Field-Emission Characteristics from Wide-Bandgap Material-Coated Carbon Nanotubes

Yi, Whikun; Jeong, Tae Moon; Yu, SeGi; Heo, Jungna; Lee, C. S.; Lee, J. H.; Kim, W. S.; Yoo, Jae‐Hyoung; Kim, J. M.

doi:10.1002/1521-4095(20021016)14:20<1464::aid-adma1464>3.0.co;2-4

Cited by 136 publications

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“…Figure 1 shows the X-ray diffraction pattern of multiwall(MW) CNTs as-CVD-grown by Illjin Nanotech (Korea) which were made with a purity of 98 % having uniform diameter of 20 ∼ 30 nm. [14] XRD patterns of NiO coated CNT, Ni coated CNT and bare CNT were shown in Figures 1(a), (b), and (c), respectively. Taking into account the experimental error of 5 % in XRD, the MWCNTs were considered to be identical graphite spacing of 0.34 nm.…”

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“…[13,14] Such a coating gives excellent emission characteristics and protection from adsorption or ion bombardment of residual gas molecules in the vacuum cavities such as display panel or field-emission lamps.…”

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“…Accordingly LiF, [8] CaF 2, [9] AlN [10] and c-BN [11] were applied to metal emitters to decrease the effective work function of emitters, which correspondingly increases emissivity and also MgO and SiO 2 were applied to CNT emitters. [13,14] Such a coating gives excellent emission characteristics and protection from adsorption or ion bombardment of residual gas molecules in the vacuum cavities such as display panel or field-emission lamps.…”

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Enhanced Field‐Emission Obtained from NiO Coated Carbon Nanotubes

Yang¹,

Park²,

Cho³

2007

Adv Eng Mater

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Carbon nanotubes(CNTs) have drawn much interests because of their unique electrical, mechanical properties and their potential applications in field emission displays, sensors, transistors, nano-tweezers and AFM tips. [1][2][3][4] Above all, the field emission from CNTs have been extensively studied due to the nanometer-size diameter, structural integrity, high electrical conductivity and chemical stability after first demonstration in 1995. [5] According to Fowler-Nordheim's theory the FE current density (J) is a function of the electric field E and the work function f of emitter. [6,7] For metal, with typical work function and a flat surface the threshold field is typically around 10 4 V/lm, but it can be easily generated by the field-enhancing properties of tip-like structures such as CNT. All the field emission sources rely on the field enhancement originated from the apex of a needle of height and radius. A CNT with a diameter of 10 nm and a length of 2 lm was reported to exhibit a field-enhancement factor (b) up to 400 which is equal to the ratio of height/radius and the field emission from CNTs can be generated at the apex of CNT by a very low applied field of 7.5 V/lm.In advances in research, the enhancement of the fieldemission properties was achieved by coating the emitter's tip with wide band gap materials (WBGM). Accordingly LiF, [8] CaF 2,[9] AlN [10] and c-BN [11] were applied to metal emitters to decrease the effective work function of emitters, which correspondingly increases emissivity and also MgO and SiO 2 were applied to CNT emitters. [13,14] Such a coating gives excellent emission characteristics and protection from adsorption or ion bombardment of residual gas molecules in the vacuum cavities such as display panel or field-emission lamps.In this communication, we introduce NiO coated CNT emitters for enhancing the field-emission properties in terms of electron emissivity and structure stability protective from residual gas and corrosive environment as well. Since the field emission lighting devices comprise a planar substrate with arrays or bundle of emitters (cathode) and a phosphor coated display screen (anode) that is mounted in a parallel with the cathode plate for the electron bombardment from emitters.The both cathode and anode plates are assembled with micron scale spacers in between and sealed using frit glass under high vacuum grade. The pressure inside the device panel would be 10 -6 ∼ 10 -5 Torr. The inside pressure will be always degraded by the residual gas evaporating from the inner walls of phosphor layer during device operation. Besides the ion arcing from residual gas will deteriorate the emitting CNT tips resulting in a critical reduction of brightness. The authors developed CNTs coated all around with NiO in nanoscale aiming at the enhanced field-emission and environmental inertness for long life of electron emitter. The coating of NiO around CNTs was possible employing an electroless plating technique. Figure 1 shows the X-ray diffraction pattern of multiwall(MW) CNTs as-...

