Dresden 2003 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
CPP: Chemische Physik und Polymerphysik
CPP 8: Neue Methoden
CPP 8.1: Vortrag
Mittwoch, 26. März 2003, 17:00–17:15, ZEU/160
Contact mechanics at MHz frequencies with a combined QCM/AFM setup — •J. Lübben1 and D. Johannsmann2 — 1MPI, Ackermannweg 10, 55128 Mainz — 2TU Clausthal, Arnold-Sommerfeld-Str. 4, 38678 Clausthal-Zellerfeld
We report on the combination of a QCM with an AFM in order to perform nanotribology at MHz frequencies. The MHz shear motion of the quartz is transmitted through the sample and is picked up by the cantilever. The cantilever’s static and dynamic deflections are recorded simultaneously. The dynamic signal is assumed to give access to the contact stiffness directly. Its magnitude depends on the vertical force. As soon as a Si-tip contacts the Au-electrode of the quartz, the dynamic signal reaches its maximum. Upon retraction one observes an adhesive static force. The dynamic signal decreases gradually at the same time. There is no discontinuity in the dynamic signal. We attribute the latter effect to a decrease in contact radius. We show the dependence of the dynamic coupling between the tip and the quartz surface on the amplitude of quartz shear motion. At a critical speed of 5-6 m/s the dynamic signal disappears. Presumably, sliding sets in at this speed. In case of thick adhesive films spread out on the quart z surface, fibers are pulled out from the film. We have demonstrated by measuring the dynamic signal that the transmission of shear waves occurred through the fibers and decreased with elongation, suggesting that the fiber’s stiffness decreased during stretching.