Advancement and Refinement of HyperSoar Modeling (open access)

Advancement and Refinement of HyperSoar Modeling

This report discusses the topic of periodic cruise trajectories for hypersonic flight. An extensive review of previous work associated with periodic cruise trajectories for subsonic, supersonic and hypersonic flight is presented to provide the background for this investigation. The primary objective of this report is to discuss why periodic cruise trajectories lead to near fuel-optimal trajectories from a heuristic, mathematical and computational perspective with air breathing propulsion. Results to date indicate that periodic achieves greater fuel savings by exchanging kinetic and potential energy more efficiently. The vehicle attempts to chatter back and forth between where the vehicle wants to fly for optimum aerodynamic and propulsive performance. Results from computational simulations are inconclusive and require further work to define appropriate interfaces for aerodynamic and propulsion data decks for input into the POST software. The notional design of a vehicle to fly periodic hypersonic cruise trajectories was improved by including concepts for engine installation, flight controls and by including considerations for off-design performance. This notional design provides a better starting point for more serious and complete vehicle design studies.
Date: February 25, 2000
Creator: Carter, P. H., II; Pines, D. J. & vonEggers Rudd, L.
Object Type: Report
System: The UNT Digital Library
The use of pressurized bladders for stress control of superconducting magnets (open access)

The use of pressurized bladders for stress control of superconducting magnets

None
Date: February 16, 2000
Creator: Caspi, S.; Gourlay, S.; Hafalia, R.; Lietzke, A.; O'Neill, J.; Taylor, C. et al.
Object Type: Article
System: The UNT Digital Library
Innovative Confinement Concepts Workshop 2000 (Book ofAbstracts) (open access)

Innovative Confinement Concepts Workshop 2000 (Book ofAbstracts)

None
Date: February 22, 2000
Creator: Celata, Christine & Staff, Accelerator and Fusion Research
Object Type: Article
System: The UNT Digital Library
Integration of Radiation-Hard Magnetic Random Access Memory with CMOS ICs (open access)

Integration of Radiation-Hard Magnetic Random Access Memory with CMOS ICs

The research undertaken in this LDRD-funded project addressed the joint development of magnetic material-based nonvolatile, radiation-hard memory cells with Sandia National Laboratory. Specifically, the goal of this project was to demonstrate the intrinsic radiation-hardness of Giant Magneto-Resistive (GMR) materials by depositing representative alloy combinations upon radiation-hardened silicon-based integrated circuits. All of the stated goals of the project were achieved successfully. The necessary films were successfully deposited upon typical integrated circuits; the materials retained their magnetic field response at the highest radiation doses; and a patterning approach was developed that did not degrade the as-fabricated properties of the underlying circuitry. These results establish the feasibility of building radiation-hard magnetic memory cells.
Date: February 15, 2000
Creator: Cerjan, C. J. & Sigmon, T. W.
Object Type: Report
System: The UNT Digital Library
Ignition assist systems for direct-injected, diesel cycle, medium-duty alternative fuel engines: Final report phase 1 (open access)

Ignition assist systems for direct-injected, diesel cycle, medium-duty alternative fuel engines: Final report phase 1

This report is a summary of the results of Phase 1 of this contract. The objective was to evaluate the potential of assist technologies for direct-injected alternative fuel engines vs. glow plug ignition assist. The goal was to demonstrate the feasibility of an ignition system life of 10,000 hours and a system cost of less than 50% of the glow plug system, while meeting or exceeding the engine thermal efficiency obtained with the glow plug system. There were three tasks in Phase 1. Under Task 1, a comprehensive review of feasible ignition options for DING engines was completed. The most promising options are: (1) AC and the ''SmartFire'' spark, which are both long-duration, low-power (LDLP) spark systems; (2) the short-duration, high-power (SDHP) spark system; (3) the micropilot injection ignition; and (4) the stratified charge plasma ignition. Efforts concentrated on investigating the AC spark, SmartFire spark, and short-duration/high-power spark systems. Using proprietary pricing information, the authors predicted that the commercial costs for the AC spark, the short-duration/high-power spark and SmartFire spark systems will be comparable (if not less) to the glow plug system. Task 2 involved designing and performing bench tests to determine the criteria for the ignition system and the …
Date: February 23, 2000
Creator: Chan, A.K.
Object Type: Report
System: The UNT Digital Library
Device characteristics of the PnP AlGaAs/InGaAsN/GaAs double heterojunction bipolar transistor (open access)

Device characteristics of the PnP AlGaAs/InGaAsN/GaAs double heterojunction bipolar transistor

