DIRECT AND INDIRECT MEASUREMENTS OF HYDROGEN

We have demonstrated that the content of hydrogen in carbon-based film s can be reliably calculated from a measurement made either directly u sing forward recoiled hydrogen or indirectly using backscattered heliu m. The method makes use of the surface signal height ratio of a sample of unknown composition to a standard of known composition. This appro ach allows elimination of several experimental parameters. The method assumes validity of Bragg's rule, potential deviations from which acco unt for the majority of the absolute uncertainty in the hydrogen fract ion. In general however, we have found agreement in hydrogen content b etween the two techniques for several carbon-based films.