Bendable Membranes Based on Silicene and Silicene-Stanene Heterostructures

Two-dimensional (2D) materials exhibit a variety of physical properties with potential exploitation in nanotechnology [1]. In particular, when reduced in the form of 2D bendable membranes, they hold promises in the framework of flexible electronics, photonics and related applications including wearable and strain-responsive devices. Here, we demonstrate the realization of bendable membranes based on Xenes, [2] the monolelemental class of 2D materials, and Xene heterostructures. Starting from silicene and silicene-stanene heterostructure grown by molecular beam epitaxy [3], we show that it is possible to transfer them onto arbitrary flexible substrates [4], thus making feasible the realization of bendable membranes. The application of macroscopic mechanical deformations induces a strain-responsive behavior in the Raman spectrum of silicene. Under tensile strain, the bendable membrane shows Raman frequency shift comparable to other promising flexible systems, like those based on transition metal dichalcogenides, and high stability up to one thousand bending cycles. We also show that the membranes under elastic tension relaxation are prone to form microscale wrinkles displaying a local generation of strain in the silicene layer consistent with that observed under macroscopic mechanical deformation. Moreover, optothermal Raman spectroscopy measurements on wrinkled silicene reveal a curvature-dependent heat dispersion larger than that observed in the unstrained case [5]. Finally, as compelling evidence of the technological potential of the silicene membranes, we demonstrate that they can be readily introduced into a lithographic process flow resulting in the definition of flexible device-ready architectures, e.g. piezoresistor, and thus paving the way to a viable advance in a fully silicon-compatible technology framework. The work is within the ERC-COG 2017 Grant N0. 772261 "XFab" and ERC-PoC 2022 Grant N. 101069262 “XMem”.<br/>References<br/>[1] A. Molle and C. Grazianetti, “Xenes: 2D Synthetic Materials Beyond Graphene”, Elsevier.<br/>[2] C. Martella, C. Massetti, D.S. Dhungana, E. Bonera, C. Grazianetti, and A. Molle, Adv. Mater.. Accepted Author Manuscript 2211419 (2023) https://doi.org/10.1002/adma.202211419<br/>[3] D. S. Dhungana, C. Grazianetti, C. Martella, S. Achilli, G. Fratesi, A. Molle, Adv. Funct. Mater. 31, 2102797 (2021).<br/>[4] C. Martella, G. Faraone, M. H. Alam, D. Taneja, L. Tao, G. Scavia, E. Bonera, C. Grazianetti, D. Akinwande, A. Molle, Adv. Funct. Mater. 30, 2004546 (2020).<br/>[5] E. Bonaventura, D. S. Dhungana, C. Martella, C. Grazianetti, S. Macis, S. Lupi, E. Bonera, and A. Molle, Nanoscale Horiz. 7, 924 (2022).