In the field of display phosphors, the efficiency of the cathodoluminescence process is a characteristic that is often used to assess the potential of a phosphor for use in flat-panel display applications such as field emission displays (FEDs). Cathodoluminescence characterization in a demountable vacuum chamber is important for preliminary evaluation and lifetesting of phosphor powders and screens prior to incorporation into an actual display device. There are many experimental factors that influence accurate measurement and calculation of the cathodoluminescence efficiency. These include electron beam profile (uniform, Gaussian), current density, electron accelerating voltage, secondary electron collection, and optical detection system. This paper will present some methods for achieving improved accuracy of cathodoluminescence measurements in systems at Sandia National Laboratories, using Y2O3:Eu as a representative phosphor.

Need for efficient blue light emitting source for optoelectronic device applications such as flat panel displays has made the research in luminescent material ever so important. Tungsten doped zinc oxide (ZnO:W) has been identified as a blue light emitting phosphor exhibiting cathodoluminescence near 490 nm. This paper details work done on ZnO:W phosphor preparation conditions for efficient light emission from the phosphor. Material characterization to identify the possible source of blue light emission will also be discussed.

This investigation studied the effects of Ho3+ and Er3+ on the luminescence of the blue emitting phosphor yttrium silicate, (Y1−mCem)2SiO5. Yttrium silicate has a large emission tail that extends into the red portion of the visual spectrum. To improve the chromaticity of this phosphor to give it a more saturated blue color, the emission intensity of the tail needs to be decreased. Photoluminscence and low-voltage cathodoluminescence measurements were performed on yttrium silicate phosphors with varying concentrations of Gd3+, Ho3+ and Er3+. It was found that when co-doping with Ho3+ and Er3+, the relative intensity of the emission tail was decreased, but so to was the overall luminescence intensity of this phosphor.

Europium-activated yttrium oxide (Eu:Y2O3) thin films were deposited on (100) silicon and (0001) sapphire substrates using 248 nm KrF pulsed laser. To investigate the effect of the Eu:Y2O3 film roughness on cathodoluminescence (CL) and photoluminescence (PL) properties, the substrate surfaces with various roughnesses were used. The roughness was found to play an important role in determining CL and PL brightness of the Eu:Y2O3 films. The improvement in brightness by increasing the film roughness is due to increase in total portion of light that escapes from the surface of the phosphor film. A model has been proposed which supports strongly this explanation. Our results show that depositions with slower growth rate and lower laser energy are more important parameters than increasing the roughness to improve CL brightness of the Eu:Y2O3 thin film phosphors.

In this paper, we introduce rare earth- or transition metal-activated oxide phosphor thin films prepared by magnetron sputtering and dip-coated solution deposition. Thin-film electroluminescent (TFEL) devices using these oxide phosphor thin films as the emitting layer were investigated with a single insulating layer device structure using a thick ceramic sheet insulating layer. High-luminance multicolor emissions and high luminous efficiencies were obtained in TFEL devices using various oxide phosphors: binary compound, Ga2O3; ternary compound, Zn2SiO4, CaGa2O4 and ZnGa2O4; and multicomponent oxide, Zn2SiO4-Zn2GeO4 system. Luminances above 2000 cd/m2were obtained in CaGa2O4:Mn and Zn2Si1-XGeXO4:Mn TFEL devices driven at 1 kHz. Maximum luminous efficiencies of 2.53, 1.7 and 1.2 Im/W were obtained in Zn2Si0.7Ge0.3O4:Mn, Ga2O3:Mn and ZnGa2O4:Mn TFEL devices, respectively. Stable long-term operation was obtained in dip-coated and sputtered Ga2O3:Mn phosphor TFEL devices even when driven at 10 kHz. Various thin-film oxide phosphors activated with transition metals are suitable for the emitting layer of full-color electroluminescent displays (ELD) without the use of color filters. In particular, Ga2O3 is very promising as a phosphor host material for ELDs.

This study has used secondary ion mass spectrometry (SIMS) as a technique for thin film EL material characterization. It has shown that the Cu dopant concentration in the SrS films directly correlates with the luminescent brightness of the EL devices. A series of SrS:Cu, Y were grown using MBE to study the Y co-doping effects. It has been found that Y peak concentration and areal density in the SrS increased as the Y evaporation cell temperature was increased. The maximum PL intensity was found in the sample grown in the middle of the Y cell temperature range used. The Y co-doping has shown to reduce the thermal quenching effects in SrS EL devices. Therefore, in this series of samples, a good correlation has been found between Y and Cu concentration and the EL device performance characteristics.

