Field-Emission Characteristics of Molded Molybdenum Nanotip Arrays With Stacked Collimation Gate Electrodes

Abstract

Double-gate field-emission characteristics of metallic field-emitter-array (FEA) cathodes fabricated by molding with stacked collimation gate electrodes with planar end plane are reported. The collimation of field-emission electron beam with minimal reduction of emission current is demonstrated when a negative bias is applied to the collimation gate, whereas when the two electrodes are at the same potential, the emission characteristic of the double-gate device is the same as that of the single-gate device that shows an emission current of 1 mA from 40 × 40 tip arrays. Results indicate that the device structure of the fabricated double-gate FEAs is promising for high-brilliance cathode applications

Electron beam collimation with a 40 000 tip metallic double-gate field emitter array and in-situ control of nanotip sharpness distribution

“…35 Patterning the gate apertures with this ratio was difficult with the polymer-etch back method but critically important to achieve a high current density enhancement with a small transverse electron velocity spread. [24][25][26] …”

“…These so-called double-gate FEAs have been proposed as high current and high brightness cathodes 15,16 and have been actively studied. [17][18][19][20][21][22][23][24][25][26] One of the critical obstacles for the realization of high performance double-gate FEAs is the reduction of the emission current during the beam collimation. Recent developments show that this can be circumvented by devising the gate aperture shapes as demonstrated with volcano-shaped FEAs 23 and stacked double-gate device with large G col apertures.…”

“…Recent developments show that this can be circumvented by devising the gate aperture shapes as demonstrated with volcano-shaped FEAs 23 and stacked double-gate device with large G col apertures. [24][25][26] For the practical application of FEAs it is important to prepare an array with uniform nanotip apex distribution. Due to the exponential sensitivity of the field emission current on the electric field at the emitter apexes, even a small nonuniformity of the emitter tip apex radius of curvature r tip results in a highly non-uniform beam across the array and limits the total current, making the requirement for the r tip uniformity stringent.…”

Fabrication of metallic double-gate field emitter arrays and their electron beam collimation characteristics

“…Research on field emitter arrays (FEAs) has been actively pursued [1][2][3][4][5][6][7][8][9][10][11][12][13] with the aim of realizing high current and high current density cathodes, e.g., for compact microwave vacuum electronic amplifiers, such as traveling wave tubes (TWTs) [14][15][16][17] and compact free electron lasers. 7,18 FEAs are expected to help simplify the gun design and extend the operation range of such TWTs.…”

“…More than a factor of 10 reduction of this divergence could significantly simplify the gun design to inject electrons into micro-machined waveguides for THz devices. 8,9 In addition, FEAs with a normalized transverse emittance below 0.1 mm mrad for a 1 mm diameter FEA and emission current densities of $1 kA cm À2 have a potential to improve the stability and performance of X-ray free-electron lasers significantly. 3,7 Such FEAs are also promising as cathodes for massively parallel electron beam lithography tools.…”