It was demonstrated [1] that hydrocarbon contamination in a SEM chamber can be cleaned by oxygen radicals generated by a RF-plasma device. The SEM chamber is so large that reactive oxygen radicals readily distribute throughout the chamber during cleaning.

However, most part of a TEM column is narrow like tubes, and thus it is difficult to achieve high flows of activated oxygen (O) radicals in the column. Therefore, in order to clean a TEM column, Horiuchi et al. [2] developed a process which can achieve high conductance of oxygen radicals under a relatively low vacuum level for the stable generation of plasma.  Their results clearly showed that the developed process successfully delivered the active oxygen radicals into the TEM chamber and thus the contaminants in the TEM column were chemically removed away.

Figure 3181. Cleaning setups in TEM for (a) Specimen chamber, and (b) Upper pole-piece of objective lens.

Not only has plasma cleaning technique been used to clean contaminants on EM specimens, but EM columns or/and chambers can also be cleaned by plasma techniques.

[1] A. E. Vladar, M. T. Postek and R. Vane, Proc. SPIE, 835, (2001), p. 4344; R. Vane and V. Carlino, Microsc. Microanal. 11 (Suppl 2), (2005), p. 900.
[2] Shin Horiuchi, Takeshi Hanada, and Masaharu Ebisawa, Development of a process for cleaning a TEM column by chemical etching of oxygen radicals, EMC 2008: Vol 1: Instrumentation and Methods, Martina Luysberg, Karsten Tillmann, Thomas Weirich.