Ion-beam induced compositional and structural changes of Al-Cu-Co multilayer stacks

The present work deals with the investigation of ion-beam assisted annealing/mixing effects on compositional and structural changes in Al-Cu-Co multilayers. 800 nm thick Al64Cu20Co16 multilayers prepared by magnetron sputtering deposition, consisting of 28 successive single-metal Al-, Cu-, and Co-nanolayers were treated by thermal annealing at 300 °C, 400 °C, or 500 °C as well as ion irradiation by 30 MeV Cu5+ ions at fluences of 1x1013 to 5x1014 with an average flux of 2.38 × 1010 at.cm−2s−1. The samples were characterized with SEM, EDX, XRD, and TEM including HAADF. In contrast to the original multilayer, the treated samples were found to consist of two types of alternating nanolayers. A wider coarse-grained structurally and chemically homogeneous single-phase nanolayer formed by Al2Cu, and a narrow fine-grained two-phase nanolayer, which has a heterogeneous composite structure in which the central Co sublayer (being a residue of the original single-metal Co nanolayer) is surrounded from both sides with Al-Co sublayers, consisting of Al9Co2. This Co sublayer is considered to be a diffusion blocker for Al and Cu as well as hindering the movement of borders between particular nanolayers. The formation of a ternary phase in the investigated samples was not confirmed in any of the samples.