Fabrication and electrical characteristics of carbonnanotube field emission microcathodes with an integrated gateelectrode

Abstract

We report on the fabrication of field emissionmicrocathodes which use carbon nanotubes as the field emissionsource. The devices incorporated an integrated gate electrode inorder to achieve truly low-voltage field emission. A single-mask,self-aligned technique was used to pattern the gate, insulator andcatalyst for nanotube growth. Vertically-aligned carbon nanotubeswere then grown inside the gated structure by plasma-enhancedchemical vapour deposition. Our self-aligned fabrication processensured that the nanotubes were always centred with respect to thegate apertures (2 µm diameter) over the entire device. In orderto obtain reproducible emission characteristics and to avoiddegradation of the device, it was necessary to operate the gate in apulsed voltage mode with a low duty cycle. The field emission deviceexhibited an initial turn-on voltage of 9 V. After the firstmeasurements, the turn-on voltage shifted to 15 V, and a peak currentdensity of 0.6 mA cm-2 at 40 V was achieved, using a duty cycleof 0.5%.