Figure 1: Schematic view of the impact of the electrostatic forces on the high-resolution AFM images.
From: Mapping the electrostatic force field of single molecules from high-resolution scanning probe images
(a) Blue and pink lines represent the positions of sharp edges observed in high-resolution AFM images acquired using positively charged and neutral tips, respectively. Corresponding x,y cut-plane of the Hartree potential VS(x, y) above the molecule is displayed in the background. (b) Variation of the frequency shift Δf as function of the tip positions xTIP for the neutral 
and positively charged 
probe particle. (c) The lateral relaxation Δx of the probe particle with (blue) and without (pink) an effective charge on the tip is different above a molecule due to the presence of the electrostatic force. The electrostatic force originates from the interaction between the electrostatic potential of the molecule (VS) on the surface and the effective charge on the probe particle at its given position xPP.
