scholarly journals Small-Sized Flat-Tip CNT Emitters for Miniaturized X-Ray Tubes

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Hyun Jin Kim ◽  
Jun Mok Ha ◽  
Sung Hwan Heo ◽  
Sung Oh Cho
Keyword(s):  
Silver Nanoparticles ◽  
Electric Field ◽  
Field Emission ◽  
Enhancement Factor ◽  
Flat Surface ◽  
Field Enhancement ◽  
X Ray ◽  
Field Emission Properties ◽  
Inner Diameter ◽  
Metal Tip

Small tip-type CNT emitters with the diameter of 0.8 mm were fabricated for miniaturized X-ray tubes. The CNT emitters were prepared by dropping CNTs and silver nanoparticles on a flat surface of a W metal tip followed by annealing at 800°C for 2 h under vacuum. The CNT emitters exhibit good field emission properties with the threshold electric field of 1.15 V/μm and the field enhancement factor of 12,050. CNTs were well attached to a flat W tip surface without coating on the side plane of the tip, and thus beam divergence could be minimized. Consequently, a miniaturized X-ray tube with the inner diameter of 5 mm was successfully demonstrated using the tip-type CNT emitter.

scholarly journals Microconical Structure Formation and Field Emission From Atomically Heterogeneous Surfaces Created by Microwave Plasma–Based Low-Energy Ion Beams

2021 ◽  
Vol 9 ◽  
Author(s):  
Jayashree Majumdar ◽  
Sudeep Bhattacharjee
Keyword(s):  
Work Function ◽  
Field Emission ◽  
Enhancement Factor ◽  
Field Enhancement ◽  
Ion Beams ◽  
Emission Current ◽  
Force Microscopy ◽  
Field Emission Properties ◽  
Argon Ion ◽  
Local Work

We report the formation of self-organized microconical arrays on copper surface when exposed to high flux (5.4 × 1015 cm−2 s−1) of 2 keV argon ion beams at normal incidence. The created microconical arrays are explored for field emission properties. The surface morphologies are investigated by scanning electron microscopy and atomic force microscopy. The local work function variation is analyzed by Kelvin probe force microscopy, and the argon content in the irradiated layer is measured with X-ray Photoelectron Spectroscopy. The average aspect ratio (base width/height) of microstructures for individual irradiated samples is found to increase from 0.7 to 1.5 with a decrease in ion fluence. The ion concentration is highest (3.89 %) for a fluence of 4.7 × 1018 cm−2, which asserts the formation of atomically heterogeneous surface due to subsurface ion implantation. An enhancement in the field emission properties of the argon ion–treated copper substrates at a fluence of 4.7 × 1018 cm−2 with a low turn-on voltage of 2.33 kV and with electron emission current 0.5 nA has been observed. From the Fowler–Nordheim equations, the field enhancement factor is calculated to be 5,561 for pristine copper, which gets enhanced by a factor of 2–8 times for irradiated substrates. A parametric model is considered, by taking into account the modified local work function caused due to structural undulations of the microstructures and presence of implanted argon ions, for explaining the experimental results on the field enhancement factor and emission current.

Field Emission Site Densities of Nanostructured Carbon

2001 ◽  
Vol 675 ◽  
Author(s):  
J B Cui ◽  
J Robertson ◽  
W I Milne
Keyword(s):  
Field Emission ◽  
Applied Field ◽  
Enhancement Factor ◽  
Field Enhancement ◽  
Carbon Films ◽  
Vacuum Arc ◽  
Nanostructured Carbon ◽  
Field Emission Properties ◽  
Site Density ◽  
Enhancement Factors

ABSTRACTThe field emission properties of nanostructured carbon films deposited by cathodic vacuum arc in a He atmosphere have been studied by measuring the emission currents and the emission site density. The films have an onset field of ∼3 V/μm. The emission site density is viewed on a phosphor anode and it increases rapidly with applied field. It is assumed that the emission occurs from surface regions with a range of field enhancement factors but with a constant work function. The field enhancement factor is found to have an exponential distribution.

