image #D11-236-96

November 20, 1996


They look like blades of grass sticking up from the ground. But the vertical structures in this image are actually soap-like molecules called alkylthiols acting in a surprising way - instead of lining up like orderly soldiers on a parade ground, as expected, they are scattered about like restless children on a playground. The reason seems to be the "ground" on which they're standing, a pool of liquid mercury (horizontal layers) whose own lack of organization has thrown off the alkylthiols' usual orderly tendencies. Physicists at Brookhaven National Laboratory and their collaborators deduced this model from experiments using X-rays at the lab's powerful National Synchrotron Light Source. They carefully glanced the X-rays off the mercury-alkylthiol layers to reveal the disordered structure seen here.

The structure is in stark contrast to the strictly aligned alkylthiols previously seen on gold, suggesting that the strong interactions between the yellow end groups on the chains and the underlying disordered liquid mercury are enough to overcome the order-producing interactions between neighboring chains.

Being able to control the structure of organic thin films is important in areas as diverse as nanoscale electronics and corrosion resistance.

The scientists published their findings in the November 21 issue of Nature.


O.M. Magnussen*, B.M. Ocko*, M. Deutsch^, M. Regan~, P.S. Pershan~, D. Abernathy+, G. Grübel+, J-F. Legrand+|, Nature 384, 6606, pp. 250-252

* Brookhaven National Laboratory, ^ Bar-Ilan University, ~ Harvard University, + European Synchrotron Radiation Facility, | Laboratoire de Spectrometrie Physique