Field emission cathode with emitters formed of acicular protrusions with secondary emitting protrusions formed thereon

A field emission cathode comprising:

• a substrate having formed thereon an emitter electrode layer, a dielectric layer and a gate electrode layer in this order;
• and
• an emitter having a structure in which plural gate openings are formed on the emitter electrode layer, the dielectric layer and the gate electrode layer being removed in the gate openings, and
• in which plural primary acicular protrusions for emitting electrons are developed from points each having an area smaller than that of each gate opening, the primary protrusions having tips that are separated from each other without overlapping, all of or part of the primary protrusions having secondary protrusions for emitting electrons formed thereon,
• wherein said primary protrusions extend from said emitter electrode layer in a first direction, and said secondary protrusions extend from said primary protrusions in directions different from said first direction.