Field Emission Display Research Articles

Electron field emission from transparent multiwalled carbon nanotube sheets for inverted field emission displays

Strong, conducting, transparent carbon nanotube sheets were prepared by solid-state draw from well-ordered, aligned multiwalled carbon nanotube (MWCNT) forests [Zhang et al., 2005] [1]. Study of electron field emission from such transparent MWCNT sheets shows threshold fields of less than 0.5 V/μm with current densities high enough for display applications. Step-like field emission current increase and hysteresis behavior in I– V curves has been observed. The origin of such behavior is discussed in terms of mechanical rearrangement of the nanotube network in high electric field. Studied MWCNT transparent sheet field emission cathodes have several advantages when used as multi-functional electrodes. They are high current, high stability, transparent, and flexible field emission sources and can be used in an inverted geometry, with cathode being in front of the light emitting plate. At the same time transparent CNT sheets may serve as a transparent conducting electrode for electrical connection and pixel addressing in field emission displays (FEDs). Also, these sheets can be used as an optical polarizer in FEDs.

Fabrication and Luminescence Properties of One-Dimensional CaMoO4: Ln3+ (Ln = Eu, Tb, Dy) Nanofibers via Electrospinning Process

One-dimensional CaMoO(4):Ln(3+) (Ln = Eu, Tb, Dy) nanofibers have been prepared by a combination method of sol-gel and electrospinning process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and low voltage cathodoluminescence (CL) as well as kinetic decays were used to characterize the resulting samples. SEM and TEM analyses indicate that the obtained precursor fibers have a uniform size, and the as-formed CaMoO(4):Ln(3+) nanofibers consist of nanoparticles. Under ultraviolet excitation, the CaMoO(4) samples exhibit a blue-green emission band with a maximum at 500 nm originating from the MoO(4)(2-) groups. Due to an efficient energy transfer from molybdate groups to dopants, CaMoO(4):Ln(3+) phosphors show their strong characteristic emission under ultraviolet excitation and low-voltage electron beam excitation. The energy transfer process was further studied by the emission spectra and the kinetic decay curves of Ln(3+) upon excitation into the MoO(4)(2-) groups in the CaMoO(4):x mol % Ln(3+) samples (x = 0-5). Furthermore, the emission colors of CaMoO(4):Ln(3+) nanofibers can be tuned from blue-green to green, yellow, and orange-red easily by changing the doping concentrations (x) of Ln(3+) ions, making the materials have potential applications in fluorescent lamps and field emission displays (FEDs).

Using patent analyses to monitor the technological trends in an emerging field of technology: a case of carbon nanotube field emission display

Carbon nanotube field emission display (CNT-FED) represents both emerging application of nanotechnology and revolutionary invention of display. Therefore, it is an important subject to monitor the states and trends of CNT-FED technology before the next stage of development. The present paper uses patent bibliometric analysis and patent network analysis to monitor the technological trends in the field of CNT-FED. These results firstly reveal the different aspects of patenting activities in the field of CNT-FED. Then, patent network analysis indicates the developing tendency of worldwide FED production based on the synthesis of CNT materials. Furthermore, key technologies of three clusters can be identified as the depositing CNT on substrate, coating phosphor on screen and assembling process for whole device. Finally, emitter material is taken for the key factor in R&D work to improve the efficacy in CNT-FED technology.

디지털 FID용 패널제작과 패키 방법에 관한 연구

Field emission displays(FED) are currently being study as a potential flat technology. The purpose of this project shows the research result of vacuum packaging technology for the development of FED. For FED vacuum packaging, the bonding of glass/glass, the exhaust of vacuum and getter technology have been studied for vacuum packaging technology The simulation and vacuum sealing, and glass/glass bonding are also extensively studied. The glass/glass bonding is formed by using the frit glass and the Inside pressure of complete panel showed of [Torr]. As a getter result, the increase of pressure has been showed the decrease of outgassing effect by using thin film getter.