Field Emission from Nanocrystalline Diamond/Carbon Nanowall Composite Films Deposited on Scratched Substrates

2012 ◽  
Vol 1395 ◽  
Author(s):  
C.Y. Cheng ◽  
M. Nakashima ◽  
K. Teii
Keyword(s):  
Field Emission ◽  
Enhancement Factor ◽  
Composite Films ◽  
Diamond Films ◽  
Field Enhancement ◽  
Nanocrystalline Diamond ◽  
Field Emission Properties ◽  
Turn On ◽  
Carbon Nanowalls ◽  
Wall Spacing

ABSTRACTWe report the deposition and field emission properties of nanostructured composites consisting of carbon nanowalls (CNWs) and nanocrystalline diamond films by introducing two kinds of substrate scratching pretreatment, i.e., undulation and ultrasonic vibration. With increasing duration of scratching pretreatment, the morphology of the deposits changes from simple CNWs to a film/CNW composite and lastly to CNWs on a film, and then the space between the walls is increased. The emission turn-on field is reduced from 2.1 V/μm for simple CNWs to around 1.2 V/μm for the composite films, accompanied by an increase in field enhancement factor. The results indicate that electric field screening between the walls is successfully suppressed by widening of the wall spacing.

Field emission properties of spinel ZnCo2O4 microflowers

RSC Advances ◽  
2015 ◽  
Vol 5 (7) ◽  
pp. 5372-5378 ◽  
Author(s):  
Satyajit Ratha ◽  
Ruchita T. Khare ◽  
Mahendra A. More ◽  
Ranjit Thapa ◽  
Dattatray J. Late ◽  
...  
Keyword(s):  
Field Emission ◽  
Enhancement Factor ◽  
Field Enhancement ◽  
Field Enhancement Factor ◽  
Emission Performance ◽  
Emission Properties ◽  
Field Emission Properties ◽  
Field Emission Performance ◽  
Facile Route

Spinel ZnCo2O4 microflowers were synthesized by a facile route and their field emission properties were studied in detail. They showed intriguing Field emission performance in terms of good field-enhancement factor and stability.

Field Emission Properties of Al-Doped ZnO Nanostructures

2009 ◽  
Vol 5 ◽  
pp. 231-237 ◽  
Author(s):  
Shalaka C. Navale ◽  
Farid Jamali Sheini ◽  
Sandip S. Patil ◽  
Imtiaz S. Mulla ◽  
Dilip S. Joag ◽  
...  
Keyword(s):  
Field Emission ◽  
High Vacuum ◽  
Field Enhancement ◽  
Ultra High Vacuum ◽  
Precipitation Method ◽  
Threshold Field ◽  
Zno Nanostructures ◽  
X Ray ◽  
Field Emission Properties ◽  
Doped Zno

Field emission from Al-doped ZnO nanostrcutures has been investigated in planar diode configuration under ultra high vacuum conditions. The Al-doped ZnO nanostructures were synthesized by co-precipitation method with varying aluminium concentrations. The as- synthesized product was characterized by x-ray diffraction, scanning electron microscope and energy dispersive x-ray analysis. The threshold field required to draw a current density of ~ 1 μA/cm2 was observed to be ~ 2.0 V/μm and ~ 2.3 V/μm for Al-doped ZnO nanostructures synthesized with aluminium concentrations of 1% and 3%, respectively. The Fowler- Nordheim (F-N) plots for both the specimens exhibit non-linear behaviour, which is observed to be specimen dependent. The non-linearity observed in the F-N plots has been interpreted on the basis of the theory of electron emission from semiconductor emitters. The field enhancement factors, estimated from the slope of the F-N plots, are found to be ~ 9.3 x 103 and 3.9 x 103 for 1% and 3% Al-doped ZnO emitters, respectively. The high values of the field enhancement factor suggest that the emission is from the nanostructures. The emission current stability measured at the preset value of ~ 2 μA over a period of more than three hours is found to be fairly stable. The results indicate use of Al-doped ZnO nanostructures as promising emitters for field emission based devices.

scholarly journals Studies of enhanced field emission relevant to high field superconducting radio frequency devices

