• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.353-353
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• 2008

Carbon nanotubes (CNTs) are attractive for field emitter because of their outstanding electrical, mechanical, and chemical properties. Several applications using CNTs as field emitters have been demonstrated such as field emission display (FED), backlight unit (BLU), and X-ray source. In this study, we fabricated a CNT cathode using transparent ultra-thin CNT film. First, CNT aqueous solution was prepared by ultrasonically dispersing purified single-walled carbon nanotubes (SWCNTs) in deionized water with sodium dodecyl sulfate (SDS). To obtain the CNT film, the CNT solution in a milliliter or even several tens of micro-litters was deposited onto a porous alumina membrane through vacuum filtration process. Thereafter, the alumina membrane was solvated by the 3 M NaOH solution and the floating CNT film was easily transferred to an indium-tin-oxide (ITO) glass substrate of $0.5\times0.5cm^2$ with a film mask. The transmittance of as-prepared ultra-thin CNT films measured by UV-Vis spectrophotometer was 68~97%, depending on the amount of CNTs dispersed in an aqueous solution. Roller activation, which is a essential process to improve the field emission characteristics of CNT films, increased the UV-Vis transmittance up to 93~98%. This study presents SEM morphology of CNT emitters and their field emission properties according to the concentration of CNTs in an aqueous solutions. Since the ultra-thin CNT emitters prepared from the solutions show a high peak current density of field emission comparable to that of the paste-base CNT emitters and do not contain outgassing sources such as organic binders, they are considered to be very promising for small-size-but-high-end applications including X-ray sources and microwave power amplifiers.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.468-468
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• 2011

Carbon nanotubes (CNTs) have been considered as one of the promising candidate for next-generation field emitters because of their unique properties, such as high field enhancement factor, good mechanical strength, and excellent chemical stability. So far, a lot of researchers have been interested in field emission properties of CNT itself. However, it is necessary to study proper field emitter shapes, as well as the fundamental properties of CNTs, to apply CNTs to real devices. For example, specific applications, such as x-ray sources, e-beam sources, and microwave amplifiers, need to get a focused electron beam from the field emitters. If we use planar-typed CNT emitters, it will need several focal lenses to reduce a size of electron beam. On the other hand, the point-typed CNT emitters can be an effective way to get a focused electron beam using a simple technique. Here, we introduce a fabrication of CNT fibers with nanoscale point tips which can be used as a point-typed emitter. The emitter made by the CNT fibers showed very low turn-on electric field, high current density, and large enhancement factor. In addition, it showed stable emission current during long operation period. The high performance of CNT point emitter indicated the potential e-beam source candidate for the applications requiring small electron beam size.

• Journal of Information Display
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• v.2 no.3
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• pp.60-65
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• 2001

Lateral type poly-silicon field emitters were fabricated by utilizing the LOCOS (Local Oxidation of Silicon) process. For the implementation 'of an ideal field emission device with quasi-zero tunneling barrier, a new and fundamental approach has used conducted by introducing an intelligent carbon-based thin layer on the cathode tip surface via a field-assisted self-aligning of carbon (FASAC) process. Fundamental lowering of the turn-on field for the electron emission was feasible through the control of both the tip shape and surface barrier height.

• Applied Microscopy
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• v.47 no.1
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• pp.36-42
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• 2017

Field electron emission measurements were performed on dielectric-coated tungsten emitters, with apex radii in the nanometer and micrometer range, which were prepared by electrochemical etching in NaOH solution. Measurements were performed in a field electron microscopy (FEM) with a base pressure <$10^{-6}$ Pascal ($10^{-8}$ mbar). Four different types of dielectric were used, namely: (1) Clark Electromedical Instruments epoxylite resin, (2) Epidian 6 produced by Ciech Sarzyna S. A., (3) a Radionox solution of colloidal graphite; and (4) Molyslip 2001 E compound ($MoS_2$ and MoS). Current-voltage measurements and FEM images were used to investigate the characteristics of these composite emitters, and to assess how the different types of dielectric coating affect the suitability of the composite emitter as a potential electron source.

