Data for: Fabrication and Structural Analysis of Trilayers for Tantalum Josephson Junctions with Ta2O5 Barriers

Published: 2 February 2026| Version 2 | DOI: 10.17632/h88jp5rrk6.2
Contributors:
Raahul Potluri, Rohin Tangirala, Jiangteng Liu, Alejandro Barrios, Praveen Kumar, Sage Bauers, Peter Sushko, David Pappas, Serena Eley

Description

Tantalum (Ta) has emerged as a promising low-loss material, enabling record coherence times in superconducting qubits. This enhanced performance is largely attributed to its stable native oxide, which may host fewer two-level system (TLS) defects — key contributors to decoherence in superconducting circuits. Nevertheless, aluminum oxide remains the predominant choice for Josephson junction (JJ) barriers in most qubit architectures. Here, we investigate techniques for forming high-quality oxide layers on α-phase tantalum films to develop tantalum-oxide JJ barriers. We explore thermal oxidation in a tube furnace, rapid thermal annealing, and plasma oxidation of both room-temperature and heated Ta films, characterize the resulting structures using X-ray techniques and electron microscopy, and propose a mechanistic picture of the oxidation pathways. We find that plasma oxidation provides the smoothest Ta2O5 layers, is compatible with in situ Ta deposition, and offers thickness control through the annealing temperature, advantageous for JJ fabrication. Lastly, we evaluate methods for growing Ta/TaOx/Ta trilayers. All trilayers showed c- axis- oriented columnar growth of the bottom Ta layer, with sapphire substrates producing larger, better-aligned grains yet higher dislocation densities than silicon. Nucleation of c- axis- oriented α-Ta on tantalum-oxide required an Nb seed layer, as direct Ta deposition yielded amorphous Ta. These results demonstrate the feasibility of α-Ta/Nb/TaOx/α-Ta stacks for JJs with clean interfaces. This dataset includes Origin files (.opju) that contain data spreadsheets for all the samples and figures used in this paper, which can be opened using Origin Viewer, a free application that permits viewing and copying of data contained in Origin project files.

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Superconducting Thin Films, Device Fabrication, Scanning Transmission Electron Microscopy, Tantalum, Josephson Junction

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