Nanocomputing: Simple Optoelectronic Devices Perform Logic Operations

Researchers at the Georgia Institute of Technology have demonstrated a new type of nanometer-scale optoelectronic (which combine light and electronics technologies) device that can perform addition and other complex logic operations.

These quantum devices are based on arrays of individual electroluminescent silver nanoclusters.
"In effect, we are demonstrating optoelectronic transistor behavior," said Robert Dickson, a professor in Georgia Tech's School of Chemistry and Biochemistry. "Instead of measuring current output as in standard electronic transistors, we measure electroluminescent output for a given voltage input. Our devices act in a way that is analogous to a transistor with light as the output instead of electrical current."

Each cluster contains between two and eight silver atoms, and emits light when electrically excited by a specific voltage. Operating the device requires a pair of separate electrical pulses, the second of which generates electroluminescence when specific nanoclusters are activated according to voltage level.

Individual clusters can operate as logic gates with AND, OR, NOT, and XOR functions via the application of different pulses, while more complex operations can be performed by increasing the number of clusters.
"By using this complicated on-off behavior and the discrete energy levels of different molecules, we can get complicated behavior in a relatively simple device," said Dickson.
Increasing the number of clusters operating together could permit formation of large optoelectronic arrays able to perform complex operations. As long as each cluster could be separated enough to be resolved by a camera, arrays could contain thousands of clusters.
Dickson doesn't expect the new optoelectronic devices to replace traditional semiconductor-based computers for ordinary tasks. Instead, they might be used for complex and highly specialized computations that are difficult for traditional computing systems.

He also hopes that the breakthrough will inspire other researchers to reconsider nanometer-scale computing.

This research is funded by the National Science Foundation and will be reported in the March 18 issue of the journal Proceedings of the National Academy of Sciences.