Fyzikální ústav Akademie věd ČR

In cooperation with Bristol university, we proposed a technique for preparation of samples with highly localized in form of thin foils for high-resolution transmission electron microscopy (HRTEM).

This method consists in preparation of a sample of a selected locality using focused ion beam (FIB): from the selected locality, the sample is prepared which contains a characteristic structural object – in our case the triple junction of three grain boundaries in a tricrystal (Fig. 1a). (For information, the distance of the triple junction from the edge of prepared sample is 5 µm.) the sample is mounted to a nanomanipulator (Fig. 1b) and transported to a HRTEM holder (Figs. 1c,d). Fig. 1e documents that the foil thickness after final thinning by means of the FIB technique is ca 100 nm. In the samples prepared in this way we did study atomic structure (Fig. 2, bright field) and chemical composition (Fig. 3) in an Fe–Si(P,Sn) alloy by means of HRTEM. Concentration profile was measured using EDS perpendicularly to the grain boundary in distance of 20 nm from the triple junction and shows an enrichment of the grain boundary monatomic layer by phosphorus; in contrast, the boundary is depleted by tin in this layer. Tin enrichment is observed in atomic layers vicinal to the grain boundary.

F. Sorbello, G.M. Hughes, P. Lejček, P.J. Heard, P.E.J. Flewitt: Preparation of location-specific thin foils from Fe–3% Si bi- and tri-crystals for examination in a FEG-STEM, Ultramicroscopy 109 (2009) 147–153. doi:10.1016/j.ultramic.2008.08.011