Buckyball-Like Structures Identified in Inorganic Semiconductor Material

Experiments carried out in the United States and Germany in May 1990 were described by one of the participants as the "ultimate eureka experience" of his scientific career: the production of the first crystals of buckminsterfullerene (C₆₀), a brand new and technologically fascinating type of solid carbon.

Less than two years later, a team at the Institute's Department of Materials and Interfaces could have let out a "Eureka" of its own. The group, headed by Prof. Reshef Tenne and including Dr. Lev Margulis, Dr. Gary Hodes and Dr. Menachem Genut, discovered that completely closed, "buckyball"-like molecular structures are not limited to carbon: they can also be formed from the semiconductor material tungsten disulfide. This finding, published in the British journal Nature, has attracted wide attention because the chemical and physical properties of this new cage-like material are expected to be completely different from those of buckminsterfullerene.

The family of fullerene molecules, which take the form of closed soccer-ball-shaped C₆₀, of nested cages and of tubular structures, are now studied by academic and industrial laboratories worldwide. Although specific uses for these new forms of carbon are hard to predict, they have already been shown to exhibit three-dimensional superconductivity at relatively high temperatures, ferromagnetic qualities in the absence of metals (an unparalleled physical observation), and the ability to transform into diamond under high pressure. Many are considering their use as components in ultra-strong polymers, in steel and in electronic devices.

The Weizmann investigators believe that the very discovery of this new form of tungsten disulfide (WS₂) may be of even greater interest than its presently unexplored physical and chemical properties. This is because the standard crystal forms of carbon and standard WS₂ are composed of planar layers stacked one atop another. This may indicate that any material known to form planar crystal structures could be a good candidate for producing additional varieties of "buckyballs." In fact, a few additional planar crystalline solids have already been shown at the Institute to form such completely closed configurations.