Influence of the spot field on field emission from composites

Field emission from composite cathodes made of materials with greatly differing work functions (lanthanum hexaboride-pyrographite and hafnium carbide-pyrographite) and also from homogeneous lanthanum hexaboride cathodes, is studied experimentally. The effective emission from the composite cathodes the constituents of which differ greatly in work function and much worse emission properties of the homogeneous cathode are explained by making allowance for the influence of high (≥2 × 10⁷ V/cm) fields of spots arising at the contact of materials with different work functions on the field emission. The emission current density and the flow of electrons emitted under the action of the spot fields toward the anode are estimated by numerical computation.