Three-dimensional atomic scale microscopy with the atom probe

A new type of high resolution nanoanalytical microscope, the three-dimensional atom-probe, has been recently developed. The tomographic atom-probe (TAP) developed in our laboratory provides three-dimensional maps of chemical heterogeneities in a metallic material on a near-atomic scale. The basic principle of this new generation apparatus relies on the field evaporation and ionisation of atoms from the material. Chemical species are identified by time-of-flight mass spectrometry. The position of atoms at the specimen surface is determined with the aid of a specially designed position-sensitive multidetector. In this paper the high spatial resolution of the TAP is illustrated through some metallurgical examples by studying the very early stages of unmixing and ordering reactions and the mapping of interfacial segregations.