Field Emission Display Research Articles

Highly transparent and conducting C:ZnO thin film for field emission displays

Incorporation of carbon into a zinc oxide (ZnO) thin film has led to a potential new application as a transparent and conductive oxide thin film. Here, we fabricated carbon doped zinc oxide (C:ZnO) films by RF sputtering at a low temperature, aiming to produce a transparent and conductive screen for transparent field emission displays. The incorporation of highly inert carbon atoms into ZnO thin films can tune the intrinsic defect sites. A co-sputtering technique was used for carbon doping into ZnO, where the dopant amount was controlled by varying the number, size and position of the graphite plates used as the carbon source. A sheet resistance of 37 Ω □−1 and a transmittance of 84% at a wavelength of 550 nm were achieved for the C:ZnO thin film with a nominal carbon concentration of 2.7%. The bonding of carbon with ZnO was analyzed using de-convolution of XPS peak C1s. We also demonstrated the light emission properties of the C:ZnO thin films by fabricating a field emission device. A high current density of 1 mA cm−2 was obtained with a lower applied electric field of 5 V μm−1. Our findings showed that the C:ZnO thin films can be a promising transparent and conducting phosphor screen for a field emission display.

Life cycle assessment study of a field emission display television device

An life cycle assessment (LCA) study of a field emission display (FED) television device was established. The first objective of this study was to get an up-to-date and comprehensive picture by applying the latest developments in the area of LCA, especially concerning the use of nanoparticles. In its second part, the study shows a comparison with today’s display technologies (i.e. CRT, LCD, plasma) and the timely development of the assessment of a FED television device. This LCA study covers the complete life cycle of a FED television device in accordance with the ISO 14040 standard, from the extraction of raw materials until the final end-of-life treatment in a European WEEE recycling system. Two different functional units were applied in this study: For the in-depth analysis of the FED television device, an entire device along its complete life cycle was considered as functional unit—for the subsequent comparison with today’s display technologies, “one square-inch of display during 1 h of active use” was used as an appropriate functional unit. Main data source for the FED device was patent information; ecoinvent was used as default background database. The in-depth analysis of this FED television device shows a clear dominance of the production phase (independently of the impact category). Within the production of such a device, the electronics part (i.e. the printed wiring boards) shows the highest contribution—while, even when focussing on the glass and its various coating layers only, the carbon nanotubes (CNTs) production has a very minor influence. The releases of CNTs during the End-of-Life treatment do not contribute in a relevant manner to the overall impact neither—even when focussing on the “ecotoxicity potential” by using conservative CFs reported for this type of releases. Last but not least, the comparison with the existing television display technologies shows that an FED device has an environmental advantage over all three other technologies using the above stated functional unit of “one square-inch of display during 1 h of active use”. Traditional impact categories as well as the ecotoxicity factor results in clear environmental advantages for an FED television device when comparing it to the three display technologies used today. Concerning the general issue of evaluating applications of manufactured nanomaterials in LCA studies, this case study shows the high relevance of an adequate integration of nanoparticle releases into LCA studies in order to achieve an actually comprehensive evaluation.

Low-temperature solution growth of ZnO nanocone/highly oriented nanorod arrays on copper.

Solution-phase approaches to one-dimensional (1D) ZnO nanostructure arrays are appealing because of their good potential for scale-up. Allowing for a wide variety of substrate material compatibility and saving energy, it is very essential to further research the low-temperature growth process of 1D ZnO nanostructure arrays and its detailed growth mechanism. In this study, large-scale misaligned hexagonal ZnO nancone arrays were synthesized on bare copper foil, while large-scale well-aligned, and highly oriented ZnO nanorod arrays were grown on seeded copper foil through a facile solution processing method at normal atmospheric pressure at 35 °C. X-ray diffraction analysis verified the crystalline nature of the ZnO nanocone/nanorods, and transmission electron microscopy further confirmed the single-crystal nature and the preferential growth direction of the ZnO nanocone/nanorods. The room-temperature photoluminescence measurement qualitatively identified the intrinsic point defects in the ZnO nanocones/nanorods. Besides, the detailed growth behavior of ZnO was discussed with and without a ZnO seed layer, which provides useful information to propose the growth mechanism of the nanocone/nanorods in the low-temperature solution. The method developed here can be easily scaled up to fabricate ZnO nanostructures for many important applications in field emission display, gas sensors, and superhydrophobic surfaces.

