Surface Dynamics of Field Evaporation in Silicon Carbide

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.