Dynamic Versus Static Oxidation of Nb/Al-AlOx/Nb Trilayer

Tannaz Farrahi; Alan W. Kleinsasser; Michael Cyberey; Jie Wang; Micahel B. Eller; Jian Z. Zhang; Anthony R. Kerr; Joseph G. Lambert; Robert M. Weikle; Arthur W. Lichtenberger

arXiv · 2306.12684

Dynamic Versus Static Oxidation of Nb/Al-AlOx/Nb Trilayer

Tannaz Farrahi·Alan W. Kleinsasser·Michael Cyberey·Jie Wang·Micahel B. Eller·Jian Z. Zhang·Anthony R. Kerr·Joseph G. Lambert·Robert M. Weikle·Arthur W. Lichtenberger

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Abstract

High quality Nb-based superconductor-insulator-superconductor (SIS) junctions with Al oxide (AlO$_x$) tunnel barriers grown from Al overlayers are widely reported in the literature. However, the thin barriers required for high critical current density (J$_c$) junctions exhibit defects that result in significant subgap leakage current that is detrimental for many applications. High quality, high-J$_c$ junctions can be realized with AlN$_x$ barriers, but control of J$_c$ is more difficult than with AlO$_x$. It is therefore of interest to study the growth of thin AlO$_x$ barriers with the ultimate goal of achieving high quality, high-J$_c$ AlO$_x$ junctions. In this work, 100\%\ O$_2$ and 2\%\ O$_2$ in Ar gas mixtures are used both statically and dynamically to grow AlO$_x$ tunnel barriers over a large range of oxygen exposures. In situ ellipsometry is used for the first time to extensively measure AlO$_x$ tunnel barrier growth in real time, revealing a number of unexpected patterns. Finally, a set of test junction wafers was fabricated that exhibited the well-known dependence of J$_c$ on oxygen exposure (E) in order to further validate the experimental setup.

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Tannaz Farrahi, Alan W. Kleinsasser, Michael Cyberey, Jie Wang, Micahel B. Eller, Jian Z. Zhang, Anthony R. Kerr, Joseph G. Lambert, Robert M. Weikle, Arthur W. Lichtenberger. 2023-06-22. Dynamic Versus Static Oxidation of Nb/Al-AlOx/Nb Trilayer. https://arxiv.org/abs/2306.12684

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