Optical direct write of Dolan–Niemeyer-bridge junctions for transmon qubits

Monroe, Jonathan; Kowsari, D.; Zheng, Kaiwen; Gaikwad, C.; Brewster, Jacob; Wisbey, David; Murch, Kater

doi:10.1063/5.0060246

Cited by 4 publications

(3 citation statements)

References 67 publications

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“…31 The Al/AlO x /Al junctions are often fabricated by exposing the metallic surface to O 2 (at room temperature in the mbar range). 32 Moreover, the uncontrolled oxidation of the Al electrodes and the formation of a lossy amorphous dielectric oxide can be a source of decoherence for the qubit. 33−36 We preferred to study the oxidation on aluminum single crystals, Al(111), rather than on the deposited polycrystalline film.…”

Section: Introductionmentioning

confidence: 99%

“…We have considered Al oxidation in O 2 because of its historical role in establishing the oxidation models ,, and because it keeps attracting considerable attention both experimentally − and theoretically. ,,− ,, Aluminum is also the material of choice in the fabrication of Josephson junction qubits, for which the oxidation of the metal is a vital issue . The Al/AlO x /Al junctions are often fabricated by exposing the metallic surface to O 2 (at room temperature in the mbar range) . Moreover, the uncontrolled oxidation of the Al electrodes and the formation of a lossy amorphous dielectric oxide can be a source of decoherence for the qubit. − We preferred to study the oxidation on aluminum single crystals, Al(111), rather than on the deposited polycrystalline film.…”

Section: Introductionmentioning

confidence: 99%

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Testing the Cabrera–Mott Oxidation Model for Aluminum under Realistic Conditions with Near-Ambient Pressure Photoemission

et al. 2022

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Using the nascent band theory of solids, Cabrera and Mott designed in the late 1940s a model for the lowtemperature oxidation of metals that still stands today as a landmark. The core assumption is that an electric field set up in the growing oxide at thermodynamic equilibrium drives the transport of the ionic species responsible for the oxidation process. The existence of an electrostatic potential has long been sought experimentally by in situ measurement of the work function changes in the presence of gaseous O 2 . Here, we demonstrate that the work function measurement is insufficient to test the model. Instead, the oxide band structure characteristics (surface dipole energy barrier and band bending) should be followed. We exemplify this for the paradigmatic case of the Al(111) surface oxidation at room temperature using near-ambient pressure X-ray photoemission spectroscopy (operated up to a pressure of 1 mbar). Using an in situ spectroscopic tool, we monitor the oxide growth in real time and obtain detailed energetic information on the metal/oxide/gas system. This allows us to validate the central hypothesis of the Cabrera−Mott model (i.e., the existence of the Cabrera−Mott potential). The original assumption that oxygen anions are adsorbed at the oxide/gas interface is also discussed. The concept of "realistic conditions" also means that the issue of water coadsorption (inherent to near-ambient O 2 conditions) is addressed. The specific consequences of the Cabrera−Mott regime of oxidation are also discussed with respect to the functioning of aluminum-based superconducting qubits. The in situ, real-time spectroscopic methodology used here is effective and can be generalized far beyond the specific case of aluminum oxidation.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Testing the Cabrera–Mott Oxidation Model for Aluminum under Realistic Conditions with Near-Ambient Pressure Photoemission

et al. 2022

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“…It has been shown that TLS defects are mainly located at metal-air (MA), substrate-air (SA), and metal-substrate (MS) interfaces [15][16][17][18][19] . The contribution of losses from these interfaces can be minimized by implementing careful surface treatments thus enhancing the coherence of the devices 20,21 .…”

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confidence: 99%

Fabrication and surface treatment of electron-beam evaporated niobium for low-loss coplanar waveguide resonators

Kowsari,

Zheng,

Monroe

et al. 2021

Preprint

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Fabrication and surface treatment of electron-beam evaporated niobium for low-loss coplanar waveguide resonators

Kowsari

Zheng

Monroe

et al. 2021

Applied Physics Letters

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We characterize low-loss electron-beam evaporated niobium thin films deposited under ultra-high vacuum conditions. Slow deposition yields films with a high superconducting transition temperature (9.20±0.06 K) as well as a residual resistivity ratio of 4.8. We fabricate the films into coplanar waveguide resonators to extract the intrinsic loss due to the presence of two-level-system fluctuators using microwave measurements. For a coplanar waveguide resonator gap of 2 μm, the films exhibit filling-factor-adjusted two-level-system loss tangents as low as 1.5×10−7 with single-photon regime internal quality factors in excess of one million after removing native surface oxides of the niobium.

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Optical direct write of Dolan–Niemeyer-bridge junctions for transmon qubits

Cited by 4 publications

References 67 publications

Testing the Cabrera–Mott Oxidation Model for Aluminum under Realistic Conditions with Near-Ambient Pressure Photoemission

Testing the Cabrera–Mott Oxidation Model for Aluminum under Realistic Conditions with Near-Ambient Pressure Photoemission

Fabrication and surface treatment of electron-beam evaporated niobium for low-loss coplanar waveguide resonators

Fabrication and surface treatment of electron-beam evaporated niobium for low-loss coplanar waveguide resonators

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