Characteristics of an electron source of a surface‐conduction electron‐emitter display

Abstract— The electron source is an essential part of a surface‐conduction electron‐emitter display (SED). An electron source for an SED was obtained after certain procedures were performed. By introducing a carbon atmosphere, the electron‐emission characteristics of a SED were studied experimentally. The electron‐emission characteristic curves were drawn after comparing the experimental data of the electron source obtained in a vacuum environment with the data obtained in a carbon atmosphere, from which it had proved that a carbon atmosphere could significantly improve the electron‐emission characteristics of a SED. As a result, both the device current and the emission current had become stronger and the efficiency of surface‐conduction electron emission had been improved significantly. The possible reasons were analyzed: more carbon, which could possibly form the electron‐emission region of a SED, was produced from the carbon atmosphere during the electrical activation process.     

Characteristics of surface‐conduction electron emitters made by ion‐exchange technology

Abstract— The principle and preparation method of the ion‐exchange technology used in surface‐conduction electron emitters is introduced in this paper. Surface‐conduction electron emitters through the use of ion‐exchange technology were developed. The relationships between device current and emission current on device voltage has been determined. The electronic emission characteristic of surface‐conduction electron emitters were also determined. The results indicate that the relationship between emission current and device voltage is non‐linear. A device‐voltage range between 20 and 27 V results in the best emission efficiency.     

Development of high‐brightness flat field‐emission lamp with a special electrode system for block dimming BLUs for LCDs

Abstract— A flat field‐emission lamp (FFEL) has been developed that utilizes a specially designed electrode structure and an unique nanostructure carbon electron emitter called a carbon nanometer electron exit (CNX) emitter. CNX emitters have been developed on metal‐wire substrates with a special plasma chemical‐vapor‐deposition technique. Field electron emission from CNX emitters has been investigated in a vacuum of 2×10^?4 Pa by using a diode configuration with an A–K space of 1 mm, which shows that an emission current of 5.7 A/cm² can be obtained at an electrical‐field strength of 2.2 V/μm. Then, the emission‐current stability was also carried out to investigate the CNX‐emitter lifetime. Also, scanning electron microscopy (SEM) and micro‐Raman spectrum was used to characterize the CNX film. Furthermore, the design of the special diode emission system was optimized by simulating the electron orbits with a commercial software, the result of which indicates that the emission system was used to effectively extract electrons from the emitter and control the local block dimming. And, also, a simple FFEL structure was used to illustrate the simulation results. Finally, a 7‐in. FFEL has been successfully fabricated, demonstrating a luminance of 15,000 cd/m² with an anode voltage of 6 kV.     

Eu2+‐doped barium thioaluminate EL devices prepared by two‐target pulsed‐electron‐beam evaporation

Abstract— New blue‐emitting thin‐film‐electroluminescent (TFEL) devices that satisfy the requirements for full‐color TFEL displays were developed. Eu²⁺‐doped BaAl²S⁴ thin films were used for the emission layer. BaAl²S⁴:Eu thin films were prepared by two‐target pulsed‐electron‐beam evaporation suitable for the deposition of multinary compounds that have difficulty in obtaining stoichiometoric thin films. The EL spectrum only had a peak at around 470 nm. The Commission Interantionale de l'Eclairge (CIE) color coordinates were x = 0.12 and y = 0.10. The luminance level from a 50‐Hz pulses voltage was 65 cd/m².     

Displacement‐current analysis of organic light‐emitting diodes

Abstract— Organic light‐emitting diodes (OLEDs) having multiple organic layers were fabricated to analyze the physical phenomena occurring in an OLED according to the amplitude of the applied voltage. The staircase voltage with both an increasing period and a constant period was designed and applied to an OLED. The displacement current began to change at a voltage where the conduction current began to change, and partly originated from the formation of space charge due to the low mobility of the majority carrier. The displacement current was shown to be constant at low voltage and decreased after showing a maximum value as the applied voltage increased. The exact voltage for the injection of two types of carriers and light emission could be obtained from the variation in the displacement current.     

