This article presents a numerical model dedicated to the simulation of field ion microscopy (FIM). FIM was the first technique to image individual atoms on the surface of a material. By a careful control of the field evaporation of the atoms from the surface, the bulk of the material exposed, and, through a digitally processing a sequence of micrographs, a three-dimensional reconstruction can be achieved. 3DFIM is particularly suited to the direct observation of crystalline defects such as vacancies, interstitials, vacancy clusters, dislocations, and any combinations of theses defects that underpin the physical properties of materials. This makes 3DFIM extremely valuable for many material science and engineering applications, and further developing this technique is becoming crucial. The proposed model enables the simulation of imaging artefacts that are induced by non-regular field evaporation and by the impact of the perturbation of the electric field distribution of the distorted distribution of atoms close to defects. The model combines the meshless algorithm for field evaporation proposed by Rolland et al. (Robin-Rolland Model, or RRM) with fundamental aspects of the field ionization process of the gas image involved in FIM.

Silicon carbide (SiC) may be considered as a model system for the study of field ion evaporation of carbides, which must be understood to perform accurate analyses of these systems by atom probe tomography (APT). As for other wide-bandgap semiconductors, the measurement of the composition of SiC by APT presents biases depending on the experimental parameters. Unlike silicon, carbon is characterized by a complex surface behavior, including the formation of molecules and the tendency to produce correlated evaporation. Furthermore, the spatial precision of three-dimensional (3D) reconstructions is strongly degraded in the direction parallel to the specimen surface, which points out to a strong roughening or dynamic degradation of the surface. This is confirmed by field ion microscopy (FIM) analysis, which reveals that atoms may move on the specimen surface under the influence of the high electric field. This complex surface behavior eventually translates into hidden detection events and, therefore, to errors in the measurement of composition.

Atom probe tomography (APT) is often introduced as providing “atomic-scale” mapping of the composition of materials and as such is often exploited to analyze atomic neighborhoods within a material. Yet quantifying the actual spatial performance of the technique in a general case remains challenging, as it depends on the material system being investigated as well as on the specimen's geometry. Here, by using comparisons with field-ion microscopy experiments, field-ion imaging and field evaporation simulations, we provide the basis for a critical reflection on the spatial performance of APT in the analysis of pure metals, low alloyed systems and concentrated solid solutions (i.e., akin to high-entropy alloys). The spatial resolution imposes strong limitations on the possible interpretation of measured atomic neighborhoods, and directional neighborhood analyses restricted to the depth are expected to be more robust. We hope this work gets the community to reflect on its practices, in the same way, it got us to reflect on our work.