• Mass Spectrometry Letters
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• v.7 no.1
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• pp.21-25
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• 2016

Dual-channel nano-electrospray has recently become an ionization technique of great promise especially in biological mass spectrometry. This unique approach takes advantage of the mixing processes that occurs during electrospray. Understanding in more detail the fundamental principles influencing spray formation further study of the origins of the mixing processes: (1) in a Taylor cone region, (2) in charged droplets or (3) in both environments. The dual-channel emitters were made from borosilicate theta-shape glass tubes (O.D. 1.2 mm) and had a tip diameters of less than 4 μm. Electrical contact was achived by deposition of a thin film of an appropriate metal onto the surface of the emitter. The experimental investigation of the Taylor cone formation in a dual-channel electrospray emitter has been carried out by injection of polystyrene beads (diameter 3 μm) at very low concentrations into one of the channels of the non-tapered theta-glass tubes. High-speed camera experiments were set up to visualize the mixing processes in Taylor cone regions for dual-channel emitters. Mass spectra from dual nano-electrospray are presented.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.4
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• pp.232-237
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• 2014

We have fabricated white organic light-emitting diodes (OLEDs) by co-doping of red and blue phosphorescent guest emitters into the single host layer. Tris(2-phenyl-1-quinoline) iridium(III) [$Ir(phq)_3$] and iridium(III)bis[(4,6-di-fluorophenyl)-pyridinato-$N,C^{2^{\prime}}$]picolinate (FIrpic) were used as red and blue dopants, respectively. The effects of dopant concentration on the emission, carrier conduction and external quantum efficiency characteristics of the devices were investigated. The emissions on the guest emitters were attributed to the energy transfer to the guest emitters and direct excitation by trapping of the carriers on the guest molecules. The white OLED with 5% FIrpic and 2% $Ir(phq)_3$ exhibited a maximum external quantum efficiency of 19.9% and a maximum current efficiency of 45.2 cd/A.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1670-1674
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• 2014

Two red emitters, 2-(7-(4-(diphenylamino)styryl)-2-methyl-4H-chromen-4-ylidene)malonitrile (Red 1) and 2-(7-(julolidylvinyl)-2-methyl-4H-chromen-4-ylidene)malonitrile (Red 2) have been designed and synthesized for application as red-light emitters in organic light emitting diodes (OLEDs). In these red emitters, the julolidine and triphenyl moieties were introduced to the emitting core as electron donors, and the chrome-derived electron accepting groups such as 2-methyl-(4H-chromen-4-ylidene)malononitrile were connected to electron donating moieties by vinyl groups. To explore the electroluminescence properties of these materials, multilayered OLEDs using red materials (Red 1 and Red 2) as dopants in $Alq_3$ host were fabricated. In particular, a device using Red 1 as the dopant material showed maximum luminous efficiencies and power efficiencies of 0.82 cd/A and 0.33 lm/W at $20mA/cm^2$. Also, a device using Red 2 as a dopant material presented the CIEx,y coordinates of (0.67, 0.32) at 7.0 V.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.1
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• pp.75-80
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• 2006

We have fabricated a carbon nanotube field emission display(CNT-FED) panel with a 2 inch diagonal size using a screen printing method and in-situ vacuum sealing technology. The field emission properties of CNT FED panel with square-type CNT emitters. As results, the square-characterized and compared with those of the line-type CNT emitters. As results, the square-type CNT emitters showed much larger emission current and more stable I-V characteristics. Light emission started to be occurred at an electric field of 3.5 V/${\mu}m$ corresponding to the anode-cathode voltage of 700 V. The vacuum level inside of the in-situ vacuum sealed panel was obtained with $1.4 {\times} 10^{-5}$ torr. The sealed panel showed the similar I-V characteristics with the unsealed one and the uniform light emission with very high brightness at a current density of $243 {\mu}A/ cm^2$ obtained by the electric field of 10 V/${\mu}m$.

• Carbon letters
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• v.15 no.3
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• pp.214-217
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• 2014

A filtration-taping method was demonstrated to fabricate carbon nanotube (CNT) emitters. This method shows many good features, including high mechanical adhesion, good electrical contact, low temperature, organic-free, low cost, large size, and suitability for various CNT materials and substrates. These good features promise an advanced field emission performance with a turn-on field of $0.88V/{\mu}m$ at a current density of $0.1{\mu}A/cm^2$, a threshold field of $1.98V/{\mu}m$ at a current density of $1mA/cm^2$, and a good stability of over 20 h. The filtration-taping technique is an effective way to realize low-cost, large-size, and high-performance CNT emitters.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1220-1221
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• 2008

Submicron-sized conical-type tungsten(W) field-emitters based on carbon nanotubes(CNTs) are fabricated with the configuration of CNTs/catalyst(Ni)/buffer(Al/Ni/TiN)/W-tip. This study focuses on elucidating how the Al/Ni/TiN stacked buffer layer affects the structural properties of CNTs and the electron-emission characteristics of CNT-emitters. Field-emission scanning electron microscopy(FESEM), high-resolution transmission electron microscopy(HRTEM), and x-ray photoelectron spectroscopy(XPS) are used to monitor the nanostructures, surface morphologies, chemical bonds of all the catalysts and CNTs grown. The crystalline structure of CNTs is also characterized by Raman spectroscopy. Furthermore, the measurement of field-emission characteristics for the field-emitters fabricated shows that the emitter using the Al/Ni/TiN stacked buffer reveals the excellent performances.