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Comparative Insights into Native and In Situ Deposited Oxides on Epitaxial Superconducting Aluminum Films

ORAL

Abstract

Heterostructures of oxide/aluminum (Al) film are crucial in the fabrication of Josephson junctions and microwave resonators, which serve as fundamental building blocks in superconducting qubits for quantum computing. Traditionally, native oxides (AlOx) spontaneously form on Al surfaces when exposed to ambient oxygen. Departing from this conventional approach, we have successfully in situ deposited nanometer-thick Al2O3 films onto freshly grown Al films in UHV. This study compares the electronic and structural properties of native AlOx and in situ deposited Al2O3 films, using X-ray photoelectron spectroscopy (XPS) and X-ray reflectivity (XRR), respectively. The XPS data show that the deposited Al2O3 serves as an effective blocker against air oxidation, unlike O2-purged AlOx, which permits air interaction with Al. Furthermore, XRR measurements of the in situ deposited Al2O3/Al samples were accurately modeled using a tri-layer structure in the deposited Al2O3, with distinct densities at the Al interface, the oxide bulk, and the top air-exposed surface layer. The complex XRR oscillations measured from the native AlOx/Al samples defied the tri-layer simplification. Our results underscore the superior protective capabilities of the in situ deposited Al2O3 films, making them a promising alternative for enhancing the durability of Al-based superconducting devices.

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Presenters

  • Chao-Kai Cheng

    National Taiwan University, Graduate Institute of Applied Physics and Department of Physics, National Taiwan University

Authors

  • Chao-Kai Cheng

    National Taiwan University, Graduate Institute of Applied Physics and Department of Physics, National Taiwan University

  • Wan-Sin Chen

    National Taiwan University

  • Yen-Hsun Glen Lin

    National Taiwan University

  • Hsien-Wen Wan

    National Taiwan University, Graduate Institute of Applied Physics and Department of Physics, National Taiwan University

  • Yi-Ting Cheng

    National Taiwan University, Graduate Institute of Applied Physics and Department of Physics, National Taiwan University

  • Tun-Wen Pi

    National Synchrotron Radiation Research Center

  • Chien-Chun Ting

    National Tsing Hua University

  • Chia-Hung Hsu

    National Synchrotron Radiation Research Center, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan

  • Yen-Hsiang Lin

    National Tsing Hua University, Department of Physics, National Tsing Hua University;Taiwan Semiconductor Research Institute, Department of Physics, National Tsing Hua University, Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan

  • Jueinai Kwo

    National TsingHua University, National Tsing Hua University, Department of Physics, National Tsing Hua University

  • Minghwei Hong

    National Taiwan University, Graduate Institute of Applied Physics and Department of Physics, National Taiwan University