Field emission from carbon nanotubes for displays

Growth of carbon nanotubes on spontaneously detached free standing diamond films and their field emission properties

Few-layer graphene (FLG) and carbon nanotube (CNT) hybrid is prepared by in situ growth of FLG on the walls of CNTs, using PECVD, without catalyst. The amount and size of FLG can be controlled by total gas pressure and growth time. The field emission (FE) characteristics of CNTs coated with different-density FLG were studied, and an FE phenomenon schematic and electrostatic field equipotential model of these FLG-CNTs were proposed. These results show that the geometrical morphology of FLG plays an important role in the FE property of hybrid FLG-CNTs. The medium-density FLG on the CNTs exhibits excellent FE properties, with a low turn-on electric field and threshold field, as well as large field enhancement factor, which are much better than those of the as-grown CNTs. The excellent FE properties of the FLG-CNT hybrids make them promising candidates for high-performance FE emitters.

Laterally aligned carbon nanotube (CNT) arrays “blossomed” homogeneously in honeycomb holes of a metal grid substrate were explored as rational architecture for field emission. A low turn-on field (TOF) of 1.09 V/μm for 10 μA/cm2 emission was achieved, which approaches or exceeds the lowest reported TOF values for field emitter arrays. We interpret that these lateral CNT arrays act as source of CNT “loop” arrays enabling a structure suited toward low TOF field emission.

The vertical aligned carbon nanotubes (CNTs)-based pillar architectures were created on laminated silicon oxide/silicon (SiO2/Si) wafer substrate at 775 °C by using water-assisted chemical vapor deposition under low pressure process condition. The lamination was carried out by aluminum (Al, 10.0 nm thickness) as a barrier layer and iron (Fe, 1.5 nm thickness) as a catalyst precursor layer sequentially on a silicon wafer substrate. Scanning electron microscope (SEM) images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. The CNTs have approximately 2–30 walls with an inner diameter of 3–8 nm. Raman spectrum analysis shows G-band at 1580 cm−1 and D-band at 1340 cm−1. The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission analysis of the CNTs revealed high field emission current density (4mA/cm2 at 1.2V/μm), low turn-on field (0.6 V/μm) and field enhancement factor (6917) with better stability and longer lifetime. Emitter morphology resulting in improved promising field emission performances, which is a crucial factor for the fabrication of pillared shaped vertical aligned CNTs bundles as practical electron sources.

A fully sealed field-emission display 4.5 in. in size has been fabricated using single-wall carbon nanotube (CNT)-organic binders. The fabricated displays were fully scalable at low temperature, below 415 °C, and CNTs were vertically aligned using paste squeeze and surface rubbing techniques. The turn-on fields of 1 V/μm and field emission current of 1.5 mA at 3 V/μm (J=90 μA/cm2) were observed. Brightness of 1800 cd/m2 at 3.7 V/μm was observed on the entire area of a 4.5 in. panel from the green phosphor-indium–tin–oxide glass. The fluctuation of the current was found to be about 7% over a 4.5 in. cathode area.

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.

A single step in-situ process for improvement in electron emission properties of surface-modified carbon nanotubes (CNTs): Titanium dioxide nanoparticles attachment

This paper reports a novel implanting micromachining technology. By using this method, for the first time, we could implant nano-scale materials into milli-scale metal substrates at room temperature. Ni-based flexible carbon nanotube (CNT) field emitters were fabricated by the novel micromachining method. By embedding CNT roots into Ni foil using polymer matrix as transfer media, effective direct contact between Ni and CNTs was achieved. As a result, our novel emitter shows relatively good field emission properties such as low turn-on field and good stability. Moreover, the emitter was highly flexible with preservation of the field emission properties. The excellent field emission characteristics attributed to the direct contact and the strong interactions between CNTs and the substrate. To check the practical application of the novel emitter, a simple X-ray imaging system was set up by modifying a traditional tube. The gray shadow that appears on the sensitive film after being exposed to the radiation confirms the successful generation of X-ray.

A comparison between field-emission properties of three one-dimensional carbon materials

Synthesis and field emission properties of vertically aligned carbon nanotube arrays on copper

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.

Fabricating vertically aligned ultrathin graphene nanosheets without any catalyst using rf sputtering deposition

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

CNT supported NiO hierarchal nanostructure on stainless steel substrate for efficient field emitters

Screen-printed carbon nanotube (CNT) emitter arrays were prepared by using slurry of mixture of multiwall CNTs, organic vehicles, and inorganic binder, i.e., silicon dioxide sol. The composition of the slurry was optimized by varying the CNT content in the mixture. It was found that only the cathode with appropriate CNT contents had low turn-on field and high emission current density. A post-treatment process was introduced to further improve the field emission properties which selectively etches away the silicon dioxide binder by inductively coupled plasma etching. The results show that the selective etching process could effectively remove the inorganic binder layer from screen-printing CNT emitters and improve field emission performances.