Hembacher, Stefan and Giessibl, Franz J. and Mannhart, Jochen and Quate, Calvin F.
Local Spectroscopy and Atomic Imaging of Tunneling Current, Forces, and Dissipation on Graphite.
Physical Review Letters (PRL) 94 (5), 056101.
Other URL: http://link.aps.org/doi/10.1103/PhysRevLett.94.056101
Theory predicts that the currents in scanning tunneling microscopy (STM) and the attractive forces measured in atomic force microscopy (AFM) are directly related. Atomic images obtained in an attractive AFM mode should therefore be redundant because they should be similar to STM. Here, we show that while the distance dependence of current and force is similar for graphite, constant-height AFM and STM images differ substantially depending on the distance and bias voltage. We perform spectroscopy of the tunneling current, the frequency shift, and the damping signal at high-symmetry lattice sites of the graphite (0001) surface. The dissipation signal is about twice as sensitive to distance as the frequency shift, explained by the Prandtl-Tomlinson model of atomic friction.