Large-area Source Research Articles

Three-color organic light-emitting diodes patterned by masked dye diffusion

A method of masked dye diffusion to locally pattern the emissive color of organic light-emitting devices (OLEDs) over a large area is introduced. By using a large-area diffusion source, which may be a spin-coated doped polymer film, the entire process of masked diffusion of dye into a polymer film of an OLED to create an integrated three-color device has been demonstrated at atmospheric pressure. The materials used to demonstrate this method are the polymer poly(9-vinylcarbazole) combined with electron transport molecules, and the dyes bimane, coumarin 6, and Nile red.

Development of a large-area transformer coupled plasma source

A large-area transformer coupled plasma (TCP) source has been designed and constructed. In our design, a plasma generation chamber and a radio-frequency (RF) antenna chamber have been separated with a dielectric material, and differentially pumped to accommodate large-area, relatively thin dielectric windows against mechanical pressures. With a large diameter (78 cm) chamber, a low frequency (4 MHz) RF source has been chosen. By calculating the plasma impedance from TCPRP codes based on a 2D heating theory [1], the diameter of a single-turn copper coil antenna was optimized to provide high-density plasmas in the large area. Also the impedance matching circuit of this large-area TCP source has been designed from the calculated plasma impedance.

Three-Color Doping of Polymer Oleds by Masked Dye Diffusion

ABSTRACTA method to locally pattern the distribution of dye by diffusion into the polymer film of organic light-emitting diodes is introduced. Using a large-area diffusion source, the diffusion of dye into the polymer film can be controlled with a shadow mask. The materials used are the polymer poly(9-vinylcarbazole) (PVK) combined with electron transport molecules (PBD), and the dyes bimane, coumarin 6 and Nile red. The temperature dependence of the diffusion is investigated along with the effect of annealing of the polymer film. A model of the dye distribution is introduced and estimations of the dye profile based on this model and PL measurement are discussed. A 3-color integrated device was demonstrated.

The NIST EOS thermal-infrared transfer radiometer

A portable thermal-infrared transfer radiometer (TXR) has been developed for use in comparisons and scale verifications of sources used to calibrate thermal-infrared (TIR) channels of the National Aeronautics and Space Administration's (NASA's) Earth Observing System (EOS) flight instruments. The TXR is designed to measure the radiance temperature of large-area black-body sources in cryogenic vacuum environments, either at the National Institute of Standards and Technology (NIST) or at the EOS instrument-calibration facilities. It can be operated in ambient conditions of room temperature and pressure, or in EOS instrument thermal/vacuum chambers at temperatures as low as 77 K. The TXR is a liquid-nitrogen-cooled filter radiometer with two channels: one centred at 5 µm based on a photovoltaic InSb detector, and the other centred at 10 µm based on a photovoltaic HgCdTe (MCT) detector. The spectral, spatial and temporal characterization of the TXR using state-of-the-art NIST ambient-infrared instrumentation is reported.

A method for determining the 2π-counting efficiency of betaparticle sources

This paper is concerned with the efficiency of large-area beta-particle sources. Attention is focussed on sources in which the radioactivity is distributed in a surface layer of an anodized aluminum foil. The efficiency takes into account the reflection and absorption of particles in the aluminum foil, and is defined as the ratio of the number of particles emerging from the foil to the number of particles emitted. A method of estimating the efficiency is proposed which combines measurements and transport calculations. The experimental part of the method consists of measuring the thickness of the layer of mylar which, when inserted between source and detector, cuts the counting rate in half. The theoretical part consists of calculations of beta-particle transport in a two-layer aluminum-mylar medium, which relate the efficiency of the source to the thickness of the measured half-value layer.

Preparation and standardization of large-area sources for calibration of alpha-particle contamination monitors

Large-area sources of 241Am for calibration of surface-contamination monitors have been produced by incorporating the radionuclide into a thin layer of anodized Al. A measurement chamber has been developed which allows the standardization of alpha-particle emitting sources with active areas up to 12 × 17 cm 2. The counter can be operated as an ionization chamber or in the proportional region. The sources can be standardized in terms of alpha-particle emission rate or activity with uncertainties in the order of 1%.

Point projection radiography with the flexible x-ray imager

Radiography techniques utilizing large-area x-ray sources (typically ⩽7 keV) and pinhole-imaging gated x-ray diagnostics have long been used at the Nova laser facility. However, for targets requiring higher-energy x-ray backlighters (>9 keV), low conversion efficiencies and pinhole losses combine to make this scheme unworkable. The technique of point projection radiography has been improved upon to make imaging at high x-ray energies feasible. In this scheme a “point” source of x-rays, usually a small diameter (⩽25 μm) fiber, is illuminated with a single, 100-ps pulse from the Nova laser. A gated x-ray imager with a 500-ps electronic gate width is used to record the projected image. [K. S. Budil et al., Rev. Sci. Instrum. 67, 485 (1996).] The experimental challenges this technique presents and experimental results will be discussed.

