ABSTRACT
The force modulation mode [50, 51] is an extension of the dynamic mode that uses very large vertical oscillations in which the AFM tip is actually pressed against the surface and the z feedback loop maintains a constant cantilever deflection (as for constant-force mode AFM). The tip moves laterally, point-by-point, over the surface and a complete distribution of the surface elastic properties (amplitude signal) and/or energy dissipation characteristics (phase signal) is collected concurrently with the topographical image [52]. The amplitude damping is determined by the elastic surface deformation against a hard tip. Usually, the elastic constant of the cantilever should be large to achieve reasonable contrast in the force modulation mode. In this mode experiments are typically conducted at the resonant frequency of the driving bimorph element (8-10 kHz) and oscillation amplitudes of 1 to 5 nm [53].
