Edge enhancement control in linear arrays of ungated field emitters

Abstract

In arrays of ungated field emitters, the field enhancement factor of each emitter decreases as the distance between the emitters decreases, an effect known as screening. At the edge of these arrays, emitters experience reduced screening, leading to higher field enhancement factors than emitters at the array center, causing nonuniform emission across the array. Here, we consider this effect in linear arrays of ungated field emitters spaced at distances comparable to their heights, which is the regime that generally maximizes their average current density. A Line Charge Model is used to assess the degree to which these edge effects propagate into the array interior, and to study the impact of varying the height, location, and tip radius of emitters at the ends of an array on the edge enhancement. It is shown that each of these techniques can accomplish this edge enhancement control, but each has advantages and disadvantages that will be discussed.

100 years of the physics of diodes

“…73,77,[222][223][224][225] These studies are very useful for design of emitter arrays to optimize emitter spacing for maximum current density 225 (not including space charge effects) and avoiding edge effects. 226 However, the analysis of shielding has not properly taken into account the effect of space charge from one emitter in an array on its neighbors, and vice versa. This calls for a combined model of the three dimensional environment in the immediate neighborhood of the emitting protrusion and a model of the neighborhood of the entire emitter array.…”

Electric field distribution and current emission in a miniaturized geometrical diode

“…The theoretical analysis of the current rectification g here would provide insights into the design of geometric diode with optimal rectification efficiency for various applications. [13][14][15][16][17][18][19][20][21][22][23] Figures 6(a) and 6(b) show the effective field enhancement factors b eff 1;2 as a function of a/h for d/h ¼ 1.3, 2, and 10, with a ¼ p/2. For a given d=h, as a=h increases, b eff 1 decreases, while b eff 2 increases.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12] The geometrically asymmetric metal-vacuum (insulator)-metal nanoscale diode shows great potential for applications in energy harvesting and energy conversion in solar cells, [13][14][15] as well as for high power high frequency applications in signal rectification and electron source development. 2, [16][17][18][19][20][21][22][23] Bringing a sharp anode tip sufficiently close to the graphene surface has realized electron emission from flat graphene surfaces. 24 Thus, it is of value to assess the electrical field distribution and current emission inside the miniaturized A-K gap and their asymmetry introduced by the protruding surface of the electrode.…”

Field emission characteristics of a small number of carbon fiber emitters

“…[14][15][16][17][18][19] We can analyze these geometries in terms of nearest-neighbor emitter attributes by comparing each of the four configurations considered in this paper. Notably, linear and square arrays, quite obviously, share common geometrical attributes that influence the overall field enhancement of the arrays.…”

“…Hence, in previous work, we explored the emission characteristics of two-and four-fiber arrays of carbon emitters in a carefully prepared, simple geometry. [13][14][15][16][17][18][19] Our configuration allows a much more pristine and straightforward experimental geometry for isolating and interpreting the electric field screening from other effects such as work function variation across the cathode surface or statistical inhomogeneities in the geometry of the individual emitters that comprise the array.…”