Post–Focused Ion Beam (FIB) Transmission Electron Microscopy (TEM) Sample Processing: Low-Angle Ion Mill Cleanup

Author(s):

Wendy L. Sarney, Xiaohang Zhang, Mihee Ji, and Asher C. Leff

Abstract:

Focused ion beam (FIB) milling is a widely used technique for preparing thin lamellae for transmission electron microscopy. While FIB can yield foils with sufficient electron transparency, challenges remain in achieving optimal final thickness due to limitations in low-energy imaging and the need to preserve protective surface layers. Incomplete thinning, gallium ion (Ga⁺) damage, and post-milling oxidation can degrade image quality. To address these issues, a post-FIB treatment using low-energy, low-angle argon ion milling is employed in a Gatan precision ion polishing system. This report outlines the alignment and milling procedures, emphasizing careful control of milling angle and time to avoid removal of the protective platinum/carbon cap layers. Examples demonstrate enhanced image clarity and improved high-resolution lattice imaging in hafnium zirconium oxide and aluminum gallium nitride/aluminum nitride samples after post-FIB ion milling.