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DS: Fachverband Dünne Schichten
DS 1: Organic Thin Films
DS 1.2: Talk
Monday, March 9, 2026, 09:45–10:00, REC/C213
Organic self-assembled monolayers as barrier material in Josephson junctions — •Moritz Singer1, Harsh Gupta1, Rui Pereira2, Benedikt Schoof1, and Marc Tornow1,2 — 1TU Munich, Garching, Germany — 2Fraunhofer EMFT, Munich, Germany
Superconducting qubits employ Josephson junctions (JJs) to provide the non-linearity needed to address a unique two-state system. The JJs consist of two superconducting electrodes which are separated by a nanometer-thin layer acting as tunnel barrier and is mostly fabricated from oxides. The thickness of the oxide is highly sensitive to process variations, and it hosts many two-level systems (TLS) which give rise to dielectric losses, thereby limiting the qubit coherence times. In this study, we report on JJs comprising an organic self-assembled monolayer (SAM) as the insulating barrier material. Our JJs consist of Ta electrodes on a Nb seed layer, separated by a SAM of octadecene (C18H36) molecules that are grown on the thin native TaOx layer of the bottom electrode. We fabricated JJs with three different electrode sizes in the μm - range and measured critical currents Ic between 3.7 μA and 30.6 μA at 100 mK, in good quantitative agreement with the expected values according to the Ambegaokar-Baratoff relation. We further analyzed the data using the Simmons tunneling model, adapted to account for the two-layer TaOx/SAM barrier. We obtain barrier heights ranging from 0.43-0.57 eV for the SAM-JJs, which is significantly higher than for JJs fabricated with a Ta-oxide barrier only (barrier height 0.25 eV). This shows that the properties of JJs can be modified and tuned by introducing a SAM as barrier material.
Keywords: Organic self-assembled monolayer; Josephson junctions; Tunnel junctions; Tantalum electrodes; Superconducting qubits