AFM measures charges of individual atoms

Scientists would like to create devices using molecular-scale manufacturing, but this requires measurement of forces and charges on very small scales. Researchers have now accomplished a feat that could aid such tiny manufacturing by using atomic force microscopy to measure forces on a scale small enough to distinguish neutral atoms from positively and negatively charged ones. 

The work was performed by scientists from IBM’s Zurich Research Laboratory, the University of Regensburg, Germany, and Utrecht University, Netherlands.  Achieving such high-resolution measurements required very high stability. In the June 12 issue of Science, they describe how the required stability was accomplished with a qPlus tuning fork atomic force microscope AFM operated in a vacuum at a very low temperature (5 Kelvin). 

The setup produced measurement conditions stable enough to achieve accuracies of better than 1 piconewton, enough to distinguish the charge of individual atoms. For example, the researchers found the difference in force between a neutral gold atom and that of a gold atom charged with an additional electron to be only about 11 piconewton.

These atomic-scale measurements add to other scientific advances that are aimed at building computing elements that are on the molecular scale, which could create smaller, faster, and more energy-efficient processors and memory devices for tomorrow’s computers.

Free research paper: Measuring the Charge State of an Adatom with Noncontact Atomic Force Microscopy, Leo Gross, Fabian Mohn, Peter Liljeroth, Jascha Repp, Franz J. Giessibl, and Gerhard Meyer, Science 12 June 2009: 1428-1431.

Listen to a podcast interview with author here.

View a video on the research below.