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Preparation of high‐quality ultrathin transmission electron microscopy specimens of a nanocrystalline metallic powder
Author(s) -
Riedl Thomas,
Gemming Thomas,
Mickel Christine,
Eymann Konrad,
Kirchner Alexander,
Kieback Bernd
Publication year - 2012
Publication title -
microscopy research and technique
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 118
eISSN - 1097-0029
pISSN - 1059-910X
DOI - 10.1002/jemt.21116
Subject(s) - materials science , nanocrystalline material , focused ion beam , transmission electron microscopy , lamella (surface anatomy) , composite material , foil method , ion milling machine , surface finish , micrometer , ion beam , ion , optics , nanotechnology , layer (electronics) , beam (structure) , quantum mechanics , physics
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. Microsc. Res. Tech. 75:711–719, 2012. © 2011 Wiley Periodicals, Inc.