Theoretical study of the transition metal ring functionalized tips of open-ended (5,5) boron nitride nanotube (BNNT)

The nanotube with open edges is an excellent candidate for designing efficient tip for atomistic scanning probes or field emission display (FED) devices. In the present work, we have studied the functionalization of an open-ended boron nitride nanotube (BNNT) with a series of transition metal rings and the effects on the properties of open-ended BNNT through density functional theory (DFT) calculations. The results show that the TM-BNNT complexes are energetically favorable. Moreover, it is found that the functionalization (a) significantly decreases the band gap of BNNT to different degrees, which might effectively modify the electronic properties of the open-ended BNNT; and (b) efficiently lowers the work function, which might improve the field emission properties. Our results might be helpful not only to design specific BNNT-based tips but also to further discuss the chemical vapor deposition (CVD) growth of BNNT on nanoparticles.

Novel tapered macrogate structure for carbon nanotube based field emission display

The tapered macrogate (TMG) structure is proposed to overcome the difficulties in carbon nanotube (CNT) based field emission display (FED) with high-voltage phosphors used in cathode ray tube screens. In order to achieve an ideal triode operation for field emission devices, the TMG was designed to have a very thick gate insulator with the inclined gate holes compared with the CNT emitters. The inclined gate holes with a narrower outlet than the bottom of the hole were shown to protect the CNT emitters from the anode field perfectly, enabling the authors to apply a high anode voltage over 10 kV needed for high-voltage FED. Also, the TMG structure had additional useful functions such as an electron-beam self-focusing and high durability against electrical damage. The authors successfully fabricated and demonstrated a 5 in. active-matrix CNT-FED panel with the TMG, showing color moving images with a low addressing voltage of about 15 V using amorphous silicon thin-film transistor as a switching device.

Measurement of the properties of a flat-panel gas X-ray detector

Recently, large-area image detectors were investigated for X-ray imaging in medical diagnostic and other applications. In this paper, a new flat-panel gas detector for diagnostic X-ray imaging is proposed, and its characteristics are investigated. Research on flat-panel gas detectors is scarce, because of the difficulties of injecting gas against atmospheric pressure. So almost all gas detectors are designed as a chamber. We made a flat-panel sample by display technique (e.g. plasma display panel, field emission display, etc.). Transparent electrodes, dielectric layer, and MgO protection layer were formed in the front glass. Additionally, X-ray phosphor layer and address electrodes were formed in the rear glass. Dark current, X-ray sensitivity, and linearity as a function of electric field were measured to investigate the electrical properties. From the results, the stabilized dark current density and significant X-ray sensitivity were obtained. A good linearity as a function of exposure dose could be realized in a wide diagnostic energy range. These results mean that the passive matrix-addressed flat-panel gas detector can be used for digital X-ray imaging.

Improved Performance of Spherical BaWO4 : Tb3 + Phosphors for Field-Emission Displays

Spherical phosphors were prepared by the polyol method and postannealed at . A variety of properties were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform IR spectra, low-voltage cathodoluminescence, photoluminescence spectra, and lifetime. The as-prepared phosphors were well-crystallized under relatively low synthesis temperature and composed of spherical particles with an average size of . After postannealing treatment, crystallinity of the phosphors is significantly improved and average particle size is increased to around . Under low-voltage excitation of electron beam, bright green cathodoluminescence was observed, which is attributed to the characteristic emissions from ( and transitions). The luminance was significantly improved from after postannealing, which is mostly attributed to the improvement of crystallinity.

Microscopic origin of current degradation of fully-sealed carbon-nanotube field emission display

The current-degradation mechanism of a fully sealed, carbon-nanotube field emission display is investigated experimentally and theoretically. From residual gas analysis, it is strongly evidenced that CH 3 radicals from the organic materials in the paste deteriorate emission properties. Based on ab initio methods, it is found that CH 3 radicals can increase electrical resistance of the nanotube and suppress emission currents. In addition, molecular dynamics simulations demonstrate that thermal destruction of CH 3-attached nanotubes occurs at lower temperatures than for pristine nanotubes. Our results suggest that the material selection of the paste is crucial for extending the lifetime of nanotube-based field emission displays.

Design and fabrication of an ultrahigh-luminance field-emission display

An ultrahigh-luminance field-emission display (FED) is designed in which a field emitter array (FEA) and memory function are integrated in every pixel of the display panel. The memory function consists of an emission-control thin-film transistor (TFT), a memory capacitor, a write-enable TFT, and a memory-discharging TFT. The operation mechanism is that the time of luminance of the pixel is made longer by the memory function; thus, luminance becomes higher. In principle, the maximum luminance of such a display is expected to be more than 100 000 cd/m2. The ultrahigh-luminance FED is applicable for daylight-readable displays used in mobile electronic equipment. The authors fabricated a prototype of the ultrahigh-luminance FED using Spindt-type FEA and poly-Si TFT technology. It was confirmed that the luminance of the display panel is controlled by the signal for the memory-discharging TFT, which means that the luminance can be dynamically controlled by the input signal. The maximum luminance of 1700 cd/m2 was achieved at a relatively low anode voltage of 1.5 kV. The higher luminance can be expected by applying higher anode voltage.

