How to Move a Single Electron

(Inside Science) -- Every time you brush your hair, hundreds of trillions of electrons jump from your hair onto the brush. These particles are so small and sensitive that it is almost impossible to handle them individually, but a group of scientists from Canada have figured out a way to do it using an atomic force microscope. This newfound approach to manipulating individual electrons may one day find applications in future nanoscale electronics.

Atomic force microscopes are instruments commonly used by scientists to visualize things that are too small for optical microscopes to see. Their operating principle has been compared to fingers rubbing against surfaces with Braille lettering, except the “finger” of the instrument is a superfine tip just a few nanometers across.

But even such a super sharp tip is still way too big to move an electron directly -- it would be like trying to scoot around a speck of dust using the top of the Washington Monument. So, instead of trying to perform the task directly, the scientists brought the tip within a nanometer of a silicon atom, close enough for Van der Waals forces -- a kind of weak, short-range electrostatic interaction -- to change the orientation of the silicon atom. This is more like using the Washington Monument to tip over a teacup -- still difficult, but possible.

The new configuration then caused a single electron, either from the AFM tip or from elsewhere in the underlying material itself, to hop atop the reoriented silicon atom.

The researchers published their method in the journal Physical Review Letters. According to the paper, most other ways of placing single electrons onto surfaces use electric currents and voltages, which tend to create disturbances for other electrons in the material. The new method has the advantage of being purely mechanical and being able to place single electrons that are stable up to a few seconds.