Cold cathode

A field emission device comprising:

• a substrate of either a conductive type or a semiconductive type;
• an insulating layer deposited on said substrate;
• a first metal layer deposited on said insulating layer;
• minute emitters each with a pointed tip formed of an electrode of either a conductive type or a semiconductive type, and provided in cavities formed in parts of said metal layer and said insulating layer, said metal layer, said insulating layer, said cavities and said minute emitters being formed in a matrix aroumd a center portion of the field emission device, wherein the center portion of the field emission device is for protecting the emitters of said plural elements from ions and has a diameter much longer than the distance between two emitters next to each other, and
• a second metal layer formed directly on said first metal layer at said center portion of said substrate, said second metal layer having a greater thickness than that of said first metal layer.

A field emission device comprising:

• a substrate;
• an insulating layer formed on said substrate;
• a metal layer formed on said insulating layer;
• cavities formed in said insulating and metal layers;
• emitters formed in at least some of said cavities in a matrix around a center portion of the field emission device wherein the center portion of the field emission device is for protecting the emitter of said plural elements from ions and has a diameter much longer than the diameter between two emitters next to each other;
• and
• means for protecting said emitters from ions which impact on a center portion of said field emission device.