To detect the electron dislocations, the physicists upgraded a 15-year-old method called coherent acoustic phonon spectroscopy (CAPS). "CAPS is similar to the seismic techniques that energy companies use to search for underground oil deposits, only on a much smaller scale," said Steigerwald.

The physicists tested their technique on a layer of gallium arsenide semiconductor that they had irradiated with high-energy neon atoms. They found that the structural damage caused by an embedded neon atom spread over a volume containing 1,000 atoms – considerably more extensive than that shown by other techniques.

"This is significant because today people are creating nanodevices that contain thousands of atoms," said Steigerwald. One of these devices is a solar collector made from quantum dots, tiny semiconductor beads that each contains a few thousand atoms. "Our results may explain recent studies that have found that these quantum-dot solar collectors are less efficient than predicted," he said.

"The fact is that we really don’t understand how any atomic-scale defect affects the performance on an optoelectronic device," said Tolk. "Techniques like the one that we have developed will give us the detailed information we need to figure this out and so help people make nanodevices that work properly."

A. Steigerwald, A. B. Hmelo, K. Varga, L. C. Feldman and N. Tolk: Determination of optical damage cross-sections and volumes surrounding ion bombardment tracks in GaAs using coherent acoustic phonon spectroscopy, In: Journal of Applied Physics, Volume 112, Issue 1, Article 013514 [7 pages]:

http://dx.doi.org/10.1063/1.4732072 http://youtu.be/Wds3pbFn2vM