Electrostatic Force Microscopy Techniques for Interphase Characterization

Atomic force microscopy (AFM) allows profiling of solid surfaces with nanometer-scale resolution. For characterization of interphases, the transition region can be imaged by suitable sample preparation, exposing a cross-sectional surface by, for example, cleavage or cutting by microtomy. A variety of different properties can be measured along with topography that may indicate different materials or phases on the sectioned surface. Electrical properties of interfaces can be investigated by AFM-based electrostatic probes, namely, Kelvin probe microscopy for contact potential difference and electrostatic force microscopy for surface charge density, capacitance, and dielectric permittivity. All such distinctive properties can be characterized at the interface with state-of-the-art spatial resolution of 20-30 nm. Buried interfaces can also be detected, facilitating, for instance, the study of nanocomposites. Local dielectric spectroscopy (electrical permittivity as a function of frequency) can be probed to monitor changes of materials properties like glass transition across an interface section. In this chapter, AFM electrostatic probes will be described, and examples of application to interphase characterization will be shown.