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

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Transmission Electron Microscopy (TEM) requires precisely prepared specimens.
• Focused Ion Beam (FIB) milling is a common technique for preparing TEM specimens, especially for complex multilayers like LaAlO(3)/SrTiO(3).
• Optimizing FIB parameters is crucial to minimize artifacts and preserve the material's native structure.

Purpose of the Study:

• To compare different FIB cleaning procedures for LaAlO(3)/SrTiO(3) multilayer TEM specimen preparation.
• To evaluate the impact of various cleaning methods on specimen quality and potential artifacts.
• To identify the most suitable FIB cleaning strategy for high-resolution imaging.

Main Methods:

• Preparation of TEM specimens from LaAlO(3)/SrTiO(3) multilayers using the focused ion beam (FIB) internal lift-out method.
• Application of a 5 kV Ga(+) beam for final cleaning steps, including top, top-angle, side, and bottom-angle cleaning.
• Comparative analysis of the resulting lamellae using High-Resolution TEM (HRTEM) and High-Angle Annular Dark-Field STEM (HAADF-STEM).

Main Results:

• All tested FIB cleaning methods produced thin lamellae suitable for atomic-resolution imaging.
• Top cleaning resulted in significant curtain effects.
• Top-angle cleaning created a ~5 nm amorphous surface layer due to ion damage and redeposition, and preferentially amorphized the LaAlO(3) layers.

Conclusions:

• While top-angle cleaning offers improvements, the amorphization of LaAlO(3) layers during FIB thinning remains a significant challenge.
• Careful selection and implementation of FIB cleaning procedures are essential for obtaining high-quality TEM specimens of oxide multilayers.
• Further research may be needed to mitigate LaAlO(3) layer amorphization during FIB preparation.