Focused ion beam fabrication of field-ion microscope specimens from mechanically milled pearlitic steel powder

Sharp needle-like specimens for atom-probe field-ion microscope (APFIM) analysis have been prepared successfully from mechanically milled pearlitic steel powders. Mechanically milled powders were packed in a stainless steel tube with carbonyl steel powders and then consolidated by sheath cold-rolling to obtain a bulk composite. A small square rod was cut out from the bulk and electropolished to a blunt needle. It was then fabricated to a nanometre-sized needle by a focused ion beam technique using an annular gallium ion beam. The tip radius of the specimen was <50 nm, which is suitable for use in APFIM.