Isothermal desorption of hydrogen from polycrystalline diamond films

The kinetics of isothermal H2 desorption from polycrystalline diamond are studied in real time. The surface H coverage (θH) is measured by mass analyzing the recoiled H+ ion signal during the desorption. We find that the H2 desorption is 1st order in θH with an activation energy of 69 ± 6 kcal mol and a prefactor of 1010.5 ± 0.9 s-1. We suggest that formation of a CC π-bond on the clean surface plays a key role in H2 desorption from diamond, a view consistent with previous theoretical calculations of H2 desorption from diamond. © 1994.