ELECTRON-EMISSION FROM A SINGLE SPINDT-TYPE FIELD EMITTER STRUCTURE -CORRELATION OF THEORY AND EXPERIMENT

The performance characteristics of rf power amplifiers will be signifi cantly enhanced if a cathode source capable of producing current densi ties greater than 10 A/cm(2) under gigahertz modulation can be created . Characterization of single- and multiple-tip arrays is imperative to determine performance characteristics in order to design and implemen t inductive output amplifiers (IOA): knowledge of the beam spread is p aramount in the design of the helix or cavity power extraction region. Nevertheless, a simple analytic model for gated field emitters for un derstanding the spatial dispersion of the emitted electrons has not em erged. We provide such a model, approximating the tip by a smooth sphe re and the gate by a ring of charge (Saturn model), and correlate it w ith experimental measurements made on a single Spindt-type molybdenum field emitter using a nanofabricated anode whose position from the emi tter was determined using laser interferometry. Methods used to correl ate theory with experiment are explained, and the dependence of the be am profile on tip sharpness, gate diameter, anode distance, and tip wo rk function are examined. There is good agreement between theory and e xperiment. Measurement has shown that the rms spread angle is between 15 degrees and 29 degrees.