 Hydrocarbon contamination in electron microscopy

Hydrocarbon contamination in electron microscopy is carbonaceous material present on, or deposited onto, a specimen during examination. Material from specimen preparation or the chamber can accumulate in an irradiated region and alter the measured electron scattering or chemical signal.

A darkening patch that follows repeated scanning can therefore be a measurement-induced deposit rather than a pre-existing structure. Compare a repeatedly exposed field with a fresh neighboring field, and repeat at lower exposure if possible. Cleaning and suitable specimen handling reduce contamination, while such controls distinguish it from genuine specimen features or other forms of electron beam damage.