Practical Electron Microscopy and Database

The partial pressure of hydrocarbon (HC) or silicon oils from the diffusion pump, the grease of vacuum seals, and fingerprints on TEM sample holder induce HC contamination in the EMs (electron microscopes) specimen chamber.

In general, contamination of aperture surfaces is normally originated from deposition of organic compounds. The contamination sources are:
        i) Vacuum pump oil used in the pumping system.
        ii) Gaskets.
        iii) O-rings used to seal the vacuum system.
        iv) Greases used to lubricate O-rings.
        v) Specimen itself.

To reduce specimen contamination, a diffusion pump oil of low vapor pressure should be employed.