Nanotip formation on a carbon nanotube pillar array for field emission application
TL;DR: In this paper, a carbon nanotube (CNT) pillar array has been improved significantly by plasma treatment in a mixture of hydrogen and nitrogen gases, which decreased the turn-on electric field from 0.48 to 0.37V∕μm and increased the field enhancement factor from 6200 to 6900.
Abstract: The field emission of a carbon nanotube (CNT) pillar array has been improved significantly by plasma treatment in a mixture of hydrogen and nitrogen gases. The plasma treatment for 30s on a pillar array decreased the turn-on electric field from 0.48to0.37V∕μm and increased the field enhancement factor from 6200 to 6900. The emission current density increased by a factor of ≈40. We report in this letter the technique of generating nanotips on CNT pillars with an enormous potential to become a tool for the control and manipulation of CNTs and nanostructures.
Citations
More filters
TL;DR: A review of the state-of-the-art in carbon nanotube-based field emission X-ray sources can be found in this article, where various fabrication techniques and functional advantages associated with their use, including the ability to produce ever smaller electron beam assembles, shaped cathodes, enhanced temporal stability and emergent fast switching pulsed sources.
Abstract: Since the discovery of X-rays over a century ago the techniques applied to the engineering of X-ray sources have remained relatively unchanged. From the inception of thermionic electron sources, which, due to simplicity of fabrication, remain central to almost all X-ray applications, there have been few fundamental technological advances. However, with the emergence of ever more demanding medical and inspection techniques, including computed tomography and tomosynthesis, security inspection, high throughput manufacturing and radiotherapy, has resulted in a considerable level of interest in the development of new fabrication methods. The use of conventional thermionic sources is limited by their slow temporal response and large physical size. In response, field electron emission has emerged as a promising alternative means of deriving a highly controllable electron beam of a well-defined distribution. When coupled to the burgeoning field of nanomaterials, and in particular, carbon nanotubes, such systems present a unique technological opportunity. This review provides a summary of the current state-of-the-art in carbon nanotube-based field emission X-ray sources. We detail the various fabrication techniques and functional advantages associated with their use, including the ability to produce ever smaller electron beam assembles, shaped cathodes, enhanced temporal stability and emergent fast-switching pulsed sources. We conclude with an overview of some of the commercial progress made towards the realisation of an innovative and disruptive technology.
129 citations
Cites background from "Nanotip formation on a carbon nanot..."
...By subsequent surface treatments, it is also possible to enhance the native FE characteristics of such arrays by means of the formation of nano tips, tepees and micro cones, as outlined previously [190,205]....
[...]
...In addition, if the emission pattern of the field emitter is not uniform CVD growth can result in individual CNTs, or structures such as CNT pillar arrays and toroids [160,167,188-191]....
[...]
TL;DR: In this paper, a plasma etching treatment for 3min on few layer graphene sheets (FLGSs), synthesized by plasma enhanced chemical vapour deposition, has been performed for enhancing their field emission properties.
Abstract: Plasma treatment in Ar gas on few layer graphene sheets (FLGSs), synthesized by plasma enhanced chemical vapour deposition, has been performed for enhancing their field emission properties. The plasma etching treatment for 3?min on the FLGSs, forming an extremely sharp edge, decreases the turn-on electric field from 3.91 to 2.23?V??m?1, and increases the maximum emission current density, drawn at a field of 4.4?V??m?1, from 33 to 1330??A?cm?2. It is expected that plasma treatment provides an efficient way to improve the field emission properties of FLGSs.
72 citations
TL;DR: In this article, the effects of nitrogen plasma (NP) treatment on the surface of carbon nanowalls (CNWs) have been investigated in order to improve the electron field emission properties.
Abstract: Carbon nanowalls (CNWs) are two-dimensional carbon nanostructures consisting of stacked graphene sheets standing vertically on the substrate. The sharp edges of CNWs provide us with opportunities for applications as electron field emitter arrays. The effects of nitrogen plasma (NP) treatment on the surface of CNWs have been investigated in order to improve the electron field emission properties. The electron emission current from the edges of CNWs was drastically increased by the NP treatment. Morphological and chemical changes in the CNWs after the NP treatment were characterized using scanning electron microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy.
58 citations
TL;DR: In this article, planar and morphologically disordered planar graphene (PG) and MDG were fabricated on the doped silicon substrate by transfer of as-grown graphene, which resulted in a dramatic increase in the maximum current density by a factor of 500, considerable increase in enhancement factor, and decrease in the turn-on field of MDG compared to PG.