High‐efficiency red‐phosphorescent organic light‐emitting diode with the organic structure of 2‐TNATA/Bebq2:SFC‐411/SFC‐137

Abstract— High‐efficiency and simple‐structured red‐emitting phosphorescent devices based on the hole‐injection layer of 4,4′,4″‐tris(2‐naphthylphenyl‐phenylamino)‐triphenylamine [2‐TNATA] and the emissive layer of bis(10‐hydroxybenzo[h] quinolinato)beryllium complex [Bebq²] doped with SFC‐411 (proprietary red phosphorescent dye) have been researched. The fabricated devices are divided into three types depending on whether or not the hole‐transport layer of N,N′‐bis(1 ‐naphthyl)‐N, N'‐diphenyl‐1,1′‐biphenyl‐4,4′‐diamine [NPB] or the electron‐transport layer of SFC‐137 (proprietary electron transporting material) is included. Among the experimental devices, the best electroluminescent characteristics were obtained for the device with an emission structure of 2‐TNATA/Bebq²:SFC‐411/SFC‐137. In this device, current density and luminance were found to be 200 mA/cm² and 15,000 cd/m² at an applied voltage of 7 V, respectively. Current efficiencies were 15 and 11.6 cd/A under a luminance of 500 and 5000 cd/m². The peak wavelength in the electroluminescent spectral distribution and color coordinates on the Commission Internationale de I'Eclairage (CIE) chart were 628 nm and (0.67, 0.33), respectively.     

Tetrahedrally bonded amorphous carbon for field‐emission displays

Abstract— Field emission from a series of tetrahedrally bonded amorphous‐carbon (ta‐C) films, deposited in a filtered cathodic vacuum arc, has been measured. The threshold field for emission and current densities achievable have been investigated as a function of sp³/sp² bonding ratio and nitrogen content. Typical as‐grown undoped ta‐C films have threshold fields of the order 10–15 V/μm and optimally nitrogen doped films exhibit fields as low as 5 V/μm. In order to gain further understanding of the mechanism of field emission, the films were also subjected to H₂, Ar, and O₂ plasma treatments and were also deposited onto substrates of different work function. The threshold field, emission current, and emission site densities were all significantly improved by the plasma treatment, but little dependence of these properties on work function of the substrate was observed. This suggests that the main barrier to emission in these films is at the front surface.     

Efficient white organic light‐emitting diodes based on a balanced split of the exciton‐recombination zone using a graded mixed layer as an electron‐blocking layer

Abstract— Efficient white organic light‐emitting diodes with both a graded mixed layer as the blue‐emitting layer and an electron‐blocking layer, and a DPVBi:Rubrene layer as a yellow‐emitting layer have been demonstrated. The mixing of the two colors occurs due to a balanced split of the exciton‐recombination zone by the graded mixed layer serving as the electron‐blocking layer. The white organic light‐emitting diode with an ITO/2‐TNATA 30 nm/NPB 30 nm/DPVBi:Rubrene (1.0 wt.%) 5 nm/NPB:DPVBi (9:1) 150 nm/NPB:DPVBi (5:5) 75 nm/NPB:DPVBi (3:7) 75 nm/NPB:DPVBi (2:8) 75 nm/NPB:DPVBi (0.5:9.5) 75 nm/BCP 5 nm/Alq³ 30 nm/LiF 0.5 nm/Al 100 nm structure is chosen as a device with an optimal configuration among devices investigated in this study. The employment of the graded mixed layer in the device is effective in suppressing the color shift at different voltages. The white light, with a Commission Internationale d'Eclairage chromaticity coordinates of (0.33, 0.34), is obtained with an applied voltage of 10.5 V for the device. At the applied voltage, the luminance is 4882 cd/m² and the current efficiency is 5.03 cd/A.     

A field‐emitter‐array cathode‐ray tube (FEA‐CRT)

Abstract— High‐resolution bright CRT monitors with Spindt‐type field‐emitter arrays (FEA‐CRTs) as electron guns have been realized for the first time. The FEA chip consists of 868 electron sources arranged within an emitter circle 50 μm in diameter and a vertical current limiter (VECTL) which protects the FEA chips from damage caused by an arc electric discharge. The FEA‐CRT has a minimum electron beam diameter of 0.84 mm at 18 kV and 100 μA.     

