An Astonishing Advance in Thin-Film Superlattice Materials

"We developed an approach to improve the speed of cooling of thermoelectric devices"

Throughout the 1990s, RTI researchers had investigated thermoelectricity–the phenomenon by which a temperature difference can yield electricity or an electrical input can produce cooling. "The field was essentially deserted from 1965 to 1992," says project scientist Rama Venkatasubramanian, who led the initiative. "When I was in graduate school, my advisor mentioned the lack of progress in thermoelectric research, so I went to the NC State library and started reading up on it and got interested."

Venkatasubramanian and his colleagues in RTI's thermoelectrics group not only revived this moribund research field, but also pioneered the development of efficient, affordable thermoelectric devices by engineering them at the nanoscale level. "Using innovative, thin-film superlattice materials deposited via a process we patented, we developed an approach to improve the material efficiency and other aspects, such as the speed of cooling and cooling power per unit area, of thermoelectric devices," says Venkatasubramanian. RTI filed several patents for the application of this technology, developed largely while performing work for the Office of Naval Research and the Defense Advanced Research Projects Agency.

In just a short time, around the turn of the century, Venkatasubramanian and his colleagues produced one of the most significant breakthroughs in thermoelectric research in 40 years–a thin-film superlattice material 2.4 times more efficient and 23,000 times faster than customary thermoelectric materials, and with 100 times the cooling power. The discovery, published in Nature in 2001, energized similar nano-scale approaches and garnered RTI its first R&D 100 Award in 2002.

The technology developed by RTI addressed the thermal management needs of the electronics, photonics, biomedical and aerospace industries, leveraging the technology to relieve "hot spots" that reduce reliability and lead to chip failures. "The potential enabling impact of RTI's discovery is staggering," said Valerie Browning, then program manager at DARPA's Defense Sciences Office. "This revolutionary development will almost certainly improve the performance and capability of many cooling and power generation systems for DOD and commercial applications."

In 2005, RTI launched a spinoff company, Nextreme Thermal Solutions, to take its thin-film superlattice thermoelectric technology out of the laboratory and into commercial production. Devoted to sampling products across a wide range of applications in the electronics and optoelectronics markets, Nextreme was acquired in 2013 by Laird Technologies, a global leader in the design and supply of customized performance-critical components and systems for advanced electronics and wireless products.