The authors have demonstrated a functional PnP double heterojunction bipolar transistor (DHBT) using AlGaAs, InGaAsN, and GaAs. The band alignment between InGaAsN and GaAs has a large {triangle}E{sub C} and a negligible {triangle}E{sub V}, and this unique characteristic is very suitable for PnP DHBT applications. The metalorganic vapor phase epitaxy (MOCVD) grown Al{sub 0.3}Ga{sub 0.7}As/In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01}/GaAs PnP DHBT is lattice matched to GaAs and has a peak current gain of 25. Because of the smaller bandgap (Eg = 1.20 eV) of In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} used for the base layer, this device has a low V{sub ON} of 0.79 V, which is 0.25 V lower than in a comparable Pnp AlGaAs/GaAs HBT. And because GaAs is used for the collector, its BV{sub CEO} is 12 V, consistent with BV{sub CEO} of AlGaAs/GaAs HBTs of comparable collector thickness and doping level.
Date: February 9, 2000
Creator: Chang, Ping-Chih; Li, N. Y.; Laroche, J. R.; Baca, Albert G.; Hou, H. Q. & Ren, F.
Object Type: Article
System: The UNT Digital Library
AZU-1: A Candidate Breast Tumor Suppressor and Biomarker for Tumor Progression (open access)

AZU-1: A Candidate Breast Tumor Suppressor and Biomarker for Tumor Progression

To identify genes misregulated in the final stages of breast carcinogenesis, we performed differential display to compare the gene expression patterns of the human tumorigenic mammary epithelial cells, HMT-3522-T4-2, with those of their immediate premalignant progenitors, HMT-3522-S2. We identified a novel gene, called anti-zuai-1 (AZU-1), that was abundantly expressed in non- and premalignant cells and tissues but was appreciably reduced in breast tumor cell types and in primary tumors. The AZU-1 gene encodes an acidic 571-amino-acid protein containing at least two structurally distinct domains with potential protein-binding functions: an N-terminal serine and proline-rich domain with a predicted immunoglobulin-like fold and a C-terminal coiled-coil domain. In HMT-3522 cells, the bulk of AZU-1 protein resided in a detergent-extractable cytoplasmic pool and was present at much lower levels in tumorigenic T4-2 cells than in their nonmalignant counterparts. Reversion of the tumorigenic phenotype of T4-2 cells, by means described previously, was accompanied by the up-regulation of AZU-1. In addition, reexpression of AZU-1 in T4-2 cells, using viral vectors, was sufficient to reduce their malignant phenotype substantially, both in culture and in vivo. These results indicate that AZU-1 is a candidate breast tumor suppressor that may exert its effects by promoting correct tissue morphogenesis.
Date: February 4, 2000
Creator: Chen, Huei-Mei; Schmeichel, Karen L; Mian, I. Saira; Lelie`vre, Sophie; Petersen, Ole W & Bissell, Mina J
Object Type: Article
System: The UNT Digital Library
Electron irradiation effect on bubble formation and growth in a sodium borosilicate glass (open access)

Electron irradiation effect on bubble formation and growth in a sodium borosilicate glass

In this study, the authors studied simultaneous and intermittent electron irradiation effects on bubble growth in a simple sodium borosilicate glass during Xe ion implantation at 200 C. Simultaneous electron irradiation increases the average bubble size in the glass. This enhanced diffusion is also shown by the migration of Xe from bubbles into the matrix when the sample is irradiated by an electron beam after the Xe implantation.
Date: February 8, 2000
Creator: Chen, X.; Birtcher, R. C. & Donnelly, S. E.
Object Type: Article
System: The UNT Digital Library
Vacuum seals design and testing for a linear accelerator of the National Spallation Neutron Source (open access)

Vacuum seals design and testing for a linear accelerator of the National Spallation Neutron Source

Vacuum seals are very important to ensure that the Spallation Neutron Source (SNS) Linac has an optimum vacuum system. The vacuum joints between flanges must have reliable seals to minimize the leak rate and meet vacuum and electrical requirements. In addition, it is desirable to simplify the installation and thereby also simplify the maintenance required. This report summarizes an investigation of the metal vacuum seals that include the metal C-seal, Energized Spring seal, Helcoflex Copper Delta seal, Aluminum Delta seal, delta seal with limiting ring, and the prototype of the copper diamond seals. The report also contains the material certifications, design, finite element analysis, and testing for all of these seals. It is a valuable reference for any vacuum system design. To evaluate the suitability of several types of metal seals for use in the SNS Linac and to determine the torque applied on the bolts, a series of vacuum leak rate tests on the metal seals have been completed at Los Alamos Laboratory. A copper plated flange, using the same type of delta seal that was used for testing with the stainless steel flange, has also been studied and tested. A vacuum seal is desired that requires significantly less …
Date: February 1, 2000
Creator: Chen, Z.; Gautier, C.; Hemez, F. & Bultman, N. K.
Object Type: Report
System: The UNT Digital Library
Laboratory Investigation of Electro-Osmotic Remediation of Fine-Grained Sediments (open access)

