Pyrolytic graphite, fine grain graphite and amorphous a-C:H films were
irradiated with energetic oxygen in the energy range 1-5 keV between
room temperature and 1800 K. CO and CO2 molecules released during impl
antation were analyzed by residual and line-of-sight mass spectroscopy
and their velocity distributions were determined by time-of-flight me
asurements. The retained oxygen was determined by thermal desorption s
pectroscopy after irradiation. The impact of energetic oxygen (E > 1 k
eV) on these materials results in the formation of CO and CO2 with an
erosion yield close to unity. The observed CO release behavior can be
described by a local saturation model. Special experiments indicate th
at the underlying release mechanism is driven by ion-induced collision
processes at the end of the ion trajectory of the impinging oxygen. T
ime-of-flight measurements have shown that released CO molecules have
two different energy distributions with a thermal component correspond
ing to the target temperature and an overthermal component at a maximu
m energy of about 0.12 eV, whereas the CO2 molecules are exclusively r
eleased with thermal energies. (C) 1997 Elsevier Science B.V.