Stable, self-ballasting field emission from zinc oxide nanowires grown on an array of vertically aligned carbon nanofibers

Abstract

A structure composed of zinc oxide nanowires (ZNWs) grown hydrothermally on an array of vertically aligned carbon nanofibers (CNFs) was fabricated and its field emission properties determined and compared with bare CNF arrays. The combination produced a macroscopic turn-on field of 1.2 V/μm which was found to be the lowest reported from ZNWs deposited on a two-dimensional substrate and much less than the equivalent CNFs array (5.2 V/μm). Crucially, field emission was found to be much more stable at higher pressures of 5×10−6 mbar without exhibiting current degradation for a fixed external field, while emitting with a current density of 1 mA/cm2, the current density typically required for backlighting and field emission displays. We propose a self-ballasting mechanism, in which the low carrier density in the zinc oxide prevents current runaway in the presence of adsorbed species.

X-ray generation using carbon nanotubes

“…As discussed previously, such low work function adlayers do indeed increase the emission current density, though they also, depending on the adlayer material and means of deposition, hermetically seal the CNTs -which act as a high aspect support structure -thereby increasing the emitters stability [225].…”

“…Yet to be applied immediately to the design of an X-ray source, the group of Milne have developed a novel field effect transistor (FET) ballasted field emission source, where each individual CNF electron source is equipped with its own dedicated FET ballast layer which is capable of limiting, and electronically controlling, the emission current to prevent emitter sublimation and significant temporal instabilities [183]. Other thin film deposition techniques have also been considered [204,225] though these too have yet to gain any significant interest.…”

Growth of ZnO nanowires on multi-layered polymer structures fabricated by UV liquid transfer imprint lithography

“…Since the zinc and oxide planes are electrically charged by the polar Zn-O bonds [2], ZnO has been synthesized in a variety of nano-morphologies, including wires, rings, belts, flowers, and particles, each applicable to different device designs. ZnO nanowires in particular have been rigorously studied as one-dimensional (1-D) nanostructures for optical [3][4][5][6][7][8], biological [9][10][11][12], electrical [3,7,[13][14][15][16][17], and sensing devices [7,18].…”

Suppressed Hysteretic Field Emission from Polymer Encapsulated Silver Nanowires

“…Though certainly not all, most mechanisms proposed relate to the fine physiochemistry of the emitters surface. Emitter encapsulation has been shown elsewhere to enhance the temporal stability of various one-dimensional nanoscale electron sources [14,15], with various polymer adlayers [16][17][18][19][20] evidencing potential as emission enhancing and hysteresis suppressing over-coatings. Here, via broadband optical excitation, we investigate the hysteretic field emission performance of percolative networks of polyvinylpyrrolidone (PVP) encapsulated Ag NWs.…”