ADSORPTION STUDY OF CO AND H2O ON CARBON MATERIALS, NI AND STAINLESS-STEEL

Adsorption of CO and water vapor on single crystalline graphite, diamond and an amorphous carbon film at room temperature was investigated by low energy ion scattering (ISS) and compared with stainless steel and nickel surfaces. Even for a CO exposure up to 10(4)L, the C intensity stayed constant and no O peak appeared in the ISS spectra from graphite while Ni and O intensities from the Ni surface changed strikingly. Intensities of Fe and O signals from stainless steel seriously de- and increase with increasing exposure of H2O, respectively, but did not reach saturation even at an exposure of 10(3)L. On the other hand, C and O intensities from carbon surfaces changed moderately to reach saturation at an exposure of some 100 L. These results indicate that CO and H2O do not adsorb significantly on carbon surfaces in contrast to nickel and stainless steel surfaces. As a by-product survival probabilities of scattered He+ ions from graphite for the primary energy of 0.6-2 keV were measured to be in a range of 10(-4) to 10(-2) and the survival parameter was deduced to be 5.0 X 10(7) cm s-1.