Helium depth profiling in tantalum after ion implantation and high-temperature annealing

We have studied the depth profiles of 3He implanted into tantalum with concentrations ranging between 500 and 2500 at. ppm. We used the 3He nuclear reaction analysis based on the 3He(d,p)4He ‘resonant’ reaction which yields a specific signal, independent of the Ta host. Excitation curves were obtained by measuring the 13-MeV proton yield as a function of the incident deuteron energy for as-implanted and annealed Ta samples. These curves are 3He depth profiles convoluted with the reaction cross-section. The as-implanted depth profile is approximated by a Gaussian curve which is fitted to match the experimental excitation curve. The same process is used for data on annealed samples at high-temperatures from 1000 K to 1773 K. Diffusion constant data are deduced from the depth profile standard deviations of the same sample at two consecutive annealing temperatures. The small diffusion constant values found are consistent with helium trapping at vacancies or vacancy clusters.