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.

Effect of Catalyst Thickness and Plasma Pretreatment on the Growth of Carbon Nanotubes and Their Field Emission Properties

2007 ◽  
Vol 7 (11) ◽  
pp. 3731-3735 ◽  
Author(s):  
Hyung Soo Uh ◽  
Sang Sik Park ◽  
Byung Whan Kim
Keyword(s):  
Carbon Nanotubes ◽  
Field Emission ◽  
Field Enhancement ◽  
Close Relation ◽  
Emission Current Density ◽  
Ni Catalyst ◽  
Emission Characteristics ◽  
Field Emission Properties ◽  
Turn On ◽  
Plasma Pretreatment

We demonstrated that the diameter and the density of carbon nanotubes (CNTs) which had a close relation to electric-field-screening effect could be easily changed by the control of catalytic Ni thickness combined with NH3 plasma pretreatment. Since the diameter and the density of CNTs had a tremendous impact on the field-emission characteristics, optimized thickness of catalyst and application of plasma pretreatment greatly improved the emission efficiency of CNTs. In the field emission test using diode-type configuration, well-dispersed thinner CNTs exhibited lower turn-on voltage and higher field enhancement factor than the densely-packed CNTs. A CNT film grown using a plasma-pretreated 25 Å-thick Ni catalyst showed excellent field emission characteristics with a very low turn-on field of 1.1 V/μm @ 10 μA/cm2 and a high emission current density of 1.9 mA/cm2 @ 4.0 V/μm, respectively.

Plasma Enhanced Chemical Vapour Deposited Carbon Nanotubes for Field Emission Applications

2001 ◽  
Vol 706 ◽  
Author(s):  
K. B. K. Teo ◽  
G. Pirio ◽  
S.B. Lee ◽  
M. Chhowalla ◽  
P. Legagneux ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Field Emission ◽  
Chemical Vapour ◽  
Field Enhancement ◽  
Nanotube Arrays ◽  
Emission Characteristics ◽  
Electrical Measurements ◽  
Multiwalled Carbon ◽  
Uniform Array ◽  
Versatile Technique

AbstractPlasma Enhanced Chemical Vapour Deposition is an extremely versatile technique for directly growing multiwalled carbon nanotubes onto various substrates. We will demonstrate the deposition of vertically aligned nanotube arrays, sparsely or densely populated nanotube forests, and precisely patterned arrays of nanotubes. The high-aspect ratio nanotubes (~50 nm in diameter and 5 microns long) produced are metallic in nature and direct contact electrical measurements reveal that each nanotube has a current carrying capacity of 107-108 A/cm2, making them excellent candidates as field emission sources. We examined the field emission characteristics of dense nanotube forests as well as sparse nanotube forests and found that the sparse forests had significantly lower turn-on fields and higher emission currents. This is due to a reduction in the field enhancement of the nanotubes due to electric field shielding from adjacent nanotubes in the dense nanotube arrays. We thus fabricated a uniform array of single nanotubes to attempt to overcome these issues and will present the field emission characteristics of this.

Effect of Catalyst Thickness and Plasma Pretreatment on the Growth of Carbon Nanotubes and Their Field Emission Properties

2007 ◽  
Vol 7 (11) ◽  
pp. 3731-3735
Author(s):  
Hyung Soo Uh ◽  
Sang Sik Park ◽  
Byung Whan Kim
Keyword(s):  
Carbon Nanotubes ◽  
Field Emission ◽  
Field Enhancement ◽  
Close Relation ◽  
Emission Current Density ◽  
Ni Catalyst ◽  
Emission Characteristics ◽  
Field Emission Properties ◽  
Turn On ◽  
Plasma Pretreatment

We demonstrated that the diameter and the density of carbon nanotubes (CNTs) which had a close relation to electric-field-screening effect could be easily changed by the control of catalytic Ni thickness combined with NH3 plasma pretreatment. Since the diameter and the density of CNTs had a tremendous impact on the field-emission characteristics, optimized thickness of catalyst and application of plasma pretreatment greatly improved the emission efficiency of CNTs. In the field emission test using diode-type configuration, well-dispersed thinner CNTs exhibited lower turn-on voltage and higher field enhancement factor than the densely-packed CNTs. A CNT film grown using a plasma-pretreated 25 Å-thick Ni catalyst showed excellent field emission characteristics with a very low turn-on field of 1.1 V/μm @ 10 μA/cm2 and a high emission current density of 1.9 mA/cm2 @ 4.0 V/μm, respectively.

