Self-aligned, gated bulk molybdenum field emitter arrays

This paper reports the fabrication of bulk molybdenum field emitter arrays with integrated, self-aligned gates. Based on molybdenum deep reactive ion etching, the fabrication process is significantly simplified compared with that of conventional Spindt-type arrays. In the present structures, the distance between the gate and emitter has been precisely controlled by the thickness of SiO
₂
dielectric layer. In this work, current densities of 84mA/cm
²
were produced from a uniform array of 2500 tips covering a total emission area of just 1 mm
²
, driven at gate-emitter voltages of just 120 V. Compared to diode-type emitters we reported elsewhere [1], the emission current densities increased by 240 times to 33.6nA/tip, owing to the extractor gates. Further scaling down of the pitch to may lead to an increase of the current densities to several A/cm
²
, which is very promising for high-current cathode applications such as X-ray sources.