Scanning Electron Microscopy

Scanning electron microscopy (SEM) is a traditional electron microscopy technique widely used for structure characterization in materials science, chemistry, biology and polymer science. In this chapter, we introduce the principles of SEM operation and the set up of a typical SEM, including the electron sources, electron beam, lenses and apertures. In SEM, secondary electrons, backscattering electrons and characteristic X-rays can be collected to give structural or chemical composition information. Environmental scanning electron microscopy (ESEM), which operates without exposing volatile samples to high vacuum, is introduced for biological applications. SEM is one of the most powerful and maneuverable tools in nanotechnology. We present, as an example, the use of SEM for the characterization of protein (zein) micro- and nanostructures formed by evaporation-induced self-assembly. Finally, we introduce three limitations encountered in SEM experimentation that can impact the quality of the SEM images. These are radiation damage, contamination and charging effect.