Emission of high-energy electron from ITO layers

The effects of electric field induced electron emission from the complex emitters are studied. As the emitters were used the thin doped films of In2O3 and SnO2 (ITO-indium tin oxide) of thickness 10-300 nm deposited on 0.2 mm thick sodium glass plate. A negative voltage U-pol was applied to the sample's field electrode. The ITO film was subjected to the bombardment by primary electron beam of energy E-p, which equals 200 eV. The field induced the secondary emission effect was studied in the 10(-7) hPa vacuum. The dependence of the secondary emission coefficient delta on the electric field was found to be not monotonic. The dependence delta = f (E-p) was also found to be different from that typically described in the literature. Energy examination of the emitted electrons revealed some electrons of energy higher than E-p. After removing the primary electron beam the electron emission still existed due to the applied electric field and it is called the electric field induced electron emission (EFIEE). The emission currents were of the order of nA. About 80% of the emitted electrons were found of energy within 1-2 eV, however few percent of the electrons exhibited energy approaching 10 eV. With increasing the applied voltage the emitted electron flux increased. It concerns mainly the low-energy electrons. The energy distribution of the electrons emitted under the EFIEE conditions from Si-SiO2-ITO structures was also studied. The phenomenological model was proposed of the EFIEE effects. The main assumptions of the model are supported on the basis of the field induced division of the ITO semiconductor into two zones: depleted and enhanced of electrons.