Ion irradiation induced atomic transport and phase formation in the system nickel–aluminum

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Abstract
Nickel–aluminum bi‐, multi‐, and marker layers were irradiated with 80–900 keV Ar, Kr, and Xe ions at 80 and 300 K. The ion induced mass transport through the interface(s) was measured via Rutherford backscattering spectrometry. A bilayer mixing efficiency of 157 Å5/eV was obtained, independent on the irradiation temperature, and the ion species. In the mixing of 0.5–5 nm Ni marker layers embedded in Al, the influence of thermodynamic driving forces was verified by varying the Ni marker thickness. The results as discussed in the light of current ion beam mixing models, are neither consistent with the ballistic nor the global thermal spike model. The phases formed after multilayer mixing were studied by means of x‐ray diffraction and perturbed angular correlation spectroscopy. The latter is a novel method to investigate early stages of ion beam induced phase transformations and changes produced by single implanted (111In) tracer ions. For the RT mixing of equiatomic multilayers, the formation of crystalline NiAl was followed. By changing the multilayer composition different crystalline and amorphous Ni–Al phases were identified.