Focused ion beam (FIB) instruments have become essential for the preparation of atom probe samples from heterogeneous materials. Previous sample preparation methods such as electropolishing are limited in their application due to either geometrical or electrochemical constraints. Recent developments in sample preparation using a FIB have enabled the production of AP samples from various materials and, more importantly, from non-traditional sample geometries that contain multilayered thin film structures (MLF).
Most sample preparation using a FIB first involves a sample that has been reduced in size through some manual sample preparation technique like tripod polishing or cutting. Smaller, thinner samples require less milling time in the FIB. A silicon wafer etched with the “Bosch” process was used to produce a surface that contains millions of 20, 16, 12, 8, and 4 μm square by -180 μrn long “posts”, Fig. 1. A multilayer film structure is deposited on the flat surface of the silicon posts in a standard deposition process.