Superconducting transistor debuts

By Kimberly Patch, Technology Research News

Researchers from the UK and Italy have found a way to make a superconducting transistor, a development that promises to pave the way for higher resolution instruments like electron microscopes, and may eventually lead to ultralowpower electronic circuitry.

Superconductors are materials that, when cooled to very low temperatures, offer very little resistance to current. Thus, circuits made of superconductors would consume very little power.

The superconducting transistor, or quatratran, is made of very thin layers of the superconductor niobium, insulation, and aluminum, which is a nonsuperconducting metal. When a voltage is applied to one of the superconducting layers, the increase in energy causes electrons from the aluminum layer to stream into a superconducting layer, causing a gain, or change in current, 70 times larger than the amount of current applied.

"The quatratran ... superconducting transistor's have current gain and power gain not too different than conventional transistors, but operate typically with much lower power consumption," Norman Booth, a physics professor at the University of Oxford.

Devices like electron microscopes use streaming electrons to image microscopic objects. The superconducting transistor could make for better scientific imaging instruments in several ways. First, the 70 times gain could provide for finer resolution electron microscope pictures because more electrons streaming enable a finer-grained image. Second, higher resolution also means increased sensitivity to very small energies, which is important at low temperatures. "For very sensitive detection [it is important] to work at low temperatures where random noise is small," said Booth.

The superconductor transistors will operate both at very low temperatures and in close proximity to highly sensitive superconducting sensors and detectors used for astrophysics, x-ray microanalysis and time-of-flight mass spectrometry, according to Booth.

The devices also have the potential to work at temperatures that can be reached with closed-cycle refrigeration units rather than more expensive liquid helium. The current device works at four degrees above absolute zero, but could be boosted to 10 degrees above absolute zero, according to Booth.

"They've unlocked the important key to a much better device," said Kenneth Gray, a senior scientist at Argonne National Lab. "Detectors are usually running at the ragged edge of noise and so this would greatly enhanced their capabilities. I think it's a major, important result," he added.

Eventually the principles the researchers used to build the quatratran could lead to further electronic devices made of superconductors, according to Booth. The work "opens up the possibility to design and fabricate a whole new class of electronic circuits... in the field of superconducting electronics," said Booth.

Booths colleagues were Antonio Barone from the University of Naples, who headed the research team along with Booth, Giovanni Piero Pepe, Giussepe Ammendola, Giapino Peluso from the University of Naples; Loredana Parlato from the second University of Naples; and Emanuela Esposito and Roberto Monaco from the Cybernetics Institute in Naples. The researchers published their findings in the July 17 issue of Applied Physics Letters.

The research was funded by the UK particle physics and Astronomy Research Council (PPARC) and the European Community Teaching and Mobility of Young Researchers (EC-TMR) program.

Timeline:   > 2, < 5
Funding:   Government
TRN Categories:  Semiconductors and Materials
Story Type:   News
Related Elements:   Technical paper "Superconducting Device with Transistor like Properties Including Large Current Amplification" in Applied Physics Letters, July 17, 2000


September 20, 2000

Page One

Hue-ing to quantum computing

Robots emerge from simulation

Software sorts Web data

Processor design tunes memory on the fly

Superconducting transistor debuts


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