Determination of the critical ionization distance and ionization zone during high-temperature field evaporation of molybdenum

Abstract

Steady-state field evaporation of molybdenum at high emitter temperatures (T ∼ 2000 K) has been studied using a magnetic mass spectrometer equipped with a field ion source. Only low-charge ions (Mo⁺² and Mo⁺) have been observed in the course of evaporation. The measured ion energies and evaporating field strengths (F_ev) were used to determine the critical ionization distances (x_cr) and ionization zones (Δ) for singly and doubly charged ions. The obtained x_cr and Δ values show that the formation of ions takes place at a certain distance from the emitter surface.