Electric Force Microscopy (EFM) and Surface Potential (SP) imaging are two AFM techniques, which characterize materials for electrical properties. A conductive AFM tip interacts with the sample through long-range Coulomb forces. These interactions change the oscillation amplitude and phase of the AFM cantilever, which are detected to create EFM or SP images (see Resonance Shift, page 8). In an EFM image (Figure 1) the phase, frequency, or amplitude of the cantilever oscillation is plotted at each in-plane (X,Y) coordinate. This phase, frequency, or amplitude is related to the gradient of the electric field between the tip and the sample. In a SP image (Figure 2), variations in the surface potential on the sample are plotted. A voltage carrying AFM tip also enables electrical modification of materials on or beneath the surface, such as depicted in Figures 1 and 10.

Applications include electrical failure analysis, detecting trapped charges, quantifying contact potential difference (CPD) between metals and/or semiconductors, mapping relative strength and direction of electric polarization, testing electrical continuity, and performing electrical read/write.