Single crystal nm-thick aluminum superconducting microwave resonators with internal quality factors above one million

ORAL

Abstract

Single-crystal thin films with a highly ordered atomic structure can host controlled interfaces to their adjacent layers, as the key to reducing dielectric loss in superconducting quantum circuits. In this work, we have demonstrated single-crystal aluminum (Al) thin films on sapphire substrates with very high crystallinity and high internal quality factors (Qi). Using in-situ oxide deposition instead of a conventional oxidation process, we have achieved a well-controlled interface between oxide and Al film and protected these nm-thick Al films from oxidation in the ambient.

High crystallinity of single-crystal Al films was characterized using synchrotron radiation X-ray diffraction. Clear Pendellosung fringes were observed, indicative of high crystallinity of the Al films and small interface roughness (< 0.5 nm) between the Al films and the adjacent layers. The full-width at half-maximum (FWHM) of θ-rocking curves of the Al films are record-low values of 0.015 degrees (54 arcsec) from samples with thicknesses from 3 nm to 20 nm-thick. The samples exhibited smooth surfaces and interfaces confirmed by X-ray reflectivity (XRR) and atomic force microscope. Microstrip resonators made from such single-crystal Al films reveal internal quality factors over 1 million around 7 GHz in the low power limit at 10 mK. Such single-crystal materials offer excellent potential of low dielectric loss, thus improving the coherence of superconducting quantum circuits.

*The authors would like to thank the support from the Ministry of Science and Technology (MOST) in Taiwan through Nos. MOST 110-2112-M-002-036-, 111-2119-M-007-005-, and the National Science and Technology Council (NSTC) in Taiwan through Nos. NSTC 111-2622-8-002-001-, NSTC 111-2811-M-002-123-. The authors acknowledge the support from YuShan Fellowship Program from the Ministry of Education, Taiwan, and the Center for Quantum Technology, Taiwan

–

Presenters

  • Yen-Hsun Glen Lin

    • National Taiwan University
    • Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei 10617, Taiwan

Authors

  • Yen-Hsun Glen Lin

    • National Taiwan University
    • Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei 10617, Taiwan

  • Lawrence Boyu Young

    • National Taiwan University
    • Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei 10617, Taiwan

  • Li-Shao Chiang

    • National Taiwan University

  • Chao-Kai Cheng

    • National Taiwan University

  • Wan-Sin Chen

    • National Taiwan University

  • Kuan-Hui Lai

    • National Taiwan University

  • Hsien-Wen Wan

    • National Taiwan University

  • Yi-Ting Cheng

    • National Taiwan University

  • Chia-Hung Hsu

    • National Synchrotron Radiation Research Center
    • Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
    • National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
    • National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan

  • Chi-Te Liang

    • Natl Taiwan Univ
    • National Taiwan University

  • Juhn-Jung Lin

    • National Yang Ming Chiao Tung University

  • Yen-Hsiang Lin

    • National Tsing Hua University

  • Jueinai Kwo

    • National Tsing Hua University
    • Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan

  • Minghwei Hong

    • National Taiwan University
    • Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei 10617, Taiwan