Extracting TEM lamellae from micro/nano particles through a thin film embedding strengthened FIB approach

A cross-sectional lamella in thickness around 20 ∼ 100 nm is essential for (S)TEM characterizations of micro/nano particles with compositional gradients or structural inhomogeneity including core shell, surface doped and coated structures, or those with excessive thickness in one or more dimensions. Focused ion beam (FIB) remains as the most reliable technique for extracting site-specific, thin cross-sectional TEM samples. However, conventional bulk epoxy resin embedding often compromises precision for site-specific processing due to particle aggregation with surrounded bubble defects resulting in particle detachment, poor observability, and failed sample preparation under ion beam milling. In this paper, we have proposed a thin film embedding-strengthened focused ion beam (FES-FIB) technique to improve precision for site-specific and mitigate particles detachment during ion beam milling, enabling precise extraction of ultra-thin lamellae for (S)TEM characterization. Consequently, the feasibility of this FES-FIB process is verified by site-specific extraction of the cross-sectional lamellae from two typical structures: spherical microparticles and nanoflakes, successfully collecting the morphology and structural details by (S)TEM.