Dynamic force microscopy (DFM) phase signals were studied using heterogeneous films of polyvinyl alcohol (PVA). The phase was measured as a function of distance and drive frequency over regions of the film with different dissipative properties. When driving below the free resonance frequency at moderate amplitudes, the tip-sample interaction jumps between non-contact and intermittent contact regimes, giving rise to large, region- specific changes in phase within a single image. Amplitude damping largely determines the imaging regime. Resistance to intermittent contact can be overcome by selecting larger drive amplitudes at drive frequencies below the free resonance. Phase contrast then is related primarily to differences in viscoelastic loss. Upon nearing quasistatic contact, viscoelastic loss can produce a transition from intermittent contact to non-contact as the amplitude is heavily damped.
|Original language||English (US)|
|Number of pages||10|
|State||Published - Feb 1999|
Bibliographical noteFunding Information:
Support by the Center for Interfacial Engineering, a National Science Foundation Engineering Research Center, is gratefully acknowledged. Thanks also to Professor Wayne Gladfelter for valuable discussions.
- Dynamic force microscopy
- Intermittent contact
- Polyvinyl alcohol
- Tapping mode
- Ultrathin films