Large‐screen displays using metal—insulator—metal cathode arrays

Abstract— Large‐screen (32‐in. WXGA and 17‐in. VGA) displays using metal—insulator—metal (MIM) cathode arrays have been developed. A cathode structure with low‐resistance electrodes and low‐capacitance emitters shortens signal delay and decreases the voltage drop in large MIM‐cathode arrays. By using a dual‐scan method, the signal delay was suppressed to less than 30% of the horizontal scan time in the 32‐in. WXGA panel. Emission efficiency of the cathode array was improved to 3% by reducing the surface work function of the top electrode from 4.7 to 3.9 eV. The cathode life was also improved to more than 10,000 hours. The display panel incorporating the cathode arrays and high‐efficiency P22‐phosphor screens with 3‐mm spacers showed high screen brightness (average brightness, 378 cd/m²; peak brightness, 832 cd/m²) at an anode voltage of 10 kV.     

Mercury‐free 18‐in. flat fluorescent lamp with good uniformity

We have developed an 18‐in. 287 × 359‐mm flat fluorescent lamp (FFL) that uses a xenon dielectric barrier discharge and analyzed its electro‐optical characteristics. The surface luminance of the lamp having a diffuser sheet thickness of 3 mm was 5600 cd/m² and the luminance uniformity was 92% at an applied voltage of 950 Vrms. The luminous efficacy of the FFL was 24.5 lm/W for a luminance of 4200 cd/m² when driven by a sine‐wave voltage.     

Flexible color LCD panel driven by low‐voltage‐operation organic TFT

Abstract— A flexible color LCD panel driven by organic TFTs (OTFTs) was successfully demonstrated. A pentacene OTFT with an anodized Ta₂O₅ gate insulator, which can be operated at low voltage, was developed. In order to improve the electrical performance of the OTFT, the gate insulator was surface treated by processes such as O₂ plasma, UV light irradiation, and hexamethyldisilane treatments. The fabricated OTFT exhibited a mobility of 0.3 cm²/V‐sec and a current on/off ratio of 10⁷ with a low operating drain voltage of ?5 V. A fast‐response‐time flexible ferroelectric LCD, which contains polymer networks and walls, was integrated with the OTFTs by using a lamination and a printing technique. As a result, color images were achieved on the fabricated panel by using a field‐sequential‐color method at a low driving voltage of less than 15 V_pp.     

Mercury‐free 18‐in. flat fluorescent lamp with good uniformity

Abstract— We have developed an 18‐in. 287 × 359‐mm mercury‐free flat fluorescent lamp (FFL) having a new structure that utilizes dielectric barrier discharge and contains pure xenon gas. The electro‐optical characteristics have been analyzed. The surface luminance of the lamp having a diffuser sheet is 5600 cd/m² and the luminance uniformity is 92% at an applied voltage of 1050 Vrms and an applied frequency of 20 kHz in the form of a sine wave.     

Numerical analysis of density of energy states for electron‐emission sources in MgO

Abstract— An analytical method to determine the density of energy states of electron‐emission sources (EESs) in chemical‐doped MgO is described using a discharge probability model and a thermal excitation and emission model. The density of energy states for multiple types of EESs is represented by using a linear combination of Gaussian functions of which parameters are determined by the theoretical emission time constant of an exoelectron and statistical delay time ts extracted from experimental stochastic distributions of discharge delay time in plasma‐display panels. When applied to Si‐doped MgO, the effective number of Si EES is calculated to be 1.8 × 10⁶ per cell. The average and standard deviations of activation energy have an energy level of 770 meV and a large value of 55 meV. In Si and H co‐doped MgO, the high peak density of [H^2?]⁰ appears at 550 meV. ts at the short time interval of 1 msec decreases and is independent of temperature due to exoelectron emission from the [H^2?]⁰. The dependence of ts at a time interval of 10 msec on temperature becomes weak because the energy structure of the Si EES broadens significantly attributed to the electrostatic effects of the doped H atoms.     

