Charging gold with a single electron

By transferring a single electron to a gold atom, scientists have converted a neutral atom into a negatively charged ion. The switching of the electronic state of an individual atom is not only a demonstration of the exquisite control over matter that scientists now wield but could also lead to new ways of encoding data for making ultrahigh-density memory chips.

Jascha Repp of the IBM Zurich Research Laboratory in Switzerland and his colleagues allowed gold atoms to adsorb onto a thin film of sodium chloride atop a copper base. Then, they finessed the styluslike tip of a scanning tunneling microscope to a position directly over one gold atom and applied a positive-voltage pulse. This pulse delivered an electron to the atom, tagging the gold atom with a negative charge. Applying a negative voltage to the tip yanked the electron back, returning the gold atom to its neutral state.

Reporting in the July 23 Science, the researchers suggest that such an atomic-switching mechanism could be used to store bits of data—neutral atoms might encode the 1s of digital data, for instance, while charged atoms would encode the 0s.