Field emission from phosphorus-doped polycrystalline diamond films

Field emission characteristics have been investigated for P-doped polycryst alline diamond films. It is demonstrated that the turn-on voltage of the el ectron emission decreases with increasing temperature for the P-doped diamo nd film, while no variation in the turn-on voltage occurs for the undoped d iamond film. The temperature-dependent field emission characteristics are f ound to be inherent to the P-doped diamond film. A behavior of the field em ission characteristics can be well explained by means of the thermionic fie ld emission model combined with the temperature dependence of the ionized d onor concentration. This means that an increase of the ionized donor concen tration with increasing temperature may lead to a reduction in the tunnel b arrier width at the interface between the diamond and the cathode, resultin g in an enhancement of the internal emission current. It is suggested that the internal electron emission is important to the field emission character istics of the P-doped diamond films. A variation in the field emission char acteristics of P-doped diamond films with various cathode metals and with v arious P-doping concentrations can be consistently understood on the basis of the internal electron emission model. (C) 1999 American Institute of Phy sics. [S0021-8979(99)01317-1].