ABSTRACT
Development of superesolution optical microscopy proceeded in parallel with the development of stylus profilometry. Scanning profilometers typically employ a diamond stylus, which contacts the sample surface and produces a threedimensional map. Lateral resolution is limited by the size of the stylus and the minimum force necessary for a detectable deflection. A major problem associated with this technique is the contact interaction between the stylus and sample, which can lead to contamination and damage of the sample surface. In 1972 a group at the National Bureau of Standards led by R. Young, developed a noncontacting profilometer [3,4]. This instrument used field emission to pass a current between the probe and the sample. By injecting a constant current of electrons into the sample and monitoring the voltage, the distance between probe and sample could be determined from Fowler-Nordheim theory [5]. The last step necessary to produce a microscope involved feeding the junction voltage into a servo loop and raster scanning the field emission probe. By recording the correction signal from the servo loop, a map of the surface was produced. Young named this instrument the ''topografiner'' from the Greek ''to describe a place.'' Typical resolution of the instrument was 4 nm vertically and 400 nm laterally. The topografiner is the forerunner of the scanning tunneling microscope.
