Holograms serve as guiding light for atoms.

Holograms-those ghostly, hovering, three-dimensional images-arise through an optical illusion. They derive from interference patterns created when light diffracts as it passes through a two-dimensional grid.

Scientists have shown that, under certain conditions, they can diffract beams of atoms almost as if they were rays of light. In theory, a beam of atoms passing through a holographic pattern should spread out in a prescribed pattern and settle neatly onto a surface.

Demonstrating this principle for the first time, Jun-ichi Fujita, a physicist at NEC Fundamental Research Laboratories in Tsukuba, Japan, and his colleagues have shown that it's possible to use holograms to place atoms into a pattern on a surface.

The researchers began by etching on a thin sheet of silicon nitride a computer-generated holographic pattern designed to produce an image of the letter F. They then sent a stream of ultracold neon atoms hurtling through the pattern, they explain in the April 25 Nature. The features of the letter, and of the resulting hologram, measured about 1.2 micrometers high. After passing through this tiny diffraction pattern, the atoms fanned out onto a detector plate hooked up to a computer, which recorded the position at which each atom landed.

In this way, the scientists produced a series of micrometer-sized neon F's. "I'm impressed," says Jabez J. McClelland, a physicist at the National Institute of Standards and Technology in Gaithersburg, Md. "This represents a first demonstration of a significant step forward in atomic beam lithography. What's really interesting about this technique is that you can place atoms into virtually any pattern you want.

"I suspect this will amount to a first step on a road toward making nanometer-scale devices," McClelland continues. "Diffracting atoms is a very new frontier. Little has been done and there's much to learn." One advantage of the technique, says Donald M. Eigler, a physicist at the IBM Almaden Research Center in San Jose, Calif., stems from its flexibility. "It should work for virtually any atom," he says. "It's not limited to neon." Moreover, "the pattern can be made as complex as one wants," Eigler adds. "This method offers a lot of freedom."

In estimating the technique's capacity to fashion tinier and more detailed pictures, Fujita and his team point out that they managed to form the minuscule F's without using a focusing lens, which limited the resolution they could achieve to the diameter of the atomic beam-roughly 10 to 100 nanometers. "However, it is possible to combine the function of a focusing lens into the hologram," they add, suggesting that it may become possible to carve yet finer details into future patterns.

Possible applications for the new holographic manipulation method may turn up in making circuits, says Hans J. Coufal, a physicist at the IBM Almaden Research Center. "There's potential here to replicate complicated patterns in a simple way."

In addition, he says, because of the way holograms disperse information, they are "relatively insensitive to defects." This characteristic makes them, in principle, more reliable as templates for making microcircuits than existing techniques, which involve etching with masks.

"There's a long way to go before this could lead to a manufacturing tool," says Coufal. "But it's clearly moving in that direction." "Most of the time when scientists do experiments, they don't make major discoveries," says Eigler. "They just take the next step. But this is a really cool next step."