Ultrafast time resolution in scanning tunneling microscopy

Recent work combining scanning probe microscopy with ultrafast laser techniques has been stimulated by interest in the high speed dynamics of microscopic structures. The goal is to achieve state-of-the-art temporal and spatial resolution simultaneously with a single probe. Conventional scanning probe microscopy lacks the bandwidth required for experimental studies of the dynamics of nanoscale systems, while standard optical methods do not offer the necessary spatial resolution. It is now possible to employ stroboscopic methods with scanned probes to yield high combined resolution for studies of repetitive phenomena. After a brief review of the development of the field, we discuss two methods enabling the extraction of fast signals from the scanning tunneling microscope: junction mixing and distance modulation. (C) 1997 Elsevier Science B.V.