Detrapping and diffusion of H and D implanted in carbon studied by high temperature laser annealing and depth profiling

The depth profiles of H and D implanted at low energy (0.7 and 1.5 keV) in Highly Oriented Pyrolytic Graphite (HOPG) ( a -axis) and vitreous carbon (v-C), and then partially released by pulsed laser induced desorption were investigated in order to understand the H behaviour in carbon at high temperature. During the laser desorption experiment, the re-emitted gas quantity was measured as a function of laser energy density by mass spectrometry. Depth profiles of H and D remaining after partial desorption were also obtained by means of the elastic recoil detection (ERD)- E × B technique. Firstly, a significant difference between the re-emitted H 2 or D 2 gas quantity and the released amount deduced from the ERD profiles is observed. This could be explained by atomic H release or by far in-depth diffusion of molecules. Secondly, it is seen from the depth profiles of hydrogen in HOPG that no profile modification is observed below 1500 K. The desorption process is compatible with a local molecular recombination model with fast diffusion of the molecules. At higher temperatures, significant diffusion of atomic hydrogen allows it to be retrapped in the vacancy profile created during the implantation.