1. General presentation

The interaction of the electrons with the material results in a non-uniform distribution of beam intensity on the exit face of the thin plate. In general, however, this non-uniformity does not result in an image with sufficient contrast. To obtain usable images, it is only necessary to select part of the electron beam using a diaphragm. Contrast is therefore created by the operator's manipulations (orientation, sample thickness, centering of the device, beam aperture, diaphragms used...) and depends on the operating process. To take full advantage of the possibilities offered by the instrument, it is essential to have a good knowledge of the details of the origin of contrasts [1][2][3]...