Synthesis and micro- & nanoscale characterization of nanoengineered thin films with superior mechanical/electrical properties
Résumé
Novel high-performance nanostructured materials with superior mechanical and electrical properties are required for advanced applications such as micro-/nanoelectronics, energy production, sensors and wear protection. Especially, mutually excluding structural properties such as high strength and ductility need to be combined, but also low electrical resistance enabling reduction of energy losses. In order to trigger microstructure-induced material properties, control of the micro-scale porosity, atomic composition, average grain size, and layer/film thickness must be optimized based on nanoengineering design concepts.
In addition, the need of probing locally the properties of bulk materials combined with the ongoing trend for miniaturization of micro electro mechanical systems (MEMS), microelectronic components and thin films require the development of novel techniques in order to acquire information about the local mechanical/electrical behavior.
Here, I will present recent results for several class of advanced materials including nanostructured metallic glasses [1] and multilayer high entropy alloys [2], while discussing the local electrical properties across grain boundaries for bulk materials and thin films [3]. Special emphasis will also be dedicated to present several cutting-edge techniques used to extract the mechanical/electrical behavior at the micro- and nanometer scale, involving i.e. micro-scale tensile tests, in-situ SEM micro-pillar compression/splitting [4], tensile test in-situ TEM, and in-situ SEM electrical resistivity measurements [3].
Finally, I will show one example of applications with the development of a wirelessly rechargeable transparent heater for thermotherapy patch based on metallic glass films reporting excellent stretchability (70%) and low sheet resistance (~3 Ω/sq) [5].
[1] M. Ghidelli et al., Novel class of nanostructured metallic glass films with superior and tunable mechanical properties, Acta Materialia, 213, 116955, 2021.
[2] G. Wu, C. Liu, A. Brognara, M. Ghidelli, Y. Bao, S. Liu, X. Wu, W. Xia, H. Zhao, J. Rao, D. Ponge, V. Devulapalli, W. Lu, G. Dehm, D. Raabe, Z. Li, Symbiotic crystal-glass alloys via dynamic chemical partitioning, Materials Today, 2020 (accepted).
[3] H. Bishara, S. Lee, T. Brink, M. Ghidelli, G. Dehm, Understanding grain boundary electrical resistivity in Cu: the effect of boundary structure, ACS Nano, 2020 (accepted).
[4] J. Ast, M. Ghidelli, K. Durst, M. Göken, M. Sebastiani, A.M. Korsunsky, A review of experimental approaches to fracture toughness evaluation at the micro-scale, Materials & Design, 173, 107762 (2019).
[5] S. Lee, H. S. An, S.-W. Kim, M. Ghidelli, A. Li Bassi, S.-Y. Lee, J.-U. Park, Transparent Supercapacitors and Electrodes Using Nanostructured Metallic Glass Films for Wirelessly Rechargeable Heat Patches, NanoLetters, 20(7), 4872-4881, 2020.