The force curves between an AFM probe and paraffin films deposited by casting of paraffin solutions in heptane onto crystalline silicon substrates were studied. The results show that paraffin deposits undergo a permanent deformation when the first force curve is performed not recovering its original situation. When subsequent force curves are performed at the same location, the force curves present a reproducible behavior. Gradual response of retraction curves indicate that an interaction of viscous adhesion occurs during jump-out of the AFM probe. In case of measurements performed many hours after the deposition of the films, the jump-in and jump-out distances are situated around 310 and 420 nm, respectively; while adhesion forces values are around 60 nN in the case of the first contact between the AFM probe and paraffin film and 40 nN for the subsequent contacts. Force curves results obtained for different times after deposition of the layers show that the interaction between the AFM probe and paraffin films is dependent on elapsed time. Fresh films appear to be damp and sticky, changing their properties as the solvent is evaporated. Adhesion force and pull-off distance decrease as a function of time up to about 30 min and then for longer times decrease at a much smaller rate. The separation energy between the tip and paraffin films is large just after paraffin deposition, decreasing abruptly with time and reducing very slowly after 15 min.
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