Interaction of energetic oxygen ions with lithium-containing amorphous hydrogenated carbon films: a mass spectrometry study

Lithium-containing amorphous hydrogenated carbon coatings (a-C:H/Li) have been prepared by a modified plasma assisted chemical vapor deposition (rf-PACVD) technique. In order to investigate the interaction of energetic oxygen with these films they were irradiated with oxygen ions of 3 keV energy. Erosion and retention behavior was measured by direct detection of emitted particles using a differentially pumped line-of-sight quadrupole mass spectrometer. Results are compared to those of previous studies on pure and boron-containing carbon materials. Like in these materials, emission of reaction products from a-C:H/Li is dominated by CO and CO2, to a smaller extent also emission of lithium oxide, Li2O, is observed. As compared to pure carbon the emission of reaction products is delayed, and the erosion yield after oxygen saturation of the surface layer is lower for lithium-containing films. Taking into account results of X-ray photoelectron spectroscopy, it can be concluded that the interaction of a-C:H/Li with energetic oxygen follows the same general trends as observed for boron-containing carbon materials. However, chemical reactions and their dependence on conditions of irradiation are more complex in a-C:H/Li than in boron-containing carbon. (orig.)