Atom Probe Specimen Preparation with a Dual Beam FIB Miller

Several methods have been developed to fabricate atom probe specimens from different forms of materials, including thin ribbons, mechanically ground sheet and fine powders. In addition, FIB-based methods can be used in conjunction with electropolishing methods to improve the shape, surface finish and taper angle of specimens. Several lift-out (LO) methods have been developed for selecting specific microstructural features or other regions of interest such as phases, interfaces, grain boundaries, subsurface or implanted regions and interdendritic regions. These LO methods make use of an in-situ micromanipulator and platinum deposition to transfer and attach the lifted out volume to a post for final annular milling into a sharp needle-shaped specimen. In order to improve the efficiency and to facilitate the lift-out procedure, some special specimen mounts that hold both the specimen and the support post at the appropriate working distance have been developed. The advantages and disadvantages of some different variants of the lift-out method will be described. The dual beam SEM/FIB instruments enable gallium implantation to be reduced as the milling process may be monitored with the electron beam rather than the gallium ion beam. One approach of reducing the depth of the implanted gallium is to reduce the accelerating voltage of the gallium ion source for the final stages of specimen preparation. This was shown by SRIM calculations of the range and struggle of gallium ions into an iron substrate