The potential energy landscape of surfaces governs the dynamics of adsorbed molecules, as well as atomic scale friction processes. We measure the potential energy landscape of a single-atom tip interacting with a vicinal nonconducting NaCl(100) surface in real space using noncontact atomic force microscopy. We find that the shape of the potential energy profile is of sinusoidal form with a barrier height of 48 meV. Furthermore, we observe a discontinuity in the force curves at specific lattice sites, indicating the onset of reversible yet hysteretic mechanical relaxations.

In this study, we analyze the noncontact atomic force microscopy ͑NC-AFM͒ imaging mechanism on the Ag͑110͒ surface by experiment and ab initio theory. The experimental NC-AFM images exhibit atomic-scale resolution in the topography and dissipation signal. Interestingly, the maximum of the damping signal is between the maxima of the topography image. Comparing the geometry of the Ag͑110͒ surface with the topography of a simulated NC-AFM image, we found that the first surface layer silver atoms are imaged as maxima in the topographic NC-AFM images. The overall structure and the corrugation height of the theoretical NC-AFM image are in good agreement with the experimental ones. Furthermore, the analysis of the shortrange tip-sample interactions calculated at specific lattice sites revealed strong hysteresis effects. Our simulations also indicate that clean silicon tips might become contaminated with silver atoms during a NC-AFM experiment. Indeed, the NC-AFM experiments showed that the Ag͑110͒ surface is difficult to image probably due to contamination of the silicon tip during the imaging process.

Dynamic force spectroscopy experiments were conducted with a silicon tip on graphite in ultrahigh vacuum. Spectroscopy curves were acquired in the constant-amplitude as well as in the constant-excitation mode. From both modes we extract quantitative force and energy dissipation curves. We show that the calculated tip-sample interaction curves are independent of the operational mode. This proves that quantitative dynamic force spectroscopy is also possible in the constant-excitation mode.