Machine Design

Miniature electronics

The newest frontier in electronic miniaturization is molecular-scale electronics. But it is tough to manipulate single molecules so their electronic capabilities can be tested and applied.

Researchers at Arizona State University have taken a step in the right direction by creating a way to make through-bond electrical contacts with single molecules. They begin with a uniform atomic layer of gold atoms and attach long, octanethiol insulator molecules to it through chemical bonds, forming a coating of aligned molecules. A few of the insulators are removed with a solvent and replaced with molecules of 1,8-octanedithiol, which is capable of bonding with gold and both ends and acts as a molecular wire.

Two nanometer-sized gold particles are added to the solvent and bond to the free ends of the 1,8-octanedithiol molecules, creating a bonded metallic contact at either end of the conducting molecules. A gold-coated atomic force microscope, run over the surface, measures conductivity as it touches the gold particles.

Researchers found these conductivity measurements fell into one of five groups of distinct conductivity curves, each some whole-number multiple of a single fundamental curve. According to Professor Deven Gust, "This answers the basic question of how you know when you are measuring just one molecule. The fundamental curve represents conduction by a single molecule of octanedithiol attached to two gold contacts. When more than a single molecule was bound, each additional molecule increased the current capacity by the single unit amount of current that could be carried by one molecule."

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