Nonlinear Dynamic Behavior of an Oscillating Tip-Microlever System and   Contrast at the Atomic Scale
  In this paper the dynamic behavior of an oscillating tip-microlever system at the proximity of a surface is discussed. We show that the nonlinear behavior of the oscillator is able to explain the high sensitivity of the oscillating tip microlever and the observed shifts of the resonance frequency as a function of the tip surface distance without the need of introducing a particular short range force. 
Jean-Pierre Aim\'e (CPMOH), Rodolphe Boisgard (CPMOH), Laurent Nony   (L2MP), G\'erard Couturier (CPMOH)