Stress in thin films is an ongoing research topic in materials science and technology. Many efforts were made to better understand, adapt and manage stresses in various applications.

Besides the unfavorable effects such as a drastic reduction in performance, reliability and durability of material components and devices, stresses can have a positive influence on the properties of thin films and nanostructures if controlled correctly. It is known from previous investigations that mechanical stresses – either internal or external – have an influence on phase transformation and phase equilibrium [1]. This can be caused by effects on the diffusion coefficient as well as on the diffusion driving force [2].

The self-propagating high-temperature synthesis in reactive multilayer systems is a diffusion-based process. Therefore, studies on the effects of extrinsically induced and intrinsic stresses are essential to investigate the impact on the synthesis of Al and Ni nanolayers. Different layer parameters (bilayer- and total thickness) and different substrates were used in the investigations on extrinsically induced stress. These were loaded in tension and the synthesis was initiated under these conditions. A distinction was made between samples that showed no cracks [3] and samples in which cracks were deliberately introduced. The reaction was recorded via high-speed camera and high-speed pyrometer. To investigate the formed phases, X-ray diffraction was performed before and after the reaction. According to the investigations on intrinsic stress the parameters of the sputter deposition process were changed to generate different initial stress states within the reactive layer. The reaction was than recorded as before with a high-speed camera and pyrometer. The insights in the results will give a correlation between sputtering parameters, initial stress state and the parameters of the reaction such as reaction front velocity, reliability and durability.

[1] R.W. Cahn, Phase equilibria under stress, Advanced Materials 1 ,1989, 300–302. https://doi.org/10.1002/adma.19890010812 [2] R. Grieseler, I.S. Au, T. Kups, P. Schaaf, Diffusion in thin bilayer films during rapid thermal annealing, Phys. Status Solidi A 211, 2014, 2635–2644, https://doi.org/10.1002/pssa.201431039

[3] S. Matthes, M. Glaser, E. Vardo, Y. H. Sauni Camposano, K. Jaekel, J. P. Bergmann, P. Schaaf, Influence of extrinsic induced tensile stress on the self-propagating high-temperature synthesis of nanosized Al/Ni multilayers, J Mater Sci, 2023, DOI: 10.1007/s10853-023-08618-w