'1/f' Noise Discovery Could Improve Sensors, Detectors
ARGONNE, Ill., May 11, 2007 -- More sensitive sensors and detectors based on semiconductor electronics could result from new findings by researchers from the US, Norway and Russia. Their work has taken a decisive step forward in identifying the origin of the universal "one-over-f" (1/f) noise phenomenon; "f" stands for "frequency."
"One-over-f noise appears almost everywhere, from electronic devices and fatigue in materials to traffic on roads, the distribution of stars in galaxies, and DNA sequences," said Valerii Vinokour of Argonne National Laboratory's Materials Science Div, who conducted the research at Argonne with Andreas Glatz. "Finding the common origin of one-over-f noise in its many forms is one of the grand challenges of materials physics. Our theory establishes the origin and lower limit to one-over-f noise in semiconductor electronics, helping to optimize detectors for commercial application."
This illustration of a Coulomb glass system shows electrons (red) in a random landscape, interacting with each other (yellow-orange lines). Noise of the resistance of the system (1/f noise) is created by collective "hopping" of the electrons (green arrow).
Noise is a fluctuation in time, a deviation from the average. Humans and other animals carry a common example in their heartbeats, where 1/f noise can be detected as a deviation from normal pulse. In nanomaterials, such as the tiny circuits in semiconductor electronics, the noise generated by the random motion of a single electron can be devastating, since there are so few electrons in the system.
Vinokur and his team showed that the 1/f noise in doped semiconductors, the platform for all modern electronics, originates in the random distribution of impurities and the mutual interaction of the many electrons surrounding them. These two ingredients -- randomness and interaction -- trap electrons in the Coulomb glass, a state like window glass where electrons move by hopping from one random location to another. 1/f noise arises from the electrons' hopping motion. After discovering the theoretical connection between 1/f noise and formation of the Coulomb glass, Vinokur and his collaborators confirmed it with large-scale computer simulations: suppression of the interactions was found to remove the Coulomb glass behavior and 1/f noise.
“Our results," Vinokour said, "establish that one-over-f noise is a generic property of Coulomb glasses and, moreover, of a wide class of random interacting systems and phenomena ranging from mechanical properties of real materials and electric properties of electronic devices to fluctuations in the traffic of computer networks and the Internet.”
The findings were published in the May 11 issue of Physical Review Letters. Collaborating with Vinokur and Glatz were Y.M. Galperin of the University of Oslo, Oslo, Norway, and A.F. Ioffe of the Physico-Technical Institute of the Russian Academy of Sciences, St. Petersburg, Russia.
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