Field emission displays are currently undergoing rapid transition from laboratory prototypes into commercial display components. Display lifetime and reliability are critical issues that will determine success of these displays in the marketplace. In this paper, we will summarize issues affecting field emission display lifetime and a roadmap for creating long life field emission display devices.

Carbon based materials are considered to be amongst the most promising field emitters for use in displays. Semiconducting polymer (regioregular poly3 octylthiophene) has been found by the authors to have the lowest threshold field reported to date for any carbon based material. The emission process is, we believe, associated with surface irregularities, voids, possibly resulting from solvent evaporation. Field intensification occurs, and as a consequence there is field emission from the top ridges of the voids. The current flowing through these regions is controlled by space charge in traps in the upper half of the energy gap. There is, in addition, current injected from the base of the voids and the two currents mix to give field emission with current IαV1.8 where V is the anode voltage. Measurements on capacitor samples using Aluminium, Gold and Calcium electrodes have been used to examine the conduction processes in the material and these are linked to results of field emission to further illuminate the mechanisms involved and provide a model for the emission process.

Field emission characteristics from n- and p-type silicon gated emitter tips have been investigated in detail by means of experiments and theoretical estimation of band-bending induced by surface states. Single-tip emitters have been fabricated from n- and p-type silicon and their current-voltage characteristics have been evaluated. The field emission from the p-type emitter has been found to occur at lower extraction voltage than that of the n-type emitter. As the theoretical approach to the origin of the phenomena, potential distribution in the emitter tips has been calculated by using device simulation technique. The surface states of the n-type emitter tip are negatively charged and form a potential barrier against the electrons. On the contrary, there is no potential barrier in the p-type tips. The potential barrier in the n-type tip prevents electrons from reaching the tip apex. This is the reason why the emission current of the n-type emitter was suppressed lower than that of the p-type emitter.

We report observation of electron emission from individual carbon nanotubes. Two classes of emitters are observed, one emitting electrons with momentum nearly parallel to the nanotube axis, the other emitting electrons with nonzero momentum perpendicular to the tube axis. The emission pattern reflects the electronic structure of a particular tube and allows us to distinguish between structurally different nanotubes. These nanotube emitters exhibit excellent macroscopic emission properties; they can operate at a very large current density, as high as 4 A/cm2. At electric fields as low as 4-7 V/μm, they emit technologically useful current densities, e.g. 10 mA/cm2. The emission characteristics and durability of the carbon nanotube cold cathodes offer promising applications for vacuum microelectronic devices.

Field emission current-voltage characteristics and simultaneous field emission electron energy distributions have been measured using single tip gate diodes. An energy distribution is generated at each step of a current-voltage characteristic using a compact low-cost simulated hemispherical energy analyzer. A PC programmed with graphics-based data acquisition software is used for data acquisition and control. The PC is connected to a CAMAC crate and a picoammeter through a GPIB interface. The picoammeter measures the current leaving the tip and the field emission electrons are energy analyzed, detected and processed in the CAMAC crate. The CAMAC crate also sends control voltages. to the gate anode and the energy analyzer. This apparatus was used to measure tip work functions and Fowler-Nordheim tip shape parameters for Mo and IrO2 field emission tips. Work function measurements from field emission tips are compared to photoelectric work function measurements from flat surfaces.

We have developed a novel technique for the selective area deposition of rare earth hexaborides: laser-induced solution deposition (LISD). This technique is both simple and efficient and combines many advantages of both chemical vapor deposition and electrolytic deposition. The results of LISD deposition show that the polycrystalline thin films of rare earth hexaborides and sub-borides such as MB6, MB4, and MB2 (M = Gd, La) are formed through the light initiated chemical reaction of nido-decaborane (B10H14) and rare earth chloride in solution. These films grow with a strong texture growth axis and morphology that is dependent both on the selection of solvents and laser wavelengths and power used in LISD.

We present the results of tests measuring the life of carbon cold cathodes and determining what conditions limit the life of the cathode. Cathode life and stability are important for a broad range of applications, including displays, electron sources for satellite thrusters, x-ray tubes and microwave devices. Cathodes were tested in vacuum chambers using different gas environments as well as in sealed and gettered glass envelopes. We measured emission current half-lives of 10,000 - 20,000 hours or more in sealed display devices, depending on operating conditions. The presence of a significant oxygen or water partial pressure degrades the life of the cathode. After removing the gases the decay rate was restored to near the original value. A similar partial pressure of hydrogen gas has little or no effect on the life of the cathode. Initial results of operation in a xenon environment indicate carbon cold cathodes are much more robust compared to microtip cathodes. These results will be discussed with respect to the various applications considered for carbon cold cathodes.