Laboratory Investigation of Electro-Osmotic Remediation of Fine-Grained Sediments

Electro-osmosis, a coupled-flow phenomenon in which an applied electrical potential gradient drives water flow, may be used to induce water flow through fine-grained sediments. We plan to use this technology to remediate chlorinated solvent-contaminated clayey zones at the LLNL site. The electro-osmotic conductivity (k{sub e}) determined from bench-top studies for a core extracted from a sediment zone 36.4-36.6 m below surface was initially 7.37 x 10{sup -10} m{sup 2}/s-V, decreasing to 3.44 x 10{sup -10} m{sup 2}/s-V, after electro-osmotically transporting 0.70 pore volumes of water through it (195 ml). Hydraulic conductivity (k{sub h}) of the same core was initially measured to be 5.00 x 10{sup -10} m/s, decreasing to 4.08 x 10{sup -10} m/s at the end of processing. This decline in permeability is likely due to formation of a chemical precipitation zone within the core. Water splitting products and ions electromigrate and precipitate within the core; H{sup +} and metal cations migrate toward the cathode, and OH{sup -} from the cathode moves toward the anode. We are now exploring how to minimize this effect using pH control. The significance of this technology is that for this core, a 3 V/cm voltage gradient produced an initial effective hydraulic conductivity of …
Date: February 23, 2000
Creator: Cherepy, N.; Wildenschild, D. & Elsholz, A.
Object Type: Article
System: The UNT Digital Library
Status and Needs for Tank Isolation System Contingencies at the Oak Ridge National Laboratory (open access)

Status and Needs for Tank Isolation System Contingencies at the Oak Ridge National Laboratory

This document assesses the need for additional tank isolation systems and tooling at the Oak Ridge National Laboratory (ORNL). Locations for future operations at ORNL include the South and North Tank Farms and various Federal Facilities Agreement tanks. The goal of this report is to identify future needs for development of remote tools and systems to isolate inactive waste storage tanks. Remote tools have been developed to support waste-retrieval and tank-isolation operations at the Gunite and Associated Tanks (GAATs) at ORNL. The tools developed for in-tank remote operations include a pipe-cutting tool (a modified band saw), a pipe-cleaning tool (a modified drill with a wire brush), and a pipe plug. A review of the planned future operations revealed several desirable modifications to improve the efficiency, operability, and flexibility of the existing tank-isolation tools. For example, the pipe-cutting tool needs improvements to provide better alignment, a blade-cutting-release device, improved tire replacement, sensors to prevent operation of the saw when the blade stops, blade speed controls, and force feedback sensors. In addition, the need to test the existing pipe plug for use on corroded piping was identified. The pipe plug has been used on only relatively clean in-tank stainless steel (SS) piping …
Date: February 2, 2000
Creator: Chesser, J.B.
Object Type: Report
System: The UNT Digital Library
Fabrication and Test Results of a Nb3Sn Superconducting Racetrack Dipole Magnet (open access)

Fabrication and Test Results of a Nb3Sn Superconducting Racetrack Dipole Magnet

A 'proof-of-principle' Nb{sub 3}Sn superconducting dual-bore dipole magnet was built from racetrack coils, as a first step in a program to develop an economical, 15 Tesla, accelerator-quality magnet. The mechanical design and magnet fabrication procedures are discussed. No training was required to achieve temperature-dependent plateau currents, despite several thermal cycles that involved partial magnet disassembly and substantial pre-load variations. Subsequent magnets are expected to approach 15 Tesla with substantially improved conductor.
Date: February 6, 2000
Creator: Chow, K.; Dietderich, D. R.; Gourlay, S. A.; Gupta, R.; Harnden, W.; Lietzke, A. F. et al.
Object Type: Article
System: The UNT Digital Library
Three-dimensional control of light in a two-dimensional photonic crystal slab (open access)

