Enhanced thermionic electron emission from a stacked structure of phosphorus-doped diamond with a nitrogen-doped diamond surface layer

A novel stacked emitter based on phosphorus-doped diamond with a nitrogen-doped diamond surface layer was fabricated for enhanced thermionic emission. The emission current of the emitter was 18 mA cm−2 at 893 K and exhibited a significant increase compared to the emission current 6 mA cm−2 observed in a nitrogen-doped emitter and 1 mA cm−2 observed in a phosphorus-doped emitter. This remarkable emission is attributed to the reduction of the film resistance owing to the presence of a phosphorus-doped layer and to a low effective work function with weak upward band bending owing to the presence of the nitrogen-doped surface layer.