TRANSITION-METAL CARBIDES FOR USE AS FIELD-EMISSION CATHODES

Field emission characteristics of clean ZrC, HfC, and TaC cathodes are reported. High current density emission, greater than 1 X 10(8) A/cm2, is discussed, and a method for determining the cathode changes leading to this high current. emission condition is proposed. A close-spaced triode designed for testing individual emitters is described, and results are reported. The effective thermionic work functions of clean and partially oxygen covered surfaces of ZrC(x), specimens of two different bulk compositions are reported and discussed. Clean values of 3.5 and 3.4 eV were observed for ZrC0.92 and ZrC0.86 specimens, respectively, at 1500 K. With adsorbed oxygen, values as low as 3.4 and 3.2 eV, respectively, were observed for these surfaces at 1500 K.