Monday, April 7, 2014

UC San Diego has developed ALD process for superconducting tunnel junctions.

According to a report: Researchers from UC San Diego have developed a new process for fabricating high quality tunnel barriers in NIS and SIS tunnel junctions. Specifically, the inventors have demonstrated a large area superconducting tunnel junction using atomic layer deposition (ALD) to form a high quality insulating tunnel barrier.


• Epitaxial deposition using ALD eliminates defects that previously prevented commercial viability of this technology.
• Application of ALD to create tunnel junction barriers allows the barrier thickness to be precisely tuned down to 0.02nm, allowing for further improvements in device properties.
• High quality tunnel barriers can be deposited on materials that do not natively oxidize.
• Tunnel junction cryogenic refrigerators, cryogenic thermometers, superconducting quantum computer bits (qubits).

Read more about it in this paper:

Atomic Layer Deposition of Tunnel Barriers for Superconducting Tunnel Junctions
Stephanie M. Moyerman, Guangyuan Feng, Lisa Krayer, Nathan Stebor, Brian G. Keating
Journal of Low Temperature Phyiscs, March 2014

We demonstrate a technique for creating high quality, large area tunnel junction barriers for normal–insulating–superconducting or superconducting–insulating–superconducting tunnel junctions. We use atomic layer deposition and an aluminum wetting layer to form a nanometer scale insulating barrier on gold films. Electronic transport measurements confirm that single-particle electron tunneling is the dominant transport mechanism, and the measured current–voltage curves demonstrate the viability of using these devices as self-calibrated, low temperature thermometers with a wide range of tunable parameters. This work represents a promising first step for superconducting technologies with deposited tunnel junction barriers. The potential for fabricating high performance junction refrigerators is also highlighted.