News

posted on 22 February 2008 08:53

How much force does it take to move an atom? IBM Almaden scientists, working with Regensburg University in Germany, have found out.

How much is it? In a paper, “The Force Needed to Move an Atom on a Surface,” the scientists show that the force required to move a cobalt atom over a smooth platinum surface is 210 piconewtons, while moving a cobalt atom over a copper surface takes only 17 piconewtons.  To put this in perspective, the force required to lift a copper penny that weighs just three grams is nearly 30 billion piconewtons – 2 billion times greater than the force to move a single cobalt atom over a copper surface.

A Newton in the meter-kilogram-second system is the unit of force required to accelerate a mass of one kilogram one meter per second per second, equal to 100,000 dynes. A piconewton is a millionth of a millionth of a newton.

The researchers used a sensitive atomic force microscope (AFM) to measure both the strength and direction of the force exerted on an atom or molecule on a surface using a sharp metal tip to move the atom. The team discovered that the force varies dramatically depending on the material used for the surface.  The amount of force also changes greatly when a small molecule is used instead of a single atom. 

The AFM uses a sharp tip mounted on a flexible beam – akin to a tiny diving board – to measure the interaction between the tip and the atoms on a surface.  In the present work, the flexible beam was actually a miniature quartz tuning fork of the type commonly found in clocks and wrist watches.  When the tip is positioned close to an atom on the surface, the frequency of the tuning fork changes slightly. The frequency change can be analyzed to determine the force exerted on the atom.

Professor Franz Giessibl of the University of Regensburg, said: “It is amazing to see how this tool, which at its heart uses the tuning fork of an everyday wrist watch, can be used to measure forces between individual atoms."

Because scientists and engineers now know the amount of force needed to shift an atom they will be better able to design atomic-scale computert chips and storage devices some time in the future.

Andreas Heinrich, lead scientist in the scanning tunneling microscopy lab at the IBM Almaden Research Center, said: “This result provides fundamental information about atomic scale fabrication and could pave the way for new data storage and memory devices. Our mission is to create the foundation for what could someday be called the IBM nanoconstruction company.”

I guess that would be a very small company then :-)

IBM is currently promoting its scientific research credentials, for example, with carbon nanotubes and we can expect another mountain of patent applications and scientific papers from Almaden. The head of the IBM Research Center recently changed.