Permeation of deuterium implanted into copper

The ion driven permeation of deuterium through a copper membrane has been investigated using a 5 keV D3+ beam of 1.0x1015 D-atoms cm-2 s-1 at 80-800deg C. Above 400deg C the temperature dependence of the permeation rate in a steady state is characterized by a local minimum at ∝ 700deg C and a local maximum at ∝ 500deg C. Under continuous Ar+ bombardment on the backside surface of the sample, however, such a complex dependence disappears. These results indicate that the process on the backside surface limits the permeation rate at least in the absence of the continuous Ar+ bombardment. The complex temperature dependence also suggests that the surface condition and/or mechanism of recombinative release changes with temperature. Below 300deg C, on the other hand, the permeation rate seems to decrease with increasing temperature. This can be attributed to a transition in the transport regime. (orig.)