Quasicrystals, first reported by Shechtman and colleagues in 1984, exhibit a characteristic ordered arrangement known as a quasi-periodic structure. Experimental observations have shown that high-quality samples of stable quasi-crystalline phases exhibit exceptionally high resistivity, ranging from Mohm/cm to Ohm/cm, combined with a negative temperature coefficient of resistivity, which distinguishes them from typical metallic materials. This unique conductivity behavior is attributed to the tendency of conduction electrons to become localized within the quasi-crystalline structure.
The formation of the icosahedral phase in Al–Cu–Fe thin films was investigated in situ using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The films were prepared by co-sputtering of Al, Cu and Fe onto amorphous Si3N4 substrates. The films obtained by deposition were amorphous, and the icosahedral phase was formed upon annealing at temperatures from 400 to 600 °C.
Transmission electron microscopy observations showed that the icosahedral phase nucleated at grain boundaries and triple junctions. The growth of the icosahedral phase was found to be diffusion-controlled. X-ray diffraction measurements showed that the icosahedral phase had a composition close to Al62Cu25.5Fe12.5. The icosahedral phase was stable up to 700 °C, above which it transformed into crystalline phases. These results provide insights into the formation and stability of the icosahedral phase in Al–Cu–Fe thin films, which is important for the development of new materials with unique properties. The in-situ approach allows direct observation of phase transformations, which is a valuable tool for materials research.
The production of thin-film samples of quasicrystalline materials is critical for potential future applications in electronic devices. There are various methods for producing such thin-film materials, including multilayer metal deposition, co-deposition from metal targets, or deposition from composite targets. Regardless of the method, thermal treatment is usually required to form the junction.
Due to the difficulties in precisely controlling the stoichiometry of compounds in co-deposition or vapor deposition, the most suitable approach for producing high-quality crystals in industrial conditions is multilayer metal deposition followed by annealing.
To optimize thin film production and understand the formation and growth of quasi-crystalline phases, it is necessary to investigate the reaction mechanisms in metallic multilayer structures during thermal processing. This study focuses on the creation of quasi-crystalline thin films by annealing metallic multilayer structures obtained by sputtering.
Author: F. Haidara, B. Duployer, D. Mangelinck, M.-C. Record
Institute: IM2NP, UMR 6242 CNRS– Université Aix-Marseille, Av. Escadrille Normandie-Niemen, Case 142, 13397 Marseille Cedex 20, France, Université Paul Sabatier CIRIMAT-LCMIE 2R1, 118, Route de Narbonne, 31062 Toulouse Cedex 09, France