High-performance carbon-nanotube-based cold cathode electron beam with low-thermal-expansion gate electrode

Abstract

The emission of a high-performance electron beam via a carbon nanotube cold cathode requires a higher electron transmission through the gate electrode. The transmittance of electrons through the gate mesh electrode strongly depends on the gate electrode structure and material properties. Therefore, thermal expansion of the gate electrode induced by the thermal load owing to the gate leakage current is a significant hurdle to be overcome. Using a high-thermal-expansion gate electrode comprised of SUS304 grid mesh, electron emission was brought to saturation when the mesh was bent upward, which was the result of a reduction of the effective electric field under the grid mesh. To mitigate the effect of this bending, a Mo grid mesh material possessing low thermal expansion introduced. The Mo grid material properties of low linear temperature expansion coefficient, high tensile strength, and low resistivity are necessary. With this grid mesh improvement, the electron emission current increased to ten times that of the SUS304 mesh grid.