An electron-emission mechanism for cold cathodes is described based on
the enhancement of electric fields at metal-diamond-vacuum triple jun
ctions. Unlike conventional mechanisms, in which electrons tunnel from
a metal or semiconductor directly into vacuum, the electrons here tun
nel from a metal into diamond surface states, where they are accelerat
ed to energies sufficient to be ejected into vacuum. Diamond cathodes
designed to optimize this mechanism exhibit some of the lowest operati
onal voltages achieved so far.