White Noise and Pink Noise Improve Sensors and Detectors

White noise has been made popular by a Hollywood movie bearing the same name, where the main character, an architect, has a burning desire to speak with his wife from beyond the grave, which becomes an obsession with supernatural repercussions. To do that, he starts recording white noise, or background noise, where he starts hearing voices of dead people and not all of them are benevolent.

The new finding involves something called pink noise, or 1/f noise (one over f noise - where f stands for frequency) and it could greatly improve detectors and sensors using semiconductor electronics. Pink noise is a signal or process with a frequency spectrum such that the power spectral density is proportional to the reciprocal of the frequency. The name arises from being intermediate between white noise (1/f0) and red noise (1/f2, more commonly known as Brownian noise).

It's a background noise that occurs widely in nature and has drawn a lot of attention from scientists in many fields.

Now, new findings by scientists from the US, Norway and Russia, are considered a decisive step in identifying the origin of the universal "one-over-f" (1/f) noise phenomenon.

"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 or Argonne's Materials Science Division. "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."

Noise is actually a fluctuation in time that deviates from known patterns and can widely be found in humans and other animals, for instance in the heartbeat, where pink noise can be detected as a deviation from normal pulse.

In the smallest circuits in semiconductor electronics made of nanomaterials, the noise generated by the random motion of a single electron can be devastating, since there are so few electrons in the system.

The research team discovered that the 1/f noise in doped semiconductors, the basis for all of today's electronics, has its origins in the random distribution of impurities and the mutual interaction of the many electrons surrounding them.

The 1/f noise results from electrons hopping when trapped in the Coulomb glass, a state like window glass where electrons move by hopping from one random location to another.

Now scientist believe that suppression of the interactions was found to remove the Coulomb glass behavior and 1/f noise, which will lead to important improvements in applications like electronic sensors and detectors, where the continuous hopping of the electrons interferes with the actual object of their search.