Description of the frequency dependence of the amplitude and phase angle of a silicon cantilever tapping on a silicon substrate by the harmonic approximation

The frequency dependence of the amplitude and phase angle of a silicon cantilever tapping on a silicon surface was examined. The amplitude and phase angle curves exhibit hysteresis depending on the driving and set-point amplitudes. The main features of these curves are explained in terms of the harmonic approximation. The frequency shifts determined from the phase curves vary almost linearly as a function of the set-point ratio, in support of the harmonic approximation. The quality factor of a tapping cantilever was estimated from amplitude and phase curves using the harmonic approximation. The quality factor is reduced by the tip-sample interaction, and this reduction is stronger when the interaction is dominated by repulsive forces than by attractive forces. (C) 1998 Elsevier Science B.V. All rights reserved.