Sticking coefficient and surface loss probability of eroded species during bombardment of carbon with deuterium

Investigations on the deposition behaviour of eroded carbon species under controlled ion beam conditions were performed to evaluate absolute sticking coefficients. Pyrolytic carbon was eroded by D ions at energies between 45 eV and 1 keV and temperatures between 20 and 475 °C. The sticking coefficient of the eroded species was obtained from a quantitative comparison of the total deposition inside a cavity with the flux of carbon entering the cavity as well as from the distribution of deposited atoms inside the cavity. High sticking coefficients of the order of 0.6 were obtained at room temperature and high ion energy, as expected from physically eroded atoms. In contrast, hydrocarbon molecules chemically emitted at either elevated temperature or low ion energy have typical sticking coefficients around 0.02. At elevated temperatures, the quantitative comparison with weight-loss measurements indicate the dominance of saturated hydrocarbons with zero sticking to the cavity walls.