Hydrocarbon decontamination is an essential tool for high resolution SEM imaging and low voltage soft x-ray analysis in the EPMA. Depending on the situation, the specimen may be either uncoated or carry a thin carbon coat for conductivity. With the two mainstream decontamination systems, downstream plasma and UV, it is assumed that these systems are gentle and do no damage to either the specimen or the carbon coating[1].
Two commercial decontamination systems are investigated, a downstream RF plasma cleaner (DPC) and a UV radiation cleaner (UVR), both of which remove hydrocarbon contamination in a low vacuum environment as a pretreatment before electron beam irradiation. Both systems were investigated by XPS chemical state analysis as a function of time. It was found that both produce similar changes to the carbon coating chemistry in a similar time frame. In this respect DPC and UVR cleaning appear similar, and both produce a measurable effect under XPS analysis when the cleaners were operated in ways consistent with the manufacturers recommendations. Both cleaners showed an increase in carbon oxidation levels early in the cleaning process, that plateaued as cleaning time increased. It should also be noted that previous work[2]has shown that DPC decontamination of polyetheretherketone and polystyrene results in the alteration of the chemical structure of said polymers.
However morphological SEM imaging of uncoated copper (I) sulphide (chalcocite) bearing minerals indicated altered surface morphology and mineral erosion after DPC cleaning in dry air, but no alteration after UVR cleaning.
[1]Levesqueet al, Application of Plasma Cleaning Technology in Microscopy, XEI Scientific
[2]Rasch et al, Effects of downstream RF plasma cleaning on the surface of polystyrene and polyetheretherketone, 19th International Microscopy Congress