Abstract
High-temperature field emission of Re, Pt, Ta, and W is studied by field-emission methods. Metal ions are found to evaporate mainly from the tops of thermal-field microprotrusions produced by high electric fields and temperatures on the emitter surface. For fi eld intensities of up to F=1–2 V/A and temperatures of 1500–2000 K, the ion currents i are recorded from the entire emitter surface. They range from several tenths of nanoamperes to several nanoamperes. The activation energies of field evaporation determined from the Arrhenius plots logi=f(1/T) are found to be appreciably lower than those calculated within the charge exchange model for known parameters of the process and the metals evaporated. Reasons for such a difference in the activation energies and mechanisms of ion evaporation at high F and T are discussed.
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