59.3: High-Resolution CNT-FED for Graphic Displays

For reducing the energy consumption of carbon nanotubes (CNTs) being used as emitters in various applications such as field emission display, electron-beam-induced deposition (EBID), new nano-sized metallic super-particles, ruthenium dioxide, are decorated to the surface of CNTs. The field emission characteristics are investigated and found that the onset voltage can be reduced much - about 23% lower than that of the same CNT emitters in the investigated ones. To obtain conductive nanostructures, electron-beam-induced deposition with individual multi-walled carbon nanotubes (MWNTs) emitters decorated with ruthenium dioxide is realized by introducing tungsten hexacarbonyl (W(CO)/sub 6/) as precursor. The mass of tungsten in deposits is rich up to 98% determined with energy X-ray dispersive spectrometer (EDS), nearly pure-metal deposits are obtained.

Vacuum nanoelectronics has been expected to provide a number of advanced devices such as flat panel displays, high- frequency devices and so on. Especially, field emission displays (FEDs) including Surface-conduction electron-emitter displays (SEDs) have been showing tremendous progress and become attractive nanoelectronic technology for a new generation of flat panel displays. Nowadays, nanomachining and nanomaterials are coming to new targets in the development for new generation devices. However, there are important limitations of their reliability and efficiency in FEDs and SEDs, mainly attributed to the emitters. The Transfer Mold emitters, the carbon nanotube emitters, the Si nano crystalline emitters, and the surface conduction electron emitters (SCEs) have been the candidates for getting and controlling the emitter structures. Also, recently, field emission lamps (FELs) have become new research target as promising mercury-free fluorescent lamps. In this paper, the recent progress and the technical issues on FEDs and FELs are overviewed.

A 10? carbon nanotube field emission display device was fabricated with a novel structure with a hopping electron spacer (HES) by screen printing technique. HES plays a role of preventing the broadening of electron beams emitted from carbon nanotubes without electrical discharge during operation. The structure of the novel tetrode is composed of carbon nanotube emitters on a cathode electrode, a gate electrode, an extracting electrode coated on the top side of a HES, and an anode. HES contains funnel‐shaped holes of which the inner surfaces are coated with MgO. Electrons extracted through the gate are collected inside the funnel‐shaped holes. They hop along the hole surface to the top extracting electrode. In this study the effects of the addition of HES on emission characteristics of field emission display were investigated. An active ozone treatment for the complete removal of residues of organic binders in the emitter devices was applied to the field emission display panel as a post‐treatment.

Using carbon nanotube (CNT) as cathode material, the field emission display (FED) panel with enhanced bar electrode was fabricated. With the photolithography process, the indium tin oxide (ITO) film was divided to form the cathode ITO electrode. The printed silver slurry was sintered to act as the cathode silver electrode, which was prepared on the cathode ITO electrode surface. The insulation layer was also fabricated on the cathode plate. The CNT paste was screen-printed on the surface of cathode ITO electrode and cathode silver electrode to form the field emitter. The detailed fabrication process of FED panel was given, and the sealed FED panel showed better field emission properties. Because of the enhanced bar electrode, the large field emission current was obtained.

We studied the residual gases inside field emission displays (FEDs) with carbon nanotube(CNTs) emitters, and found that the main residual gases inside sealed CNT-FEDs are Ar and CO, both of which are typical residual gases inside electronic vacuum tubes

Since carbon nanotube was discovered by S. Ijima in 1991, it has become one of the main academic research subjects. Carbon nanotube is the thinnest tube human can make presently. It has advantages in lightweight, high strength, high toughness, flexibility, high surface area, high thermal conductivity, good electric conductivity and chemical stability. Carbon nanotube can be applied to manufacture smaller transistors or electronic devices. Samsung Korea has made carbon nanotube into Field Emission Display. When the technology is matured and the cost is reduced, it will replace traditional bulky cathode ray tube (CRT) screen. Carbon nanotube has high toughness, so it can be made into highstrength composite with other materials. Thus, carbon nanotube is a material with high economic value and very worth researching. Besides, carbon nanotube has both conductor and semiconductor properties. Therefore, for electronic circuit, the semiconductor property of carbon nanotube enables its application to field emission transistor (FET) gate electrode, which has 100 times higher electric conductivity than silicon semiconductor when voltage is applied and 1000 times higher operational frequency than current Complementary MetalOxide Semiconductor (CMOS). The conductor property makes carbon nanotube have similar thermal conductivity to diamond and superior current carrying capacity to copper and gold. For the application of display, its long-term reliability is very excellent [Iijima, 1991, Lee et. al., 1977]. In order to create new material systems with superior properties, various nanoparticle morphologies have been used as reinforcing fillers in elastomeric matrices. These nanometerscale reinforcing particles include spherical particles such as silica or titania [McCarthy et. al., 1997, Kohjiya et. al., 2005], platelets such as layered silicates [Osman et. al., 2001, Joly et. al., 2002, Varghese & Karger-Kocsis, 2003, Kim et. al., 2004, Arroyo et. al., 2003, Bala et. al., 2004, Jeon et. al., 2004], carbon [Gauthier et. al., 2005] or clay fibers [Bokobza & Chauvin, 2005] and multiwall or singlewall carbon nanotubes[Barraza et.

