Regensburg 2002 – scientific programme
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O: Oberflächenphysik
O 26: Postersitzung (Rastersondentechniken, Nanostrukturen, Teilchen und Cluster, Methodisches, Oxide und Isolatoren, Grenzfl
äche fest-flüssig, Struktur und Dynamik reiner Oberfl
ächen, Oberfl
ächenreaktionen, Zeitaufg. Spektroskopie, Phasenüberg
änge
O 26.13: Poster
Wednesday, March 13, 2002, 14:30–17:30, Bereich C
Amplitude- and Phase-Distance-Curves at variable Relative Humidity: Experiments and Simulations — •Lothar Zitzler, Frieder Mugele, and Stephan Herminghaus — Angewandte Physik, Universität Ulm
We studied the dependence of amplitude- and phase-distance curves (APD curves) in Atomic Force Microscopy on the relative humidity. Because of the non-linear interaction between tip and sample, the shape of the APD curves depends (among other parameters) on the free oscil-lation amplitude A0 of the cantilever (which is measured at No-dqinfiniteNo-dq tip-sample separation). For small A0, the APD curves indicate a predominantly attractive tip-sample interaction for all separations between tip and surface. For values of A0 above a certain threshold Ac, a transition from predominantly attractive to predominantly repulsive interaction occurs as the average tip-sample separation is reduced. For hydrophilic tip and sample (i.e. Si) the value of Ac is found to increase with rising relative humidity. Systems with hydrophobic tip and sample do not show this dependence.
Furthermore we present numerical simulations of APD curves which qualitatively reproduce the experimental results. These simulations allow us to study the forces between tip and sample in more detail, especially the effect of a meniscus of adsorbed water.