The first layer is seeded with nanodiamond particles. The substrate with the first layer disposed thereon is maintained at a first temperature and a first pressure in a mixture of gases which includes nitrogen. The first layer is exposed to a microwave plasma to form a nitrogen doped ultrananocrystalline diamond film on the first layer, which has a percentage of nitrogen in the range of about 0.05 atom % to about 0.5 atom %. The field emitter has about 10¹² to about 10¹⁴ emitting sites per cm². A photocathode can also be formed similarly by forming a nitrogen doped ultrananocrystalline diamond film on a substrate similar to the field emitter, and then hydrogen terminating the film. The photocathode is responsive to near ultraviolet light as well as to visible light.

Benefits

• Prototype planer filed emission based electron source for RF injectors in accelerators 
• At surface gradients 45–65 MV/m, peak currents of 1–80mA were achieved. 
• Good operation at moderate high vacuum (10^-6 Torr)