Researchers Induce Superconductivity in an Insulator

November 24, 2008 By Laura Mgrdichian feature

(PhysOrg.com) -- To continue to improve semiconductor devices, such as transistors, which form the backbone of the consumer electronics industry, researchers need to be able to control the movement and density of the electric charge within them.

Many scientists are particularly interested in finding ways to increase the maximum density of charge in semiconductor devices. Doing so could lead to a major achievement in semiconductor research: inducing superconductivity in field-effect transistors (FETs) -- tiny semiconductor-based devices essential to integrated circuits (a single computer chip can contain millions). FETs could be vastly improved, eventually leading to better products for consumers.

One key way to control charge density is by mixing in impurity atoms, a process called doping. Another way is using external electric fields. But in the latter method, problems arise with FET types that have insulating layers, such as the metal-oxide-semiconductor FET, or MOSFET (where the oxide layer is an insulator).

Recently, researchers from Tohoku University in Sendai, Japan, and the Japan Science and Technology Agency demonstrated that it is possible to make an insulator superconduct within an FET structure. In the October 12 online edition of Nature Materials, the scientists describe their unusual FET structure, which incorporates an organic current-carrying material (an electrolyte) consisting of a polymer mixed with a salt.

The basic structure is layered: a top platinum electrode, the electrolyte, and strontium titanate (SrTiO3), a mineral and strong insulator. Attached to the SrTiO3 surface are two gold islands that serve as electric leads and contacts. The total structure has a thickness of only a few hundred nanometers (billionths of a meter).

When a voltage is applied across the platinum layer and gold contacts using a battery, turning the structure "on," the effect is of a double-layer capacitor. The voltage splits the positive and negative ions in the electrolyte, sending negative charge to upward to the platinum surface and positive charge downward. This induces a very large negative "image" charge on the SrTiO3 surface, forming a conduction path between the two gold contacts. The electrolyte acts as a dielectric, an insulating material used between two capacitor plates to allow more charge to be stored before the capacitor breaks down.

Corresponding author Masashi Kawasaki, who is affiliated with both Tohoku University and the Japanese Science and Technology Agency, told PhysOrg.com, "The problem with past attempts to use electric fields to induce superconductivity in an insulator is there were no dielectric materials that could sustain a high enough field to build up the necessary charge in the insulator. So instead of the standard dielectric oxide, we've used a conducting polymer."

Using this method the researchers increased the SrTiO3 charge-carrier density from zero to approximately 10 trillion carriers per square centimeter. When cooled down to 0.4 K (about -460 degrees Fahrenheit), it becomes superconducting.

Kawasaki and his colleagues think their approach is a promising way to discover superconducting behavior in other unlikely materials.

"We do not need to worry about the complicated chemistry involved in mixing materials. All we need is a polymer and a battery. This way of making a superconductor may open a door to unexplored superconducting materials," said Kawasaki.

Citation: K. Ueno, S. Nakamura, H. Shimotani, A. Ohtomo, N. Kimura, T. Nojima, H. Aoki, Y. Iwasa and M. Kawasaki, Nature advance online publication 12 October 2008; doi:10.1038/nmat2298

Copyright 2007 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

Explore further: 3-D printed microfibers could provide structure for artificially grown body parts

Related Stories

Juno probes the depths of Jupiter's great red spot

December 12, 2017

Data collected by NASA's Juno spacecraft during its first pass over Jupiter's Great Red Spot in July 2017 indicate that this iconic feature penetrates well below the clouds. Other revelations from the mission include that ...

Researchers discover new way to power electrical devices

December 11, 2017

A team of University of Alberta engineers developed a new way to produce electrical power that can charge handheld devices or sensors that monitor anything from pipelines to medical implants.The discovery sets a new world ...

Recommended for you

Single-photon detector can count to four

December 15, 2017

Engineers have shown that a widely used method of detecting single photons can also count the presence of at least four photons at a time. The researchers say this discovery will unlock new capabilities in physics labs working ...

Real-time observation of collective quantum modes

December 15, 2017

A cylindrical rod is rotationally symmetric - after any arbitrary rotation around its axis it always looks the same. If an increasingly large force is applied to it in the longitudinal direction, however, it will eventually ...

A shoe-box-sized chemical detector

December 15, 2017

A chemical sensor prototype developed at the University of Michigan will be able to detect "single-fingerprint quantities" of substances from a distance of more than 100 feet away, and its developers are working to shrink ...

An ultradilute quantum liquid made from ultra-cold atoms

December 14, 2017

ICFO researchers created a novel type of liquid 100 million times more dilute than water and 1 million times thinner than air. The experiments, published in Science, exploit a fascinating quantum effect to produce droplets ...

5 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

zevkirsh
not rated yet Nov 24, 2008
cool.and cold.

NeilFarbstein
1 / 5 (1) Nov 24, 2008
a polymer and a battery... hey you never know!!!!!
Alexa
1 / 5 (2) Nov 25, 2008
This results corresponds the AWT mechanism of superconductivity - a highly compressed electrons are moving without friction through material, because their repulsive forces are stronger, then those between electrons and other atoms.


The problem in using of this mechanism for energy transmission is, how to compress electrons at larger scales - but this system can result into new kind of superconductive FET switches with zero resistance in connected state.
theophys
not rated yet Nov 28, 2008
I wonder if this could be used on a large scale in hybrid cars and solar panals to make them more efficient. It seems like this would be relatively cheap to manufacture.
Alexa
not rated yet Feb 04, 2009
The only problem is, we're required to use very stiff and inert material at the same moment, capable to keep holes in it even under strong electrostatical field intensity. Currently only diamond was proven to be able to keep holes in the form of oxide atoms and able to form a superconductive layer at the surface.

http://aetherwave...ity.html

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.