Intense green emission of ZnS:Cu, Al phosphor obtained by using diode structure of carbon nano-tubes field emission display

ZnS:Cu, Al phosphor is prepared by conventional solid-state reaction and is confirmed as an efficient phosphor for field emission display (FED). Broad photoluminescence (PL) band centered at 528 nm is obtained from the phosphor. The ZnS:Cu, Al and carbon nano-tubes (CNTs) are screen-printed on indium tin oxide (ITO) substrate to prepare the anode and the cathode plates of FED, respectively. The luminous performance is studied by using a diode structure and is controllable by adjusting space distance between the anode and cathode plate as well as thickness of phosphor-layer on the anode plate. The optimized luminance is around 6231 cd m −2 when using a 0.25 mm spacer and applying an electric field of 6 V μm −1.

Low-temperature synthesis of amorphous carbon nanoneedle and study on its field emission property

Amorphous carbon needle-like structure has been synthesized at temperature as low as 250 °C via reaction of ammonium chloride with ferrocene. The microstructure of the as-prepared carbon powder has been investigated with the help of a scanning electron microscope and a transmission electron microscope. The X-ray diffraction pattern as well as selected area electron diffraction pattern confirmed the amorphous nature of the samples. The prepared carbon needles show a good field emission property with turn-on field as low as 3.85 V/μm. The method developed here has the simplicity both in terms of process control and the equipmental set up, so that it may provide a possibility for large-scale production and may find applications in field emission display.

A Study on the Bonding Conditions and Mechanism for Glass-to-Glass Anodic Bonding in Field Emission Display

Here we have investigated the bonding conditions and mechanism for glass-to-glass anodic bonding in indium-tin-oxide (ITO)-coated glass using an Al/Cr composite thin film as an interlayer prepared by RF magnetron sputtering. The experimental results show that the bond strength increases with increasing the bonding temperature, bonding voltage, and Al film thickness. The optimum experimental parameters in the anodic bonding were found to be an Al film thickness of 300 nm, bonding temperature of 300°C, and bonding voltage of 700 V. Oxygen content within the bonded interphase increases and aluminum content decreases on increasing both the temperature and voltage during the bonding process. According to EDS analysis results, the main bond mechanism is proposed to be due to the following chemical reactions: 4Na+ + 4e− → 4Na, xAl + yO2− → Al x O y + 6e−, x = 2, y = 3.

One-dimensional CaWO4 and CaWO4:Tb3+ nanowires and nanotubes: electrospinning preparation and luminescent properties

One-dimensional CaWO4 and CaWO4:Tb3+ nanowires and nanotubes have been prepared by a combination method of sol-gel process and electrospinning. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), low voltage cathodoluminescence (CL) and time-resolved emission spectra, as well as kinetic decays were used to characterize the resulting samples. The results of XRD, FT-IR, TG-DTA indicate that the CaWO4 and CaWO4:Tb3+ samples begin to crystallize at 500 °C with the scheelite structure. Under ultraviolet excitation and low-voltage electron beams excitation, the CaWO4 samples exhibit a blue emission band with a maximum at 416 nm originating from the WO42−groups, while the CaWO4:Tb3+ samples show the characteristic emission of Tb3+ corresponding to 5D4–7F6,5,4,3 transitions due to an efficient energy transfer from WO42− to Tb3+. The energy transfer process was further studied by the time-resolved emission spectra as well as kinetic decay curves of Tb3+ upon excitation into the WO42−groups. Furthermore, the PL emission colour of CaWO4: x mol %Tb3+ can be tuned from blue to green by changing the concentrations (x) of the Tb3+ ion, making the materials have potential applications as fluorescent lamps and field emission displays (FEDs).

