The effect of MeV ion irradiation on the hydrogen content and resistivity of direct ion beam deposited diamondlike carbon
Diamondlike carbon films fabricated by direct ion beam deposition have been irradiated with 6.4 MeV fluorine and 1 MeV gold ions. Both beams reduce the hydrogen content with the fluorine beam being much more efficient than the gold beam. The resistivity of the materials is also reduced by both beams with the fluorine beam producing a much larger drop in resistivity and a lower fluence than the gold beam. It is concluded that defects produced by electronic energy loss of the bombarding ions are responsible for both the loss of hydrogen and the change in resistivity. The magnitude of both of these effects is reduced with increasing ion mass as the proportion of nuclear to electronic energy loss is increased. This is due to the production of retrapping centers in the case of hydrogen and ion induced annealing in the case of resistivity. There is a threshold in fluence for both effects and this may be associated with fluctuations in the rate of deposition of the electronic energy loss along an individual ion track.