Tailored colloidal AFM probes and their TEM investigation

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 <1µm 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.