Intermolecular, Inc.

Northrop Grumman Systems Corporation

Andrew Steinbach

Dipankar Pramanik

Frank Greer

Sergey V Barabash

Chris Kirby

Yun Yu Wang

Kurt Pang

Tony Bonetti

Amorphous silicon (a-Si) is hydrogenated for use as a dielectric (e.g., an interlayer dielectric) for superconducting electronics. A hydrogenated a-Si layer is formed on a substrate by CVD or sputtering. The hydrogen may be integrated during or after the a-Si deposition. After the layer is formed, it is first annealed in an environment of high hydrogen chemical potential and subsequently annealed in an environment of low hydrogen chemical potential. Optionally, the a-Si (or an H-permeable overlayer, if added) may be capped with a hydrogen barrier before removing the substrate from the environment of low hydrogen chemical potential.

Hydrogenated amorphous silicon dielectric for superconducting devices

Provided are superconducting circuits, methods of operating these superconducting circuits, and methods of determining processing conditions for operating these superconducting circuits. A superconducting circuit includes a superconducting element, a conducting element, and a dielectric element disposed between the superconducting element and the conducting element. The conducting element may be another superconducting element, a resonating element, or a conducting casing. During operation of the superconducting element a direct current (DC) voltage is applied between the superconducting element and the conducting element. This application of the DC voltage reduces average microwave absorption of the dielectric element. In some embodiments, when the DC voltage is first applied, the microwave absorption may initially rise and then fall below the no-voltage absorption level. The DC voltage level may be determined by testing the superconducting circuit at different DC voltage levels and selecting the one with the lowest microwave absorption.

Superconducting circuits with reduced microwave absorption

Provided are superconducting tunnel junctions, such as Josephson tunnel junctions, and a method of fabricating thereof. A junction includes an insulator disposed between two superconductors. The junction may also include one or two interface layers, with each interface layer disposed between the insulator and one of the superconductors. The interface layer is configured to prevent oxygen from entering the adjacent superconductor during fabrication and operation of the junction. Furthermore, the interface layer may protect the insulator from the environment during handling and processing of the junction, thereby allowing vacuum breaks after the interface layer is formed as well as new integration schemes, such as depositing a dielectric layer and forming a trench in the dielectric layer for the second superconductor. In some embodiments, the junction may be annealed during its fabrication to move oxygen from the superconductors and/or from the insulator into the one or two interface layers.

Superconducting junctions

An amorphous silicon (a-Si) dielectric for superconducting electronics is fabricated with reduced loss tangent by fluorine passivation throughout the bulk of the layer. Complete layers or thinner sub-layers of a-Si are formed by physical vapor deposition at low temperatures (&#x3c;350 C, e.g. &#x2dc;200 C) to prevent reaction with superconducting materials, then exposed to fluorine. The fluorine may be a component of a gas or plasma, or it may be a component of an interface layer. The fluorine is driven into the a-Si by heat (e.g., &#x3c;350 C) or impact to passivate defects such as dangling bonds.

Fluorine passivation of dielectric for superconducting electronics

A tunnel barrier layer in a superconducting device, such as a Josephson junction, is made from catalytically grown silicon dioxide at a low temperature (&#x3c;100 C, e.g., 20-30 C) that does not facilitate oxidation or silicide formation at the superconducting electrode interface. The tunnel barrier begins as a silicon layer deposited on a superconducting electrode and covered by a thin, oxygen-permeable catalytic layer. Oxygen gas is dissociated on contact with the catalytic layer, and the resulting oxygen atoms pass through the catalytic layer to oxidize the underlying silicon. The reaction self-limits when all the silicon is converted to silicon dioxide.

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Andrew Steinbach