si_cage
Image: AIP

Since their discovery in 1985, buckminsterfullerenes, or buckyballs, have found a number of interesting uses. These spheres of carbon atomswhether left hollow, filled with metal atoms or fashioned into tiny tubeshave become the basis for mini-abacuses, ultrafine scanning tunneling microscope tips and high-temperature superconductors, to name just a few applications. Now Hidefumi Hiura and colleagues at the Joint Center for Atomic Research in Japan have created what may prove to be an even more practical cousin: cages made from silicon instead of carbon. They describe these so-called silicon cage clusters in this week's issue of Physical Review Letters.

Given silicon's chemical nature, scientists presumed it couldn't assume a stable, closed configuration, as can a carbon buckyball. The new research reveals, however, that silicon atoms will gather around a central metal atom. One particularly stable variety that Hiura's group describes contains 12 silicon atoms in a regular, hexagonal cage, surrounding a single atom of tungsten (see image). Changing this central metal alters the cluster's properties, and so the scientists are hoping to tailor these molecules to suit a range of purposes. In particular, the clusters are good at isolating their core metal atoms from environmental influences. Thus, Hiura suggests that they may serve as excellent quibits, which store single bits of information in quantum computers. The spin state of the metal atom could encode the bit, and the silicon cage would protect it from corruption.