Microstructural development and helium bubble formation in Cu/W(Re) nanometer multilayer films irradiated by He+ ion

A series of 60 keV He+ implantations was conducted on Cu/W(Re, 5.9 at.%) multilayered structures with ion doses from 5 × 1019 to 5 × 1021 m2 under different temperature. Three distinct, temperature-dependent He release mechanisms were found by subsequent X-ray diffraction (XRD) and scanning electron microscope (SEM) investigations. Firstly, with implantation at 300 K (about T/Tm (Cu) = 0.22), a certain degree of blistering was observed with a critical dose higher than 5 × 1021 m−2. But, at higher temperature irradiation (about T/Tm (Cu) = 0.35), samples implanted were characterized by extensive blisters at the dose of 2 × 1021 m−2. Finally, at 673 K (about T/Tm (Cu) = 0.5), the specimen flaked and a rough, porous surface formed when the dose was higher than 1 × 1021 m−2. The mechanisms involved have been analyzed based on the detailed characterization studies.