Mesoscopic modeling of field evaporation on atom probe tomography

Abstract

Reconstructions in Atom Probe Tomography (APT) are biased by image distortions arising from dynamic changes of the specimen geometry that controls image projection. Despite the strong efforts to build realistic models for understanding and reproducing image artefacts, current models are too slow or not adapted to be routinely used in image correction approaches. To understand the APT imaging process for real size samples submitted to realistic experimental conditions of electric field and temperature, we propose an alternative simulation tool based on a coarse-grained model of the sample surface. The surface electric field on a meshed surface is calculated by using continuous models describing field evaporation. The dynamic evolution of the sample surface and the image projection are predicted using materials properties. We show that the interplay between temperature and electric field is an important ingredient in predicting the ion projection, in pure metals and in more complex materials. This fast approach accurately reproduces the well-known local magnification and trajectory overlaps effects in the evaporation of small particles. By combining prior knowledge about the sample structure and properties, the model could be used to improve the reconstruction approaches for complex sample geometries.