Trapping and surface permeation of deuterium in Fe, Ni, and stainless steel: an ion-beam study

Ion implantation and ion beam analysis were used to investigate trapping and surface permeability for deuterium (D) in Fe, Ni, and 304 stainless steel. In He-implanted Fe containing approx. 1 nm He bubbles, D was trapped with an enthalpy of 0.75 + - 0.07 eV, referenced to a solution site. The proposed trapping mechanism is chemisorption on the walls of the bubbles. Deuterium was also bound to implantation defects, hypothesized to be vacancies and vacancy clusters, with enthalpies of 0.5 and 0.7 eV respectively. The permeability of the electropolished and air-exposed Fe surface was characterized by a recombination coefficient of K/sub L/ = 10/sup -14/ /sup + -/ /sup 0/ /sup 7/ mm/sup 4//s at a temperature of 500 K. Trapping of D was also observed in Ni and 304 stainless steel implanted with He, the measured binding enthalpy being about 0.5 eV in both cases. Bubble traps similar to those observed in Fe are presumed responsible. No surface-barrier effect was detected for Ni, implying K/sub L/ greater than or equal to 10/sup -15/ mm/sup 4//s at approx. 350 K. In contrast, for electropolished and air-exposed stainless steel, K/sub L/ less than or equal to 10/sup -19/ mm/sup 4//s at approx. 500 K.