Scanning Electron Microscopy (SEM) is an imaging technique in which a focused electron beam is scanned on the surface of a sample to generate secondary and backscattered electrons.  Images formed by these electrons provide topographical and structural information of the sample.   Electron imaging is required when the feature size of your sample is sub-micron and ordinary light microscopy is not able to resolve the smaller features.  Careful sample preparation allows examination of metals, semiconductors, ceramics, and some polymers

Energy Dispersive X-ray Spectroscopy(EDS or EDX) is an elemental analysis technique commonly integrated with SEMs.  In SEM-EDS, X-rays generated during electron scanning are collected by an attached Si:Li detector to generate spectra of local composition.  Elemental analysis by EDS can be done at specific points as well as linescans and elemental maps of structures.  Accurate quantitative analysis is possible with the use of standards and simulation software.  The electron penetration in the sample is dependent on the electron energy and the material density thus in some samples you may be analyzing sub-surface material.  If very near surface (20-50A) is needed then XPS would be a more appropriate technique. 

Instruments: