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| Home > Publications database > Microstructural analysis of corrosion inhibition in sub-100nm-scale Josephson circuits |
| Conference Presentation (After Call) | FZJ-2025-04255 |
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2025
Abstract: We have studied sub-100nm-scale nanobridge Josephson junctions (nJJs) and nJJ-based circuits using microstructural analysis and measurements of electron transport properties to reveal the possible origins of a spread in superconducting parameters (Tc, Ic, etc.) and long-term stability. The structures were prepared by dc magnetron sputtering from Nb, Ti and TiN targets, with electron beam exposure of HSQ resist and reactive ion etching in pure SF6 gas. Microstructural characterization was performed using aberration-corrected scanning transmission electron microscopy imaging and elemental mapping using energy-dispersive X-ray spectroscopy (FEI Titan G2 80-200 ChemiSTEM). The distributions of elements in nanostructures based on Ti-Nb-Ti heterostructures and TiN films were compared. Oxygen-free TiN nJJs, which have been reported previously [1, 2] are of interest for the realization of corrosion-resistant superconducting circuits, including qubits with operating temperatures down to 10 mK. Ti-Nb-Ti heterostructures, including nanoSQUIDs described in a recent paper [3], contain oxygen that has been chemisorbed by the Ti layers and are intended primarily for operation at 4.2 K. Superconducting through-silicon vias (TSVs) between circuits on opposite sides of a wafer will also be realized by using direct writing of superconducting current leads with focused-ion-beam-induced deposition and sputter deposition of superconducting films. Particular emphasis will be paid to the inhibition of oxygenation and corrosion on the nanometer scale by using new materials and methods, which promise to bring superconducting chip manufacture closer to circular economy objectives. Our work helps to realize the large-scale integration of long-term-stable superconducting circuits that include nanoSQUIDs, qubits and classical superconducting digital circuits, such as Single Flux Quantum (SFQ) based circuits and the Josephson digital phase detector (JDPD) described in ref. [4].References1. M. I. Faley, Y. Liu and R. E. Dunin-Borkowski, Nanomaterials 11, 466 (2021).2. M. I. Faley, H. Fiadziushkin, B. Frohn, P. Schüffelgen and R. E. Dunin-Borkowski, Supercond. Sci. Technol. 35, 065001 (2022).3. M. I. Faley, J. V. Vas, P.-H. Lu and R. E. Dunin-Borkowski, IEEE Transactions on Appl. Supercond. 35, 1600105 (2025).4. L. Di Palma, A. Miano, P. Mastrovito, D. Massarotti, M. Arzeo, G. P. Pepe, F. Tafuri and O. Mukhanov, Phys. Rev. Applied 19, 064025 (2023).
Keyword(s): Condensed Matter Physics (2nd)
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