Electron emission distribution from a single Spindt-type field emitter

Abstract

Summary form only given. RF power amplifier performance characteristics can be significantly enhanced if an emission modulated cathode source capable of producing current densities greater than 10 A/cm/sup 2/ under gigahertz modulation can be created. Refractory metal Spindt-type field emitter arrays (FEAs) are a promising candidate for the microfabricated emitter. Emission characterization of single- and multiple-tip arrays is imperative for the determination of array performance characteristics in order to design and implement Inductive Output Amplifiers (IOA) or integrable (on-chip) microtriode devices. For IOAs especially, knowledge of the beam spread is paramount in the design of the helix or cavity power extraction region. In this work, we provide a simple analytic model for gated field emitters useful for understanding the spatial dispersion of the emitted electrons and to correlate it with experimental measurements made on a single Spindt-type molybdenum field emitter. The analytical results are based on the Saturn Model of a gated field emitter, in which the emitter tip is approximated by a sphere, the gate by a ring of charge, and the anode by an external field. The experimental measurements were made using a nanofabricated anode whose position from the single gated emitter was determined using laser interferometry. The methods used to correlate theory with experiment are explained, and the dependence of the beam profile on tip sharpness, gate diameter, anode distance, and tip work function are examined.