Diffusion during annealing of Al/Cu/Fe thin films

The Al–Cu–Fe system is interesting due to the existence of the quasicrystalline phase Al62.5Cu25Fe12.5 as well as its approximant phases. A two-step procedure of thin film preparation is considered: deposition of a multilayer structure of individual elements and consequential annealing. To analyze the diffusion processes trilayers of individual elements were deposited by sputtering with a total thickness of about 400 nm. Afterwards, the samples were annealed in tube furnace in inert atmosphere. Rutherford backscattering spectrometry, Auger electron spectrometry and X-ray diffraction were used to quantify the depth profiles. The results point out to a three-stage process as a function of rising temperature: first Al and Cu form the γ-Al4Cu9 compound layer; second the aluminium spreads throughout the film with copper and iron mainly divided. The β-Al(Cu,Fe) phase is observed. Complete homogenization is followed afterwards.