Room-Temperature FIB-Based TEM Specimen Preparation for Radiation-Sensitive Solid-State Electrolytes

Focused ion beam (FIB) preparation of garnet-type solid-state electrolytes such as Li6.4La3Zr1.4Ta0.6O12 (LLZTO) is complicated by beam-induced charging, amorphization, and lithium exsolution. In this work, we develop a room-temperature FIB-based transmission electron microscopy (TEM) workflow that effectively mitigates these artifacts without the need for cryogenic protection. Molecular dynamics simulations show that localized electric fields driven by charge accumulation induce defect accumulation, sequential ion loss, and structural collapse, with structural amorphization already emerging at the stage where the detected elemental loss is limited to Li and O. Monte Carlo simulations quantify Ga+ implantation ranges and establish an empirical thickness-voltage relationship to prevent lamella bending. The optimized workflow integrates substrate-supported prethinning, alternating dual-side milling, and low-voltage grazing-incidence polishing, which minimizes Ga+ implantation, Li/O sputtering, and amorphization. The resulting LLZTO lamellae exhibit high crystallinity and chemical fidelity, confirmed by low-dose high-resolution TEM, selected area electron diffraction, and scanning transmission electron microscopy (STEM) imaging at 200 and 300 kV. This combined experimental and computational approach provides a reproducible route for preparing sensitive solid-state electrolyte specimens.