Joong-Woo Nam

Relationship between field emission property and composition of carbon nanotube paste for large area cold cathode

CNT paste was made by mixture of multi-walled carbon nanotubes (MWNT) powder, organic vehicles and inorganic binder. Then firing process was performed at different temperature under air and N/sub 2/ atmosphere. It was found that emission property of CNT paste was changed by firing temperature due to remained resin. We obtained good emission property from CNT paste treated at 350/spl deg/C.

Uniformity measurement of electron emission from carbon nanotubes using electron-beam resist

The field-emission sites’ distribution was measured to monitor the emission uniformity from randomly oriented carbon-nanotube (CNT) emitters using electron-beam resists (ER). The dot-patterned CNT emitters were fabricated by screen-printing a photoimageable CNT paste on an indium doped tin oxide (ITO) coated glass plate. An ER-coated Si substrate used as an anode provides the detection of the location and amount of the electron emission from the partial number of active emission sites among many existing CNTs. The measurements were carried out with the variation of electrical fields through continuous- or pulsed-voltage applications on a diode-type configuration. Developed ER images after a similar dosage of field-emission current flow indicate that emission uniformity is improved as the electrical field is increased. This method suggests that the emission uniformity could be estimated for various conditions of emitter preparation, such as CNT type, paste composition, and dispersion process, as well as th...

Stable and high emission current from carbon nanotube paste with spin on glass

We prepared carbon nanotube (CNT) pastes with different inorganic binders such as glass frit and spin on glass (SOG). MWNT powders grown by CVD were used for electron emissive source. The three-roll mill process was carried out for mixing and dispersion of CNT powders in organic vehicle as polymer matrix. CNT paste was printed onto various substrates such as an indium thin oxide (ITO) coated soda lime glass and a nickel plate. Then CNT paste was sintered under different ambient and temperature. For the analysis of the surface morphology of the cathode layer, field-emission scanning electron microscopy (FESEM) was used. The FE characteristics of CNT paste were measured in a high vacuum chamber with a parallel diode type configuration at 5/spl times/10/sup -6/ Torr. We obtained stable and high emission current from CNT paste with SOG. Our experiments have shown that CNT paste with SOG can use as efficient electron emitter in vacuum nanoelectronics such as radio frequency amplifier, field emission display and X-ray tube.

Fabrication and characteristics of flat lamp with CNT based triode structure for back light unit in LCD

Instead of the CVD method to form a gate oxide layer, a wet-etching method was used to form an insulating layer and isolate cathode layer from gate electrode. The wet-etching process has many advantages such as simple manufacture process, mass production and low cost. A gate triode structure was fabricated because of its simplicity in fabrication process and beam broadening. A new type of triode structure using wet-etching process was made and their field emission characteristics, uniformity and efficiency for light source for backlight units(BLU) were investigated

Field emission properties of plasma treated multiwalled carbon nanotube cathode layers

Improved field emission stability and lifetime have been observed for multiwalled carbon nanotube (MWCNT)-paste cathode layers, after plasma conditioning. Initially, MWCNT paste was synthesized and screen printed on an indium tin oxide coated glass substrate to obtain the cathode layers. These cathode layers were exposed to the Xe∕Ne plasma for a period of ∼1 or ∼3min under different biasing conditions (∼250 and ∼300V). The scanning electron microscopy micrographs, recorded for the untreated (virgin) and plasma treated cathode layers, showed significant variations in their morphology. The field emission analysis showed that the onset macroscopic field was increased from its virgin value of ∼4.65to∼9.05±0.05V∕μm for the plasma treated samples, with a subsequent decrease in the mean field-enhancement factor γav from 1251±13 to 779±43, computed from the Fowler-Nordheim plot. The variations in the current density was measured as a function of time, under low (∼10−6Torr) as well as high (∼10−8Torr) vacuum cond...

Long lifetime of field emitters fabricated using carbon nanotube paste

We have measured electron emission from carbon nanotube (CNT) emitter prepared using CNT paste and obtained long-term stability of field emission. Its lifetime observed in the sealed device at constant applied voltage was longer than 20,000 hrs. CNT emitter was treated by plasma in order to increase the stability. We observed that plasma treatment changed the surface morphology in CNT layer. The plasma etched the protruded CNT, resulting in the uniform height of CNT on the emitter layer.

Effect of electrical aging on emission stability of carbon nanotube field emitter

In this study, the effects of electrical aging on emission stability of screen-printed carbon nanotube(CNT) emitter is investigated. Results show that stable and uniform emission currents from CNT emitter are obtained during the multiple field emission cycling. During the initial stage of electrical aging, an emission current fluctuation is observed and is gradually reduced and electron emission stabilized as time passes.

Field emission properties of carbon nanotube paste on cathode with a curved surface for microwave power amplifier

In this report, we present field emission properties of the carbon nanotube (CNT) paste on cathode with a curved surface for MPA. The CNT paste was prepared using a mixture of multiwalled CNTs powders synthesized by chemical vapor deposition method, organic vehicles, and inorganic binders. We made use of both spin on glass (SOG) and a sensitizer as an inorganic binder and additive to the CNT paste. Then the paste was rubbed over a round cathode (diameter, D-4.3 mm) with a curved surface (a radius of curvature, R/spl sim/9.7 mm) designed specifically for our X-band (8-12 GHz) TWT-MPA.

Structural deformation of single-wall carbon nanotubes during field emission process

Stable electron emission from CNT emitters at required current densities is necessary to apply to the commercial devices. Generally, the current degradation during field emission has been understood as evaporation of emitter or breaking apart of tip end under intensive electrical field. In this report, we suggest one more possible mechanism that the emission current degradation may occur by increased resistance of emitters through structural deformation under field emission. The effect of current density and time on the structure of SWNT emitters was studied with TEM, low current density (100 /spl mu/A/cm/sup 2/ for 1 h) application gave no detectable structural deformation with comparison to pristine SWNTs. However, the bundles of SWNTs were deformed to amorphous structure starting at tip ends or defect sites when a high current density (500 /spl mu/m/cm/sup 2/ for more than 1h) was applied. It supports that the deformation of SWNT results from heat during emission at emitters. It is understood that the heat during emission could give a rise to destruct the crystalline structure and reconstruct the carbon bonding in SWNTs bundles. We also understood that the increase of the turn-on voltage is attributed to the increase of electrical resistance of emitters raising from structural deformation during emission process.

Screen printed carbon nanotube field emitter array for lighting source application

Photosensitive carbon nanotube (CNT) paste was synthesized with spin on glass (SOG) as inorganic binder. The field emission characteristics of this CNT paste was studied. CNT field emitter arrays (FEAs) was then fabricated using screen-printing method, photolithography and vacuum-in-line sealing technology. It is concluded that the diode type FEA using CNT paste with SOG can be used for lighting system applications such as the back light unit in TFT-LCD.