Field emission from microstructured cesiated surfaces

A comparative analysis of three experiments on field electron emission from microstructured cesiated surfaces is presented. In this context, the term ‘‘cesiated surface’’ implies generally any coverage of cesium on a metallic substrate, while the term ‘‘microstructure’’ includes the intrinsic microstructure of any solid substrate as well as the induced microstructure of the liquid cesium coverage due to electrohydrodynamic effects. These experiments concern a thin-film field-emission microcathode, a single pin-and-tube-type liquid metal electron source, and a large-area microstructured liquid metal electron source. The electron sources are compared by their emission characteristics and the resulting Fowler–Nordheim plots. The existence of both a stable and unstable field-emission mode from microstructured cesiated surfaces had been proven. Whether the first mode is of importance to vacuum microelectronics is a question which needs further investigation; the second mode seems to be of importance for regenerative and indestructible field electron sources with possible applications in pulsed power technology.

Novel high-density plasma tool for large area flat panel display etching

A novel dry etch tool—large area source supported ion etching (LASSIE)—has been developed appropriate for the processing of substrate sizes of presently up to 600×400 mm2. The plasma is produced through an array of four inductively coupled plasma sources driven by one common 13.56 MHz generator. A second rf generator serves for substrate biasing. Plasma diagnostic data suggest that LASSIE has strong capabilities for future large area etch applications avoiding several drawbacks of conventional reactive ion etching (RIE) in parallel-plate reactors. In particular considerably higher etch rates are to be expected since the plasma densities are roughly one order of magnitude higher than in conventional RIE. In addition the processing will be more flexible and better controlled due to the decoupling of plasma densities and ion bombardment energies. A scale-up with respect to the processing of wafer sizes larger than presently envisaged is easily achieved by the LASSIE concept.

Characterization of large-area reference sources for the calibration of beta-contamination monitors

A method has been developed whereby the activity of a large-area reference source for the calibration of beta-contamination monitors can be determined from a series of measured countrates in a suitable detection system as a function of the distance between the surface of the source and the front face of the detector.

Modeling and experimental studies of a transformer coupled plasma (TCP/sup TM/) source design for large area plasma processing

Extension of a planar inductively coupled source designed for 200-mm wafer processing to a large area plasma application, i.e., flat panel display manufacturing, has been studied by both computer simulation and Langmuir probe measurements. The large area source utilized multiple inductive elements operated in parallel, thereby generating a planar plasma which was uniform over a large area substrate, e.g., a 600/spl times/720 mm panel. Cold plasma simulation of this source using commercially available three-dimensional (3-D) electromagnetic software (Maxwell Eminence, Ansoft Corp.) reveals the spatial distribution of inductive RF power coupling for this source. Langmuir probe measurements of the ion current distribution for the same plasma conditions are in general agreement with the model predictions and confirm that uniform plasmas can be obtained over a large area with this source.

Pilot experiments on microstructured liquid metal ion and electron sources

Ion or electron beams can be emitted from liquid metal wetted needles, or from capillaries or slits into which the liquid metal is allowed to flow. Large-area liquid metal field emission sources have been proposed recently, using either two-dimensional, regular arrays of cones or capillaries, or even a substrate with an intrinsically microstructured surface covered by a liquid metal film. Now this latter concept has been realized in a pilot experiment by in situ wicking and wetting of a porous sintered metal disk. A similar concept has been applied formerly on a mercury-film cathode supporting a low pressure arc discharge. Microstructured liquid metal ion or electron sources are capable to operate in a pulsed mode at a current level which is orders of magnitude above that for steady-state operation.

Microstructured liquid metal ion and electron sources (MILMIS/MILMES)

Ion or electron beams can be emitted from liquid metal wetted needles, or from capillaries or slits into which the liquid metal is allowed to flow. Large-area liquid metal field emission sources have been proposed recently, using either two-dimensional, regular arrays of cones or capillaries, or even a substrate with an intrinsically microstructured surface covered by a liquid metal film. Now this latter concept has been realized in a pilot experiment by in situ wicking and wetting of a porous sintered metal disk. A similar concept had been applied formerly on a mercury film cathode supporting a low pressure arc discharge. Microstructured liquid metal ion or electron sources (MILMIS/MILMES) are capable of operating in a pulsed mode at a current level which is orders of magnitude above that for steady-state operation.

Silicon field-effect transistor based on quantum tunneling

This letter explores regulation of current flow within a silicon field-effect transistor by gate-induced tunneling through a Schottky barrier located at the interface between a metallic source electrode and the Si channel. The goal here is to forestall short-channel effects which are expected to prevent further size reductions in conventional devices when linewidths reach ∼1000 Å. Control of tunneling appears to be possible at minimum channel lengths L∼250 Å or less while simultaneously eliminating the need for large-area source and drain contacts, so that scaling of Si transistors could be significantly extended if this principle proves technically feasible.

