Gas re-emission during the implantation of deuterium in nickel: Influence of radiation damage and surface recombination

The re-emission of gas following implantation of deuterium in polycrystalline nickel was examined for the 295 K≤T≤900 K temperature range. The fact that re-emission was seen to be delayed for the initial implantation and repeat exposure was explained by the binding of deuterium atoms to adhesion sites. Depth-related measurements of the deuterium concentrations after irradation showed these to be density profiles for the captured deuterons, which are gradually degraded with no changes to their shape in terms of increases in width. It was thus for the first time possible to establish a profile of hydrogen bond sites arising in response to radiation damage during implantation in nickel. As the temperature rose, increases in re-emission were first seen to occur within shorter periods, which was thought to be consistent with the subsiding influence of bond site capturing and faster rate of diffusion. This tendency was, however, reversed for the T>500 K range. The curve plotted shows a transitional process from a range, in which re-emission is determined by diffusion and bond site capturing, into one where superficial recombination is the limiting and rate-determining factor of re-emission. Numeric mathematical models were found quite satisfactory to describe the re-emission behaviour for the temperature ranges investigated. (orig./RB)