Synthesis and Cathodoluminescent Properties of Y2O3: Eu3+ Phosphor with Micron-sized Controllable Particles

Abstract The luminescent properties of phosphors are sensitive to their morphologies, particularly to the sizes of phosphor particles. The optimal morphology of the phosphor for the field emission display (FED) is the microsized sphere-like particles. However, less attention has been paid to the phosphors with micron-size controlled particles. In this paper, we reported an improved co-precipitation method to synthesize the red-emitting Y 2 O 3 :Eu 3+ phosphor with the particle sizes controlled in several microns. The optimum phosphors were obtained at the calcination temperature of 1050 °C and pH=5.5, showing the sphere-like particles with the size distribution from 0.9 μm to 3.1 μm. Compared with the commercial phosphors, such optimum phosphors greatly enhance the cathodoluminescent properties and the corresponding luminescence intensity under the low excitation voltage of 1 kV is increased by 50%. Results indicate an effective way to develop the high-quality FED phosphors.

Study on the Driving Circuit of Carbon Nanotube Field Emission Display Based on Luminance Control

Carbon nanotube field emission display (CNT-FED) is one of the most significant subjects due to its unique qualities and perfect performance. But there are still some problems in FED, for example, the modulation of each pixel unit of field emission display device is discrete, and the traditional voltage pulse-width modulation driving mode cannot solve luminance non-uniformity and non-linearity of FED. So a novel driving circuit based on cathode current source is proposed. The current driving circuit can be fabricated on Si substrate in advance, and then carbon nanotube is grown at room temperature, carbon nanotube and constant current source circuits are integrated on the same Si substrate. Current source circuit and cathode emission part are integrated together, which not only can solve the FED luminance problem, but also can meet FED thin design.

Influence of Vacuum on Nano-Diamond Cathode Field Emission Characteristics

The test of nano-diamond cathode field emission characteristics was conducted by changing the vacuum, the influence of vacuum change on nano-diamond field emission characteristics was also explored. It was found that under the condition of low vacuum, nano-diamond field emission turn-on field is relatively high, as the vacuum increases, turn-on field decreases gradually, and current density increases. When system vacuum reaches to above 10-4Pa level, turn-on field becomes stable, the stable value is 4.5 V/μm; and current density also becomes stable, the stable value is 117 μA/cm2; the luminescence effect of anode which is 200μm distant from the cathode in the vacuum chamber also becomes stable. Results show that 10-4Pa is system vacuum limit parameter of stable working of field emission display, the experiment provides a basis to the design and manufacture of nano-diamond field emission display.

Monodisperse and hollow structured Y2O3:Ln3+ (Ln = Eu, Dy, Er, Tm) nanospheres: A facile synthesis and multicolor-tunable luminescence properties

A novel, fast and simple method was developed to synthesize the undoped and lanthanide-doped yttrium oxide hollow nanospheres (Y2O3⋅HNSs) with multicolored downconversion emission under mild conditions by employing poly (acrylic acid sodium salt) microspheres (PAAS MSs) as active templates followed by a subsequent calcination process. The structure, morphology, formation process, and fluorescent properties are well investigated using various techniques. The results show that the samples can be well indexed to the pure cubic phase of Y2O3. The possible formation mechanism of the PAAS MSs, PAA-Y precursor, and Y2O3 HNSs are proposed and discussed in detail. Upon ultraviolet excitation, the obtained Y2O3:Ln3+ (Ln=Eu, Dy, Er, Tm) HNSs exhibit strong red, yellow–green, blue, yellow emission, respectively. Moreover, a novel single-phased and near-UV-pumped white-light-emitting phosphor Y2O3:Tm3+, Dy3+ was also successfully fabricated through optimizing the molar ratio among Tm3+ and Dy3+ in the Y2O3 host. This material may find potential applications in field-emission display devices and white ultraviolet light-emitting diodes (UV LEDs). Furthermore, this synthesis route may be of great significance in the preparation of other hollow spherical materials.

