Control of bulk and edge screening effects in two-dimensional arrays of ungated field emitters

In arrays of ungated field emitters, nearby emitters introduce a screening effect, reducing each emitter's field enhancement factor below its value in isolation. At the edge of the array, however, the strength of this screening effect is reduced because the number of nearby emitters is reduced, leading to a variation in the emitted current with position in the array. This may have detrimental effects on the emitted beam properties and lead to increased damage to the emitters near the edge due to increased current, heating, and ion bombardment. In this work, the authors apply line and point charge models to study the impact of screening on the performance of two-dimensional field emitter arrays, with an emphasis on quantifying the extent of the edge enhancement effect, and on assessing potential means to control it.