Scanning Polarization Force Microscopy: a Technique for Studies of Wetting Phenomena At the Nanometer Scale

We describe a technique developed recently based on the use of electrostatic forces in the atomic force microscope (AFM) to image liquid films and droplets. The technique, named scanning polarization force microscopy (SPFM), is a truly non-contact technique where the tip scans the surface at a height of a few hundred angstroms, which is sufficient to minimize perturbation of the liquid film. The resolution of the technique is a few hundred angstroms horizontally and one angstrom vertically. The information provided by SPFM includes topography, contact potential, and dielectric (frequency dependent) mapping. After a brief introduction to basic wetting concepts, we describe the technique and illustrate with several examples its potential applications.