Minimum necessary adaptations are described that are sufficient for obtaining very low energy electron micrographs (VLEEMs) from commercially available routine scanning electron micrographs (SEMs) with the electrons accelerated to an energy of the order of tens of keV. A cathode lens inserted into the specimen chamber enables one to decelerate electrons in front of the specimen surface to a desired low landing energy, which can be freely varied even down to zero. When a potential slightly more negative than the accelerating voltage is applied, a scanning mirror electron microscopy mode can be effected. The achievable point resolution at very low energies proves to be not too dependent on the objective lens parameters, so that the physical limit of aberrations of the homogeneous field of the cathode lens is nearly attainable. The detection efficiency for the standard Everhart‐Thornley secondary electron detector is discussed, and results for the routine Tesla BS 340 SEM are presented.

The modern trend towards low electron energies in scanning electron microscopy (SEM), characterised by lowering the acceleration voltages in low‐voltage SEM (LVSEM) or by utilising a retarding‐field optical element in low‐energy SEM (LESEM), makes the energy range where new contrasts appear accessible. This range is further extended by a scanning low‐energy electron microscope (SLEEM) fitted with a cathode lens that achieves nearly constant spatial resolution throughout the energy scale. This enables one to optimise freely the electron beam energy according to the given task. At low energies, there exist classes of image contrast that make particular specimen data visible most effectively or even exclusively within certain energy intervals or at certain energy values. Some contrasts are well understood and can presently be utilised for practical surface examinations, but others have not yet been reliably explained and therefore supplementary experiments are needed.