Abstract: Graphene was synthesized on copper foil by thermal chemical vapor deposition technique. To investigate the field electron emission property, planar graphene (PG) and morphologically disordered graphene (MDG) were fabricated on the doped silicon substrate by transfer of as-grown graphene. Incorporation of morphological disorder in graphene creates more emission sites due to the additional defects, edges, and atomic scale ripples. This resulted in (1) a dramatic increase in the maximum current density by a factor of 500, (2) considerable increase in the enhancement factor, and (3) decrease in the turn-on field of MDG compared to PG.
50 citations
TL;DR: It is proposed that the nature of the tunneling barrier changes significantly for a nanosize tip at very high local electric field and may lead to the saturation in the emission current density.
Abstract: Nanostructures based on multiwalled carbon nanotubes (MWNTs) are fabricated using plasma of the mixture of hydrogen and nitrogen gases. The plasma-sharpened tips of nanotubes contain only a few tubes at the apex of the structure and lead to the dramatic enhancement in the emission current density by a factor >106 with the onset field as low as 0.16 V/μm. We propose that the nature of the tunneling barrier changes significantly for a nanosize tip at very high local electric field and may lead to the saturation in the emission current density.
38 citations
Cites background from "Nanotip formation on a carbon nanot..."
...tips with very few CNTs at the apex to give rise to very large electric field at the vicinity of the CNT tip.(14) At such high fields, these tips exhibit the field emission, which demonstrates the constancy of emission current at very low threshold voltage and a saturation region which can be explained by the tunneling of the electrons through a square hill potential barrier of constant value (V0)....
[...]
References
More filters
TL;DR: In this paper, a high-intensity electron gun based on field emission from a film of aligned carbon nanotubes has been made, which consists of a nanotube film with a 1-millimeter-diameter grid about 20 micrometers above it.
Abstract: A high-intensity electron gun based on field emission from a film of aligned carbon nanotubes has been made. The gun consists of a nanotube film with a 1-millimeter-diameter grid about 20 micrometers above it. Field-emission current densities of about 0.1 milliampere per square centimeter were observed for applied voltages as low as 200 volts, and current densities greater than 100 milliamperes per square centimeter have been realized at 700 volts. The gun is air-stable, easy and inexpensive to fabricate, and functions stably and reliably for long times (short-term fluctuations are on the order of 10 percent). The entire gun is only about 0.2 millimeter thick and can be produced with virtually no restrictions on its area, from less than 1 square millimeter to hundreds of square centimeters, making it suitable for flat panel display applications.
3,103 citations
TL;DR: The synthesis of massive arrays of monodispersed carbon nanotubes that are self-oriented on patterned porous silicon and plain silicon substrates is reported and the mechanisms of nanotube growth and self-orientation are elucidated.
Abstract: The synthesis of massive arrays of monodispersed carbon nanotubes that are self-oriented on patterned porous silicon and plain silicon substrates is reported. The approach involves chemical vapor deposition, catalytic particle size control by substrate design, nanotube positioning by patterning, and nanotube self-assembly for orientation. The mechanisms of nanotube growth and self-orientation are elucidated. The well-ordered nanotubes can be used as electron field emission arrays. Scaling up of the synthesis process should be entirely compatible with the existing semiconductor processes, and should allow the development of nanotube devices integrated into silicon technology.
3,093 citations
TL;DR: Field emission of electrons from individually mounted carbon nanotubes has been found to be dramatically enhanced when the nanotube tips are opened by laser evaporation or oxidative etching, in a process that resembles unraveling the sleeve of a sweater.
Abstract: Field emission of electrons from individually mounted carbon nanotubes has been found to be dramatically enhanced when the nanotube tips are opened by laser evaporation or oxidative etching. Emission currents of 0.1 to 1 microampere were readily obtained at room temperature with bias voltages of less than 80 volts. The emitting structures are concluded to be linear chains of carbon atoms, Cn, (n = 10 to 100), pulled out from the open edges of the graphene wall layers of the nanotube by the force of the electric field, in a process that resembles unraveling the sleeve of a sweater.
1,538 citations
TL;DR: In this paper, high-purity aligned multi-walled carbon nanotubes were synthesized through the catalytic decomposition of a ferrocene-xylene mixture at ; 6758C in a quartz tube reactor and over quartz substrates, with a conversion of ; 25% of the total hydrocarbon feedstock.
950 citations
TL;DR: In this article, the vibrational modes of carbon nanotubes are reviewed and the number of these modes is found to depend on the tubule symmetry and not on the diameter.
600 citations