Large Field Emission Current Density Research Articles

High-current field emission from “flower-like” few-layer graphene grown on tip of nichrome (8020) wire

ABSTRACTWe report a novel tip-type field emission (FE) emitter by synthesizing the few-layer graphene (FLG) flakes on tip of nichrome (8020) wire (ϕ≈80 μm) by microwave plasma enhanced chemical vapor deposition(PECVD). These resultant random arrays of free-standing FLG flakes are aligned vertically to the substrate surface in a high-density and stacked to each other to form several larger “flower-like” agglomerates in spherical shapes. The FE performance of the tip-type FLG flakes emitter shows a low threshold field of 0.55 V/μm, a large field enhancement factor of 9455 ± 46, a large field emission current density of 22.18 A/cm2 at 2.70 V/μm, and an excellent field emission stability at high emission current densities (6.93 A/cm2). It can be used in variety of applications that include cathode-ray tube monitors, X-ray sources, electron microscopes, and other vacuum electronic applications.

Large field emission current from Si-doped AlN film grown by MOCVD on n-type (001) 6H-SiC

A large field emission current density of 2.55A/cm2 at 20.9V and a low turn-on voltage of 7.28V is obtained from the Si-doped 50nm-thick AlN film, synthesized by metalorganic chemical vapor deposition on the n-type SiC substrates, which is the best result reported for AlN film. Accompanying with atomic force surface micro-images, it is found that this current is achieved owing to a blunting process under a high voltage of 95V, which can lead to a decrease of the root mean square roughness from 4.23 to 1.03nm.

A theoretical analysis of field emission from graphene nanoribbons

The characteristics of field-emission current of a graphene nanoribbon along the direction without finite size effect in the graphene sheet have been theoretically studied. After the work function of graphene nanoribbon is assumed not to change with its width, numerical calculations show that field-emission current density at a given external field decreases with decreasing width of nanoribbon. Such a decrease is especially large when the width of graphene ribbon is a few nanometers. Thus it will lead to an increase in the turn-on electric field. Numerical calculations also show that the effect of the image potential on the field-emission current density decreases with decreased temperature. This implies that to ensure in a workable field-emission device fabricated by graphene nanoribbon, a wider nanoribbon is needed to keep a large field-emission current density.

Molecular Template Assisted Growth of Ultrathin Silicon Carbide Nanowires with Strong Green Light Emission and Excellent Field‐Emission Properties

A novel molecule template assisted chemical co-reduction method has been successfully developed for the controlled synthesis of ultrathin beta-SiC single-crystalline nanowires on a large scale. The ultrathin beta-SiC single-crystalline nanowires are about 8 nm in diameter and 200-800 nm in length. The resulting thin beta-SiC single-crystalline nanowire is new in the family of beta-SiC one-dimensional (1D) nanostructures. A synergistic action of pi-stacking and steric hindrance result from the 1,10-phenanthroline molecule template are proposed to explain the growth mechanism of the ultrathin beta-SiC single-crystalline nanowires based on the experimental observation. Importantly, such ultrathin beta-SiC nanowire has shown a strong structure-induced enhancement of photoluminescence properties and has exhibited a very strong green light emission, which can be seen by naked eye. Furthermore, the unique beta-SiC ultrathin nanowire structure exhibits a low turn-on field (3.57 V microm(-1)) and a large field-emission current density (20 mA cm(-2)). These results suggest that the ultrathin beta-SiC nanowires can be expected to find promising applications as field emitters and photoelectronic devices.

Large field emission current density from well-aligned carbon nanotube field emitter arrays

We have grown well-aligned carbon nanotube arrays by thermal chemical vapor deposition at temperatures below 800°C on Fe nanoparticles deposited by a pulsed laser on a porous Si substrate. Porous Si substrates were prepared by the electrochemical etching of p-Si (1 0 0) wafers with resistivities of 3–6 Ω cm . These well-aligned carbon nanotube field emitter arrays are suitable for electron emission applications such as cold-cathode flat panel displays and vacuum microelectronic devices like microwave power amplifier tubes. Field emission characterization has been performed on the CNT-cathode diode device at room temperature and in a vacuum chamber below 10 −6 Torr. The anode is maintained at a distance of 60 μm from the carbon nanotube cathode arrays through an insulating spacer of polyvinyl film. The measured field emitting area is 4.0×10 −5 cm 2 . Our carbon nanotube field emitter arrays emit 1 mA/cm 2 at an electric field of 2 V/μm; they emit a large current density as high as 80 mA/cm 2 at 3 V/μm, which is orders of magnitude higher than any other results reported so far. The open tip structure of our carbon nanotubes and their good adhesion through Fe nanoparticles to the Si substrate are part of the reason why we can attain a large field emission current density within a low field. The field emitter arrays in our diode device are vertically well-aligned carbon nanotubes on the Si-wafer substrate.

Large Field Emission from Vertically Well-aligned Carbon Nanotubes

AbstractWe have grown well-aligned carbon nanotube arrays by thermal chemical vapor deposition at 800°C on Fe nanoparticles deposited by a pulsed laser on a porous Si substrate. Porous Si substrates were prepared by the electrochemical etching of p-Si(100) wafers with resistivities of 3 to 6 ωcm. These well-aligned carbon nanotube field emitter arrays are suitable for electron emission applications such as cold-cathode flat panel displays and vacuum microelectronic devices like microwave power amplifier tubes. Field emission characterization has been performed on the CNT-cathode diode device at room temperature and in a vacuum chamber below 10−6 Torr. The anode is maintained at a distance of 60[.proportional]m away from the carbon nanotube cathode arrays through an insulating spacer of polyvinyl film. The measured field emitting area is 4.0×10−5cm2. Our carbon nanotube field emitter arrays emit 1mA/cm2at the electric field, 2V/[.proportional]m. And they emit a large current density as high as 80mA/cm2 at 3V/[.proportional]m. The open tip structure of our carbon nanotubes and their good adhesion through Fe nanoparticles to the Si substrate are part of the reason why we can attain a large field emission current density within a low field. The field emitter arrays in our diode device are vertically well-aligned carbon nanotubes on the Si-wafer substrate.

Fabrication and characteristics of an emitter-sharpened double-gate racetrack-shaped field emitter structure

In this article, numerical and experimental characterizations of an emitter-sharpened double-gate racetrack-shaped field emitter structure are reported. The racetrack-shaped edge emission with double-gate control is used to provide good uniformity, large field emission current density, and small turn-on voltage. In order to improve the performance of this structure further, an emitter-sharpened structure is used to minimize gate current. Experimental results show that the gate current of the emitter-sharpened double-gate structure is 7 times and 15 times smaller than that of the nonemitter-sharpened double-gate structure and the single-gate structure, respectively. Simulated results also show that the gate current of the emitter-sharpened double-gate structure can almost be eliminated.

Numerical and experimental characterization of single- and double-gate race-track-shaped field emitter structures

In this paper, numerical and experimental characterization of new singleand double-gate race-track-shaped field emitter structures are reported. The race-track-shaped edge emission is used to provide good uniformity and large field emission current density, and the double-gate control is used to provide small turn-on voltage and minimum gate current. Experimental results show that the turn-on voltage of the single-gate structure is approximately 100 V, and the field emission current density is approximately 2.4 A/cm/sup 2/. Furthermore, field emission characteristics of the single- and double-gate structures are numerically simulated. Results show that turn-on voltage of the double-gate structure is reduced by 30% and ratio of anode current to gate current is increased by 36 times compared to that of the single-gate structure at a gate voltage of 350 V.