Improved Interface of Niobium Superconducting Resonator with Ruthenium as a Capping Layer

Improved Interface of Niobium Superconducting Resonator with Ruthenium as a Capping Layer

ACS Applied Electronic Materials

10.1021/acsaelm.4c01268

https://doi.org/10.1021/acsaelm.4c01268

Senthil Kumar Karuppannan, Ding Huang, Naga Manikanta Kommanaboina, Kamma Anil, Guangxu Yan, Durga Venkata Maheswar Repaka, Yiyu Zhang, Kuan Eng Johnson Goh, Wong Seng Kai, Nelson Lim Chee Beng, Yap Lee Koon Sherry, Manas Mukherjee

04 October 2024

Karuppannan, S. K., Huang, D., Kommanaboina, N. M., Anil, K., Yan, G., Repaka, D. V. M., Zhang, Y., Goh, K. E. J., Kai, W. S., Chee Beng, N. L., Sherry, Y. L. K., & Mukherjee, M. (2024). Improved Interface of Niobium Superconducting Resonator with Ruthenium as a Capping Layer. ACS Applied Electronic Materials, 6(10), 7372–7379. https://doi.org/10.1021/acsaelm.4c01268

The current performance of superconducting circuit-based quantum processors is limited by the poor understanding of interface physics, including native surface oxide formation on the superconducting metal, which causes two-level system (TLS) loss. Niobium (Nb), a superconducting metal with a high energy gap, is an ideal choice for superconducting processors, but unfortunately, it is marred by TLS. Several methods have been proposed to minimize surface oxide on the Nb film, and considerable improvement in TLS loss has been demonstrated. These methods include surface passivation through metal capping, self-assembly of organic molecules, and post-cleaning processes. Among these, metal capping is a suitable choice despite forming a 3–5 nm thick oxide, as self-assembly and post-treatment do not protect the Nb film surface during further fabrication. Here, we have proposed ruthenium (Ru) as a capping layer, forming a self-limiting oxidation with a 0.6 nm oxide thickness and predominantly producing fewer oxide compositions while being chemically resistant for further wafer fabrication processes, thus fulfilling all the criteria of an ideal capping layer. Our investigation suggests that Nb/Ru resonators have great potential as versatile and promising tools for advancing superconducting quantum technologies and integrating quantum interconnects into qubits with minimized TLS loss.

Publisher Copyright

This research / project is supported by the National Research Foundation - Quantum Engineering Programme
Grant Reference no. : NRF2021-QEP2-03-P07/W21Qpd0307

This research / project is supported by the Agency for Science, Technology and Research - Strategic Research Programme
Grant Reference no. : C222517002

This research / project is supported by the Agency for Science, Technology and Research - Manufacturing, Trade, and Connectivity Young Individual Research Grants
Grant Reference no. : M22K3c0105

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Applied Electronic Materials, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see 10.1021/acsaelm.4c01268

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