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The use of an individual particle attached to the end of a cantilever is the established method for characterizing colloidal interaction forces using an atomic force microscope. In this manner the geometry of the probe is well defined but the difficult handling of particles with diameters <1 µm and the restricted availability of different materials as ideal spheres of the desired size and low roughness limit the variability of this method.We propose a method to adjust the tip radius of commercial silicon tips from ∼30 nm up to 2 µm by an oxidation procedure. The resulting silica tips have ideal (hemi-)spherical geometry and very low roughness. It is possible to vary the surface composition and properties by combining the oxidation procedure with a coating or chemical modification process.A home-made transmission electron microscopy holder make it possible to analyse easily and very precisely the tip radius and the thickness of layers of different materials without destruction of the system cantilever chip. This means that the probe can be analysed before and after an atomic force microscopy measurement.

Abstract

No abstract

The formation of electrical charges at solid/liquid interfaces results in a diffuse electrical double layer close to the solid surface. This layer determines, for example, the behaviour of ceramic particles in aqueous media and the effective pore radius of membranes acting in liquids. The SiO2/SiO2 system is used to demonstrate that linear measurements using atomic force microscopy are suited for characterizing double layers at real surfaces. It has to be taken into consideration that the tip itself, which is acting as the probe, is also surrounded by a double layer and responds to the composition of the electrolyte in a material‐specific way. For this reason an oxidized silicon tip was used for the present investigations, so that tip and sample consisted the same material. In this way it is possible to obtain results that can be evaluated easily and compared with the DLVO theory.© 1997 John Wiley & Sons, Ltd.