Smoother Shank Profile for Atom Probe Specimens Prepared by the Multi-step Focused Ion Beam Milling

Focused ion beam (FIB) milling has been successfully used to prepare a range of atom probe specimens from metal alloys at site specific locations such as grain boundaries, thin ribbons, powders, and multilayer film materials. Commonly employed, 3-step process generates ledges that act as a stress concentration sites at the shank of the specimens. Smoother shank profile of the specimen is therefore desirable, so as to reduce the chance of specimen failure at such points. In this work, an improved method to fabricate the specimens from planar multilayer thin films was presented. The films were deposited onto etched Si posts, prepared by the lithographic patterning of a Si wafer. Capping layers (e.g. Cu, Ni, and Fe) were deposited on top to protect the films of interest from implantation damage caused by the high energy ion beams. Individual posts were attached to the tip of sharpened metal wires, and subsequently sharpened by ion milling in a FEI FIB 200 instrument without further Pt deposition required