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Science 12 June 2009:
Vol. 324. no. 5933, pp. 1428 - 1431
DOI: 10.1126/science.1172273
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Reports

Measuring the Charge State of an Adatom with Noncontact Atomic Force Microscopy

Leo Gross,1,* Fabian Mohn,1 Peter Liljeroth,1,2 Jascha Repp,1,3 Franz J. Giessibl,3 Gerhard Meyer1

Charge states of atoms can be investigated with scanning tunneling microscopy, but this method requires a conducting substrate. We investigated the charge-switching of individual adsorbed gold and silver atoms (adatoms) on ultrathin NaCl films on Cu(111) using a qPlus tuning fork atomic force microscope (AFM) operated at 5 kelvin with oscillation amplitudes in the subangstrom regime. Charging of a gold atom by one electron charge increases the force on the AFM tip by a few piconewtons. Moreover, the local contact potential difference is shifted depending on the sign of the charge and allows the discrimination of positively charged, neutral, and negatively charged atoms. The combination of single-electron charge sensitivity and atomic lateral resolution should foster investigations of molecular electronics, photonics, catalysis, and solar photoconversion.

1 IBM Research, Zurich Research Laboratory, 8803 Rüschlikon, Switzerland.
2 Debye Institute for Nanomaterials Science, Utrecht University, Post Office Box 80000, 3508 TA Utrecht, Netherlands.
3 Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany.

* To whom correspondence should be addressed. E-mail: lgr{at}zurich.ibm.com

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Novel Probes for Molecular Electronics.
E. Meyer and T. Glatzel (2009)
Science 324, 1397-1398
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