Influence of noncontact dissipation in the tapping mode: Attempt to extract quantitative information on the surface properties with the local force probe method

In the Tapping mode, a variation of the oscillation amplitude and phase as a function of the tip sample distance is the necessary measurement to acces s quantitatively to the properties of the surface. In the present work, we give a systematic comparison between experimental data recorded on two surf aces, phase and amplitude, and theoretical curves. With an interaction betw een the tip and the surface taking into account an attractive and a repulsi ve term, the analytical approach is unable to properly describe the relatio nship between the phase variation and the oscillation amplitude variation. When an additional dissipation term is involved, due to the attractive inte raction between the tip and the surface, the model gives a good agreement w ith the recorded data. Particularly, the trends in the phase variations rel ated to the noncontact situations have been found to be amenable to an anal ysis based upon a simple viscoelastic behavior of the surface. (C) 2001 Ame rican Institute of Physics.