Imaging physical phenomena with local probes: From electrons to photons

The invention of scanning tunneling and atomic force probes revolutionized our understanding of surfaces by providing real-space information about the geometric and electronic structure of surfaces at atomic spatial resolution. However, the junction of a nanometer-sized probe tip and a surface contains much more information than is intrinsic to conventional tunneling and atomic force measurements. This review summarizes recent advances that push the limits of the probing function at nanometer-scale spatial resolution in the context of important scientific problems. Issues such as molecular interface contact, superconductivity, electron spin, plasmon field focusing, surface diffusion, bond vibration, and phase transformations are highlighted as examples in which local probes elucidate complex function. The major classes of local probes are considered, including those of electromagnetic properties, electron correlations, surface structure and chemistry, optical interactions, and electromechanical coupling.