Three-dimensional control of light in a two-dimensional photonic crystal slab

A two-dimensional (2D) photonic crystal is an attractive alternative and complimentary to its 3D counterpart, due to fabrication simplicity. A 2D crystal, however, confines light only in the 2D plane, but not in the third direction, the z-direction. Earlier experiments show that such a 2D system can exist, providing that the boundary effect in z-direction is negligible and that light is collimated in the 2D plane. Nonetheless, the usefulness of such 2D crystals is limited because they are incapable of guiding light in z-direction, which leads to diffraction loss. This drawback presents a major obstacle for realizing low-loss 2D crystal waveguides, bends and thresholdless lasers. A recent theoretical calculation, though, suggests a novel way to eliminate such a loss with a 2D photonic crystal slab. The concept of a lightcone is introduced as a criterion for fully guiding and controlling light. Although the leaky modes of a crystal slab have been studied, there have until now no experimental reports on probing its guided modes and band gaps. In this paper, a waveguide-coupled 2D photonic crystal slab is successfully fabricated from a GaAs/Al{sub x}O{sub y} material system and its intrinsic transmission properties are studied. The crystal slab is shown to have …
Date: February 15, 2000
Creator: Chow, Kai-Cheung; Lin, Shawn-Yu; Johnson, S. G.; Villeneuve, P. R.; Joannopoulos, J. D.; Wendt, Joel R. et al.
Object Type: Article
System: The UNT Digital Library
Precision formed micro magnets: LDRD project summary report (open access)

Precision formed micro magnets: LDRD project summary report

A microfabrication process is described that provides for the batch realization of miniature rare earth based permanent magnets. Prismatic geometry with features as small as 5 microns, thicknesses up through several hundred microns and with submicron tolerances may be accommodated. The processing is based on a molding technique using deep x-ray lithography as a means to generate high aspect-ratio precision molds from PMMA (poly methyl methacrylate) used as an x-ray photoresist. Subsequent molding of rare-earth permanent magnet (REPM) powder combined with a thermosetting plastic binder may take place directly in the PMMA mold. Further approaches generate an alumina form replicated from the PMMA mold that becomes an intermediate mold for pressing higher density REPM material and allows for higher process temperatures. Maximum energy products of 3--8 MGOe (Mega Gauss Oersted, 1 MGOe = 100/4{pi} kJ/m{sup 3}) are obtained for bonded isotropic forms of REPM with dimensions on the scale of 100 microns and up to 23 MGOe for more dense anisotropic REPM material using higher temperature processing. The utility of miniature precision REPMs is revealed by the demonstration of a miniature multipole brushless DC motor that possesses a pole-anisotropic rotor with dimensions that would otherwise prohibit multipole magnetization using a …
Date: February 1, 2000
Creator: Christenson, Todd R.; Garino, Terry J. & Venturini, Eugene L.
Object Type: Report
System: The UNT Digital Library
Round Robin Study of Rotational Strain Rheometers (open access)

Round Robin Study of Rotational Strain Rheometers

A round robin of testing was performed to compare the performance of rotational dynamic mechanical spectrometers being used within the nuclear weapons complex. Principals from Sandia National Laboratories/New Mexico; Lockheed Martin Y12 Plant at Oak Ridge, Tennessee; Los Alamos National Laboratory, New Mexico (polycarbonate only); and Honeywell Federal Manufacturing and Technologies (FM and T), Kansas City, MO, performed identical testing of hydrogen blown polysiloxane S5370 and bisphenol-A polycarbonate. Over an oscillation frequency sweep from 0.01 Hz to 15.9 Hz at 135 C, each site produced shear storage modulus values with standard deviations of less than 5%. The data from Sandia, Y12, and Kansas City agreed to within 4%, while the Los Alamos data differed by as much as 13%. Storage modulus values for a frequency sweep of the S5370 at 35 C had standard deviations between 6% and 8%, and site-to-site agreement averaged 3%. The shear loss modulus values had standard deviations of 5%, 7%, and 52% for the sites participating, while the results differed by 12% on average.
Date: February 16, 2000
Creator: Clifford, M.J.
Object Type: Report
System: The UNT Digital Library
Hood River Production Program : Hood River Fish Habitat Protection, Restoration, and Monitoring Plan. (open access)

Hood River Production Program : Hood River Fish Habitat Protection, Restoration, and Monitoring Plan.

