Low voltage emission characteristics of the undoped polycrystalline diamond field emitter by MPCVD

Field emission characteristics of diamond films grown using a gas mixture with different methane concentration in hydrogen were investigated. Measured by using the field emitter with diode structure, the turn-on voltage (field) for emitting 0.1 mA/cm(2) current density and the critical electric field for 10 mA/cm(2) were 5 V(3 V/mu m) and 9 V(5 V/mu m), respectively for the diamond emitter of a little poor quality grown in 1.5% methane concentration. While for the good quality diamond emitter grown 0.5 % methane concentration, the values were shown as 10 V (6 V/mu m) and 21 V(13 V/mu m), respectively. It is suggested that this phenomena can be related with different NEA value, band of the surface states created by infernal stress or defects, and the field enhancement effect due to protruding small crystallites, depending on the film quality.