| 摘要 |
<p>PURPOSE:To reduce a gate voltage for emitting the same current, and stabilize the emitted current by composing an insulation layer between a substrate and a gate electrode of a multi-layer structure having different dielectric constants, and using a material of a smaller dielectric constant on the substrate side. CONSTITUTION:A conical emitter 2 to emit electrons on a conductive substrate 1 is formed, and it is electrically connected to the substrate 1. Insulation layers 3, 4, etc., of a multi-layer structure of different dielectric constants are provided surrounding the emitter 2, and the dielectric constant of the first insulation layer 3 closest to the substrate 1 is set to be smaller than the dielectric constant of the second insulation layer 4. In addition, a gate electrode 5 is laminated on the second insulation layer 4 to form an aperture 5a surrounding the emitter 2. Field strength close to a forward end of the emitter 2 is thus set larger compared with that in case of the insulation layer of uniform field strength, so a lower gate voltage is required for obtaining the same emitted current. Possibility of generation of mechanical deformation at the forward end of the emitter 2 can thus be reduced when positive ions are accelerated by the gate voltage to give impact on an electron emission part of the emitter 2.</p> |
