Schottky emitters with carbon nanotubes as electron source

In this paper we present a simple approach for making a Schottky emitter with carbon nanotubes (CNT). A tungsten wire of 0.3 mm diameter was used as a heating filament. An iron rod of 0.3 mm diameter having a sharp tip was weld-bonded to the filament. By heating the filament to around 750°C in a mixture of (C₂H₂+Ar), multi-wall CNT was grown at the Fe tip. Electron field emission and thermal-field emission properties of the fabricated Schottky emitter were measured at different temperatures. At room temperature, the field emission current well obeyed the Fowler-Nordheim (F-N) mechanism with threshold voltage of around 0.2 V/μm. At the temperature of higher than 780°C, the thermal-field emission dominated and both field emission and thermal-field emission were very stable with very low fluctuation. Enhancement factor of 1.3 × 10⁷ m^-1 and work function of 4.95 eV were evaluated for the grown CNT. The mentioned CNT-Schottky emitters for advanced electron beam instruments are expected.