Helium trapping in nickel and the use of the helium probe as a technique for defect and gas agglomeration studies

Very low energy helium ions have been injected into Ni (100) single crystal substrates previously implanted with argon ions of higher controlled energy and fluence, and the subsequent evolution of the atoms during thermal annealing have been observed mass spectrometrically. Studies of the helium evolution spectra were obtained for different argon ion energies and fluences and nickel substrate temperatures in the range 350 to 900 K during argon implantation. This temperature range includes that for rapid thermal migration of radiation generated vacancies and the defect and defect-argon agglomerate states change substantially with argon implant temperature. Comparison of the helium evolution spectra without argon pre-bombardment and with pre-bombardment at different temperatures has confirmed the occurrence of a number of different helium defect-argon interaction processes and indicated important changes in the helium trapping efficiency of different defect structures.