Three-dimensional atomic scale microscopy with the atom probe

A new type of high resolution nanoanalytical microscope, the three-dimensio nal atom-probe, has been recently developed. The tomographic atom-probe (TA P) developed in our laboratory provides three-dimensional maps of chemical heterogeneities in a metallic material on a near-atomic scale. The basic pr inciple of this new generation apparatus relies on the field evaporation an d ionisation of atoms from the material. Chemical species are identified by time-of-flight mass spectrometry. The position of atoms at the specimen su rface is determined with the aid of a specially designed position-sensitive multidetector. In this paper the high spatial resolution of the TAP is ill ustrated through some metallurgical examples by studying the very early sta ges of unmixing and ordering reactions and the mapping of interfacial segre gations. (C) 1999 Elsevier Science B.V. All rights reserved.