Surface erosion in nc-ZrN/a-ZrCu multilayer films after He irradiation

Abstract

The work is dedicated to the study of the phase stability and surface erosion of a novelZr-based multilayer system consisting of a combination of ceramic (ZrN) and metallic glass (ZrCu) nanoscale layers after He irradiation (40 keV and doses up to 1.1 × 1018 cm−2). Periodic ZrN/Zr1-xCux multilayers with elementary layer thicknesses of 5 nm/5 nm and 5 nm/10 nm and Cu content x = 0.45, 0.53, 0.61 and 0.74 were grown by magnetron sputter-deposition from Zr and Cu targets at the substrate temperature of 300 °C. X-ray diffraction and X-ray reflectivity analysis reveal that multilayered films consist of alternating nanocrystalline (nc) ZrN and amorphous (a) ZrCu layers with relatively sharp interfaces. The stability of the phase composition of nc-ZrN/a-Zr1-xCux multilayer films to irradiation with helium ions up to fluence of 1.1 × 1018 cm−2 has been established. For x = 0.74, crystallization of the metallic glass layer was observed.The surface integrity of the multilayer films remained unaltered up to an ion fluence of 5 × 1017 cm−2. At higher ion fluence, surface erosion of the nc-ZrN/a-Zr1-xCux films occurs by the flacking mechanism. In this case, an increase in the thickness of the amorphous Zr1-xCux layer and in Cu content leads to improved radiation resistance as the critical fluence for delamination increases from 5 × 1017 cm−2 upto 8 × 1017 cm−2.