Mechanical and Electrical Properties of Amorphous/Crystalline Nanolaminates for Flexible Electronic Applications
Résumé
The development of flexible electronics is driving the search for new materials that offer a combination of exceptional electrical and mechanical properties [1]. Thin film metallic glasses (TFMGs) are attractive due to their superior mechanical properties, low and negative temperature coefficient of electrical resistivity, stability of electrical properties across thickness variations, and strong fatigue resistance. However, their use in flexible electronics is limited by their higher electrical resistivity compared to crystalline materials and their macroscopic brittleness, driven by shear bands (SBs) formation [2]. Nanostructuring strategies, such as nanolaminating can hinder these downsides. Nevertheless, unresolved scientific issues involving understanding the deformation mechanisms for nanostructured crystal/glass and developing effective synthesis strategies to improve the mechanical and electrical properties simultaneously are still present.
This study presents amorphous/crystalline ZrCu/Fe-BCC nanolaminates, which offer enhanced mechanical and electrical properties through controlled ZrCu fractions (0.5 to 0.9) and bilayer periods (10 to 40 nm). We demonstrate that the number of ZrCu/Fe interfaces significantly affects hardness, with the nanolaminates achieving high hardness values up to 9.6 GPa, substantially higher than the individual components. Additionally, these nanolaminates show electrical resistivity as low as 36 µOhm.cm, similar to that of pure Fe.
In addition, we studied the deformation mechanism using micropillar compression tests. These revealed that the 20 nm Fe/20 nm ZrCu nanolaminate exhibits high strain without failure, unlike pure ZrCu, which shows shear band propagation at low strain. The superior mechanical behavior of the nanolaminates is attributed to the inhibition of the shear band propagation by their interfaces.
Furthermore, we conducted tensile tests on samples deposited on a flexible polymeric substrate to assess the potential of these materials in flexible electronics applications. The nanolaminates demonstrated crack onset strains of up to 1.36 % and promising high crack propagation strains of up to 13 %.
Overall, our findings underline the critical role of nanostructuring in improving both the mechanical and electrical properties of nanolaminates, expanding their potential for use in flexible electronics.
[1] Corzo, D. et. al., Frontiers in Electronics 1, (2020). [2] Lee, S. et al., Nano Lett 20, 4872–4881 (2020).