Looking at a force!

On the left the ball-and-stick theoretical model of the pentacene molecule. On the right the AFM image of pentacene molecule showing the pattern of the bonds in the model. The five hexagonal carbon rings are resolved clearly and even the carbon-hydrogen bonds (white in the model) are imaged. Scale bar: 5 ångstroms (0.5 nanometer). Each bond is thinner than one Ångstrom. Credit: IBM Zurich

Model showing interactions between atomic-force microscope tip (top) and silicon surface (hydrogen: white; silicon: tan and red), using a new technique for coating the tip with hydrogen — part of a study to create future electronic circuits at the atomic level. Credit: Wolkow Lab

I still remember my awe at seeing atoms for the first time. It was back in 1989 when IBM using a scanning tunneling microscope managed to manipulate single atoms (and demonstrated it by writing IBM by pushing xeon atoms around).

Now I revive that amazement by reading that scientists at the University of Alberta, Canada, have managed to "see" the bonding keeping together silicon atoms.  Actually, in 2009, IBM researchers in Zurich, in that same lab that wrote IBM with individual atoms, managed to show bonding in copper (pentacene rings, see the image). However, doing that with silicon is much more difficult. To "see" the bonding you need to get close to it but if you get too close you ruin it. Imagine you want to feel the surface of a soap bubble. As you touch it it explodes and vanishes.

What the Alberta scientists managed to do was to walk a thin line between seeing and disrupting the bonding.

Notice that the images of those bonds are doubly amazing since they are representing something that is smaller than an atom, the bond thickness is less than one Angstrom, and they actually show a "force" not a real "thing". This is the first time that I see the image of a force!

This feat was achieved by using a special tip in an atomic force microscope, covering it with hydrogen atom and using a sophisticated algorithm to regulate the distance of the atomic tip to the bond. And we are measuring the distance in Ångstrom!

Apart from the scientific interest, this news is important, according to the scientists, because it opens a door to create silicon structures designed at atomic level, nanotech. The possibility of looking at these structures and measuring their physical characteristics may lead to the design of computation structures that are way more efficient in terms of power consumption of the ones we have today. In their paper the scientists speculate the possibility of designing silicon based computation infrastructures that are 1,000 times more efficient than present ones.  As Richard Feynman noticed long time ago: "there is plenty of room at the bottom"!

Author - Roberto Saracco

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