Near field emission scanning electron microscopy
The authors report on the development of a “near field emission scanning electron microscope.” In this instrument electrons are excited from the sample surface after undergoing interactions with a primary beam of electrons field emitted from a polycrystalline tungsten tip. The tip, with an emission radius of 2nm, is scanned at less than 80nm distance to the surface. Topographic images, determined from the intensity variations of secondary and backscattered electrons, yield a vertical resolution on an atomic scale and a lateral resolution of a couple nanometers. The topographic contrast of the extracted electrons and the field emission current are indistinguishable, in agreement with theoretical models of optimal spatial resolution.