Chemical Profiles of the Oxides on Tantalum in State of the Art Superconducting Circuits

Russell A. McLellan, Aveek Dutta, Chenyu Zhou, Yichen Jia, Conan Weiland, Xin Gui, Alexander P.M. Place, Kevin D. Crowley, Xuan Hoang Le, Trisha Madhavan, Youqi Gang, Lukas Baker, Ashley R. Head, Iradwikanari Waluyo, Ruoshui Li, Kim Kisslinger, Adrian Hunt, Ignace Jarrige, Stephen A. Lyon, Andi M. BarbourRobert J. Cava, Andrew A. Houck, Steven L. Hulbert, Mingzhao Liu, Andrew L. Walter, Nathalie P. de Leon

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Over the past decades, superconducting qubits have emerged as one of the leading hardware platforms for realizing a quantum processor. Consequently, researchers have made significant effort to understand the loss channels that limit the coherence times of superconducting qubits. A major source of loss has been attributed to two level systems that are present at the material interfaces. It is recently shown that replacing the metal in the capacitor of a transmon with tantalum yields record relaxation and coherence times for superconducting qubits, motivating a detailed study of the tantalum surface. In this work, the chemical profile of the surface of tantalum films grown on c-plane sapphire using variable energy X-ray photoelectron spectroscopy (VEXPS) is studied. The different oxidation states of tantalum that are present in the native oxide resulting from exposure to air are identified, and their distribution through the depth of the film is measured. Furthermore, it is shown how the volume and depth distribution of these tantalum oxidation states can be altered by various chemical treatments. Correlating these measurements with detailed measurements of quantum devices may elucidate the underlying microscopic sources of loss.

Original languageEnglish (US)
Article number2300921
JournalAdvanced Science
Issue number21
StatePublished - Jul 27 2023

All Science Journal Classification (ASJC) codes

  • General Engineering
  • General Chemical Engineering
  • Biochemistry, Genetics and Molecular Biology (miscellaneous)
  • General Materials Science
  • General Physics and Astronomy
  • Medicine (miscellaneous)


  • X-ray photoelectron spectroscopy
  • dielectric loss
  • oxide
  • qubits
  • superconducting thin films
  • tantalum


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