The influence of nitrogen pre-implantation on the properties of He implanted materials

The influence of a surface layer of implanted nitrogen on the properties of titanium hydride further implanted by He was investigated. Samples were implanted with 45 keV N2+ ions cm-2 to a total dose of 1.25 x 1017 ions cm-2 at room temperature. These samples, as well as identical samples not irradiated by N2 ions, were implanted with He ions at energies of 25 keV and 45 keV to doses ranging from 2 x 1017 to 5.5 x 1017 ions cm-2. Helium release from the implanted samples was increased by a factor of 2-4 in nitrogen implanted samples. Nitrogen implantation also induced surface erosion and blistering at lower He fluences than in samples not irradiated by N2. It seems that radiation damaged caused by N2 implantation suppresses the possible enhancement of the irradiation resistance due to surface nitrogenation. (author)