Sung Hen Cho

Development of triode-type carbon nanotube field-emitter arrays with suppression of diode emission by forming electroplated Ni wall structure

Triode-type field-emitter arrays were developed by screen printing a photosensitive paste including single-walled carbon nanotubes. Ni wall structure (NWS) was electroplated to form a thick gate to suppress diode emission induced by strong electric strengths due to an anode potential and to focus electron beams to their destined color subpixels. It was observed in computer simulations, as well in experiments that the NWS with the optimum thickness was effective in reducing the diode emission and enhancing electron-beam focusing by modifying electrical potentials around the carbon nanotube emitters. Our fully sealed field-emission display panel using the field-emitter arrays with the NWS demonstrated full color moving images without serious diode emission and with satisfactory color separation.

Effect of high-frequency variation on the etch characteristics of ArF photoresist and silicon nitride layers in dual frequency superimposed capacitively coupled plasmaa)

In this work, the deformation of ArF photoresist (PR) and etch characteristics of the ArF PR and Si3N4 layers were investigated in the dual frequency superimposed capacitively coupled plasmas under different frequency combinations by varying the process parameters such as dc self-bias voltage (Vdc), CF4∕CHF3 flow ratio, and O2 flow rate in the CF4∕CHF3∕O2∕Ar chemistry. Surface roughness measurements and morphological investigation of the line and space patterns after etching by atomic force microscopy and scanning electron microscopy, respectively, showed increased surface roughness and deformation with increasing the Vdc, the high-frequency source frequency (fHF), the CHF3 flow percentage, and the O2 flow rate. The etch rates of the ArF PR and silicon nitride layers were also increased significantly with the Vdc and fHF increased. The Si3N4∕PR etch selectivity was increased most significantly by an increase in the CHF3 flow percentage.

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...

39.2: The Full‐Color Video Images with Uniquely‐Gated Carbon Nano‐tube Field Emission Displays

Thick-film printing processes have been applied for preparing a carbon nanotube field emission display (c-FED), which has a strong cost advantage for large-size flat panel display. For practical display applications, two types of the gated cathode structure named the normal-gate cathode and the under-gate cathode have been developed and improved. The normal-gate and the under-gate cathode structures have the driving voltages of ±35 V and ±65 V, respectively. The 5″ c-FED panel with the normal-gate cathode and the 7″ c-FED panel with the under-gate cathode were successfully implemented and excellent full-color video images were obtained.

Photochemical Deposition of Ni – Cu Patterns onto Conducting Substrates Employing TiO2 – Pd2 + Layers

The metal photopatterning process employing a thin film of amorphous TiO 2 doped with Pd 2+ and oxalic acid has been developed. The exposure of this photolayer to UV light is believed to yield Pd(I) stabilized in a titanium oxide matrix, while subsequent washing results in formation of Pd nanoparticles through disproportionation. The Pd centers at the exposed areas are capable of inducing electroless nickel plating yielding the adhesive nickel pattern. The electroless copper deposition over patterned Ni allows generation of metal patterns with a resistivity of 4-12 μΩ cm and a resolution of 7 μm on the conducting substrates (indium-tin oxide glass, Si).

Low-Temperature Fabrication of Zinc Oxide Micropatterns Using Selective Electroless Deposition

Zinc oxide ZnO micropatterns were synthesized site-selectively on photocatalytically activated regions of TiO2 in an aqueous solution of zinc nitrate and dimethylamine-borane at 55°C by an electroless deposition process. The as-deposited ZnO micropatterns showed a polycrystalline wurtzite structure with a thickness of approximately 0.1 m. The ZnO micropatterns emitted ultraviolet light at 380 nm due to the recombination of bound excitons and broad visible-light luminescence 500-800 nm .

Selective Electroless Deposition Using Photoinduced Oxidation of Sn(II) Compounds on Surface-Modified Polyimide Layers

This paper describes an electroless deposition method for fabricating microscale metal patterns on polyimide surfaces. This method uses the selective deposition of catalytic Pd seeds via the photoinduced oxidation of Sn(II) compounds. The preparation process requires three steps: a first step in which the adsorption of Sn(II) compounds occurs on the surface of the polyimide film through ion exchange reactions, a second step in which the photoinduced oxidation of the Sn(II) compounds with atmospheric oxygen occurs in ultraviolet light (UV) irradiated areas, and a third step comprising the deposition of Pd 2+ ions in nonirradiated areas, which are simultaneously reduced.

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.

Triode‐type field emission displays with carbon nanotube emitters

Abstract Carbon nanotube emitters, prepared by screen printing, have demonstrated a great potential towards low‐cost, large‐area field emission displays. Carbon nanotube paste, essential to the screen printing technology, was formulated to exhibit low threshold electric fields as well as an emission uniformity over a large area. Two different types of triode structures, normal gate and undergate, have been investigated, leading us to the optimal structure designing. These carbon nanotube FEDs demonstrated color separation and high brightness over 300 cd/m2 at a video‐speed operation of moving images. Our recent developments are discussed in details.

Half-Buried Structure Cu Bus Line in TFT LCD

As we know, we normally used stacked aluminum bus line as the Gate or Source/Drain layer in LCD now, but the next general LCD needs larger display area, higher resolution, and faster response time, so we need develop the new TFT bus line structure and select the appropriate metallization materials to decrease the resistance of bus line. There are many new kinds of structure and material were used, for example copper, silver and their alloys, pure copper have some advantages among them because of its low electric resistance and cost, but it is restricted by the problem of pure copper’s lifting and etching. In this paper, we not only use electroless copper plating to decrease the resistance and cost of bus line but also use the half-buried structure to increase the thickness of bus line, it can combine these two new technologies well in LCD. We use the half-buried structure copper bus line to make some panel samples, it can decrease the delay of RC greatly (it is lower than 1/4 of normal aluminum bus line panel in the same size).