Electron stimulated carbon adsorption in ultrahigh vacuum monitored by Auger electron spectroscopy

Electron stimulated carbon adsorption at room temperature has been studied in the context of radiation induced surface modifications in the vacuum system of particle accelerators. The stimulated carbon adsorption was monitored by Auger electron spectroscopy (AES) during continuous irradiation by 2.5 keV electrons and simultaneous exposure of the sample surface to CO, CO2, or CH4. The amount of adsorbed carbon was estimated by measuring the carbon Auger peak intensity as a function of the electron irradiation time. Investigated substrate materials are technical oxygen-free electrolytic copper and TiZrV nonevaporable getter thin film coatings, which are saturated either in air or by CO exposure inside the Auger electron spectrometer. On the copper substrate electron induced carbon adsorption from gas phase CO and CO2 is below the detection limit of AES. During electron irradiation of the nonactivated TiZrV getter thin films, electron stimulated carbon adsorption from gas phase molecules is detected when either CO or CO2 is injected, whereas the CH4 partial pressure has no influence on the carbon Auger peak intensity evolution