Author:F. Haidaraa, B. Duployer, D. Mangelinck, M.-C. Record

Institute: IM2NP, UMR 6242 CNRS – Aix-Marseille University, Avenue Escadrille Normandy-Niemen, building 142, 13397 Marseille, France

Quasicrystals, first discovered by Shechtman and colleagues in 1984, have a unique ordered structure known as quasi-periodic. Experiments have shown that high-quality samples of the stable quasi-crystalline phase exhibit exceptionally high resistivity, ranging from milliohms to ohm-centimeters, with a negative temperature coefficient of resistivity, in contrast to conventional metallic materials. This conductivity phenomenon is due to the localization of conducting electrons in the quasi-crystalline matrix. The preparation of thin-film samples of the quasi-crystalline phase is of great importance for the potential applications of these materials in electronics. Various techniques can be used to create such films, including deposition of multilayer metal films, co-deposition from metal targets, or deposition from alloys. Thermal treatment is necessary to ensure bonding. Since it is difficult to control the stoichiometry during codeposition, the multilayer deposition method followed by annealing is considered to be the most suitable for producing high-quality crystals in industrial conditions. In order to improve the process of thin film formation and understand the mechanisms of quasicrystalline phase formation, it is necessary to study in detail the reactions in multilayer metal structures during heat treatment. In this work, we analyzed the formation of quasicrystal thin films through annealing of sputtered multilayer structures. There are two known types of quasicrystals: polygonal and icosahedral. The studied alloy represented the icosahedral phase of the Al–Cu–Fe system, i-Al62.5Cu25Fe12.5, discovered by Tsai et al. The studies of the i-Al62.5Cu25Fe12.5 phase formation in thin films were previously carried out by several authors. These works mainly focused on isothermal annealing of samples and their subsequent characterization. An important study by Grene and colleagues used in situ X-ray diffraction to analyze phase formation, but questions arose about the identity of some of the phases. To clarify previous results, we repeated the phase formation studies from room temperature to 600 °C using three additional in situ techniques: X-ray diffraction, resistivity measurements, and differential scanning calorimetry.

The in situ study of the formation of the icosahedral phase of Al–Cu–Fe in thin films represents an important step in the understanding of multicomponent metallic systems. This paper examines the conditions that facilitate the formation of the icosahedral phase during the coagulation process, as well as the mechanisms that determine its stability and structural integrity.

Experimental data were obtained using scanning electron microscopy (SEM) and X-ray diffraction (XRD), which allowed identifying the structural and phase changes occurring during the cooling process. Special attention was paid to the effect of film thickness changes on the kinetics of phase formation, as well as on its morphological and compositional characteristics.

The results showed that the microstructure of thin films significantly affects the development of the icosahedral phase, where the formation of coarse-grained formations is observed with increasing layer thickness, which in turn contributes to better ordering of atoms. These findings open up new prospects for further research in the field of alloys with a high content of intermetallic phases, which can lead to the creation of new materials with unique properties.

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