Sashiro Uemura

Field emission from carbon nanotubes and its application to electron sources

Abstract Carbon nanotubes possess the following properties favorable for field emitters: (1) high aspect ratio, (2) small radius of curvature at their tips, (3) high chemical stability and (4) high mechanical strength. A field emission microscopy (FEM) study was carried out for both multiwall nanotubes (MWNTs) and single-wall nanotubes (SWNTs) produced by arc discharge between carbon electrodes. Field emission patterns as well as current versus voltage characteristics and Fowler–Nordheim plots are discussed. As an application of nanotube field emitters, we manufactured cathode-ray tube (CRT) type lighting-elements and vacuum-fluorescence display (VFD) panels. In both display elements, conventional thermionic cathodes were replaced with MWNT field emitters. Stable electron emission, adequate luminance, and long life of the emitters was demonstrated.

Cathode Ray Tube Lighting Elements with Carbon Nanotube Field Emitters

We have manufactured cathode ray tubes (CRTs) equipped with field emitters composed of multiwalled carbon nanotubes. The fabricated CRTs (20 mm in diameter by 74 mm in length) are of a triode type, consisting of a cathode (nanotube field emitter arrays), a grid and an anode (phosphor screen). The manufactured CRTs are lighting elements, which are assembled to form a giant outdoor display. Stable electron emission, adequate luminance and long life are demonstrated. The CRT lighting elements presented here are the first practical products utilizing carbon nanotubes on an industrial scale.

Field emission from carbon nanotubes and its application to cathode ray tube lighting elements

Abstract Field emission from an individual multiwall nanotube and a bundle of single-wall nanotubes was investigated using a field emission microscope with a probe hole. Measured current–voltage characteristics followed the Fowler–Nordheim equation at low current density, whereas at higher current the increase in current became dull and deviated from the F–N line. As an application of nanotube field emitters, we manufactured the lighting elements of a triode vacuum tube by replacing conventional thermionic cathodes with multiwall nanotube field emitters. Stable electron emission, adequate luminance, and long life of the emitters were demonstrated.

Ink-jet printing of nanoparticle catalyst for site-selective carbon nanotube growth

We report on site-selective growth of multiwalled carbon nanotubes (MWNTs) from a Co nanoparticle catalyst patterned by an ink-jet printing (IJP) technique. The dispersion of the Co nanoparticles was employed as “catalyst ink” for the IJP, and the catalyst pattern was subjected to chemical vapor deposition of acetylene gas. The patterned array of MWNTs was obtained with a dot size around 5–30 μm and showed field emission of electrons corresponding to the printed pattern. The present method offers a simple and powerful means to pattern carbon nanotubes at desired positions with any patterns.

Large-area FEDs with carbon-nanotube field emitter

Application of carbon nanotubes (CNTs) as field emitters for large-area FED panels is described. In 1998, we presented the first experimental devices: light-source tubes for outdoor large-area displays and a diode-type flat-panel display, both with screen-printed CNT cathodes. The fisrt practical high-luminance color CNT-FED panel was built in 1999. It employed the new triode-structure panel was x-y addressable. The CNT-FED structure was further optimized for large-area display panels by improving the luminous uniformity. This paper also describes the design and performance of a new, experimental, 40-in.-diagonal panel, which showed that the CNT-FED technology is suitable for use in large-area displays.

22.1: Invited Paper: High‐Luminance Carbon Nanotube FED

An excellent performance of carbon-nanotubes as field-emitters was demonstrated using a high-voltage FED elements at SID in 1998 where a light-source tube for outdoor large size display and diode type flat panel were presented with the screen printed nanotube cathode. After that, a triode type paper which describes an x-y addressable high-luminance FED panel was introduced at IDRC in 1999. The experimental panel was performed ca.7×105 cd/m2 green light at 6kV, ca.1mA/cm2 dc-driving condition.[2] The results show the excellent performance of carbon nanotube FED as flat panel displays which are applicable to large size TV devices. This panel will be not only suitable for future TV display but also light-sources for field sequential color LCDs.

Emission Enhancement by Excimer Laser Irradiation over a Weblike Carbon Nanotube Layer

A surface treatment of a carbon-nanotube (CNT) layer by excimer-laser irradiation was investigated to obtain a uniform emission at a low driving voltage. A CNT layer was grown by thermal-chemical vapor deposition (CVD), and CNTs in the layer formed a weblike networked structure. The tips of the CNTs were found throughout the small-mesh networklike structure in the as-grown CNT layer. After laser irradiation, the number of CNT tips increased and the CNT tips created by laser irradiation had sharp edges and clean surfaces. As a result, the emission was greatly enhanced by laser irradiation at an energy density of 50–60 mJ/cm2.

Synthesis, structure and field emission of carbon nanotubes

Abstract Multiwall and single-wall nanotubes were produced by carbon arc discharge in helium, and their structures were investigated by electron microscopy. Field emission from (1) as-grown multiwall nanotubes (MWNTs), (2) purified MWNTs and (3) purified single-wall nanotubes (SWNTs) was investigated by field emission microscopy. Of the three kinds of nanotubes studied, purified MWNTs whose tips are open provided the highest current at a fixed voltage. Although purified SWNTs provided the second highest current, SWNTs are not so robust as MWNTs against ion bombardment. As an application of nanotube field emitters, we manufactured cathode ray tube (CRT) lighting-elements by replacing conventional thermionic cathodes with nanotube field emitters. Stable electron emission, adequate luminance, and long life of the emitters were substantiated.

19.3: CNT-FED for Character Displays

A prototype of CNT-FED character display was performed for middle size message displays. The display was constructed by metal-frame-cathodes, gate substrate and anode substrate with 3mm-tall glass spacers. The technology had advantages at the size-flexibility, deposition temperature and manufacturing yield. The CNT cathode was irradiated by excimer-laser, which was effective to improve emission uniformity and lower driving voltage. The prototype panel had 48 × 480-dots and the resolution was 1- mm. The panel realized high luminance at low power consumption. It will be important characteristics for legible and ubiquitous displays.

Uniform carbon-nanotube emitter for field-emission displays

— The synthesis of carbon-nanotube (CNT) field emitters for FEDs by thermal chemical vapor deposition (CVD) and their structural and emission characterization are described. Multi-walled nanotubes (MWNTs) were grown on patterned metal-base electrodes by thermal CVD, and the grown CNTs formed a network structured layer covering the surfaces of the metal electrode uniformly, which realized uniform distribution of electron emission. A technique for growing narrow MWNTs was also developed in order to reduce the driving voltage. The diameter of MWNT depends on the growth temperature, and it has changed from 40 nm at the low temperature (675°C) to 10–15 nm at the high temperature (900–1000°C). Moreover, narrower MWNTs were grown by using the metal-base electrode covered with a thin alumina layer and a metal catalyst layer. Double-walled nanotubes (DWNTs) were also observed among narrow MWNTs. The emission from the narrow CNTs showed a low turn-on electric field of 1.5 V/μm at the as-grown layer.