Nanostructured Shadow Mask for In-Situ Josephson Junction Fabrication
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Solution Overview
Problem
Ex-situ processing of Josephson junctions introduces impurities and uncontrolled electronic environments, leading to contamination and reduced quality of quantum devices, particularly in the fabrication of advanced superconducting qubits.
Innovation Solution
The method involves using a nanostructure as a shadow mask during deposition to create a gap in the facet layer in-situ, allowing for the formation of high-quality Josephson junctions without ex-situ post-processing, utilizing VLS growth in a vacuum chamber to maintain a clean environment and achieve epitaxial interfaces between semiconductor and superconductor materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ex-situ processing is used to fabricate Josephson junctions, then standard lithography techniques can be applied, but impurities and uncontrolled electronic environments are introduced leading to contamination
Solution Approach 1:
The patent combines multiple fabrication steps (nanowire growth, facet layer deposition, and Josephson junction formation) into a single in-situ vacuum process. The shadow mask nanowires are grown and positioned within the same vacuum chamber where the facet layers are deposited, eliminating the need for ex-situ processing and preventing contamination throughout the entire fabrication sequence.
Solution Approach 2:
The patent maintains a vacuum environment throughout the entire fabrication process. All critical steps including nanowire growth by VLS mechanism, facet layer deposition, and junction formation occur in-situ under vacuum conditions, creating an inert atmosphere that prevents oxidation and contamination of the quantum materials.
2Manufacturing precision
If shadow masks are used to form Josephson junctions, then gaps can be introduced in thin films, but conventional organic bilayers are incompatible with ultra-high vacuum and high substrate temperatures
Solution Approach 1:
The patent changes the material parameters of the shadow mask from conventional organic bilayers to inorganic nanowires with high melting points. These inorganic nanowire shadow masks can withstand ultra-high vacuum conditions and high substrate temperatures required for epitaxial film growth, enabling their use in in-situ fabrication processes.
Solution Approach 2:
The patent uses composite inorganic nanowire structures as shadow masks that combine structural integrity with shadowing capability. The nanowires are grown with specific crystallographic orientations and morphologies that provide both mechanical stability at high temperatures and precise shadow patterns for gap formation in the facet layers.
3Object-affected harmful factors
If in-situ processing is used to avoid contamination, then quantum device quality is improved, but complex inorganic shadow masks are required
Solution Approach 1:
The patent employs self-assembled nanowire shadow masks that form through spontaneous aggregation and organization during the vapor deposition process. The nanowires automatically position themselves and create the required shadow patterns without requiring complex pre-fabricated mask structures, reducing overall device complexity while maintaining in-situ processing benefits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the fabrication of 100% clean, high-quality Josephson junctions with epitaxial interfaces, reducing decoherence and improving the performance of quantum devices by eliminating ex-situ contamination and ensuring precise control over the semiconductor-superconductor interfaces.
Implementation Method 1
using a nanostructure as a shadow mask during deposition to create a gap in the facet layer
Implementation Method 2
utilizing VLS growth in a vacuum chamber to maintain a clean environment
Implementation Method 3
achieve epitaxial interfaces between semiconductor and superconductor materials
Data Source
Figure 1A~1D
Figure 2A~3
Figure 4A~4B
AI summary
The present disclosure relates to a device and method for forming efficient quantum devices, in particular quantum devices that have not been contaminated in ex-situ processes. In particular the presently disclosed method can be applied for manufacturing of a Josephson junction which is an element in a tuneable superconducting qubit. One embodiment relates to a method for in-situ production of a barrier/gap in the surface layer(s) of an elongated nanostructure, the method comprising the steps of providing at least one elongated device nanostructure on a substrate in a vacuum chamber having at least one deposition source, providing at least one elongated shadow nanostructure in said vacuum chamber, and depositing at least a first facet layer on at least a part of the device nanostructure(s) and the shadow nanostructure(s) by means of said deposition source, wherein the deposition source, the device nanostructure and the shadow nanostructure during deposition are arranged such that the shadow nanostructure covers and forms a shadow mask on at least a part of the device nanostructure thereby forming a gap in the first facet layer deposited on the device nanostructure.