Towards 3D lattice reconstruction with the Position Sensitive Atom Probe

Abstract 3-dimensional atom probe (3DAP) analysis enables 3D reconstruction of the chemical variations inside materials with near atomic resolution. This technique has enabled important insights into the phase chemistry and microstructure of a range of complex engineering materials. Although individual planes can be resolved when analysing in a direction close to a low-index pole, the spatial resolution of this technique has not been sufficient for reconstruction of all the original lattice positions. The spatial resolution is thought to be fundamentally limited by small lateral displacements of the atom on the surface of the specimen during the field evaporation process due primarily to interactions with the neighbouring surface atoms. It has therefore been considered that it will be impossible to correctly reconstruct the crystal lattice from 3DAP data. Recently, we have found that a 3DAP reconstruction of a region near a grain boundary in pure tungsten (an element renown for its good imaging and evaporation behaviour) revealed several different sets of crystallographic planes visible at angles up to 45° from the direction of analysis.