EFFECTS OF ELASTIC AND INELASTIC INTERACTIONS ON PHASE-CONTRAST IMAGES IN TAPPING-MODE SCANNING FORCE MICROSCOPY

The dependence of phase contrast in tapping-mode scanning force micros copy on elastic and inelastic interactions is studied. The cantilever- tip ensemble is simulated as a driven, damped harmonic oscillator. It is found that for tip-sample elastic interactions, phase contrast is i ndependent of the sample's elastic properties, However. phase contrast associated with elastic modulus variations are observed if viscous da mping or adhesion energy hysteresis is considered during tip-sample co ntact. The phase shift versus tip-sample equilibrium separation tvas m easured for a compliant material (polypropylene) and for a stiff sampl e (mica), The agreement obtained between theory and experiment support s the conclusions derived from the model, These results emphasize the relevance of energy dissipating processes at the nanometer scale to ex plain phase contrast imaging in tapping-mode force microscopy. (C) 199 7 American Institute of Physics.