Development of Field Emitters with Advanced Functions and Narrow Energy Spread

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(a)Emitters with advanced functions : We have successfully fabricated the GaAs field emitter with an aspect ratio larger than 10 using both dry-and wet-etching. The saturation behavior is observed in the current-voltage characteristics of the GaAs emitter, suggesting that the bunched beam generated by the Gunn effect is emitted directly from the GaAs emitter. We have fabricated the novel planar emitter using polycrystalline diamond. Uniform emission with low emission angle is observed at the low gate voltage of 15V.(b)Emitters with narrow energy spread : We have measured energy spread of the electrons emitted from the single-tip Si field emitter using a parallel-type energy analyzer. We have also measured energy spread f the electrons emitted from the single-tip Si field emitter using a cylindrical energy analyzer, which is not affected by the emission angle. The energy distribution indicates that some trapped electrons contribute the field emission.(C)Novels devices with field emitters : We have successfully observed Smith-Purcell radiation at an acceleration voltage of 20 kV and a beam current of 200nA in a visible-to-near infrared light region using a single tip Si field emitter. We have also developed a miniature size x-ray tube using the novel graphite emitter formed by the etching of a graphite substrate. We have demonstrated time-resolved x-ray radiography, whose time resolution is 10μsec.