In order to obtain data corresponding to the prebreakdown and breakdown of plain vacuum gaps in the micrometric regime relevant to field emission display,!:, an automatic experimental system was developed. The DC breakdown characteristics ofthe gap in the micrometric regime varying @om 25 to I000 p were extensively studied. The experimental results show that the highly finished broad-area metal electrodes withstand fairly high fields in relatively poor vacuum. The DC breakdown strength of a 50p gap was more than 220V/p at a pressure of IO-STorr, while for a IO00 pn gap, the breakdown strength was about 44. 5V/p for highly polished chrome steel electrodes, 2cm in diameter. The breakdown of a narrow (<200p) gap resulted in rapid degradation, with the gap holding-off lower voltages after breakdown. However, a wider gap (500 -1 000p.v) was found to exhibit conditioning, with the DC breakdown voltage increming after each successive breakdown. The breakdown characteristics of ideal gaps with very smooth solid electrodes, presented in this work, will define the theoretical limits to which actual gaps can be stressed in an FED. 1. Introduction Dielectric spacers and electrical insulation for high fields are critical issues for field emission based vacuum microelectronic devices, specifically the field emission display (FED). For reliable operation of FEDs, an appropriate spacer design is of primary importance. The insulation consideration of the spacer becomes more complicated considering the operational environment of the FED - the presence of electron emission from regions surrounding the spacer, outgassing from the phosphor, and elevated operational temperature of the device. Assuming that flashover could be alleviated even at high operational fields, the voltage limitation of the device shifts to the breakdown of the active region of the device, which is the plain vacuum gap between tlhe cathode and anode. Thus the issues related to the breakdown of plain vacuum micro-gaps are also important, especially under the operating condition of the device, and can be used to define the theoretical limits to which actual gaps can be stressed in a FED. Although there is voluminous bibliography on discharge processes in plain vacuum gaps [ 1,2], data corresponding to the breakdown and prebreakdown of plain vacuum gaps is not available in the micrometric regime (25 to few hundred microns) relevant to FEDs. As part of the main investigation of our project, which is aimed to develop micro-spacer insulation for field emission displays, this paper reports the issues related to the breakdown and prebreakdown characteristics of plain vacuum micro-gaps.

We developed a field emission nano-focus x-ray source using carbon nanotube (CNT) emitters and electron beam (E-beam) focusing modules, which could be used in the applications requiring the high-resolution x-ray images. For the nano-size focusing of E-beam from CNT emitters, we designed special focusing modules consisting of electrostatic and magnetic lenses. The geometries and operating conditions of focusing modules were optimized to give the desired demagnification characteristics by performing the electron optics simulations of the designed x-ray source under external electric and magnetic fields. We constructed and operated an open-type nano-focus x-ray system using the focusing modules under a high-voltage condition to attain the high-resolution x-ray images. The results showed a possibility of field emission nano-focus x-ray sources with a relatively high current and controllable magnification through the effective focusing modules.

The effect of improvement on the surface morphology of screen‐printed carbon nanotube (CNT) films was studied by using the optically clear poly‐dimethylsiloxane (PDMS) elastomer for surface treatment. After the PDMS activation treatment was applied to the diode‐type CNT cathode, the entangled carbon nanotube (CNT) bundles were broken up into individual free standing nanotubes to remarkably improve the field‐emission characteristics over the as‐deposited CNT film. Also, the cathode film morphology of a top gated triode‐type structure can be treated by using the proposed surface treatment technique, which is a low‐cost process, simple process. The relative uniform emission image showed high brightness with a high anode current. This result shows the possibility of using this technique for surface treatment of large‐size field emission displays (FEDs) in the future.

This study presents a novel non-contact method, designated as laser induced local material transfer (LILMT), for patterning carbon nanotube (CNT) emitters on the cathode of a CNT backlight unit (CNT-BLU) under the environment of the atmosphere and at room temperature. The LILMT method makes possible the manufacturing of large-scale substrates with a higher resolution than that which can be attained using familiar screen-printing methods. The preliminary results obtained for the field emissions of square-type and line-type CNT emitters confirm the effectiveness of the proposed patterning method.

Enhanced and stable electron emission of carbon nanotube emitters with graphitization

Carbon nanotubes (CNTs) are widely considered as one of the most promising candidates for building field emission (FE) devices. These devices include X-ray tubes, scanning X-ray sources, and flat panel displays. In addition to its high aspect ratio, good electrical conduction, and superb chemical stability, the tip structure of the CNT is a crucial factor in determining its excellent performance as a field emitter. In particular, for a cappedCNT, the closed apex with each carbon atom bound to three neighbor atoms via covalent bonds shows much higher FE stability than that of an opened end, and capped CNTs have therefore become the focus of scientific and industrial interest for their potential uses as, for example, high-brightness point-electron sources. However, even for a capped CNT with a closed termination built by strong C–C bonds, the emission can be unstable. Its cap structure can be damaged at extremely strong local field levels and high temperatures resulting from current heating, and so these factors define a upper limit for the FE current from a CNT. While technically this maximum FE current (Imax) is a very important parameter, this quantity has not been investigated by directly correlating it to the CNT cap structure. The CNT emitter was found to deviate from Fowler–Nordheim (F–N) behavior in many experiments, but some recent results show that the F–N theory might still give a good description for capped CNTs. So a question arises: to what extent does the conventional F–N theory applies for an extremely curved CNT cap surface? Recently we demonstrated an in situ cap–engineering technique inside a transmission electron microscope (TEM) for fabricating conical tips with controllable size on a single CNT. This cone-shaped CNT, in fact, provides a good experimental object for us to investigate the two fundamental FE issues raised above: what is the applicability of the F–N theory, and what is themaximum stable FE current that can be extracted from a single CNT?

Field emission from carbon nanotubes for displays

Carbon nanotubes growing on rapid thermal annealed Ni and their application to a triode-type field emission device

Cold cathodes for applications in poor vacuum and low pressure air environments: Carbon nanotubes versus ZnO nanoneedles