Vacancy-type defect production in CLAM steel after the co-implantation of He and H ion beams studied by positron-annihilation spectroscopy

Vacancy-type defects induced by the co-implantation of He and H ions in China low activation martensitic (CLAM) steel at room temperature were investigated by variable-energy position beam Doppler broadening spectra (DBS). The co-implantation occurred in two patterns. In one pattern, He ions were implanted before H ions; the other pattern was of the opposite sequence. Both He- and H-vacancy complexes were formed for pre-implanted He and H at different fluences. He–H-vacancy complexes were formed for pre-implanted He, which caused the S parameter of the pre-implanted He to be smaller than that of H at the lowest fluence. The defect density increased with increased fluence for the two implanted patterns, and the difference between the S parameters of pre-implanted H and He decreased with increased fluence. Nanovoids containing a few He atoms were the dominating defects at high implanted fluences for the two kinds of implantation.