We consider the effects of different boundaries on the visibility of a specimen detail providing a compositional contrast in scanning electron microscopy, operating with backscattered electrons or secondary electrons. An object characterized by a gradual variation in composition, an As‐doped region in Si, is investigated. The different boundaries in the cross‐sectioned specimen correspond to the absence or presence of a poly‐Si layer on top of the implanted region, deposited after the annealing treatment. It is shown that the interpretation model used for image formation is of paramount relevance for understanding the experimental results, indicating that the boundaries of the doped region are important in hindering or enhancing its visibility. The relevance of experimental parameters such as electron energy and probe dimension is also reported.