Figure 1.

Principle of operation and operation modes in AFM. (A) Schematics of atomic force microscopy principle. (B-E) Four widely used atomic force microscopy operation modes: (B) DC mode, (C) AC mode, (D) lateral force microscopy, and (E) Force spectroscopy. A typical force-distance curve is shown (E). The cantilever is not deflected yet (1). As the tip approaches to the surface, the cantilever bends upward by repulsive forces (2). As the tip retracts from the surface, the cantilever bends downward by attractive forces between the tip and sample (3).