Engineering of Niobium Surfaces Through Accelerated Neutral Atom Beam Technology For Quantum Applications

• Published in: arXiv.org
• Main Authors: Kar, Soumen, Weiland, Conan, Zhou, Chenyu, Bhatia, Ekta, Martinick, Brian, Nalaskowski, Jakub, Mucci, John, Olson, Stephen, Hung, Pui Yee, Wells, Ilyssa, Frost, Hunter, Johnson, Corbet S, Murray, Thomas, Kaushik, Vidya, Kirkpatrick, Sean, Chau, Kiet, Walsh, Michael J, Liu, Mingzhao, Papa Rao, Satyavolu S
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 27.02.2023
• Subjects: Argon; Coherence; Electrons; Neutral atoms; Niobium; Physics - Applied Physics; Physics - Materials Science; Process parameters; Quantum computing; Qubits (quantum computing); Room temperature; Superconductivity; Thickness
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2302.14113

A major roadblock to scalable quantum computing is phase decoherence and energy relaxation caused by qubits interacting with defect-related two-level systems (TLS). Native oxides present on the surfaces of superconducting metals used in quantum devices are acknowledged to be a source of TLS that decrease qubit coherence times. Reducing microwave loss by surface engineering (i.e., replacing uncontrolled native oxide of superconducting metals with a thin, stable surface with predictable characteristics) can be a key enabler for pushing performance forward with devices of higher quality factor. In this work, we present a novel approach to replace the native oxide of niobium (typically formed in an uncontrolled fashion when its pristine surface is exposed to air) with an engineered oxide, using a room-temperature process that leverages Accelerated Neutral Atom Beam (ANAB) technology at 300 mm wafer scale. This ANAB beam is composed of a mixture of argon and oxygen, with tunable energy per atom, which is rastered across the wafer surface. The ANAB-engineered Nb-oxide thickness was found to vary from 2 nm to 6 nm depending on ANAB process parameters. Modeling of variable-energy XPS data confirm thickness and compositional control of the Nb surface oxide by the ANAB process. These results correlate well with those from transmission electron microscopy and X-ray reflectometry. Since ANAB is broadly applicable to material surfaces, the present study indicates its promise for modification of the surfaces of superconducting quantum circuits to achieve longer coherence times.