Influence of the presence of deuterium on displacement damage in tungsten

Abstract

The influence of the presence of deuterium on displacement damage in tungsten is studied by implanting 20 MeV tungsten ions into displacement-damaged tungsten already containing 1.7 at.% deuterium. SDTrimSP calculations reveal that for the tungsten implantation fluence used, on average each D atom is recoiled once and hence mobile deuterium should be present simultaneously while displacing tungsten atoms. Nuclear reaction analysis after the tungsten implantation shows that no deuterium is lost from the sample and the depth profile is unchanged. However, deuterium must have been de-trapped and is effectively re-trapped again because temperature programmed desorption spectroscopy reveals that deuterium is redistributed from the low temperature de-trapping peak to the high temperature de-trapping peak. Rate equation modelling can describe the measured deuterium desorption with the same de-trapping energies as for the initial material but with increased trap densities only. Decorating the samples after the additional tungsten ion implantation again with a low energy deuterium plasma shows increased deuterium retention beyond the saturation value that is known for initially deuterium free, displacement-damaged tungsten by nearly a factor of two. Both observations together indicate that deuterium is stabilizing the defects created within the collision cascade. Keywords: Defect stabilization, Deuterium retention, Self-damaged tungsten, Displacement damage, Ion radiation effects, Nuclear reaction analysis, Temperature programmed desorption