Investigation of Gate-controled Electron-Emittor

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An electron-emission phenomenons from edges of gate-electrodes of MOS or MIM structure capacitors is found when the gate-electrodes are biased by positive voltages.The evidence of the-electron-emission is confirmed by observing light spots of a fluorescent screen formed on an anode which is placed adjacent to the sample capacitor to collect the emitted electron.The MOS-type experimental device is constructed on a p-Si substrate upon which a SiO2 layer and a metal electrode are formed. Most of MIM-type experimental devices are made up of a thin CeO2 film as an insulator layer sandwiched by a lower-electrode and an upper gate-electrode. Materials of these metal electrodes are chosen in several combinations from Al, Au, Cr and Ti.The electrons are emitted from a few very small spots along the edges of the gate-electrode. Especially, the emission current can be obtained efficiently from small holes which happen to generate on the gate-electrode when the gateelectrode is evaporated.The emitted current-is generally accompanied with large fluctuation and instability but in some cases shows very large current of the order of mirriampere in spite of the electrons are emitted from a very small spot of the order of 10 micrometers.The electron-emission is considered to occur only when following 3 processes are all well-operated. (1) Electron injection from the Si-substrate or the lower-electrode to the oxide or insulator layer. (2) Electron transportation in the oxide or insulator layer. (3) Electron emission from the surface of the oxide or insulator layer.Above all, the injection of hot electrons which is considered to obey FowlarNordheim tunneling effect is most important process under the very high electric field strength. The electron injection originates from some sites of lattice imperfections or impurity atoms at the interface between the oxide and the semiconductor or the insulator and the metal electrode where the potential barriers are thinned and lowered.