Superior tolerance of Ag/Ni multilayers against Kr ion irradiation: an in situ study

Monolithic Ag and Ni films and Ag/Ni multilayers with individual layer thickness of 5 and 50nm were subjected to in situ Kr ion irradiation at room temperature to 1 displacement-per-atom (a fluence of 2x10(14)ions/cm(2)). Monolithic Ag has high density of small loops (4nm in diameter), whereas Ni has fewer but much greater loops (exceeding 20nm). In comparison, dislocation loops, approximate to 4nm in diameter, were the major defects in the irradiated Ag/Ni 50nm film, while the loops were barely observed in the Ag/Ni 5nm film. At 0.2dpa (0.4x10(14)ions/cm), defect density in both monolithic Ag and Ni saturated at 1.6 and 0.2x10(23)/m(3), compared with 0.8x10(23)/m(3) in Ag/Ni 50nm multilayer at a saturation fluence of approximate to 1dpa (2x10(14)ions/cm(2)). Direct observations of frequent loop absorption by layer interfaces suggest that these interfaces are efficient defect sinks. Ag/Ni 5nm multilayer showed a superior morphological stability against radiation compared to Ag/Ni 50nm film.