Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

To see the message, just add noise

17.12.2003


USC nanotube device uses ’Stochastic Resonance’ to enhance subthreshold signals


Stochastic resonant image of nanotube, with progressively more noise added



Paradoxical as it seems, a team of University of Southern California researchers has built a signal detector that only works when noise is added.

The device uses a novel kind of transistor made from carbon nanotubes. The principal investigator, Professor Bart Kosko of the USC department of electrical engineering, claims that the series of experiments reported in the December issue of the American Chemical Society’s Nano Letters, says the result is significant both in the development of electronic applications for nanotubes, and in the development of applications for "stochastic resonance," the counterintuitive use of noise to amplify signals.


The basic idea of stochastic resonance detection, says Kosko, is to create devices with strict threshold effects, that only respond to signals of more than a certain amplitude -- and then set this threshold around, or even below the amplitude
of the signal expected.

In the sub threshold form, "In a quiet, noise-free environment," said the scientist, "the detectors will not receive a signal." But if a moderate amount of noise is present, the signal will, as it were, float on top of the noise, triggering the detectors."

Kosko, who earlier published a theorem setting forth the mathematical basis for the phenomenon, says that the experiments made with the novel carbon nanotube detectors reported in the new paper confirm his predictions.

Carbon nanotubes are minute pipes made of graphite, the form of carbon familiar in pencil lead. Carbon atoms in graphite naturally organize themselves into two-dimensional sheets or lattices in a chicken wire or beehive like hexagonal lattice. Modern fabrication techniques can roll up such sheets into ultra thin tubes 100,000 times smaller than a human hair -- less than 2 nanometers in diameter.

Twisting such tubes can drastically change their electronic properties, from conductors, to semiconductors. A main focus of interest now is their use in flat panel displays.

The experiment used semiconductor nanotubes two nanometers in diameter and 3,000-5000 nanometers long created by Chongwu Zhou, also of the department of electrical engineering, configured to perform as a simple transistor set to detect an electronic signal.

The signal to be detected, however, was deliberately set well below this critical minimum, so that, in silent conditions, no signal at all was received.

But when the experimenters added noise -- random electrical activity -- generated by several alternate methods, the signal came through. Too much added noise wiped it out. But at moderate levels previously undetectable signals would come through.

Kosko has earlier created illustrations of the principle. " Each pixel acts as a separate threshold unit or neuron (or nanotube transistor)," he said.

"We start off by throwing away a great deal of the image’s structure and then add noise from there."

The noise makes the fragmentary picture suddenly recognizable. (See illustration).

Kosko has been studying stochastic resonant effects -- how noise can in some circumstances bring out otherwise hidden patterns -- for years, building on work done for the most part in biology. Researchers have discovered that, for example, random Brownian movement stimulation of the cochlear sensors frog ears increases their sensitivity.

Kosko believes that increased awareness of the stochastic resonance phenomenon can aid designers of communications, including especially modern spread-spectrum devices, which often rely on an array of faint signals.

"Nano-device designers can individually tailors nanotubes to specific signals and then deploy them in numbers -- rather like pipe organs tuned to different notes -- to take advantage of the SR-effects, " he said.


###
In addition to Zhou, the paper was also co-authored by USC graduate students Ian Y. Lee and Anile Liu. The National Science Foundation provided funding for the research

Bob Calverley | EurekAlert!
Further information:
http://www.usc.edu/

More articles from Power and Electrical Engineering:

nachricht Researchers measure near-perfect performance in low-cost semiconductors
18.03.2019 | Stanford University

nachricht Robot arms with the flexibility of an elephant’s trunk
18.03.2019 | Universität des Saarlandes

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Heading towards a tsunami of light

Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.

"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...

Im Focus: Revealing the secret of the vacuum for the first time

New research group at the University of Jena combines theory and experiment to demonstrate for the first time certain physical processes in a quantum vacuum

For most people, a vacuum is an empty space. Quantum physics, on the other hand, assumes that even in this lowest-energy state, particles and antiparticles...

Im Focus: Sussex scientists one step closer to a clock that could replace GPS and Galileo

Physicists in the EPic Lab at University of Sussex make crucial development in global race to develop a portable atomic clock

Scientists in the Emergent Photonics Lab (EPic Lab) at the University of Sussex have made a breakthrough to a crucial element of an atomic clock - devices...

Im Focus: Sensing shakes

A new way to sense earthquakes could help improve early warning systems

Every year earthquakes worldwide claim hundreds or even thousands of lives. Forewarning allows people to head for safety and a matter of seconds could spell...

Im Focus: A thermo-sensor for magnetic bits

New concept for energy-efficient data processing technology

Scientists of the Department of Physics at the University of Hamburg, Germany, detected the magnetic states of atoms on a surface using only heat. The...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International Modelica Conference with 330 visitors from 21 countries at OTH Regensburg

11.03.2019 | Event News

Selection Completed: 580 Young Scientists from 88 Countries at the Lindau Nobel Laureate Meeting

01.03.2019 | Event News

LightMAT 2019 – 3rd International Conference on Light Materials – Science and Technology

28.02.2019 | Event News

 
Latest News

Heading towards a tsunami of light

19.03.2019 | Physics and Astronomy

Dalian Coherent Light Source reveals hydroxyl super rotors from water photochemistry

19.03.2019 | Life Sciences

From foam to bone: Plant cellulose can pave the way for healthy bone implants

19.03.2019 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>