Analysis of atomic force curve data for mapping of surface properties in water

This paper presents an analysis of atomic force versus distance curves for a silicon nitride probe and a silicon sample immersed in water. A custom-bu ilt atomic force microscope (AFM) was adapted for working in water by build ing a water cell from a liquid drop caught between a glass lamella fixed on the top of the cantilever base and the sample surface. An algorithm for pr ocessing of force curve data for long- and short-range forces is described. The force curve data taken for a sample consisting of a silicon wafer Si(1 11) patterned with V-shaped grooves and a silicon nitride cantilever in wat er were digitally acquired and automatically processed for mapping of surfa ce properties. A weak repulsive double layer force with no relevant depende nce on sample topography was observed on the force curves taken during appr oach movement of the cantilever. On the other hand, the attractive hydratio n force showed a strong dependence on the sample topography. Large hydratio n force values were noticed on the inclined faces of the V-shaped grooves w hile small hydration force values were noticed outside the grooves. The res ult was explained by the dependence of the Lip curvature radius at the cont act region on the tilt of the sample surface.