Arrest of He bubble growth in Cu–Nb multilayer nanocomposites

Transmission electron microscopy on Cu–Nb multilayer nanocomposites implanted with 1017 cm−2 of 33 keV 4He+ at 763 K revealed uniformly dispersed He bubbles of 1–2 nm diameter in Nb and a broad distribution of larger ones in Cu. Bubbles in Cu were confined by the neighboring Nb, limiting their size normal to Cu–Nb interfaces to the Cu layer. The conditions under which layered composite morphology may be used to control He bubble distributions in materials under irradiation are discussed.