Filamentary electron-emission device having self-aligned gate or/and lower conductive/resistive region

DETAILED DESCRIPTION What is claimed is: 1.
A structure comprising: a substrate for providing structural support; a lower electrically conductive region comprising a group of generally parallel highly conductive lines situated over electrically insulating material of the substrate; a porous electrically insulating layer situated over the lower conductive region; a multiplicity of electron-emissive filaments respectively situated in corresponding pores extending through the porous layer down to the lower conductive region, the lower end of each filament contacting the lower conductive region, the pores being situated at locations substantially random relative to one another; and a patterned electrically conductive gate layer situated over the porous layer, openings which respectively correspond to the filaments being provided through the gate layer at locations generally centered on the filaments such that the filaments are separated from the gate layer.
2.
A structure as in claim 1 wherein each opening is wider than the corresponding filament.
3.
A structure as in claim 1 wherein cavities which respectively correspond to the filaments are provided in the porous layer along its upper surface at locations generally centered on the filaments, the cavities extending downward partway through the porous layer, each cavity being wider than the corresponding pore so that each filament protrudes from its pore into the corresponding cavity.
4.
A structure as in claim 1 further including: a second electrically insulating layer situated over the gate layer; and a second electrically conductive layer situated over the second insulating layer, openings which respectively correspond to the filaments being provided through the second layers at locations generally centered on, and situated above, the filaments.
5.
A structure as in claim 1 wherein the length of each filament is at least twice its maximum diameter.
6.
A structure as in claim 1 wherein the upper ends of the filaments are sharpened.
7.
A structure as in claim 1 further including means for collecting electrons emitted by the electron-emissive filaments, the collecting means situated above, and spaced apart from, the gate layer