Quasi-crystalline materials lacking the periodicity of the crystal lattice exhibit unique physical properties that make them promising for various technological applications, including as wear-resistant coatings and thermoelectric materials. Thin films based on Al–Cu–Fe–B quasicrystals, in particular, attract attention due to their high hardness, corrosion resistance and low friction coefficient. However, the formation of high-quality films with the desired properties is associated with a number of technological difficulties, one of which is the occurrence of residual stresses.
Residual stresses generated during deposition and subsequent processing can have a significant impact on the structure, stability, and performance of thin films. The presence of tensile stresses can lead to cracking and delamination of the film from the substrate, while compressive stresses can cause warping and loss of adhesion. Thus, control and minimization of residual stresses are important tasks in the creation of quasicrystalline thin films.
In quasicrystalline Al–Cu–Fe–B thin films, residual stresses were estimated by X-ray diffraction analysis and curvature measurements. The films, varying in thickness from 0.55 to 2.6 μm, were produced by magnetron sputtering on Si(100) substrates heated to 560 °C.
It was found that the tensile stresses in intact films measured by the curvature method are comparable with the stresses determined by the modified sin2ψ method using the main diffraction peaks of the icosahedral phase and are approximately 1.1 GPa. This value is close to the estimate of thermal stresses calculated based on the difference in the thermal expansion coefficients of the film and the substrate, indicating the dominant role of thermal stresses in the formation of residual stresses.
An increase in film thickness leads to the formation of cracks and partial delamination, which is accompanied by a significant decrease in stress. The hardness of the studied quasicrystalline films is estimated to be in the range from 1.5 to 1.9 GPa.
In this paper, residual stress in Al–Cu–Fe–B thin films deposited by magnetron sputtering on various substrates was investigated. The values and signs of residual stresses were determined depending on deposition parameters, such as substrate temperature, working gas pressure, and target composition, using X-ray diffraction and substrate deflection measurements. The effect of residual stresses on the microstructure and mechanical properties of the films was analyzed. The results obtained make it possible to optimize the deposition process to obtain quasicrystalline Al–Cu–Fe–B thin films with a minimum level of residual stresses and improved performance characteristics.
Author: Sergey Polischuk,Pascal Boulet, André Mezin,Marie-Cecile de Weerd,Sylvain Weber,Julian Ledieu,Jean-Marie Dubois,Vincent Fournée
Institute: Institut Jean Lamour, UMR7198 CNRS – University of Nancy – École Polytechnique Supérieure de Metz, Ecole des Mines, 54042, Nancy, France