April 22 - 26, 2024
Seattle, Washington
May 7 - 9, 2024 (Virtual)
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2024 MRS Spring Meeting & Exhibit
QT04.03.17

Probing Buried Interface Properties in Ta/Sapphire Superconducting Resonators

When and Where

Apr 23, 2024
5:00pm - 7:00pm
Flex Hall C, Level 2, Summit

Presenter(s)

Co-Author(s)

Aswin kumar Anbalagan1,Rebecca Cummings1,Chenyu Zhou1,Junsik Mun1,Jean-Jordan Sweet2,Vesna Stanic2,Kim Kisslinger1,Conan Weiland3,Steve Hulbert1,Nathalie de Leon4,Yimei Zhu1,Mingzhao Liu1,Peter Sushko5,Andrew L. Walter1,Andi Barbour1

Brookhaven National Laboratory1,IBM T.J. Watson Research Center2,National Institute of Standards and Technology3,Princeton University4,Pacific Northwest National Laboratory5

Abstract

Aswin kumar Anbalagan1,Rebecca Cummings1,Chenyu Zhou1,Junsik Mun1,Jean-Jordan Sweet2,Vesna Stanic2,Kim Kisslinger1,Conan Weiland3,Steve Hulbert1,Nathalie de Leon4,Yimei Zhu1,Mingzhao Liu1,Peter Sushko5,Andrew L. Walter1,Andi Barbour1

Brookhaven National Laboratory1,IBM T.J. Watson Research Center2,National Institute of Standards and Technology3,Princeton University4,Pacific Northwest National Laboratory5
Dielectric loss significantly impacts the coherence time of superconducting qubits, suggesting that surfaces and interfaces are the primary limiting factors. Despite constituting a smaller fraction of the qubit’s electromagnetic mode, they have the potential to exert significant influence as sources of high-loss tangents. This study investigates the structure and composition of the interfacial layer in Ta/sapphire-based superconducting qubits. Ta (222) films, comprising a pure α-phase, were sputtered onto a C-plane sapphire substrate at a growth temperature of 750 °C. Characterization of the film, including thickness, roughness, and electron density, was performed using synchrotron-based X-ray reflectivity (XRR) and Hard X-ray photoemission spectroscopy techniques. Notably, our analysis revealed an unexplored layer at the metal-substrate interface that is not possible to detect with the lab-based XRR. To establish the composition and the spatial extent of this interface layer, high-angle annular dark field–scanning transmission electron microscopy (HAADF-STEM) coupled with core-level electron energy loss spectroscopy (EELS) was employed. HAADF- STEM technique provided evidence of an interfacial layer approximately 0.7 nm thick between the metal-substrate layer, aligning well with the measurements from synchrotron XRR fitting. Further examination of the elemental composition of these interface layers using HAADF-STEM with EELS revealed an intermixing layer containing Al, O, and Ta atoms. Ab initio calculations suggest the substrate-metal interface structure’s dependence on the sapphire termination before Ta deposition, offering the potential to modulate the Ta film structure through pre-treatment of the sapphire surfaces. These findings offer valuable insights into controlling the structure and composition of the substrate-metal interface that may be able to increase qubit coherence times.

Keywords

scanning transmission electron microscopy (STEM) | Ta

Symposium Organizers

Liangzi Deng, University of Houston
Qiang Li, Stony Brook University/Brookhaven National Laboratory
Toshinori Ozaki, Kwansei Gakun University
Ruidan Zhong, Shanghai Jiao Tong University

Symposium Support

Gold
Faraday Factory Japan LLC

Session Chairs

Liangzi Deng
Yusuke Ichino

In this Session