SYNERGISTIC EFFECTS BETWEEN HELIUM AND HYDROGEN ISOTOPES ON GAS DETRAPPING IN POLYCRYSTALLINE NICKEL

The thermal desorption and SEM techniques have been used to study the effects of the presence of deuterium and hydrogen atoms on the retention of implanted helium in polycrystalline nickel. For samples pre-implanted with 40 keV helium to a dose of 1 x 10(21) ions/m2 the ratio of trapped deuterium atoms to the implanted helium was found to be about 0.4 D/He and an effective trapping energy approximately 0.5 eV was found. For samples pre-implanted with 10 keV He to doses from 1.5 x 10(21) to 4 x 10(21) ions/m2, low temperature helium release stages were observed, and resulted in a decrease of deuterium trapping efficiency to as low as 0.0075 D/He. Both deuterium and hydrogen charging were found to enhance the helium release and to decrease the release temperature. For the high dose samples, deuterium or hydrogen gas charging and thermal desorption were also found to induce blister growth and surface exfoliation.