Cathode planes for field emission devices

A substrate 200 is provided with conductive cathode tracks and a field electron emission material on the tracks. Septa 201 and pillars 202 are provided as raised elements over the emission material. An electrically insulating layer is formed over the emission material and raised elements 201, 202, such that boundary walls are formed in the insulating layer where it contacts the raised elements. The raised elements 201, 202 are then removed, to leave emitter cells and voids for other components, defined by the boundary walls with the insulating layer. A gate electrode is provided over the insulating layer.