Towards Highly Transparent and Flexible Field Emission Displays Based on Low-Dimensional Nanocarbon

Transparency and flexibility are key words required for the devices of next generation. This is also the case for displays, for example, highly intelligent information displays for the upcoming ubiquitous world. To realize the transparent and flexible devices, nanocarbon, such as carbon nanotubes (CNTs), carbon nanofibers (CNFs) and graphene, are promising. In the present talk, nanocarbon-based highly transparent and flexible displays will be dealt with. Field emission displays (FEDs) offer promising advantages such as high brightness, low power consumption, wider viewing angle, etc. Recently some groups have demonstrated the fabrication of nanocarbon based flexible (opaque) FEDs [1, 2]. The next step is the realization of transparency. To achieve this, we are tackling several approaches based on single-walled CNTs, ion-induced conical nanocarbons and their hybrid structures formed on transparent and flexible polymer substrates [3-8]. In addition, in situ transmission electron microscope (TEM) observation of graphene and CNT formation from amorphous carbon-based nanofibers by solid phase reaction during field emission process will be demonstrated [9].1. H. S. Sim, et al., Appl. Phys. Lett., 90 (2007) 143103-143105. 2. B-J. Yoon, et al., J. Am. Chem. Soc., 127 (2005) 8234-8235.3. P. Ghosh, et al., J. Am. Chem. Soc., 132 (2010) 4034-4035.4. D. Ghosh, et al., Chem. Commun., 47 (2011) 4980-4982.5. M. Tanemura and S. P. Lau: "Flexible Field Emitters: Carbon Nanofibers" in "Carbon Nanotube and Related Field Emitters: Fundamentals and Applications" Edited by Y. Saitoh, Wiley-VCH (Weinheim) (2010), Chapt. 15.6. D. Ghosh, et al., Phys. Status Solidi RRL 6 (2012) 303–305.7. D. Ghosh, et al., Phys. Status Solidi RRL 7 (2013) 1080–1083.8. P. Ghosh, et al., J. Nanoscience and Nanotechnology, 13 (2013) 5767-5772.9. M. Zamri, M. Tanemura, et al., ASC Nano, 6 (2012) 9567-9573.

Synthesis and luminescence characteristics of nitride Ca1.4Al2.8Si9.2N16:Ce3+, Li+for light-emitting devices and field emission displays

A green-emitting nitride phosphor Ca1.4Al2.8Si9.2N16:Ce3+, Li+ (CASN:Ce) has been successfully synthesized which is applicable to near-ultraviolet based light-emitting diodes (LEDs) and field emission displays (FEDs). The characteristic photoluminescence (PL) properties were studied in detail by PL excitation, emission spectra and time-resolved spectroscopy. CASN:0.10Ce exhibits broad-band green emission centered at ∼525 nm (FWHM ≈ 135 nm) under 395 nm excitation and with excellent thermal stability. The effect of host lattice composition on PL properties was also discussed. The cathodoluminescence (CL) spectra as a function of accelerating voltage and probe current were also studied. Excellent degradation resistance properties with good color stability were obtained by continuous low-voltage electron-beam excitation of the phosphor.

Effect of growth pressure on the synthesis of vertically aligned carbon nanotubes and their growth termination.

When vertically aligned carbon nanotubes (VACNTs) are synthesized by thermal chemical vapor deposition (TCVD), their structural features such as height and density can be determined by TCVD growth conditions. In this study we investigated the effect of growth pressure on the structural features of VACNTs. Changes in growth pressure significantly affected the height, density, and crystalinity of synthesized VACNTs. In addition, we suggest that the growth termination of VACNTs could be due to the lack of carbon feedstock supply to the center of the VACNT film induced by the pressure-dependent adsorption of amorphous carbon at the edge of the VACNT film. In addition, the field emission characteristics of the VACNT film were carried out. The turn-on voltage of the VACNT film was 1.62 V/microm and the field enhancement factor (beta) was 2478. These results provide useful information for practical applications of VACNTs, such as field emission display and X-ray source.