2021 ◽  
pp. 7-7
Author(s):  
Marija Radmilovic-Radjenovic ◽  
Zeljka Nikitovic ◽  
Ranislav Radjenovic
Keyword(s):  
Electric Field ◽  
Radio Frequency ◽  
Field Emission ◽  
Enhancement Factor ◽  
Field Enhancement ◽  
Field Enhancement Factor ◽  
Accurate Estimation ◽  
Cavity Surface ◽  
Planar Surfaces ◽  
Superconducting Radio Frequency

Surface roughness represents the measure of the irregularities on the surface contributing to the local field enhancement. The traditional Fowler-Nordheim equation established for perfectly planar surfaces is not suitable for describing emission from rough surfaces. Instead, it is more appropriate to use the equation that accounts for the field enhancement factor describing the effect of the surface morphology. In superconducting radio frequency cavities field emission may occur in the irises and the tips on the cavity surface may act as an emitter leading to the high electric field. For this study, calculations for hemispherical, cylindrical, and conical tips have been performed by using a multiphysics software package COMSOL. The focus was put on the dependence of the field enhancement factor on the shape and the radius of the protrusions. The electric field strength and the current density increase with increasing the root mean square average of the profile heights due to field enhancement at the cavity irises. The lowest value of the electric field has been achieved for the hemisphere. The calculated values for the field enhancement factors are consistent with the data from the literature, in which case the protrusion may represent a small local bump on the surface of a superconducting cavity. Based on the fit of the results, presented here, the relation between the enhancement factor and the radius has been suggested. The accurate estimation of the field emission may play a crucial role in the design of accelerators and other technological applications with requirements of very high precision.

scholarly journals Screening effects on the field enhancement factor of zigzag graphene nanoribbon arrays: a first-principles study

2018 ◽  
Vol 20 (21) ◽  
pp. 14627-14634 ◽  
Author(s):  
Han Hu ◽  
Tzu-Chien Lin ◽  
Tsan-Chuen Leung ◽  
Wan-Sheng Su
Keyword(s):  
Field Emission ◽  
First Principles ◽  
Enhancement Factor ◽  
Graphene Nanoribbons ◽  
Field Enhancement ◽  
First Principles Calculations ◽  
Screening Effect ◽  
Field Screening ◽  
Field Emission Properties ◽  
Zigzag Graphene Nanoribbons

The field screening effect on the electronic and field-emission properties of zigzag graphene nanoribbons (ZGNRs) has been studied using first-principles calculations.

scholarly journals Optically Induced Field-Emission Source Based on Aligned Vertical Carbon Nanotube Arrays

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1810
Author(s):  
Mengjie Li ◽  
Qilong Wang ◽  
Ji Xu ◽  
Jian Zhang ◽  
Zhiyang Qi ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Electric Field ◽  
Field Emission ◽  
Field Enhancement ◽  
Absorption Efficiency ◽  
Photon Absorption ◽  
Nanotube Arrays ◽  
Carbon Nanotube Arrays ◽  
Induced Field ◽  
Optically Induced

Due to the high field enhancement factor and photon-absorption efficiency, carbon nanotubes (CNTs) have been widely used in optically induced field-emission as a cathode. Here, we report vertical carbon nanotube arrays (VCNTAs) that performed as high-density electron sources. A combination of high applied electric field and laser illumination made it possible to modulate the emission with laser pulses. When the bias electric field and laser power density increased, the emission process is sensitive to a power law of the laser intensity, which supports the emission mechanism of optically induced field emission followed by over-the-barrier emission. Furthermore, we determine a polarization dependence that exhibits a cosine behavior, which verifies the high possibility of optically induced field emission.

Effect of distribution of field enhancement factor on field emission from cathode with a large number of emission sites

2005 ◽  
Vol 484 (1-2) ◽  
pp. 379-381 ◽  
Author(s):  
Guang Yuan ◽  
Hang Song ◽  
Yixin Jin ◽  
Hidenori Mimura ◽  
Kuniyoshi Yokoo
Keyword(s):  
Field Emission ◽  
Enhancement Factor ◽  
Field Enhancement ◽  
Field Enhancement Factor
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