Patent ID: 8604681

Claim:
A cathode, comprising: a conductive base layer; an insulating layer disposed on the conductive base layer and having a plurality of apertures therein; a conductive gate layer disposed on the insulating layer and having a plurality of apertures therein, wherein the plurality of apertures of the insulating layer and the plurality of apertures of the conductive gate layer are substantially coaxial, and wherein at least a portion of a side wall and/or a bottom surface of a distal end of each aperture of the plurality of apertures of the conductive gate layer is vertically exposed to a surface of the conductive base layer; a plurality of emitters in electrical communication with the conductive base layer, wherein each emitter of the plurality of emitters is disposed in an aperture of the insulating layer and projects toward the conductive gate layer, wherein each emitter of the plurality of emitters comprises an array of vertically aligned carbon nanotubes, and wherein a length of the carbon nanotubes is greater than a distance between the conductive base layer and the conductive gate layer such that the carbon nanotubes extend beyond the conductive gate layer; and wherein each aperture of the plurality of apertures of the insulating layer are tapered, wherein the aperture is larger at an end distal from the conductive base layer than at an end proximal to the conductive base layer.