Michael J. Therien, a professor of chemistry at the University of Pennsylvania, is taking a colorful approach to the chip density barriers that threaten to repeal Moore's Law. As conventional semiconductor technology reaches its natural limits, Therien believes that the future of high-speed electronics lies in "electrically jumpy" molecules known as chromophores.
A chromophore is the part of a molecule that's responsible for its color. When light hits a chromophore, it excites an electron, which then emits light at a specific color. Therien notes that chromophores can be harnessed into chains that send electrical charges at rates faster than any yet observed in organic semiconductors, the technology that has so far held the most promise for moving electrons quickly and freely in nanosized circuits (see the figure).
"Chromophores may represent the first relatively easy to use materials that function on the nanoscale," he says. Working with co-researcher Paul Angiolillo, a physics professor at Saint Joseph's University in Philadelphia, Therien sent electrical charges down a chromophore chain at a rate of about 10 million times per second—about three times the previous organic semiconductor benchmark.
"We showed that chromophore arrays can do anything that organic semiconductors currently do, only significantly faster," Therien says. The research discovered that building structures using long chromophores with short connectionswas crucial to creating a material that would enable electrons to move quickly and freely. "When a charge is introduced to an array of chromophores linked closely together, it allows electrons to quickly hop from chromophore to chromophore," Therien says.
As chipmakers struggle to bring processor chip density levels down to 65 nm, chromophore technology promises to allow the production of molecular conductive elements at a 10-nm length scale. Therien believes the technology will find a wide range of applications. "Everything from flexible wires to LEDs to nanoscale electronics," he says.
Already, University of Pennsylvania researchers Kimihiro Susumu and Paul Frail have built chromophore circuits that could be used as functional elements in an array of devices, including RFID tags, organic LEDs, LCD drivers, disposable plastic electronics, and lightweight solar cells.
Therien believes that his research marks a natural step in electronics evolution. "To make a serious effort at further lowering the nano-size barrier, we must develop nanostructures that allow electrons to move in the same way as they do through wires and semiconductors," he says. "Molecular conductive elements, produced on a 10-nm length scale, provide a crucial functional element for nanoscale circuitry."
Despite the research's cutting-edge nature, Therien expects to see chromophore technology used commercially within the next three to 10 years. "But then, scientists are eternal optimists," he quips.