Fabrication of low‐temperature‐polysilicon thin‐film transistors on flexible substrates using excimer‐laser crystallization

Abstract— Low‐temperature‐polysilicon thin‐film transistors (LTPS TFTs) were fabricated on polymer substrates using sputtered amorphous‐Si (a‐Si) films and excimer‐laser crystallization. The in‐film argon concentration of a‐Si films was minimized as low as 1.6% by using an argon/helium gas mixture as the sputtering gas. By employing XeCl excimer‐laser crystallization, poly‐Si films were successfully fabricated on polymer substrates with an average grain size of 400 nm. With a four‐mask process, a poly‐Si TFT was fabricated with a fully self‐aligned top‐gate structure, and the pMOS TFT device showed a field‐effect mobility of 63.6 cm²/V‐sec, ON/OFF ratio of 10⁵, and threshold voltage of ?1.5 V.     

磁控溅射SiC薄膜及其电学特性研究

用磁控溅射法(RMS)制备了SiC微晶薄膜,并对其进行了退火处理.用AFM观察了薄膜的表面形貌,测量了薄膜的厚度、方块电阻和电阻-温度曲线.结果表明:薄膜表面平整光滑;退火处理前后薄膜样品的lnR随1/kT的变化曲线均满足表达式,电子激活能的变化范围为0.0142 eV～0.0185 eV,且随退火温度的升高而增大;分析确定其导电机理为定域态间近程跳跃电导.退火前后薄膜电阻率的范围为2.4×10-3～4.4×10-Ω·cm,且随退火温度的升高而增大,与电子激活能的变化趋势一致,这进一步验证了本文提出的薄膜导电机理和激活能随退火温度的变化趋势.     

Surface‐light‐emitting transistors based on vertical‐type metal‐base organic transistors

Abstract— Light‐emitting transistors having a metal‐base organic transistor (MBOT) structure demonstrate both the function of an organic thin‐film transistor (OTFT) and organic light‐emitting diode (OLED). The MBOT is a vertical‐type organic transistor having a simple structure composed of organic/metal/organic layers demonstrating high‐current and low‐voltage operation. The light‐emitting MBOT was fabricated simply by inserting additional layers of hole‐transporting and emissive materials used in the OLED into the col lector layer. The device showed perfect surface emission similar to an OLED. A luminance modulation of 370 cd/m² was observed at a collector voltage of 20 V and a base voltage of 3 V. This device can be applied to an OLED display device to increase the numerical aperture or reduce the required current of the TFT backplane.     

Comparison of some characteristics of thin‐film‐electroluminescent ZnS: Er,F planar and edge emitters

Abstract— The following main differences have been revealed in the characteristics of an edge thin‐film‐electroluminescent ZnS: Er,F emitter compared to those of a similar planar emitter: (1) the 1.535‐μm band more highly dominates over other bands in the EL spectrum; (2) the voltage (V) dependence of the intensity of this band is the strongest; (3) the 1.535‐μm band narrows with increasing voltage and its frequency. The above differences are explained, firstly, by smaller optical losses in the ZnS: Er,F film for the near‐infrared emission than for the visible one and, secondly, by an optical amplification over the 1.535‐μm band in the edge emitter.     

Uniform carbon‐nanotube emitter for field‐emission displays

Abstract— 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.     

Dependency of PDP efficacy on gas pressure

The dependency of the efficacy of an alternating‐current surface‐discharge plasma‐display panel (PDP) on the gas pressure was investigated for several Xe‐Ne gas mixtures. Also, the sustain voltage was varied. Monochrome 4‐in. test panels, with a design which resembles the one used in mainstream commercial products, were used. The experimental panel efficacy and emission characteristics were compared to the results of a numerical discharge model. A strong increase in the efficacy for increasing voltage was found in high‐gas‐pressure mixtures with a high Xe concentration. An increase in the electron‐heating efficiency and of the Xe‐excitation efficiency contribute, about equally, to the increase in efficacy. The increase in the Xe‐excitation efficiency is due to an increase in the excitation in the lower Xe levels induced by a lowering of the electron temperature. The contribution of the increasing Xe‐dimer radiation fraction to the efficacy improvement is relatively small. These results imply an efficient panel design comprised of the combination of a high Xe concentration, a high gas pressure, and a high sustain voltage. A high luminance and a high efficacy are concurrent for such a design. A 4‐in. test panel containing a mixture of 13.5% Xe in Ne at 800 hPa has been realized, demonstrating a white luminance of 2600 cd/m² and an efficacy of 3.1 lm/Wfor continuous operation at 50 kHz and 230 V.