4. Conclusion

For many years, scanning electron microscopy saw few major upheavals, but the development of field emission guns (mainly Schottky emission) changed the technique considerably. The development of new electron column concepts and detectors has extended the capabilities of these microscopes, particularly in terms of imaging resolution, but also in terms of observation capabilities at low and very low voltages, or using detectors located in the SEM column. On the other hand, contrast interpretation has often become more complex, as secondary and backscattered electronic emissions no longer follow the same rules at low voltages as they do at higher voltages