High-current field-emission of carbon nanotubes and its application as a fast-imaging X-ray source

Abstract

The high-current field-emission (FE) characteristics of carbon nanotubes (CNTs) are reported. Powders of bismuth (Bi) were mixed with the CNTs and baked at 400°C, and because the melting point of Bi is low, the CNTs bonded strongly to the Bi blocks. In the FE characterization, the turn-on electric field was 1.54V/μm, with current density 1μA/cm2, and the threshold electric field was 4.24V/μm, with current density 1mA/cm2. Because the Bi blocks played a role in enhancing the adhesion of CNTs to the substrate and improving the FE performance, the stable FE current reached 88mA when the electric field was increased to 12.75V/μm; the current density was 11.2A/cm2. A fast-imaging X-ray tube with CNT field emitters was fabricated. The metal mesh was used as the gate electrode, which was designed to be cooled in oil in order to switch the electron beam rapidly. The X-ray image of a vibrating metronome was captured clearly when the exposure time was decreased to 20ms, showing that high-current CNT field emitters can be used to obtain X-ray images of moving objects.