Superconducting qubits have emerged as a potentially foundational platform technology for addressing complex computational problems deemed intractable with classical computing. Despite recent advances enabling multiqubit designs that exhibit coherence lifetimes on the order of hundreds of μs, material quality and interfacial structures continue to curb device performance. Two-level system defects in the thin superconducting film and adjacent dielectric regions introduce stochastic noise and dissipate electromagnetic energy at the cryogenic operating temperatures. In this study, we utilize time-of-flight secondary ion mass spectrometry to understand the role specific fabrication procedures play in introducing such dissipation mechanisms in these complex systems. We interrogated Nb thin films and transmon qubit structures fabricated through slight modifications in the processing and vacuum conditions. We find that when the Nb film is sputtered onto the Si substrate, oxide and silicide regions are generated at various interfaces. We also observe that impurity species, such as niobium hydrides and carbides, are incorporated within the niobium layer during the subsequent lithographic patterning steps. The formation of these resistive compounds likely impacts the superconducting properties of the Nb thin film. Additionally, we observe the presence of halogen species distributed throughout the patterned thin films. We conclude by hypothesizing the source of such impurities in these structures in an effort to intelligently fabricate superconducting qubits and extend coherence times moving forward.
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TOF-SIMS analysis of decoherence sources in superconducting qubits
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24 January 2022
Research Article|
January 24 2022
TOF-SIMS analysis of decoherence sources in superconducting qubits
A. A. Murthy
;
A. A. Murthy
a)
1
Fermi National Accelerator Laboratory (FNAL)
, Batavia, Illinois 60510, USA
a)Author to whom correspondence should be addressed: [email protected]
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J. Lee;
J. Lee
1
Fermi National Accelerator Laboratory (FNAL)
, Batavia, Illinois 60510, USA
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C. Kopas;
C. Kopas
2
Rigetti Computing
, Berkeley, California 94710, USA
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M. J. Reagor
;
M. J. Reagor
2
Rigetti Computing
, Berkeley, California 94710, USA
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A. P. McFadden;
A. P. McFadden
3
National Institute of Standards and Technology
, Boulder, Colorado 80305, USA
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D. P. Pappas;
D. P. Pappas
3
National Institute of Standards and Technology
, Boulder, Colorado 80305, USA
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M. Checchin
;
M. Checchin
1
Fermi National Accelerator Laboratory (FNAL)
, Batavia, Illinois 60510, USA
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A. Grassellino;
A. Grassellino
1
Fermi National Accelerator Laboratory (FNAL)
, Batavia, Illinois 60510, USA
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A. Romanenko
A. Romanenko
1
Fermi National Accelerator Laboratory (FNAL)
, Batavia, Illinois 60510, USA
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a)Author to whom correspondence should be addressed: [email protected]
Appl. Phys. Lett. 120, 044002 (2022)
Article history
Received:
November 19 2021
Accepted:
December 29 2021
Citation
A. A. Murthy, J. Lee, C. Kopas, M. J. Reagor, A. P. McFadden, D. P. Pappas, M. Checchin, A. Grassellino, A. Romanenko; TOF-SIMS analysis of decoherence sources in superconducting qubits. Appl. Phys. Lett. 24 January 2022; 120 (4): 044002. https://doi.org/10.1063/5.0079321
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