Highly efficient electron emitting diodes have been fabricated using single-crystalline diamond films epitaxially grown on high-pressure synthesized (100) diamond. These diodes have an internal electrode of a graphitized layer buried below an overgrown diamond layer with a very high resistivity, the structure of which is formed by a combination of heavy ionimplantation and overgrowth techniques. The efficiency of electron emissions from sufficiently hydrogenated p-type diamond surfaces reached 100% in the best case. It is found that H atoms can passivate internal defects created during the ion implantation process. The mechanism of the high efficiency is discussed in relation to electron-hole creations in the thin diamond layer under extremely high electric fields of 107 V/cm.

Oriented carbon nanotube films were grown using a method of chemical vapor deposition in hydrogen/methane plasma activated by glow discharge. The film phase composition and structural features were studied by Raman, SEM, TEM, and HRTEM techniques. Field emission properties of the films were examined to obtain I-V characteristics and the field emission site distribution. The I-V curves in Fowler-Nordheim coordinates were linear, that is typical for the field emission, with the threshold average field about 1.5 V/μm and the emission current density up to 50 mA/cm2 at the field of 5 V/μm. The emission site density reached 107 cm2 at the same value of electrtic field.

Molybdenum carbide and diamond films were deposited at room temperature by dielectrophoresis on molybdenum foil and field emission tips. Films deposited on flat surfaces were characterized with XPS, UPS and SEM. Field emission Fowler-Nordheim current-voltage characteristics and electron energy distribution measurements were obtained using films deposited on field emission tips as part of a single aperture gated diode in a VG ESCALAB II system. Molybdenum trioxide was present after molybdenum carbide deposition at room temperature on all samples. At a temperature of about 650 °C, the dominant oxide changes to molybdenum dioxide. At about 800 °C, the oxygen content of the films significantly decreases and molybdenum carbide with significant graphite content remains. The UPS data for these samples were obtained at different annealing temperatures and a number of photon energies to determine photoelectric work functions for molybdenum trioxide, molybdenum dioxide and molybdenum carbide. The same kind of data was obtained for diamond deposited on molybdenum and molybdenum carbide coated foils and field emission tips.

A high-voltage hydrogenated amorphous silicon thin film transistor (H-V a-Si:H TFT) with thick double layer gate insulator (∼0.95 μm) has been developed for reflective active-matrix cholesteric liquid crystal displays. The double layer gate insulator consists of 0.85 and 0.10 μm thick benzocyclobutene and hydrogenated amorphous silicon nitride, respectively. This HV a-Si:H TFT operates at the gate-tosource and drain-to-source biases up to 100V without any serious leakage current degradation and device breakdown.

As the active matrix flat panel market continues to grow, manufacturers are constantly looking for ways of gaining an advantage in the marketplace typically through increased performance, expanded functionality and/or reduced cost. The continuing trend of larger panel sizes and higher resolution poses interesting challenges for manufacturers in the areas of image quality and brightness. In particular, it has been clearly shown that as pixel dimensions shrink, relative crosstalk coupling coefficients increase while the area available for pixel electrodes and storage capacitors (Cδ,t) decreases, so that charge compensation drive schemes must be employed to eliminate visual artifacts. One approach to minimizing crosstalk and flicker is to increase Cδ,t, however this requires increased pixel area, usually at the expense of brightness due to smaller aperture ratio. Depending on design and process flow, it may be possible to replace the typical Cδ,t, insulator, SiNx:H, with a material of higher dielectric constant thereby vastly improving electrical performance without sacrificing brightness.

Constraint theory developed for bulk glasses and recently applied to thin films and single crystalline Si (C-Si) dielectric interfaces is extended in this paper to a-Si:H and polycrystalline-Si (poly-Si) dielectric interfaces in TFTs where it provides guidelines for device optimization. The constraining effects of network bonding forces are a linear function of the average bonding coordination, Nav. Nav ∼ 3 separates low-defect density networks as in Si02 (Nav =2.67), from highly-defective networks such as non-hydrogenated Si3N4 (Nay = 3.43). Nay ∼ 3 also separates device-quality from highly-defective Si-dielectric interfaces. These criteria are applied to Si-Si02 and Si-SiNx:H interfaces that are integral components of TFT devices.

Lateral FEAs which have three terminals, stable anode current, and suppressed gate current are proposed and fabricated. In order to eliminate the path of electrons between tips and anode, the proposed FEAs are sealed by evaporation of oxide while Molybdenium in our privious work. Experimental results such as controllibility of gate electrode, a portion of the gate current for the anode current, and stability of the anode current are given. The proposed FEAs exhibit an excellent controllibility by gate electrode and stability of the emission current. The gate current of new FEAs is negligible compared with the ande current while that of the privious FEAs is about 20% of the anode current.