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 access quantitatively to the properties of the surface. In the present work, we give a systematic comparison between experimental data recorded on two surfaces, phase and amplitude, and theoretical curves. With an interaction between the tip and the surface taking into account an attractive and a repulsive term, the analytical approach is unable to properly describe the relationship between the phase variation and the oscillation amplitude variation. When an additional dissipation term is involved, due to the attractive interaction between the tip and the surface, the model gives a good agreement with the recorded data. Particularly, the trends in the phase variations related to the noncontact situations have been found to be amenable to an analysis based upon a simple viscoelastic behavior of the surface. 
Jean-Pierre Aim\'e (CPMOH), Rodolphe Boisgard (CPMOH), Laurent Nony,   G\'erard Couturier (CPMOH)