Fischione 1040 NanoMill 17 .…”

Imaging of tissue sections with very slow electrons

“…Methods available for the preparation of ultrathin sections of various substances are capable of producing layers at and even below 10 nm [3] which enables one to further decrease the energy of the electrons provided the image resolution is maintained. Moreover, when using the scanning transmission electron microscopy (STEM) technique virtually all transmitted electrons can be utilised for imaging, while in TEM we are restricted to using electrons capable of forming the final direct image at acceptable quality.…”