Miniaturization of carbon fibers and its applications

Exfoliated carbon fibers (ExCFs) obtained through rapid heat-treatment of intercalation compounds of carbon fibers had changed to the bundle of thin filament. In one of applications of its ExCFs, it was tried to nanocomposite where the application of Carbon nano tube (CNT) made an attempt. Preparation of composite using Nylon 6 and the ExCFs as the matrix and fillers was carried out by the injection molding. As the result, it became clear that addition of the ExCFs as fillers could be reinforced the matrix. Bending stress and elastic modulus of composite reinforced by the ExCFs increased around 50% with increasing in addition of the ExCFs in comparison with blank. It became clear that the ExCFs also exhibited better field emission characteristic at small-applied voltage in the case of an electrode material of field emission display (FED). Its field emission characteristics surpassed the case which CNT was applied to the electrode. Future applications were expected to the ExCFs.

Calculation of electron emission from a gated single nanowire

The field-enhancement factor β on an individual nanowire with flattop was calculated analytically by the electrostatic method in a gated structure. To evaluate the influences of the geometrical parameters—including the gate-hole radius R⁠, nanowire radius r0⁠, nanowire length L⁠, and gate-anode distance d2 for β—the authors proposed an ideal model of the gated single nanowire (L<d1)⁠, where d1 is the gate-cathode space. The calculation results showed that β decreases rapidly with both R and r0 and eventually saturates to a fixed value if R tends to infinity. It increases almost linearly with an increase in the nanowire height. When d2 is not much larger than d1 and R⁠, β decreases slightly as d2 increases, but the effect of the gate-anode distance on β can be ignored if d2 is infinite. These results provide useful information on fabricating and designing gated nanowire cold cathodes for field-emission display panels and other nanoscale triodes.

Nanocrystalline LaAlO3 : Sm3 + as a Promising Yellow Phosphor for Field Emission Displays

Nanocyrstalline phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. XRD results reveal that the sample begins to crystallize at , and pure phase can be obtained at . FE-SEM images indicate that the -doped phosphors are composed of aggregated spherical particles with sizes ranging from . Under the excitation of UV light and low-voltage electron beams , the -doped phosphors show the characteristic emissions of the (, , transitions) with a yellow color. The CL intensity (brightness) of the -doped phosphor is higher than that of the commercial product (yellow) to some extent.

Enhancement of Dimension Uniformity of Wet-Etched Thick Insulator Holes in Triode Carbon Nanotube Field-Emission Display Devices

A triode structure carbon nanotube field-emission display was fabricated using the thick-film process. The critical dimensional uniformity of wet-etched thick insulator holes was enhanced by changing the wet etching mechanism from vertical dip-etching to horizontal spray-etching. The profile of the insulator holes fabricated using the new etcher was similar to anisotropic. After optimizing the operation conditions of the new etcher, the dimensional uniformity of the insulator holes increased to 97.7%. The optimal concentration of etchant was 2.2 wt % for achieving the least side etching of the insulator holes. The carbon nanotube paste was pattern-printed into the insulator holes. The uniform size of the insulator holes implied that the carbon nanotube distribution was similarly among the insulator holes. This result showed an improved uniform field emission image over the panel from 59 to 83.85%.

Diameter Control of Graphite Nanofiber Emitter for Field Emission Display Using Granulated Catalyst Thin Film

To improve the field emission characteristics of graphite nanofiber (GNF) emitter, a simple method for controlling diameters of GNFs was developed using a granulated catalyst. The catalyst was composed of catalyst metal and noncatalytic oxide, and easily formed into a thin film consisting of fine metal particles surrounded by oxide. The diameters of GNFs grown on it depended on the mixture ratio and decreased to 10 nm without high-temperature heating. The emission current was 100 times higher than that of GNFs grown using a conventional catalyst. This should lead to the realization of field emission display devices based on GNFs.

Study of electrical properties of silica glasses, intended for FED spacers, under electron irradiation

The charge properties, under electron irradiation, of three types of glasses are studied by employing scanning electron microscope (SEM) associated with the technique called the electrostatic influence method. The experimental conditions are closed to those of typical field emission display (FED) operation. To determine the amount of trapped charges during and after electron irradiation, a special arrangement adapted to the SEM was used. This arrangement allows displacement and leakage currents to be simultaneously measured. The secondary electron emission yield during electron irradiation is also deduced. The trapping ability of each glass is analyzed taking into account the regulation mechanisms involved under electron irradiation. Finally useful indications permitting an adequate selection of glasses that may be used as FED spacers are deduced.