The possibility of analyzing surfaces at the nanoscale provided by
atomic force microscopy [1] (AFM) has been explored for various
materials, including polymers [2], biological materials [3] and clays
[4]. Further uses of AFMs involved nanomanipulation [5] and measurements
of interaction forces, where the latter has been referred to as atomic
force spectroscopy (AFS) [6]. Measurements of surface-surface
interactions at the nanoscale are important because many materials have
their properties changed at this range [7]. For samples in air, the
interactions with the tip are a superimposition of van der Waals,
electrostatic and capillary forces. A number of surface features can now
be monitored with AFS, such as adsorption processes and contamination
from the environment. Many implications exist for soil sciences and
other areas, because quantitative knowledge of particle adhesion is
vital for understanding technological processes, including particle
aggregation in mineral processing, quality of ceramics and adhesives. In
this paper, we employ AFS to measure adhesion (pull-off force) between
the AFM tip and two types of substrate. Adhesion maps are used to
illustrate sample regions that had been contaminated with organic
compounds.