INTERACTION OF ENERGETIC OXYGEN IONS WITH LITHIUM-CONTAINING AMORPHOUS HYDROGENATED CARBON - AN IN-SITU PHOTOELECTRON-SPECTROSCOPY STUDY

Pure and Li-containing amorphous hydrogenated carbon films were deposi ted using an ion beam deposition technique. Depending on Li content an d deposition conditions, differences in chemical structure are detecte d. Samples were irradiated at room temperature with energetic oxygen i ons of 100 eV to 1 keV. Transient time during which layers retain oxyg en is significantly longer for Li-containing as compared to pure amorp hous hydrogenated carbon films. Oxygen uptake is found to be mainly de termined by Li content. For lower contents (c(Li) < 15 at.%) oxygen up take is only about 12 at.%. For intermediate Li contents (15 at.% < c( Li) < 50 at.%) oxygen uptake increases and saturates above Li concentr ations of about 30 at.%. In dependence on Li content, and chemical str ucture of the films, and irradiation conditions varying amounts of Li carbonate like, Li2CO3, and Li oxide like, Li2O, compounds are detecte d in the irradiated samples. At room temperature about 35 at.% oxygen are retained at the surface of these films. For high initial Li conten ts (c(Li) > 50 at.%) carbon is almost completely removed upon irradiat ion and the resulting composition of the films is found to be close to the stochiometry of Li oxide.