Using light to guide atomic deposition.

The landscape imaged by an atomic force microscope reveals a remarkably regular pattern of barren, steep-sided ridges neatly arrayed in parallel rows. indeed, it's the extreme regularity evident in the image that makes this array important as a demonstration of how laser light can be used to manipulate chromium atoms into precise locations on a silicon surface.

"Our experiments demonstrate that atom optical techniques can be used to create, in parallel, a weB-ordered array of nanometer-scale lines covering a macroscopic area:' Jabez J. McClelland and his coworkers at the National Institute of Standards and Technology in Gaithersburg, Md. report in the Nov. 5 SCIENCE.

To create this pattern, the researchers allow chromium atoms, cooled to millikelvin temperatures, to travel through a laser beam to a silicon surface. The laser beam creates a standing wave -a stationary pattern of crests and troughs parallel to and above the surface. This wave nudges the atoms into certain paths, causing them to pile up on the surface in rows corresponding to the standing wave's troughs (SN: 4/3/93, p.213).

This technique shows promise as a means of fabricating tiny metallic structures for electronic devices smaller and faster than those now available. "It's really an enabling discovery." McClelland says. "There are potential applications for electronics and magnetics, as well as other microscopic technologies? The researchers are now considering the possibility of using two standing waves of laser light at right angles to each other to focus chromium atoms into spots rather than lines.