IBM Scientists Image Charge Distribution in a Single Molecule

Researchers at IBM were able to measure for the first time how charge is distributed within a single molecule.

This achievement promises to enable fundamental scientific insights into single-molecule switching and bond formation between atoms and molecules for future applications such as solar photoconversion, energy storage, or molecular scale computing devices, says IBM.

They directly imaged the charge distribution within a single naphthalocyanine molecule using a special kind of atomic force microscopy called Kelvin probe force microscopy at low temperatures and in ultrahigh vacuum.

“This work demonstrates an important new capability of being able to directly measure how charge arranges itself within an individual molecule”, states Michael Crommie, Professor for Condensed Matter Physics at the University of 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.”

In fact, the new technique together with STM and AFM provides complementary information about the molecule, showing different properties of interest. This is reminiscent of medical imaging techniques such as X-ray, MRI, or ultrasonography, which yield complementary information about a person’s anatomy and health condition.

“The 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. This is essential as we seek to build atomic and molecular scale devices,” explains Fabian Mohn of the Physics of Nanoscale Systems group at IBM Research- Zurich.

The technique could for example be used to study charge separation and charge transport in “charge-transfer complexes,” which consist of two or more molecules and are subject of intense research activity because they hold great promise for applications such as energy storage or photovoltaics.


IBM