Growth of Arbitrary 2D TMDs Nanopatterns via Thermal Scanning Probe Lithography

Two dimensional (2D) materials have emerged as promising platforms for creating new generation, atomically thin devices in various fields, from nanoelectronics and nanophotonic, to quantum technologies and energy conversion [1–3].<br/>These materials are generally manufactured from mechanically exfoliated flakes, which suffer from stochastic positioning and micrometric sizes. The re-shaping of 2D materials is attractive, since it opens interesting possibilities for engineering optoelectronic and photonic responses, as well as it enables the fabrication of devices with optimized geometries. Nanopatterning of exfoliated flakes is generally obtained by subtractive chemical etching methods [4] which, although effective for creating single demonstrative configurations, are not suitable for fabricating scalable devices for real-life applications.<br/>Here we propose a process that allows the direct fabrication of few-layer MoS₂ nano-circuits with arbitrary geometries. Our approach combines i) a custom-developed sputtering growth for creating few-layers MoS₂ extended films and ii) a high-resolution lithography technique which makes use of a nanoscopic (∼10nm) hot silicon probe (thermal Scanning Probe Lithography – t-SPL, NanoFrazor). By the accurate manipulation of such hot nanoprobe, transiently heated by Joule effect, we write deterministic nanopaths onto a sacrificial polymer layer; these nanopatterns spread over a large-area substrate are homogeneously coated by few-layer MoS₂ by the Ion Beam Sputtering (IBS) of a MoS₂ target, leading to MoS₂ nano-circuits with complex geometries and in-series scalability. After a proper high-temperature recrystallization process in a controlled atmosphere, these arbitrary MoS₂ nano-interconnections are characterized by the means of micro-Raman spectroscopy and Kelvin Probe Force Microscopy (KPFM). The observed vibrational and electronic responses confirm the presence of the stable 2H semiconducting phase confined inside the nano-circuits.<br/>After the fabrication of a proper nano-device configuration, the local electrical transport properties of these MoS₂ nano-paths are investigated via conductive - AFM (ResiScope c-AFM), demonstrating the possibility to employ these 2D semiconducting nanocircuits as building blocks of integrated electronics devices.<br/>Finally, we show some preliminary results on alternative applications of t-SPL on 2D materials, such as multilevel patterning of polymer films by 3D grayscale lithography. Indeed, the creation of three-dimensional patterns with arbitrary submicrometric features can serve as a tool to induce and study on-demand strain engineering of 2D materials.<br/><br/>[1] Q. H. Wang, K. Kalantar-Zadeh, A. Kis, J. N. Coleman, M. S. Strano, Nat. Nanotechnol. 2012, 7, 699.<br/>[2] C. Martella, C. Mennucci, A. Lamperti, E. Cappelluti, F. B. de Mongeot, A. Molle, Adv. Mater. 2018, 30, 1705615.<br/>[3] M. Bhatnagar, M. C. Giordano, C. Mennucci, D. Chowdhury, A. Mazzanti, G. Della Valle, C. Martella, P. Tummala, A. Lamperti, A. Molle, F. Buatier de Mongeot, Nanoscale 2020, 12, 24385.<br/>[4] M. G. Stanford, P. D. Rack, D. Jariwala, Npj 2D Mater. Appl. 2018, 2, DOI 10.1038/s41699-018-0065-3.<br/>[5] Giordano, M. C., Zambito, G., Gardella, M., Buatier de Mongeot, F., Deterministic Thermal Sculpting of Large-Scale 2D Semiconductor Nanocircuits. Adv. Mater. Interfaces 2023, 10, 2201408.