scholarly journals Improvement of Lighting Uniformity and Phosphor Life in Field Emission Lamps Using Carbon Nanocoils

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Kun-Ju Chung ◽  
Nen-Wen Pu ◽  
Meng-Jey Youh ◽  
Yih-Ming Liu ◽  
Ming-Der Ger ◽  
...  
Keyword(s):  
Field Emission ◽  
Steel Wire ◽  
Chemical Vapor ◽  
304 Stainless Steel ◽  
Bright Spot ◽  
Growth Time ◽  
Multiwalled Carbon ◽  
Pd Catalysts ◽  
Spot Area ◽  
Glass Bulb

The lighting performances and phosphor degradation in field emission lamps (FELs) with two different kinds of cathode materials—multiwalled carbon nanotubes (MWCNTs) and carbon nanocoils (CNCs)—were compared. The MWCNTs and CNCs were selectively synthesized on 304 stainless steel wire substrates dip-coated with nanosized Pd catalysts by controlling the growth temperature in thermal chemical vapor deposition, and the film uniformity can be optimized by adjusting the growth time. FELs were successfully fabricated by assembling these cathode filaments with a glass bulb-type anode. The FEL with the CNC cathode showed much higher lighting uniformity and light-spot density and a lower current at the same voltage than that with the MWCNT cathode filament, and its best luminous efficiency was as high as 75 lm/W at 8 kV. We also found that, for P22, the phosphor degradation can be effectively suppressed by replacing MWCNTs with CNCs in the cathode, due to the much larger total bright spot area and hence much lower current density loading on the anode.

Optoelectronic characterization of morphology-controlled zinc oxide nanowires

2011 ◽  
Vol 1315 ◽  
Author(s):  
Shou-Yi Kuo ◽  
Fang-I Lai ◽  
Chun-Chieh Wang ◽  
Woei-Tyng Lin
Keyword(s):  
Field Emission ◽  
Visible Region ◽  
Chemical Vapor ◽  
Growth Time ◽  
Emission Measurement ◽  
Oxide Nanowires ◽  
Average Reflectance ◽  
Vertically Aligned ◽  
Metal Catalyzed

ABSTRACTIn this paper, we report the characterization of vertically aligned ZnO nanowire (NW) arrays synthesized by metal-catalyzed chemical vapor deposition. The growth mechanism of ZnO NWs may be related to vapor-solid-nucleation. Morphological, structural, optical and field emission characteristics can be modified by varying the growth time. For growth time reaches 120 min, the length and the diameter of ZnO NWs are 1.5 μm and 350 nm, and they also show preferential growth orientation along the c-axis. Moreover, strong alignment and uniform distribution of ZnO NWs can effectively enhance the antireflection to reach the average reflectance of 5.7% in the visible region as well. Field emission measurement indicated that the growth time play an important role in density- and morphology-controlled ZnO NWs, and thus ZnO NWs are expected to be used in versatile optoelectronic devices.

From Diamond to Carbon Nanotube Field Emitter

2001 ◽  
Vol 675 ◽  
Author(s):  
O. Gröning ◽  
L-O. Nilsson ◽  
P. Gröning ◽  
L. Schlapbach
Keyword(s):  
Thin Film ◽  
Distribution Function ◽  
Field Emission ◽  
Low Cost ◽  
Field Enhancement ◽  
Chemical Vapor ◽  
Multiwalled Carbon ◽  
Field Range ◽  
Field Emitter ◽  
Field Emission Properties

ABSTRACTIn this paper we review the physics and the expectations that were put into the negative electron affinity (NEA) mediated field emission of chemical vapor deposition CVD diamond films and how the emitter technology made possible by this mechanism could have challenged the classical metal micro-tip field emitter arrays. We discuss the dependency between emitter performance of micro-tip emitter arrays and feature size (size of the field enhancing tip) and due to this to the connection between emitter performance and fabrication costs.We introduce the concept of the field enhancement distribution function f(β) for a useful characterization of the field emission properties of thin film emitter and show how this distribution function can be measured by scanning anode field emission microscopy. Using f(β) measured on a thin film of randomly oriented multiwalled carbon nanotubes we show that even these kinds of low cost emitters can show a field emission performance comparable to micro-tip arrays, yet that the large spread in field enhancement values between the individual emitter prevent this performance to be fully exploited. This because the field range in which such thin film emitters can be operated is limited due to emitter disruption and triggering of vacuum arcs. Simulations show how resistor-limited emission can solve these limitations.

Field emission characteristics of carbon nanotubes synthesized by C3H4 and NH3 gases

2002 ◽  
Vol 727 ◽  
Author(s):  
Taewon Jeong ◽  
Jae Hee Han ◽  
Whikun Yi ◽  
SeGi Yu ◽  
Jeonghee Lee ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Field Emission ◽  
Gas Flow ◽  
Field Enhancement ◽  
Chemical Vapor ◽  
Emission Characteristics ◽  
Flow Ratio ◽  
Multiwalled Carbon ◽  
Turn On ◽  
Gas Flow Ratio

