Bendable Xenes-Based Membranes

Xenes, the monoelemental family of two-dimensional (2D) materials, exhibit a variety of interesting physical properties with potential exploitation in nanotechnology [1]. In the framework of flexible electronics, photonics and related applications including wearable and strain-responsive devices, 2D bendable membranes are highly desired. We report here on the realization of Xenes-based membranes by taking benefit from the recently developed scheme of the Xene heterostructure, namely silicene-stanene grown by molecular beam epitaxy [2], where silicene is sandwiched in between an alumina encapsulation layer on the top surface and stanene on thin Ag(111) crystal at the bottom face. When the so-grown Xenes-base membrane is transferred onto a flexible substrate [3], 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, similarly to the unstrained case [4], optothermal Raman spectroscopy measurements reveal a curvature-dependent heat dispersion in silicene. Finally, as compelling evidence of the technological potential of the membranes, we demonstrate that they can be readily introduced into a lithographic process flow resulting in the definition of flexible device-ready architectures. Bendable Xenes-based memebranes may thus hold high potential for flexible and silicon-compatible applications [5]. 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] D. S. Dhungana, C. Grazianetti, C. Martella, S. Achilli, G. Fratesi, A. Molle, Adv. Funct. Mater. 31, 2102797 (2021).<br/>[3] 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/>[4] E. Bonaventura, D. S. Dhungana, C. Martella, C. Grazianetti, S. Macis, S. Lupi, E. Bonera, and A. Molle, Nanoscale Horiz. 7, 924 (2022).<br/>[5] C. Martella, C. Massetti, D. S. Dhungana, C. Grazianetti, and A. Molle, submitted.