Deuterium retention in tungsten-doped amorphous carbon films exposed to deuterium plasma

Abstract

Deuterium retention in tungsten-doped amorphous carbon (a-C:W) films with 0-9.5 at.% W concentration exposed to deuterium plasma was studied by nuclear reaction analysis (NRA) and thermal desorption spectroscopy (TDS). Deuterium retention of a-C:W films decreases with increasing initial W concentration and increases monotonically with incident fluence. No saturation of retention was observed up to a fluence of 3.8×10 24 Dm -2 . All a-C:W films with a W concentration lower than 9.5 % show a higher deuterium retention than pure amorphous carbon films. This can be attributed to the formation of a highly porous W layer at the film surface. The total retained deuterium amount measured by TDS is 15-30% lower than the amount measured by NRA. The difference between these two methods is attributed to the release of deuterium in the form of long chain hydrocarbons during TDS which cannot be well quantified.