Conductive Coating (SEM)
Conductive coating with a few nanometers of carbon or noble metals is often necessary for analysis of insulating specimens in high-vacuum SEMs. Conductive coating is required when charge cannot properly dissipate and the electron beam charges and/or damages the specimen.
Carbon coating is typically recommended for elemental analysis (EDS) as noble metals have higher interference with characteristic X-ray signal from the specimen (exact requirements will vary between different materials). Carbon can also be used for imaging, or in very thin layers to coat insulating specimens requiring electron backscatter diffraction (EBSD).
Noble metal coating is typically used for secondary electron (SE) imaging of specimens, though under the right conditions can be used for other techniques.