Evaluation of top, angle, and side cleaned FIB samples for TEM analysis

TEM specimens of a LaAlO(3)/SrTiO(3) multilayer are prepared by FIB with internal lift out. Using a Ga(+1) beam of 5 kV, a final cleaning step yielding top, top-angle, side, and bottom-angle cleaning is performed. Different cleaning procedures, which can be easily implemented in a dual beam FIB system, are described and compared; all cleaning types produce thin lamellae, useful for HRTEM and HAADF-STEM work up to atomic resolution. However, the top cleaned lamellae are strongly affected by the curtain effect. Top-angle cleaned specimens show an amorphous layer of around 5 nm at the specimen surfaces, due to damage and redeposition. Furthermore, it is observed that the LaAlO(3) layers are preferentially destroyed and transformed into amorphous material, during the thinning process.