Defect studies of H⁺ implanted niobium

Highlights: • Creation of defects in niobium irradiated by 2.5 MeV protons. • Investigation of implantation-induced defects by positron annihilation spectroscopy. • Study of hydrogen attachment to vacancy-like defects in H⁺-irradiated Nb. • Identification of V + 2H defects as the dominant positron trap. - Abstract: Defects in Nb specimens implanted with H⁺ ions were investigated using three complementary techniques of positron annihilation spectroscopy: (i) the positron lifetime (LT) measurements employed for identification of defects in implanted specimens, (ii) the coincidence Doppler broadening (CDB) technique used for investigation of chemical surroundings of defects, and (iii) the variable energy positron annihilation spectroscopy (VEPAS) served for defects depth profiling studies. The virgin Nb sample exhibits a single component spectrum with lifetime of 128 ps which testifies that the sample can be considered as a defect-free material. The sample implanted with H⁺ ions exhibits two additional positron components with lifetimes of 182 and 204 ps. These components were attributed to the implantation-induced vacancies surrounded by two and one hydrogen atom, respectively. The presence of hydrogen attached to vacancies was confirmed also by CDB investigations