Nonlinear Dynamic Behavior of an Oscillating TipMicrolever System and Contrast at the Atom.pdfVIP

Nonlinear Dynamic Behavior of an Oscillating Tip-Microlever System and Contrast at the Atomic Scale J. P. Aimé,1,* R. Boisgard,2 L. Nony,1 and G. Couturier 1 1CPMOH Université Bordeaux 1, 351 Cours de la Libération, 33405 Talence, France 2IFE-SEFICESP, 40 rue Lamartine, F-33400 Talence, France (Received 5 August 1998) 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. PUBLISHED IN Phys. Rev. Lett. 82(17), 3388-3391 (1999). PACS numbers: 07.79.Lh, 61.16.Ch, 68.35.Bs A few years ago, the resonant noncontact mode (here- The key point with an AFM is that the recorded infor- after noted NC-AFM) was developed to map tip sur- mation comes from the tip-sample interaction, but when face interaction as shifts of the resonance frequency [1,2]. the CL is externally periodically excited, the recorded im- Since then, numerous experimental efforts have been per- age is a measure of the oscillating behavior of the CL. formed showing that measurements of shifts were able to When the tip-microlever system experiences an attractive produce images at the atomic scale [3–7]. The “routine” field, the oscillator can exhibit a nonlinear behavior [14– achie