Hydrothermal Fabrication and Luminescence Properties of One‐Dimensional TiO2:Eu3+ Spindlelike Nanorods

AbstractHighly crystalline and uniform TiO2:Eu3+ spindlelike nanorods have been successfully synthesized through a facile hydrothermal route with citric acid (H3Cit) and ethanediamine (en) as the assistant agents for the first time. X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected‐area electron diffraction (SAED), and photoluminescence (PL) spectroscopy were utilized to characterize the samples. In the synthetic process, the dosages of ethanediamine and citric acid are important parameters that affect the morphology and size of the final products. A possible formation process of the samples has been proposed in detail. The existence of Eu3+ sites in the TiO2 nanorods was proved by site‐selective spectroscopy. Furthermore, the TiO2:Eu3+ spindlelike nanorods exhibit bright red (Eu3+, 5D0→7F2) luminescence under ultraviolet (UV) excitation; therefore, they may find potential applications in fluorescent lamps and field‐emission displays (FEDs).

Synthesis, characterization and optical properties of NH4Dy(PO3)4

Polycrystalline powders of NH4Dy(PO3)4 polyphosphate have been grown by the flux method. This compound was found to be isotopic with NH4Ce(PO3)4 and RbHo(PO3)4. It crystallizes in the monoclinic space group P21/n with unit cell parameters a=10.474(6)Å, b=9.011(4)Å, c=10.947(7)Å and β=106.64(3)°. The title compound has been transformed to triphosphate Dy(PO3)3 after calcination at 800°C. Powder X-ray diffraction, infrared and Raman spectroscopies and the differential thermal analysis have been used to identify these materials. The spectroscopic properties have been investigated through absorption, excitation, emission spectra and decay curves of Dy3+ ion in both compounds at room temperature. The emission spectra show the characteristic emission bands of Dy3+ in the two compounds, before and after calcination. The integrated emission intensity ratios of the yellow to blue (IY/IB) transitions and the chromaticity properties have been determined from emission spectra. The decay curves are found to be double-exponential. The non-exponential behavior of the decay rates was related to the resonant energy transfer as well as cross-relaxation between the donor and acceptor Dy3+ ions. The determined properties have been discussed as function of crystal structure of both compounds. They reveal that NH4Dy(PO3)4 is promising for white light generation but Dy(PO3)3 is potential candidates in field emission display (FED) and plasma display panel (PDP) devices.

Vertically Aligned Carbon Nanotubes Transfer with Glass Frit

Nanogetters, based on carbon nanotubes (CNTs) coated Ti films, do have higher pumping speed and possibly larger sorbed quantity compared with traditional getters, such as St175 of SAES [1]. Although the nanogetter is with the outstanding performance, it is still hard to be integrated into micro electro mechanical systems (MEMS) packaging and devices due to high growth temperature of CNTs (>700°C) [2], poor adhesion with substrate [3, 4], vulnerability to pollute the wafers and difficulty to pattern. Therefore, this paper proposes a promotion of nanogetter based on transferring out vertically aligned CNTs (VA-CNTs) utilizing the glass frit. Compared with the conventional nanogetters, the promotion processes have advantages of (1) compatibility to the MEMS materials with controllable melting temperature and coefficient of thermal expansion (CTE), (2) Enhancement of the adhesion between CNTs and substrate, (3) Avoiding polluting the package wafer during CNTs growth. The results indicate that the promotion processes can be fulfilled by the silicon wafers and have wide applications such as nanogetters, field emission display, etc.

Synthesis, structural and optical properties of SrZrO3:Eu3+ phosphor

Eu3+ activated Sr1−xEuxZrO3 (x=0.01−0.04) phosphor with perovskite structure was successfully synthesized by using combustion method. The structure, morphology and optical properties of the material were characterized by X-ray diffraction, scanning electron microscopy and fluorescence spectrometry. The XRD results indicated that crystals of SrZrO3:Eu3+ belongs to tetragonal perovskite system. The phosphor could be effectively excited by UV light and the emission spectra results indicated that reddish-orange luminescence of SrZrO3:Eu3+ due to magnetic dipole transition 5D0→7F1 at 593 nm was dominant. Thus, the prepared phosphor showed remarkable luminescent properties which find applications in field emission display (FED) and plasma display panel (PDP) devices.