Highly Organized Carbon Nanotube-PDMS Hybrid System for Multifunctional Flexible Devices

2007 ◽  
Author(s):  
Yung J. Jung ◽  
Laila Jaber-Ansari ◽  
Xugang Xiong ◽  
Sinan Mu¨ftu¨ ◽  
Ahmed Busnaina ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Electric Fields ◽  
Composite Structures ◽  
Field Enhancement ◽  
Chemical Vapor ◽  
Casting Process ◽  
Dip Coating ◽  
Network Architectures ◽  
Multiwalled Carbon

We will present a method to fabricate a new class of hybrid composite structures based on highly organized multiwalled carbon nanotube (MWNT) and singlewalled carbon nanotube (SWNT) network architectures and a polydimethylsiloxane (PDMS) matrix for the prototype high performance flexible systems which could be used for many daily-use applications. To build 1–3 dimensional highly organized network architectures with carbon nanotubes (both MWNT and SWNT) in macro/micro/nanoscale we used various nanotube assembly processes such as selective growth of carbon nanotubes using chemical vapor deposition (CVD) and self-assembly of nanotubes on the patterned trenches through solution evaporation with dip coating. Then these vertically or horizontally aligned and assembled nanotube architectures and networks are transferred in PDMS matrix using casting process thereby creating highly organized carbon nanotube based flexible composite structures. The PDMS matrix undergoes excellent conformal filling within the dense nanotube network, giving rise to extremely flexible conducting structures with unique electromechanical properties. We will demonstrate its robustness under large stress conditions, under which the composite is found to retain its conducting nature. We will also demonstrate that these structures can be directly utilized as flexible field-emission devices. Our devices show some of the best field enhancement factors and turn-on electric fields reported so far.

Effect of Diameter on Electron Field Emission of Carbon Nanotube Bundles

2005 ◽  
Vol 901 ◽  
Author(s):  
Devon McClain ◽  
Mason DeRoss ◽  
Noel Tavan ◽  
Jun Jiao ◽  
Coralee M McCarter ◽  
...  
Keyword(s):  
Field Emission ◽  
Sol Gel ◽  
Field Enhancement ◽  
Chemical Vapor ◽  
Electron Field Emission ◽  
Nanotube Bundles ◽  
Turn On ◽  
Electron Field ◽  
Aggregate Structures ◽  
Field Emission Performance

AbstractArrays of multi-walled carbon nanotunbe (CNT) bundles were fabricated on silicon [100] substrate with iron-nitrate sol-gel catalyst patterned via standard photolithographic techniques. Nanotube bundles with diameters ranging from 400µm to 15µm were grown in a chemical vapor deposition reactor and electrically characterized using a scanning-anode probe apparatus. Results showed a relatively low number of graphitic layers in individual nanotubes and a definite increase in field emission performance with decreasing bundle diameter. A 400µm wide matt of CNTs yielded a turn-on field of 6.7 V/µm and field enhancement of 602 while 15µm bundles performed significantly better with turn-on fields of 1.6 V/µm and field enhancement factors of 2425. The overall trend strongly suggests that the field emission character of CNT based aggregate structures such as those presented here is proportional to their aspect ratio.

Effect of film chemistry on refractive index of plasma-enhanced chemical vapor deposited silicon oxynitride films: A correlative study

2008 ◽  
Vol 23 (5) ◽  
pp. 1433-1442 ◽  
Author(s):  
S. Naskar ◽  
S.D. Wolter ◽  
C.A. Bower ◽  
B.R. Stoner ◽  
J.T. Glass
Keyword(s):  
Refractive Index ◽  
Hydrogen Concentration ◽  
Photoelectron Spectroscopy ◽  
Gas Flow ◽  
Chemical Vapor ◽  
Silicon Oxynitride ◽  
Rf Plasma ◽  
Flow Ratio ◽  
Plasma Chemical Vapor Deposition ◽  
Gas Flow Ratio

Thick SiOxNy films were deposited by radiofrequency (rf) plasma chemical vapor deposition using silane (SiH4) and nitrous oxide (N2O) source gases. The influence of deposition conditions of gas flow ratio, rf plasma mixed-frequency ratio (100 kHz, 13.56 MHz), and rf power on the refractive index were examined. It was observed that the refractive index of the SiOxNy films increased with N and Si concentration as measured via x-ray photoelectron spectroscopy. Interestingly, a variation of refractive index with N2O:SiH4 flow ratio for the two drive frequencies was observed, suggesting that oxynitride bonding plays an important role in determining the optical properties. The two drive frequencies also led to differences in hydrogen concentration that were found to be correlated with refractive index. Hydrogen concentration has been linked to significant optical absorption losses above index values of ∼1.6, which we identified as a saturation level in our films.

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.

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