Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 65: Methods: Theory and Experiment

O 65.7: Vortrag

Donnerstag, 28. Februar 2008, 13:30–13:45, MA 141

Temperature dependence of the energy dissipation in dynamic force microscopy — •Tino Roll, Tobias Kunstmann, Markus Fendrich, Rolf Möller, and Marika Schleberger — Universität Duisburg-Essen, Fachbereich Physik, Lotharstraße 1, D-47048, Germany

Operating an atomic force microscope under UHV conditions can be used to study energy loss processes. This can be achieved by measuring the energy necessary to maintain the amplitude of the cantilever (damping) at a given frequency shift. The dissipation of energy is usually described in terms of an adhesion hysteresis mechanism. This mechanism should become less efficient with increasing temperature. To verify this prediction we have measured topography and dissipation data with dynamic force microscopy in the temperature range from 100 K up to 300 K. We used 3,4,9,10-perylenetetracarboxylic-dianhydride (PTCDA) grown on KBr(001). At room temperature, the energy dissipated into the sample (or tip) is 2.5 eV/cycle for PTCDA and 1.5 eV/cycle for KBr, respectively, and is in good agreement with an adhesion hysteresis mechanism. The energy dissipation over the PTCDA surface decreases with increasing temperature yielding a negative temperature coefficient. For the KBr substrate, we find the opposite behaviour: anincrease of dissipated energy with increasing temperature. While the negative temperature coefficient in case of PTCDA agrees rather well with the adhesion hysteresis model, the positive slope found for KBr points to a hitherto unknown dissipation mechanism.