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Quantitative Measurement of Short-Range Chemical Bonding Forces
M. A. Lantz,*H. J. Hug,R. Hoffmann,P. J. A. van Schendel,P. Kappenberger,S. Martin,A. Baratoff,H.-J. Güntherodt
We report direct force measurements of the formation of a chemical
bond. The experiments were performed using a low-temperatureatomic
force microscope, a silicon tip, and a silicon (111) 7×7surface. The
measured site-dependent attractive short-range force,which attains
a maximum value of 2.1 nanonewtons, is in good agreementwith
first-principles calculations of an incipient covalent bondin an
analogous model system. The resolution was sufficient todistinguish
differences in the interaction potential between inequivalentadatoms,
demonstrating the ability of atomic force microscopyto provide
quantitative, atomic-scale information on surface chemicalreactivity.
Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
*
To whom correspondence should be addressed. E-mail:
mark.lantz{at}unibas.ch
