Unusual Ames Lab findings may contribute to nanotechnology

Jennifer Nacin

A path to the “Holy Grail of nanotechnology” has been discovered in Ames.

For the first time, ISU researchers and the U.S. Department of Energy’s Ames Laboratory have observed an unusual and surprising growth mode that may be vital for future advancements in applications of nanotechnology.

Nanotechnology is the study and development of atom- and molecule-sized electronic circuits.

The research group is led by Michael Tringides, professor of physics and astronomy, and includes Myron Hupalo, associate scientist for the Ames Laboratory, Michael Yakes, graduate in physics and astronomy and Vincent Yeh, graduate student in physics and astronomy.

The advancements in nanotechnology deal with thin films, which are measured in nanometers. A nanometer is one billionth of a meter.

The smaller the film can be made, the smaller components such as laser materials, switches and semiconductors, can be manufactured. This objective is central to the endeavors of the silicon industry — technological production and innovation depends on miniaturizing and strengthening silicon-based electronic devices. This observed growth mode may help them do just that.

“It is very important to develop nanotechnology and find new ways to build very small electronic devices which will be used probably for the next generation of computers,” Hupalo said.

Normally, when materials are built on silicon film, epitaxy — the random “raining” of atoms onto the silicon surface — results in metal atom deposits of widely inconsistent mounds called “islands.”

The range in heights of these islands is not ideal, because height uniformity allows for faster and better transmission of electric currents.

Using atoms of lead, Ames Laboratory researchers found the “islands” reach only one height after epitaxy — seven atoms high — at certain temperatures (185 Kelvin to 220 Kelvin, or minus-100 degrees Celsius).

“These lead atoms moving in these low temperatures is really surprising in forming these kinds of structures,” Harmon said.

The growth mode was first noticed in the Ames Laboratory in 2000, but researchers thought the results were too amazing to be real.

“We didn’t believe this at first,” Tringides said. “No one has ever seen anything like this before. This is what drives you as a scientist.”

The discovery has created great interest in the world of science, Harmon said.

“People are just fascinated by it, [such as] people in Washington and other scientists that I’ve talked to,” Harmon said.

Having found the “Holy Grail of nanotechnology,” scientists have the ability to control the layer of thickness and atomic uniformity of thin films and nanostructures, Tringides said.

“They want to make things on the nanoscale, and these islands are very reproducible,” Yakes said. “It’s unusual to have something so repeatable on such a small scale.”

Acquiring these details will be the next step for Ames Laboratory researchers, Harmon said.

“We have good indications as to why this happens, but we need more details,” he said.

Tringides said this discovery could one day lead to computer chips about 100 times smaller and could make computers about 10,000 times faster than they are now.

More tests will need to be conducted before such innovations in technology will be seen on the market, he said. The process could take as long as 20 years.