Examination of the relationship between phase shift and energy dissipationin tapping mode atomic force microscopy by frequency-sweep and force-probemeasurements

The relationship between phase shift and energy dissipation in tapping mode atomic force microscopy was examined by performing frequency-sweep and for ce-probe experiments on polydimethylsiloxane (PDMS) samples of different cr oss-link densities. Phase shift is related to the reduced tip-sample energy dissipation, i.e. the fraction of the maximum energy of a tapping cantilev er that is dissipated by the tip-sample interaction. The reduced tip-sample energy dissipation varies linearly with phase shift, and increases continu ously as the tip-sample interaction increases. On a compliant polymer such as PDMS the tip-sample interaction dissipates only a small fraction of the power delivered to the tapping cantilever even under hard tapping condition s, so that the vibration of the tapping cantilever is well described in ter ms of the harmonic approximation. (C) 2000 Elsevier Science B.V. All rights reserved.