Electron emission mechanism from negative electron affinity surface and production of highly efficient electron emitter

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1) Oxidation process of Cs adsorbed on CVD diamond surfaces was investigated. The oxidation process is the same as that of Si and GaAs. Namely, with the adsorption of oxygen, oxide, peroxide and superoxide were formed. Superoxide is chemically stable upon oxygen exposure.2) Silicon and gallium arsenide with cesium on their surface is oxidized very easily. On the contrary diamond with cesium on the surface is not oxidized.3) As the result, the potential layer to disturb electron emission from the surface is not formed. This enables the stable electron emission after oxygen exposure. This fact is very important to realize practical electron emitters.4) Barium adsorbed diamond surface was also studied. The oxidation process is similar to the case of cesium adsorption. Barium adsorbed diamond surface is also potential for electron emitters.5) It was found from desorption spectrum study that barium layer deposited on diamond is thermostable up to 400℃.6) Electron emission from Cs deposited diamond surface was measured. Threshold field for electron emission was 0.8 V/μm. Emission current density of 2 μA/mm^2 was obtained for the field strength of 15 V/μm. It was fairly stable to time and exposure to air. Luminescence from ITO used for an anode was confirmed.