Krypton-sputtered tantalum films for scalable high-performance quantum devices

Nature Materials (2026) Cite this article Superconducting qubits and microwave resonators based on tantalum thin films have recently demonstrated large increases in performance. This makes Ta an attractive material for superconducting quantum computing applications, but so far direct deposition has largely relied on high substrate temperatures exceeding 400 °C to achieve the cubic (bcc) phase of tantalum. Here we show that changing the sputter gas from argon to krypton promotes synthesis of bcc tantalum films on silicon at temperatures as low as 200 °C. This provides a wide process window compatible with back-end-of-line fabrication standards. The microwave performance of coplanar-waveguide resonators fabricated from krypton-sputtered films shows an excellent tight performance distribution. Higher-temperature-grown films exhibit higher losses, in correlation with the degree of tantalum–silicon intermixing. 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Banerjee on X-ray photoemission spectroscopy. We thank multiple individuals for contributions: Z. L. Parrott, A. P. McFadden and C. R. H. McRae (NIST-Boulder) for sharing their transmon qubit design, which we adapted for this study, F. Bahrami and N. P. de Leon (Princeton) for discussions on α-Ta and Josephson-junction fabrication, S. Papa Rao (NY Creates) for discussions on scalable nanofabrication, G. D. Fuchs (Cornell) for discussions throughout the project, M. Hines (Cornell) for discussions on proper silicon preparation techniques, D. Ralph (Cornell) for access to essential equipment and L. Bhatt (Cornell) for help in collecting and interpreting electron energy loss spectrometry data. We also thank C. Alpha, J. Clark, S. Kriske, T. Pennell, M. Pfeifer and A. J. Windsor (technical staff at the Cornell Center for Materials Research and the Cornell Nanoscale Facility) for assistance in materials analysis and standing up fabrication processes. We acknowledge help from AJA International, Inc., technical staff, especially W. Sawyer.This prototype was primarily supported by the Microelectronics Commons Program, a DoW initiative, under award number N00164-23-9-G061. Funding for shared facilities used in this prototype was provided by the Microelectronics Commons Program, a DoW initiative, under award number N00164-23-9-G061. Ageing analysis and participation-ratio analysis was done with support in part by the Air Force Office of Scientific Research under award FA9550-23-1-0706. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the United States Air Force. This work was performed in part at the Cornell NanoScale Facility, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the National Science Foundation (grant NNCI-2025233). This work made use of the Cornell Center for Materials Research shared instrumentation facility, and of the Meehl cryostat donated by David W. Meehl in memory of his father James R. Meehl and supported by the Cornell College of Engineering.Department of Physics, Cornell University, Ithaca, NY, USAMaciej W. Olszewski, Saswata Roy & Luojia ZhangSchool of Applied and Engineering Physics, Cornell University, Ithaca, NY, USALingda Kong, Simon Reinhardt, Daniel Tong, Haoran Lu, David A. Muller & Valla FatemiDepartment of Materials Science and Engineering, Cornell University, Ithaca, NY, USADaniel TongCornell NanoScale Facility, Cornell University, Ithaca, NY, USAXinyi DuDepartment of Physics, University of Florida, Gainesville, FL, USAGabriele Di GianlucaNY Creates, Albany, NY, USAAleksandra B. BiedronKavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY, USADavid A. MullerSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarM.W.O. conceptualized the experiment with guidance from V.F. M.W.O. adapted the deposition chamber and developed the thin-film deposition methods with help from L.K. L.K. accomplished the AFM measurements with guidance from V.F. and D.A.M. and help from M.W.O. and S. Reinhardt. L.K. accomplished the X-ray diffraction and electron backscatter diffraction measurements with guidance from V.F. and D.A.M. D.T. accomplished the transmission electron microscopy measurements with guidance from D.A.M. A.B.B. accomplished the SIMS measurements. M.W.O. accomplished the transport measurements with help from L.K. and S. Reinhardt. M.W.O. fabricated the resonators with help from L.K. M.W.O. conducted the resonator measurements with help from H.L. G.D.G., X.D., S. Reinhardt and L.Z. developed the Josephson-junction fabrication with help from M.W.O. M.W.O. and S. Reinhardt fabricated the transmons with help from X.D. and L.K. S. Reinhardt and M.W.O. conducted the transmon measurements with help from S. Roy. S. Reinhardt set up the measurement cryostat with help from L.K. and M.W.O. X.D. conducted the electron paramagnetic resonance analysis for resonators and transmons. V.F. supervised the project. M.W.O. and V.F. led the manuscript writing with help from L.K., S. Reinhardt and D.T. All authors reviewed and provided feedback on the manuscript.Correspondence to Maciej W. Olszewski, Simon Reinhardt or Valla Fatemi.The authors declare no competing interests.Nature Materials thanks Shingo Kono and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.Supplementary Figs. 1–21 and Tables I–VI.Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.Reprints and permissionsOlszewski, M.W., Kong, L., Reinhardt, S. et al. Krypton-sputtered tantalum films for scalable high-performance quantum devices. Nat. Mater. (2026). https://doi.org/10.1038/s41563-026-02718-zDownload citationReceived: 21 December 2025Accepted: 21 July 2026Published: 18 August 2026Version of record: 18 August 2026DOI: https://doi.org/10.1038/s41563-026-02718-zAnyone you share the following link with will be able to read this content:Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative