The injected-charge contrast mechanism in scanned imaging of doped semiconductors by very slow electrons

A new contrast mechanism is reported that visualizes doped areas in semiconductors in very low-energy electron micrographs. The method is based on the use of the cathode lens principle in a scanning electron microscope, in order to form a primary beam of energy in units of electron volts. Below about 3 eV the doped areas exhibited a strong contrast, the explanation of which is based on the injection and recombination of electrons and on the ability of the small negative surface charge thereby created to decrease the very low landing energy of incident electrons near enough to conditions of total reflection. This imaging method enables one to study the charge injection effects in semiconductors, and in view of its high contrast the mode may offer fast image acquisition, while the extremely low-electron energy ensures operation free of any radiation damage to the specimen.