Josephson Junctions

The Josephson effect is observed in a Josephson Junction, and describes the flow of a supercurrent between two superconducting electrodes across a non-superconducting gap. These devices are used by researchers to utilize quantum control towards progress in quantum computing, novel sensing devices, as well as fundamental physics.
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Applications

Applications

Josephson Junction

OLED

Thin Film Transistors

Space & Environmental Simulation

Perovskite

Thin Film Batteries

Thin Film Deposition For Superconducting Circuits

Josephson Junctions form the heart of the superconducting qubit, a leading candidate for the creation of fault-tolerant quantum computation. The non-linear inductance of the Josephson Junction creates an anharmonicity in its energy level spectrum. This allows a quantum mechanical basis (1 or 0) to be established between discrete energy levels, which is essential for forming a quantum bit or qubit. Josephson Junctions can also be used as a means to detect extremely small magnetic fields, up to 1016 times less than that generated from a refrigerator magnet.

These superconducting quantum interference devices, or SQUIDS, have applications in the detection of neural activity in the brain, scientific characterization of materials, and next-generation ultra-low field MRI scanners.

SEM Image courtesy of the Institute for Quantum Computing (IQC) at the University of Waterloo.

Overview

This device can be created with a wide range of superconducting materials, but aluminum is a common choice among researchers due to the relative ease of creating a high-quality oxide with it, as well as its relatively low melting point (660 °C), making it versatile. What follows are key considerations for the equipment that will build your Josephson Junctions.

A Clean Process

Josephson circuits are extremely sensitive to contaminants.

  • For this reason, evaporation and oxidization occur in independently sealed chambers, one for evaporation and one for oxidization.
  • Perfect isolation is achieved between the oxidization chamber and the deposition chamber using load-locks and programmable, recipe-driven automation through Aeres®, our advanced process control software.
  • Both chambers are constructed from electro-polished stainless steel to minimize off-gassing, and transfer between chambers occurs in situ to minimize venting.
Unprecedented Pressure Control

The most important parameter of a Josephson Junction in certain applications is its critical current density, which is determined by the thickness of the insulating oxide layer between the two aluminum layers.

  • That insulating layer must be as thin as possible, which makes the control of how the film is oxidized of utmost importance.
  • The mass flow controller (which is user-regulated from Aeres®, Angstrom’s own process control software) allows for exact and precisely repeatable control of this variable.
Electron Beam Source

An e-beam source provides the best versatility for evaporating aluminum intended for superconducting circuits.

  • It allows for a higher volume of material and reduces the need to vent the chamber, further ensuring clean, contaminant-free films.
  • The vapor flux created by e-beam evaporation is ideal for patterning the fine features that Josephson circuits require.
Ion Beam Source

An ion source prepares the substrate for deposition with gentle cleaning or precision etching.

Magnetron Sputtering

Some materials used to create Josephson Junctions (such as Niobium) require the use of magnetron sputtering.

A sputtering source can be seamlessly integrated into your thin film deposition platform.

Connected Deposition Chambers

We create Josephson platforms that support multiple connected (though isolated) chambers for alternate deposition methods as well as analytical tools, all integrated into the overall process automation.

This results in platforms of varying configurations, from dual chamber (deposition/load lock) to in-line systems, all the way to robotic radial cluster arrays incorporating deposition, oxidization, and analytical stations.

Variable Angle Stage

Precisely angling the substrate in relation to the deposition plume is essential in the creation of Josephson Junctions. The figure below illustrates one method of creating the devices.

The tilt angle on Angstrom’s variable angle stage has better than 0.1° angular repeatability. Substrate heating and cooling can both be integrated into the stage functionality. Angle, stage rotation, and stage temperature are controlled via recipe-based user inputs from our Aeres® software package. Simply enter desired values, press start, and return to find your completed Josephson Junctions.

Josephson Junction Fabrication

Your system will be based on the type of junctions you plan to create as well as your specific throughput, material, and infrastructure requirements.

Our partners are creating Josephson Junctions on systems of different sizes and designs, but all have a few things in common: at least one load lock for isolated oxidization, a deposition chamber, a variable angle stage, e-beam or sputter sources specific to their needs, and all the thin film experience and service support that Angstrom Engineering® brings to bear.

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Advanced Process Control Software

  • PC/PLC-controlled recipes for single, batch, or automated processes.
  • Advanced data logging and process tracking ensure consistent and repeatable processes.
  • High-resolution control provides impressive low-rate stability and consistent doping ratios.
  • The central control station manages each module and schedules the processes in each chamber.
  • Independent control of multiple chambers (if applicable).
  • Complex recipes can be created and modified easily.
  • Automatic PID control loop tuning significantly reduces process development time.
alt = A screenshot of Angstrom Engineering's AERES software on a monitor. The software is showing a detailed dashboard with charts, graphs, and data for monitoring and controlling thin film deposition processes. The layout has side navigation with equipment status icons and a central graph with real-time data. The interface is designed for precise control and analysis in advanced engineering applications for Angstrom Engineering’s systems.

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” It has been a pleasure for us at Hebrew University to do business with Angstrom Engineering®: young people, fully motivated and providing first-class service. Angstrom was selected after a tight purchase process among several known companies. The process involved many interactions and demonstrations on real, complex samples. Their performance and attitude during the whole process was flawless.  Our Quantum Series® Evaporator was just installed, and now our researchers have the right tool for our work.”

Dr.Shimon Eliav 
Hebrew University of Jerusalem