Scientists come a step closer to detecting single atoms

JOM, Dec 1999

Scientists at Lehigh University have reported the detection of two atoms of an element, bringing science one step away from the detection of a single atoms using an electron microscope. The detection was reported in an article written by the scientists and published in Ultramicroscopy.

David B. Williams, professor of materials science and engineering, and Masashi Watanabe, a former research scientist at Lehigh and now a professor at Kyushu University, reported they were able to detect two atoms of manganese in an extremely thin specimen of copper-manganese alloy utilizing x-ray energy-dispersive spectrometry (XEDS). The scientists used an HB 603 analytical electron microscope (AEM) designed by Lehigh scientists.

"Experimental measurements and calculations have demonstrated the detection of two atoms, and feasibility of detecting single atoms, in the analysis volume of thin specimens using XEDS," the researchers wrote in their paper. "The use of a 300 kV VG HB 603 field-emission gun AEM, with the highest possible x-ray collection efficiency, is required."

The small collection angles of the XEDS systems on most AEMs have been blamed for limiting the AEM's ability to detect elements. The HB 603 employs two XEDS detectors, one an ultrathin window and one a windowless detector, to achieve a combined collection angle that is much greater than the angle on other AEMs.

The ability to detect and identify single atoms would help scientists better understand the interfaces that hold materials together and control their behaviors. Interfaces no thicker than a layer of atoms can cause success or failure in a material. For example, a layer of copper atoms inserted between the aluminum crystals in an integrated circuit can increase the lifetime of the circuit's wires by 50 times. A layer of sulfur that infiltrates the grain boundaries of iron can cause a large bridge to crack on a cold day.