IBM snaps an image of electric charge on the move

IBM researchers have created a subatomic snapshot of the electric charge within a molecule, an advance that could have applications in ever-smaller transistors or in solar power.

Scientists from IBM Research in Zurich, Switzerland, published a paper in Nature Nanotechnology today that describes a technique for measuring how electrons move when forming molecular bonds. This method allows them to create images of how the electric charge is distributed within molecules, giving science a better picture of chemistry at the molecular level, said Fabian Mohn, who coauthored the paper.

Having a picture of the electric charge distribution could be useful tool for research on making tiny transistors the size of a molecule or developing solar cells from inexpensive organic materials, he said.

"If you think about a transistor switch or memory element (for computing) or organic photovoltiacs, usually these applications involve the movement and the rearrangement of charges in these molecules," Mohn said. "So from this perspective, it's very nice to investigate the charge distribution in detail."

To capture the movement of electric charge, IBM researchers used a kind of atomic-level technique called Kelvin probe force microscopy that operates in a vacuum at very low temperatures on a single aphthalocyanine molecule. Measuring changes on the surface when a voltage is applied to the tip of the probe allows scientists to isolate the electric field in the molecule, Mohn explained. Scientists before have used scanning tunneling microscopy and atomic force microscopy for "seeing" the chemical structure of a molecule but not the electric charge distribution in chemical bonds.

At the basic science level, the next step for this effort is to track changes in electric charge across several molecules, Mohn said. "The first step is getting a fundamental understanding and then you can think about technical implementations," he said.