Measurement and calibration of large-area alpha-particle sources at NIST

Work has been performed at NIST to develop and calibrate large-area 238Pu alpha-particle sources and related measuring equipment. A large-area-source X-ray counting system and a 2πα internal gas-proportional counting system were used for the primary calibration of these sources. Studies have been performed to relate these calibrations to the measurement of thin, large area 239Pu sources, which are of primary interest but are generally unavailable in the necessary high specific activities required. Two systems have been characterized for the monitoring and measurement of large-area alpha sources: 1. (i) a source-detector mounting unit developed at NIST to calibrate monitoring systems by mounting a standard source of plutonium at an accurately calibrated distance from the user's alpha-monitoring detector; 2. (ii) a diffused-junction silicon semiconductor detector which is used as a transfer standard from low to high activity of large-area alpha-particle sources. A determination of the L X-ray emission probability for 239Pu has been made.

Characterization of large-area reference sources for the calibration of alpha-contamination monitors

A simple method has been developed whereby the activity of a large-area reference source for the calibration of alpha-contamination monitors can be determined from the measured alpha-particle flux. A correction factor k is determined from the pulse height spectrum of the source in a large-area proportional counter to take into account backscattering and self-absorption in the source. This correction factor is used to calculate the activity with an uncertainty not exceeding 10%.

Large-area electron-beam source

A new large-area electron-beam source which can operate continuously, stably, and indefinitely in a poor vacuum environment is described. This novel electron source produces a near monoenergetic electron beam which can uniformly expose large area substrates (i.e., 200 mm diam wafers and larger flat panel displays). The electron gun incorporates a cold cathode which is impervious to solvents and outgassing from irradiated polymer coatings. Unlike glow discharge electron sources, the accelerating voltage can be controlled independently of the emission current from the electron gun with a small bias voltage to a grid anode. Accelerating voltages of 1–60 keV and higher are possible. The principles of operation and performance characteristics of this new source are described, including its ability to expose insulating samples without requiring a conductive overcoat. This new electron source has enabled a number of new process innovations in photoresist stabilization, interlayer dielectric curing, lift-off processing, and pattern lithography.

The Evaluation of Long-Term Radon Expansion from Large Sources Using Passive Integrating Radon Monitors

The determination of the long-term dispersion of radon from large area sources is quite simple if a great number of passive radon dosemeters is used for the measurement integrating over rather long periods. Development work on, and testing of, small dosemeters for individual dosimetry and outdoor measurements which started about 10 years ago have led to a reliable measuring device, which can be applied also under extreme environmental conditions. The plotting of the concentrations distribution which is necessary to calculate the radiation exposure caused by radon in the vicinity of large sources has been demonstrated among others for the uranium mines at Menzenschwand and the milling facility at Ellweiler. The methodology and the most important parameters influencing the distribution of radon are discussed.

A Simple Model to Calculate Doses for Acute Tritium Releases, Based on HT Field Experiments in Canada and France

A significant fraction of the tritium inventory of a fusion plant will be in the elemental form HT. In this paper a simple model is proposed to calculate early doses following an HT release. The does is not dominated by the primary HT plume but by deposition of HT into the soil, subsequent oxidation to HTO by microorganisms and the following remission of HTO. The difficulty of calculating HTO concentrations from a large area source is solved by defining a remission velocity. All data available from the large scale release experiments in France (1986) and Canada (1987) are used to fit this parameter. With typical worst case conditions one gets an early dose of 0.04 Sv/kg-T as HT at 1000 m distance from the source, building wake effects included. This model can also be used to calculate HTO-release doses and predicts 0.6 Sv/kg-T as HTO for the same worst case condition. About 20% of this does is caused by remission of HTO deposited into the soil. The accuracy of the model is estimated to be a factor of 2 - 2.5 up and down.

Beta Ray Dose Distributions from Skin Contamination

Most existing tables of beta ray depth dose distributions over estimate doses from skin contamination by up to 35%, because they were calculated for infinite, homogeneous media and therefore include backscattering from non-existent tissue behind the source. The Monte Carlo method has been used to calculate dose distributions from beta contamination on an air-water interface. Distributions were calculated for monoenergetic electrons from 0.025 to 4 MeV and for more than 130 beta emitters, both for point sources such as hot particles (dose being averaged over a plane circular area of 1 cm2) and on the axis of a large area source. The present paper gives such dose distributions for point sources of 45 emitters as well as doses at 0.07, 0.4, 3 and 10 mm depth for most of the emitters calculated. More extensive tables will be presented in a report. The effects on the dose of source area and of backscattering from air and water have been studied.