Patent ID: 7737614

Claim:
A diamond electron emission cathode having single crystal diamond in at least part thereof, wherein: said diamond electron emission cathode has a columnar shape formed by a sharpened acute section and a heating section, is provided with one electron emitting portion in said sharpened acute section, and is constituted by at least two types of semiconductors that differ in electric properties, one of the at least two types of the semiconductors is an n-type semiconductor comprising n-type impurities at 2×10 15 cm −3 or higher, another of the at least two types is a p-type semiconductor comprising p-type impurities at 2×10 15 cm −3 or higher, the p-type semiconductor and the n-type semiconductor are joined together, the heating section is energized parallel to a junction surface of the p-type semiconductor and the n-type semiconductor and directly heated by a pair of current introducing terminals, and some of introduced electrons are emitted from said electron emitting portion.