Internal Electron Emission in Phosphorus-Doped Polycrystalline Diamond Field Emitters

Temperature dependence of a field emission characteristics is investigated for a phosphorus(P)-doped polycrystalline diamond film as compared with that of an undoped one. The threshold voltage decreases with increasing temperature for a P-doped diamond film, while no variation in the threshold voltage occurs for an undoped diamond film. An increase in the ionized donor concentration with increasing temperature leads to a reduction in the tunnel barrier width at the interface between the diamond and the cathode, resulting in an enhancement of the emission current. This suggests that the internal electron emission determines the field emission characteristics. A reduction in the threshold voltage with increasing P-doping concentration can also be understood to be due to internal electron emission. Field emission characteristics in the higher voltage region features a space charge limited current.