During the study of materials on electron probe devices in the field of the electron beam, a contamination hydrocarbon film is formed, which influences the results of experiments. In this paper, we studied the effect of a contamination film formed on carbon-coated dielectric samples on the intensity of cathodoluminescence and X-ray characteristic emission lines. The absorption coefficient of the film for the visible and UV ranges was determined. The mechanism of film formation for various parameters of the electron beam is discussed.