FIB-SEM procedure for APT sample preparation. a. Extraction of a silicon post using the Lift-out method. The sample has been milled with the help of a FIB in order to extract a strip of material. b. The strip is shaped in a post and welded onto a steel needle (platinum weld). c., d. and e. Successive annular milling steps permit to obtain a very sharp tip which curvature radius does not exceed 50nm.