Fundamentals of Scanning Electron Microscopy

The scanning electron microscope (SEM) is one of the most versatile instruments available for the examination and analysis of the microstructure morphology and chemical composition characterizations. It is necessary to know the basic principles of light optics in order to understand the fundamentals of electron microscopy. The unaided eye can discriminate objects subtending about 1/60 ̊ visual angle, corresponding to a resolution of ~0.1 mm (at the optimum viewing distance of 25 cm). Optical microscopy has the limit of resolution of ~2,000 Å by enlarging the visual angle through optical lens. Light microscopy has been, and continues to be, of great importance to scientific research. Since the discovery that electrons can be deflected by the magnetic field in numerous experiments in the 1890s [1], electron microscopy has been developed by replacing the light source with highenergy electron beam. In this section, we will, for a split second, go over the theoretical basics of scanning electron microscopy including the resolution limitation, electron beam interactions with specimens, and signal generation.