Record-Small Quantum Dots

Researchers at the National Institute for Nanotechnology and the University of Alberta have unveiled quantum dots composed of a single atom of silicon and measuring less than 1 nm in diameter, making them the smallest ever created.

According to the researchers, the development brings quantum dot-based devices within reach.

Four atomic quantum dots are coupled to form a "cell" for containing electrons. The cell is filled with just two electrons. Control charges are placed along a diagonal to direct the two electrons to reside at just two of the four quantum dots comprising the cell. This new level of control of electrons points to new computation schemes that require extremely low power to operate. Such a device is expected to require about 1000 times less power and will be about 1000 times smaller than today's transistors. Image courtesy of Robert A. Wolkow.

Quantum dots have extraordinary electronic properties, such as the ability to bottle up normally slippery and speedy electrons, enabling controlled interactions among electrons to perform computations. Until now, quantum dots have been usable only at impractically low temperatures, but the new atom-size quantum dots perform at room temperature.

Often referred to as artificial atoms, quantum dots previously ranged from 2 to 10 nm in diameter. Although typically composed of several thousand atoms, all the atoms pool their electrons to “sing with one voice”; that is, the electrons are shared and coordinated as if there is only one atomic nucleus at the center. That property enables numerous revolutionary schemes for electronic devices.

“Because they operate at room temperature and exist on the familiar silicon crystals used in today’s computers, we expect these single-atom quantum dots will transform theoretical plans into real devices,” explained Robert A. Wolkow, research project leader.

The single-atom quantum dots have demonstrated another advantage – significant control over individual electrons with very little energy. Wolkow sees this low-energy control as the key to quantum dot application in entirely new forms of silicon-based electronic devices, such as ultralow-power computers.

“The capacity to compose these quantum dots on silicon, the most established electronic material, and to achieve control over electron placement among dots at room temperature puts new kinds of extremely low energy computation devices within reach,” Wolkow added.

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