Interaction-induced atomic displacements revealed by drift-corrected dynamic force spectroscopy

The three-dimensional force field above an NaCl(001) surface was measured on a fine grid by small amplitude dynamic force spectroscopy at room temperature. After careful drift corrections, maps in nominally equivalent symmetry planes as well as in sections parallel to the surface reveal distance-dependent shifts of characteristic atomic-sized features. These shifts reflect asymmetries of the probing tip apex but are mainly due to atomic displacements induced by short-range forces. In addition, weak decaying force oscillations with a period close to the interlayer spacing are detected at distances where no atomic-scale variations are expected. Stronger site-dependent changes appear in the interaction-induced energy dissipation.