Scanning & Transmission electron microscopy

The scanning electron microscope (SEM) is often used when visualization of a solid material is required. Approximate particle size, shape and topographical information can be obtained. A source of electrons is focused into a fine probe that is rastered over the surface of the specimen. The sample is coated with a thin gold layer and bombarded with electrons to visualize the surface, which is constantly scanned and reconstructed. A detector collects a part of the emitted electrons and an image is built by signal modulation and amplification.

A field-emission electrode gun (FEG) yields high-resolution images in the highest magnification. Whereas SEM scans the surface, transmission electron microscopy (TEM) probes the internal structure of solids and gives access to micro structural detail. With the addition of energy dispersive x-ray spectrometry (EDS), the SEM and TEM can also be used as an elemental analysis tool.
The techniques are considered to be qualitative measurements. The obtained information is often complemented by a quantitative analysis (e.g. particle sizing, porosity, surface area).