Red LaPO4:Eu Nanophosphor for Near UV LED and Field Emission Display Applications

For the phosphor materials, lanthanum phosphate (LaPO4) phosphor is one of potential materials for use in energy-efficient lightings, especially for ultraviolet (UV) light emitting diode (LED) and field emission display (FED) applications. In recent years, with the development of nanotechnologies, the synthesis of LaPO4 phosphor with nanosize particles is of increasing scientific and technical interest. In this study, the LaPO4:Eu nanophosphor was prepared with the coprecipitation (CP) method using different phosphate sources and anionic surfactants. The phosphor particle size analyzed by the SEM was about 0.5–1.2 μm. The phosphor synthesized by the CP method had improved crystallinity, smooth morphology, and decreased nonradiative transition, consequently, a twofold increase in luminescence intensity was obtained when compared with the phosphor prepared by the solid state reaction method. Under the excitation at wavelength of 396 nm (the emission wavelength of a UV LED), the LaPO4:Eu phosphor showed a red emission with peak at 594 nm (5 D 0 → 7 F 1). The maximum luminescence intensity of phosphor was obtained when it was doped with 7 mol% Eu3+ and sintered at 1200°C for 2 h. Emission degradation measurement shows that the emission intensity at wavelength of 594 nm was decayed with single-exponential mechanism. The measured decay time was 2.95 ms. The absorption and emission spectra of the phosphor varied with the kinds of phosphate sources. Using H3PO4 as phosphate source, a strong charge transfer band (CTB) absorption and high 5 D 0 → 7 F 2 emission were measured. When (NH4)2HPO4 and Na5P3O10 were used, a red-shifted and decreased CTB absorption was observed. This shift was caused by the increase in O2- - Eu3+ distance and the crystallinity variation of the phosphor, which led to the decrease in charge transfer energy. On the other hand, for the f-f orbital absorption transitions of Eu3+ inner electrons, the energy absorptions of phosphor prepared with phosphate sources of (NH4)2HPO4 and Na5P3O10 were stronger than that of phosphor prepared with H3PO4. Hence, an increased 5 D 0 → 7 F 1 emission was observed. The highest crystallographic symmetry of Eu3+ in the lattice and a high color-purity red emission were obtained when the (NH4)2HPO4 was used as phosphate source material. To further enhance the photoluminescence (PL) of the phosphor for LED application, anionic dispersants were used to modify the surface of phosphor particles. The dominant growth plane was changed from (200) to (120) plane when the phosphor was synthesized with dispersants. The decay time of phosphor was 3.02, and 3.15 ms when SDS and (NaPO3)6 dispersants were used, respectively. A certain improvement in the decay time was observed. Apparently, the surface states of phosphor particles were modified, hence, the PL intensity was enhanced. The optimal crystallinity and the maximum PL intensity of phosphor were obtained when 1 and 3 mol% of (NaPO3)6 and SDS were used, respectively, and the corresponding increment in the PL intensity was 10 and 7%. Moreover, conductive material of carbon nanotubes (CNTs) was doped to improve the cathodoluminescence (CL) of phosphor for FED application. The addition of CNTs reduced the accumulation of electrons on the phosphor surface. Consequently, the CL intensity was increased. The maximum CL intensity was obtained when 1 wt% of CNT was doped. The CL intensity was enhanced by 1.35 times.

Energy Transfer and Tunable Luminescence of NaLa(PO3)4:Tb3+/Eu3+ under VUV and Low-Voltage Electron Beam Excitation

Series of NaLa(PO3)(4):Tb3+/Eu3+ phosphors were prepared by a hightemperature solid-state reaction technique. Structure refinements were performed based on powder X-ray diffraction (XRD) data. VUV-UV-vis photoluminescence (PL), fluorescence decays, time-resolved emission spectra (TRES), and low-voltage cathodoluminescence (CL) spectra were utilized to investigate the luminescence and energy transfer processes. Under VUV-UV light and low-voltage electron beam excitation, NaLa(PO3)(4):Tb3+ and NaLa(PO3)(4):Eu3+ exhibit characteristic emissions of Tb3+ (D-5(4) --> F-7(J)) and Eu3+ (D-5(0) --> F-7(J)), respectively. By adjusting the doping concentration of Eu3+ ions in NaTb0.70La(0.30-x)Eux(PO3)(4), tunable emission colors are realized in a large color gamut, in which energy transfer from Tb3+ to Eu3+ was observed and discussed in detail. On the basis of the good VUV-vis PL and CL properties, NaLa(PO3)(4):Tb3+/Eu3+ phosphors might be promising for applications in plasma display panels (PDPs) and field emission displays (FEDs).

