IMAGING HIGH-FREQUENCY DIELECTRIC-DISPERSION OF SURFACES AND THIN-FILMS BY HETERODYNE FORCE-DETECTED SCANNING MAXWELL-STRESS MICROSCOPY

The design and performance of the heterodyne force-detected scanning Maxwell-stress microscope (HFD-SMM), a new tool for the microscopic observation of dynamic electrical phenomena at surfaces, are described. The HFD-SMM utilizes the non-linearity of the electric Maxwell stress with respect to the field strength which serves as a frequency mixer to create a low frequency heterodyne beat force from high frequency held components so as to make them observable even with a slowly responding cantilever. Combined with the tip-surface distance control based on capacitive forces, the HFD-SMM allows reliable dielectric-dispersion imaging at arbitrarily high frequencies, while carrying out simultaneous non-contact imaging of surface potentials and topography as in the original SMM. Images with clear frequency-dispersion contrast are presented for metal, semiconductor and polymer surfaces.