Scanning electron microscope (SEM) is a powerful tool designed for studying the surface morphology of solid objects and materials characterization. SEMs use electrons for imaging, in a similar way that light microscopes use visible light. Since the wavelength of electrons is much smaller than the wavelength of light, the resolution of SEMs is superior to that of a light microscope. Therefore, surface characterization at higher resolutions requires the use of SEMs.

In a nutshell, the working principles of a SEM instrument are as follows: first, electrons are generated at the top of the column by an electron gun; the emitted electrons are then focused into a very thin beam by magnetic lenses and interact with the specimen. The interaction of electrons with the sample can result in the generation of many different types of electrons and photons. In the case of SEM, the two types of electrons used for imaging are the backscattered (BSE) and the secondary electrons (SE). The electrons reflected from the sample surface are collected by detectors; the output of detectors is converted to an electrical signal and eventually displayed as a contrast image.