A New Type Edge Effect in High Resolution Scanning Electron Microscopy

A new type edge effect has been observed with a field emission scanning electron microscope. Contrary to a conventional edge penetration effect which is caused by the scattering of the primary electron, this new type edge effect is directly related to the mean free path of the secondary electrons produced in a specimen, and the width of the edge flaring in secondary electron image is of the order of the magnitude of the escapable distance of secondary electrons, i.e. about several tens of angstroms. Using a field emission scanning electron microscope recently constructed, this edge effect is experimentally observed by means of a cleaved edge of galena, and the effect is theoretically explained by applying the Monte Carlo technique.