Electron Transport and Anode Heating Due to Field Emission From Carbon Nanotubes

2002 ◽  
Author(s):  
D. G. Walker ◽  
T. S. Fisher
Keyword(s):  
Carbon Nanotubes ◽  
Field Emission ◽  
Anode Surface ◽  
Electron Trajectory ◽  
Coulomb Interactions ◽  
Turn On ◽  
Large Current ◽  
Ring Diameter ◽  
Current Densities ◽  
Vacuum Gap

Carbon nanotubes (CNT) are being considered for field emission applications because of their low turn-on voltage and ability to support large current densities. The localization of emission and large currents from CNTs result in significant anode heating. The present work investigates the electron energy distribution at the anode surface through simulation of the field emission process and the trajectory of electrons across the vacuum gap. Field emission is modeled by Fowler-Nordheim-like expressions where the emission site is assumed to be a ring with the diameter of a nanotube. The electron trajectory is determined through a Monte Carlo simulation including Coulomb interactions between electrons. Results indicate that the electron beam spreads due to Coulomb interaction, but that the initial ring is preserved. In fact, the ring diameter at the anode spreads to 3μ per 10μ of vacuum gap in a field of 10 Vμm. This estimate matches well with reported observations. Further, the spreading becomes more significant with increased fields due to the higher current density of field emitted electrons.

Field Emission with Ultralow Turn On Voltage from Metal Decorated Carbon Nanotubes

ACS Nano ◽  
2014 ◽  
Vol 8 (8) ◽  
pp. 7763-7770 ◽  
Author(s):  
Srividya Sridhar ◽  
Chandrasekhar Tiwary ◽  
Soumya Vinod ◽  
Jose Jaime Taha-Tijerina ◽  
Srividvatha Sridhar ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Field Emission ◽  
Turn On

Low turn-on voltage field emission triodes with selective growth of carbon nanotubes

2001 ◽  
Vol 22 (11) ◽  
pp. 516-518 ◽  
Author(s):  
K.J. Chen ◽  
W.K. Hong ◽  
C.P. Lin ◽  
K.H. Chen ◽  
L.C. Chen ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Field Emission ◽  
Selective Growth ◽  
Turn On

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.

Comparison of Field Emission Performance for Different Diameter Carbon Nanotubes Films

2012 ◽  
Vol 486 ◽  
pp. 47-50 ◽  
Author(s):  
Gang Chen ◽  
Hui Zhong Ma ◽  
Lan Zhang ◽  
Hong Ye Chen ◽  
Qiue Xia ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Field Emission ◽  
Deposition Method ◽  
Emission Properties ◽  
Field Emission Properties ◽  
Turn On ◽  
Aluminum Sheets ◽  
Deposited Film ◽  
Field Emission Performance ◽  
Scanning Electron

Three kinds of different diameter carbon nanotubes (CNTS) films deposited on aluminum sheets by electrophoretic deposition method. Scanning electron microscopy was used to observe the surface morphology of the films. The field emission properties of the films were tested by using a diode structure. The turn-on field for 8nm diameter CNTs film was 0.8V/μm and the current density of 5200μA/cm2 was obtained at 2.3V/μm. While corresponding data for 15nm and 30nm CNTs films were 1.6V/μm, 1.4V/μm, and 2200μA/cm2, 850μA/cm2 at 3.0V/μm respectively. The deposited film with 8nm diameter CNTs appeared excellent emission properties.

Mechanism of Efficient Field Emission from Carbon Nanotubes

1999 ◽  
Vol 558 ◽  
Author(s):  
W. Zhu ◽  
C. Bower ◽  
O. Zhou ◽  
G. P. Kochanski ◽  
S. Jin
Keyword(s):  
Carbon Nanotubes ◽  
Electric Fields ◽  
Emission Characteristics ◽  
Emission Pattern ◽  
Cold Cathodes ◽  
Microelectronic Devices ◽  
Large Current ◽  
Large Current Density ◽  
Vacuum Microelectronic ◽  
Current Densities

ABSTRACTWe report observation of electron emission from individual carbon nanotubes. Two classes of emitters are observed, one emitting electrons with momentum nearly parallel to the nanotube axis, the other emitting electrons with nonzero momentum perpendicular to the tube axis. The emission pattern reflects the electronic structure of a particular tube and allows us to distinguish between structurally different nanotubes. These nanotube emitters exhibit excellent macroscopic emission properties; they can operate at a very large current density, as high as 4 A/cm2. At electric fields as low as 4-7 V/μm, they emit technologically useful current densities, e.g. 10 mA/cm2. The emission characteristics and durability of the carbon nanotube cold cathodes offer promising applications for vacuum microelectronic devices.

Fabrication of Field Emitter Arrays of Carbon Nanotubes Aligned on Patterned Substrates using Self-Assembly Monolayer

2003 ◽  
Vol 772 ◽  
Author(s):  
Ok-Joo Lee ◽  
Soo-Hwan Jeong ◽  
Kun-Hong Lee
Keyword(s):  
Carbon Nanotubes ◽  
Polymer Film ◽  
Silicon Wafer ◽  
Field Emission ◽  
Self Assembly ◽  
Room Temperature ◽  
Emission Current Density ◽  
Patterned Substrates ◽  
Field Emitter Arrays ◽  
Current Densities

AbstractField emissions from the singlewalled carbon nanotubes (SWNTs) attached on various patterned substrates such as silicon wafer and polymer film, are reported. SWNTs were cut into sub-micron length by sonication in an acidic solution. The SWNT emitters were aligned on Au surface at room temperature by self-assembly monolayer technique. The field emission measurements in a silicon wafer and a polymer film showed that the turn-on fields were 2.8 V/ νm and 3.9 V/ νm at the emission current density of 10 μA/cm2, respectively. The current densities were 0.9 mA/cm2 and 1.6 mA/cm2 at 6.0 V/ νm. This room temperature process is suitable for the fabrication of flexible field emission devices with carbon nanotubes.

Modeling of Carbon Nanotube Emission Using Airy Functions

2003 ◽  
Author(s):  
D. G. Walker ◽  
T. S. Fisher
Keyword(s):  
Carbon Nanotubes ◽  
Field Emission ◽  
Airy Function ◽  
Field Enhancement ◽  
Airy Functions ◽  
Function Model ◽  
Electron Field ◽  
Current Densities ◽  
The Difference ◽  
Energy Conversion Devices

Modeling of electron field emission has not advanced significantly since Fowler and Nordheim described the phenomenon eighty years ago. While their approach provides remarkable agreement with experiments for a large number of cases, the theory is strictly valid for planar geometries and low temperatures. Carbon nanotubes have been considered for field emission energy conversion devices. Under high-temperature conditions and significant field enhancement, the approximations used in the Fowler-Nordheim formalism become invalid. The present work predicts electron current densities emitted from carbon nanotubes using Airy functions to predict transmission and temperature dependent supply functions. Results indicate that Fowler-Nordheim compares favorably with the Airy function model for materials with large work function (φ ≈ 5eV, in the present study) at room temperatures. However, for materials with smaller work functions, the difference between the Airy function model and Fowler-Nordheim can be significant.

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.

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