AbstractUsing a gas mixture of propyne (C3H4) and ammonia (NH3) as a carbon precursor, we have successfully synthesized multiwalled carbon nanotubes (CNTs) by the direct current (dc) plasma enhanced chemical vapor deposition (PECVD) onto Co-sputtered glass at 550°C. As the flow ratio of NH3 to C3H4 in the mixture gas increased, the crystallinity and alignment of CNTs were improved. In addition, the field emission characteristics of CNTs were also improved. the turn-on voltage became lower, and the current density and the field enhancement factor were more increasing. Raman spectroscopy and scanning electron microscopy were utilized to confirm the effect of the gas flow ratio on CNTs. Therefore, the gas flow ratio was found to be one of important factors to govern the crystalline and field emission characteristics of CNTs. The growth mechanism of CNTs using a C3H4 gas is under investigation with the possibility that three carbon atoms in a C3H4 molecule is converted directly to a hexagon of a CNT by combining two molecules.

scholarly journals Direct Deposition of Bamboo-Like Carbon Nanotubes on Copper Substrates by Sulfur-Assisted HFCVD

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
Sri Lakshmi Katar ◽  
Adolfo González-Berríos ◽  
Joel De Jesus ◽  
Brad Weiner ◽  
Gerardo Morell
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Substrate Temperature ◽  
Field Emission ◽  
Photoelectron Spectroscopy ◽  
Chemical Vapor ◽  
Carbon Films ◽  
Growth Time ◽  
Electron Field Emission ◽  
Electron Field

Films of bamboo-like carbon nanotubes (BCNTs) were grown directly on copper substrates by sulfur-assisted hot filament chemical vapor deposition (HFCVD). The effects of substrate temperature and growth time over the BCNT structure were investigated. The films were characterized by scanning electron microscopy (SEM), Raman spectroscopy (RS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electron field emission (EFE) studies. SEM and Raman characterization indicate a transition from the growth of microcrystalline diamond to the growth of a dense entangled network of carbon nanotubes or fibers as the substrate temperature is increased from 400 to900°Cthat is accounted for by the base growth model. TEM images show that the nanotubes have regular arrays of nanocavities. These BCNTs show good electron field emission properties as other carbon films.

Highly Efficient Field Emission from Carbon Nanotube−Nanohorn Hybrids Prepared by Chemical Vapor Deposition

ACS Nano ◽  
2010 ◽  
Vol 4 (12) ◽  
pp. 7337-7343 ◽  
Author(s):  
Ryota Yuge ◽  
Jin Miyawaki ◽  
Toshinari Ichihashi ◽  
Sadanori Kuroshima ◽  
Tsutomu Yoshitake ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Carbon Nanotube ◽  
Field Emission ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Highly Efficient

scholarly journals Field Emission from Carbon Films Deposited by Controlled-Low-Energy Beams and CVD Sources

1999 ◽  
Vol 585 ◽  
Author(s):  
Douglas H. Lowndes ◽  
Vladimir I. Merkulov ◽  
L. R. Baylor ◽  
G. E. Jellison ◽  
D. B. Poker ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Surface Morphology ◽  
Field Emission ◽  
Metal Ion ◽  
Ion Beam ◽  
Pyrolytic Graphite ◽  
Carbon Film ◽  
Chemical Vapor ◽  
Carbon Films ◽  
Damage Site

AbstractThe principal interests in this work are energetic-beam control of carbon-film properties and the roles of doping and surface morphology in field emission. Carbon films with variable sp3-bonding fraction were deposited on n-type Si substrates by ArF (193 nm) pulsed-laser ablation (PLA) of a pyrolytic graphite target, and by direct metal ion beam deposition (DMIBD) using a primary Cs+ beam to generate the secondary C- deposition beam. The PLA films are undoped while the DMIBD films are doped with Cs. The kinetic energy (KE) of the incident C atoms/ions was controlled and varied over the range from ∼25 eV to ∼175 eV. Earlier studies have shown that C films' sp3-bonding fraction and diamond-like properties can be maximized by using KE values near 90 eV. The films' surface morphology, sp3–bonding fraction, and Cs-content were determined as a function of KE using atomic force microscopy, TEM/EELS, Rutherford backscattering and nuclear reaction measurements, respectively. Field emission (FE) from these very smooth undoped and Cs-containing films is compared with the FE from two types of deliberately nanostructured carbon films, namely hot-filament chemical vapor deposition (HF-CVD) carbon and carbon nanotubes grown by plasma-enhanced CVD. Electron field emission (FE) characteristics were measured using ∼25-μm, ∼5-μm and ∼1-μm diameter probes that were scanned with ∼75 nm resolution in the x-, y-, and z-directions in a vacuum chamber (∼5 × 10-7 torr base pressure) equipped with a video camera for viewing. The hydrogen-free and very smooth a-D or a-C films (with high or low sp3 content, and with or without ∼1% Cs doping) produced by PLD and DMIBD are not good field emitters. Conditioning accompanied by arcing was required to obtain emission, so that their subsequent FE is characteristic of the arc-produced damage site. However, deliberate surface texturing can eliminate the need for conditioning, apparently by geometrical enhancement of the local electric field. But the most promising approach for producing macroscopically flat FE cathodes is to use materials that are highly nanostructured, either by the deposition process (e.g. HF-CVD carbon) or intrinsically (e.g. carbon nanotubes). HF-CVD films were found to combine a number of desirable properties for FE displays and vacuum microelectronics, including the absence of conditioning, low turn-on fields, high emission site density, and apparent stability and durability during limited long-term testing. Preliminary FE measurements revealed that vertically aligned carbon nanotubes are equally promising.

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