Patent ID: 7863805

Claim:
A diamond electron emission cathode comprising 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, one electron emitting portion is provided in said sharpened acute section, said electron emitting portion and said heating section comprise a diamond semiconductor, said diamond semiconductor is a p-type semiconductor comprising p-type impurities at 2Ã—10 15 cm âˆ’3 or higher, said semiconductor is present in said electron emitting portion, a metal layer is formed on a surface of said electron emission cathode, said metal layer is present in at least part of said heating section, the shortest distance from said electron emitting portion to an end portion of the metal layer is 500 Î¼m or less, an electric current for heating is supplied to said heating section with a pair of current introducing terminals, and some of the introduced electrons can be emitted from said electron emitting portion.