IBM carbon probe views electron movement in molecule

Scanning technique vital for molecular computing

IBM researchers in Switzerland have seen the movement of charge within a molecule for the first time, using a microscope tipped with a single carbon atom.

The team adapted an existing form of atomic force microscopy called Kelvin probe force microscopy, by using a microscopic scanning bar that measures the electric field generated by a charge in a molecule. The probe has to operate at near absolute zero and in a total vacuum, but successfully traced a charge across the subject.

Kelvin microsoft scans molecular charge

Voltage variations in scanning tip measure molecular charge

"This technique provides another channel of information that will further our understanding of nanoscale physics. It will now be possible to investigate at the single-molecule level how charge is redistributed when individual chemical bonds are formed between atoms and molecules on surfaces," said Fabian Mohn of the physics of IBM Research's nanoscale systems group in a statement. "This is essential as we seek to build atomic and molecular scale devices."

Under examination was a two-nanometer molecule called Naphthalocyanine, an X shaped structure formed in part by two hydrogen atoms which swap places when a charge is applied. IBM is working on the material as part of its research into building molecular-level computing and storage devices by using the molecule's two states to store data. Details have now been published in the journal Nature Nanotechnology.

Charge image of molecule

Flipping Naphthalocyanine

"This work demonstrates an important new capability of being able to directly measure how charge arranges itself within an individual molecule," states Michael Crommie, a physics professor at the University of California, Berkeley. "Understanding this kind of charge distribution is critical for understanding how molecules work in different environments. I expect this technique to have an especially important future impact on the many areas where physics, chemistry, and biology intersect." ®

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