Fig. 1. Idealized force-distance curve describing a single approach-retract cycle of the AFM tip (modified from Shahin et al., 2005). The AFM tip is approaching the sample surface (A). The initial contact between the tip and the surface is mediated by the attractive van der Waals forces (contact) that lead to an attraction of the tip toward the sample (B). Hence, the tip applies a constant and default force upon the sample surface that leads to sample indentation and cantilever deflection (C). Subsequently, the tip tries to retract and to break loose from the surface (D). Various adhesive forces between the sample and the AFM tip, however, hamper tip retraction. These adhesive forces can be taken directly from the force-distance curve (E). The tip withdraws and loses contact with the sample upon overcoming the adhesive forces (F).