Evaluating the Environmental Impacts of a Nano-Enhanced Field Emission Display Using Life Cycle Assessment: A Screening-Level Study

Carbon nanotube (CNT) field emission displays (FEDs) are currently in the product development stage and are expected to be commercialized in the near future because they offer image quality and viewing angles comparable to a cathode ray tube (CRT) while using a thinner structure, similar to a liquid crystal display (LCD), and enable more efficient power consumption during use. To address concerns regarding the environmental performance of CNT-FEDs, a screening-level, cradle-to-grave life cycle assessment (LCA) was conducted based on a functional unit of 10,000 viewing hours, the viewing lifespan of a CNT-FED. Contribution analysis suggests the impacts for material acquisition and manufacturing are greater than the combined impacts for use and end-of-life. A scenario analysis of the CNT paste composition identifies the metal components used in the paste are key contributors to the impacts of the upstream stages due to the impacts associated with metal preparation. Further improvement of the manufacturing impacts is possible by considering the use of plant-based oils, such as rapeseed oil, as alternatives to organic solvents for dispersion of CNTs. Given the differences in viewing lifespan, the impacts of the CNT-FED were compared with a LCD and a CRT display to provide more insight on how to improve the CNT-FED to make it a viable product alternative. When compared with CRT technology, CNT-FEDs show better environmental performance, whereas a comparison with LCD technology indicates the environmental impacts are roughly the same. Based on the results, the enhanced viewing capabilities of CNT-FEDs will be a more viable display option if manufacturers can increase the product's expected viewing lifespan.

增强碳纳米管场发射性能的沟槽形冷阴极制作

Based on sintering process and screen printing technique,a novel groove shape cold cathode was developed.The black insulation slurry was sintered to fabricate the bottom insulation layer,in which a gradient surface existed.The silver slurry was screen-printed on the bar electrode. With the baking and sintering process in proper sequence,the silver electrode was formed.Using fine sandpaper,aproper polishing process for silver electrode was conducted,so a smooth electrode surface was obtained.Due to the special silver electrode shape,a larger field enhancement factor was achieved easily.Carbon nanotubes were prepared on the silver electrode to form the field emitters. The dense carbon nanotube layer would cover the silver electrode surface completely.Owing to the special edge field enhancing effect,lots of electrons would be emitted from the carbon nanotube.The top insulation layer was used to restrain the side electron emission of carbon nanotube.With the groove shape cold cathode,a triode field emission display was fabricated,which exhibited good field emission properties and better luminescence image uniformity.Comparing with the common cold cathode field emission display,the turn-on electric field could be reduced from 1.86 V/μm to1.78V/μm,the maximum field emission current had been increased from 1 537μA to 2 863μA,and the maximum luminescence image brightness would be enhanced from 1 386cd/m2 to 1 865cd/m2.The developed fabrication technology had a potential practical application in field emission display.

Synthesis, electronic structures and luminescent properties of Eu3+ doped KGdTiO4

Eu3+-activated layered perovskite ionic conductor KGdTiO4 red emitting phosphors to be used for ultraviolet based light emitting diodes (LEDs) and field emission displays (FEDs) were successfully synthesized by a modified sol–gel method.

Fabrication of Nanostructured ZnO Films for Transparent Field Emission Displays

A highly transparent field emitter was achieved by Ar+ ion irradiation onto highly transparent and conducting ZnO films deposited on glass substrates. The as-deposited flat ZnO films before ion irradiation, which showed 90% transmittance and 186 Ω/□ sheet resistance, showed no field emission current up to 15 V µm-1. The ZnO film ion-irradiated at an ion-incidence angle of 45° showed nanocone structures about 200–400 nm in height and 6–8 µm-2 in number density. Since the nanocone size was less than the wavelength of visible light, the transmittance was maintained at 86% for the ion-irradiated ZnO film. The field emission properties of the ion-irradiated ZnO film revealed that a current density of 1 µA cm-2 was achieved at 6.2 V µm-1, and that the field enhancement factor was calculated to be 2252 from the Fowler–Nordheim plot. Thus, the nanostructured ZnO film is believed to be promising as a transparent field emitter.