Images and contrasts

The scanning electron microscope is mainly used to obtain images of the sample surface. These images are formed mainly by surface electron emissions (secondary and backscattered electrons). Different contrasts can be observed, providing a wide range of information about the sample, essentially about its relief (topographic contrast), but also about the distribution of the phases present ("atomic number" contrast using backscattered electrons). Other contrasts can also be observed, depending on the case, in particular chemical contrasts (presence and distribution of chemical elements) and crystalline contrasts (crystallographic structure and texture). Scanning electron microscopy can also provide precise local chemical analysis, which can even be quantitative if the sample permits (electron probe microanalysis).

Contrast represents the relative signal variation between...