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Enhanced Field‐Emission Obtained from NiO Coated Carbon Nanotubes

Yang¹,

Park²,

Cho³

2007

Adv Eng Mater

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“…The most successful approaches proposed for the generation of promising starting blocks for vacuum electronic systems have been the embedding of nanotubes in a non-conductive polymer matrix 6 and the coating of CNTs with wide band gap materials (WBGMs). 7,8 One must consider that both non-conductive matrices and WBGM coatings are able to reduce the effective work function of the CNTs and the turn-on field for electron emission. Moreover, WBGM coatings are expected to act as a mechanical protection for the sharp conductive emitters.…”

Section: Silvia Orlanduccimentioning

confidence: 99%

Nanodiamonds for field emission: state of the art

Terranova

Orlanducci

Rossi³

et al. 2015

Nanoscale

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The aim of this review is to highlight the recent advances and the main remaining challenges related to the issue of electron field emission (FE) from nanodiamonds. The roadmap for FE vacuum microelectronic devices envisages that nanodiamonds could become very important in a short time. The intrinsic properties of the nanodiamond materials indeed meet many of the requirements of cutting-edge technologies and further benefits can be obtained by tailored improvements of processing methodologies. The current strategies used to modulate the morphological and structural features of diamond to produce highly performing emitting systems are reported and discussed. The focus is on the current understanding of the FE process from nanodiamond-based materials and on the major concepts used to improve their performance. A short survey of non-conventional microsized cold cathodes based on nanodiamonds is also reported. IntroductionMiniaturized electron sources based on the field emission (FE) process, namely "cold-cathodes", are nowadays replacing the conventional thermoionic electron sources. FE-based devices are able to operate at high frequency and at high current densities, have no need of heating and are characterized by reduced weight and by instantaneous switching on. Moreover, Maria Letizia TerranovaProfessor of Chemistry at Tor Vergata University of Rome (Italy), Maria Letizia Terranova heads the Minima lab at the Department of Chemical Science and Technology. She has expertise on different scientific topics, including nuclear chemistry, laser-induced reactions in the gas-phase, ion-and laserinduced modifications in solids, electrochemical and vapour deposition processes. Her research activity is mainly focused on the synthesis, processing and functional testing of nanomaterials: carbon nanostructures (nanodiamonds, nanotubes, graphenes, onions), nanocomposites and hybrid organic/ inorganic structures. Materials and systems are produced for applications in micro/nano-electronics, optoelectronics, energetics, sensing, thermal management and bio-related nanotechnologies. She has co-authored 290 papers, 4 patents, and co-edited 4 books. Silvia OrlanducciIn 2004 Fowler-Nordheim and the experiments by Spindt and coworkers 3 paved the way for a number of subsequent researches on FE-based vacuum electronics. The good performance of such devices is based on the fact that, according to the Fowler-Nordheim law, the emitted current density J depends strongly on the local applied electric field E and that geometric factors typical of nanostructures (sharp edges, tips, peaks, nanoprotrusions) locally increase the concentration of electric field at the emitter sites. The ratio of the local field to the applied field, the so-called electric field enhancement factor β, 1 independently of the material, is a key factor influencing the field emission characteristics. In the last two decades the design, realization and application of a new generation of cold cathodes based on advanced nanomaterials have been the object of tremendous i...

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“…6,7 This problem has been tackled by coating the tips of the CNTs with wide band gap materials that have a small electron affinity, such as magnesium oxide, nickel oxide, and silicon dioxide. [8][9][10][11] Hafnium(IV) oxide (HfO 2 ) was selected as the coating material for the CNTs in this study because of its chemical stability at high temperature, excellent electrical conductivity, high melting point (3056 K), high dielectric constant (e 1 ¼ 4), low electron affinity (EA ¼ 2), and large band gap (6 eV). 12 Atomic layer chemical vapor deposition was employed for coating the CNT emitter with hafnium oxide, rather than other methods such as magnetron sputtering, plasma-assisted chemical vapor deposition, electroless plating, or other routine chemical methods.…”

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