Effective habitat protection and rehabilitation are essential to the long-term recovery of anadromous fish populations in the Hood River subbasin. This Habitat Protection, Restoration, and Monitoring Plan was prepared to advance the goals of the Hood River Production Program (HRRP) which include restoring self-sustaining runs of spring chinook salmon and winter and summer steelhead. The HRPP is a fish supplementation and monitoring and evaluation program initiated in 1991 and funded by the Bonneville Power Administration (BPA) as part of the Northwest Power Planning Council Fish and Wildlife Program. The HRPP is a joint effort of the Confederated Tribes of the Warm Springs Reservation of Oregon (CTWSRO) and Oregon Department of Fish and Wildlife (ODFW). Using recent watershed assessment and federal watershed analysis reports, this Plan reviews the historic and current condition of riparian, instream and upland habitats; natural watershed processes; anadromous and resident fish populations; identifies limiting factors, and indicates those subbasin areas that need protection or are likely to respond to restoration. Primary habitat restoration needs were identified as (1) improved fish screening and upstream adult passage at water diversions; (2) improved spawning gravel availability, instream habitat structure and diversity; and (3) improved water quality and riparian conditions. While …
Date: February 1, 2000
Creator: Coccoli, Holly & Lambert, Michael
Object Type: Report
System: The UNT Digital Library
Pion Production Models and Neutrino Factories (open access)

Pion Production Models and Neutrino Factories

Scenarios for the building of muon colliders or storage rings suitable for the generation of robust neutrino beams call for the generation of a prodigious quantity of pions. These pions are then conducted into a decay channel where the resulting muon decay products can be collected for cooling and subsequent acceleration. Central to this concept is the design and construction of a target which will be highly efficient in producing pions of both signs while mitigating the absorption of these pions before they decay. This design effort is being facilitated by using two computer codes FLUKA and MARS. The authors present comparisons of the two computer codes and also present a comparison of these codes with available data.
Date: February 11, 2000
Creator: Collot, J.; Kirk, H. G. & Mokhov, N. V.
Object Type: Article
System: The UNT Digital Library
A high-charge high-brightness L-band photocathode RF gun (open access)

A high-charge high-brightness L-band photocathode RF gun

The Argonne Wakefield Accelerator has been successfully commissioned and used for conducting wakefield experiments in dielectric loaded structures and plasmas. Although the initial wakefield experiments were successful, higher drive beam quality would substantially improve the wakefield accelerating gradients. In this paper the authors present a new 1-1/2 cell L-band photocathode RF gun design. This gun will produce 10--100 nC beam with 2--5 ps ms pulse length and normalized emittance less than 100 mm mrad. The final gun design and numerical simulations of the beam dynamics are presented.
Date: February 25, 2000
Creator: Conde, M. E.; Gai, W.; Konecny, R.; Power, J. G.; Schoessow, P. & Sun, X.
Object Type: Article
System: The UNT Digital Library
Effects of spent fuel types on offsite consequences of hypothetical accidents (open access)

Effects of spent fuel types on offsite consequences of hypothetical accidents

Argonne National Laboratory (ANL) conducts experimental work on the development of waste forms suitable for several types of spent fuel at its facility on the Idaho National Engineering and Environmental Laboratory (INEEL) located 48 km West of Idaho Falls, ID. The objective of this paper is to compare the offsite radiological consequences of hypothetical accidents involving the various types of spent nuclear fuel handled in nonreactor nuclear facilities. The highest offsite total effective dose equivalents (TEDEs) are estimated at a receptor located about 5 km SSE of ANL facilities. Criticality safety considerations limit the amount of enriched uranium and plutonium that could be at risk in any given scenario. Heat generated by decay of fission products and actinides does not limit the masses of spent fuel within any given operation because the minimum time elapsed since fissions occurred in any form is at least five years. At cooling times of this magnitude, fewer than ten radionuclides account for 99% of the projected TEDE at offsite receptors for any credible accident. Elimination of all but the most important nuclides allows rapid assessments of offsite doses with little loss of accuracy. Since the ARF (airborne release fraction), RF (respirable fraction), LPF (leak …
Date: February 18, 2000
Creator: Courtney, J. C.; Dwight, C. C. & Lehto, M. A.
Object Type: Article
System: The UNT Digital Library
Intense Laser - Electron Beam Interactions (open access)

Intense Laser - Electron Beam Interactions

Applicants seeking a Certificate of Compliance for an Independent Spent Fuel Storage Installation (ISFSI) cask must evaluate the consequences of a handling accident resulting in a drop or tip-over of the cask onto a concrete storage pad. As a result, analytical modeling approaches that might be used to evaluate the impact of cylindrical containers onto concrete pads are needed. One such approach, described and benchmarked in NUREG/CR-6608,{sup 1} consists of a dynamic finite element analysis using a concrete material model available in DYNA3D{sup 2} and in LS-DYNA,{sup 3} together with a method for post-processing the analysis results to calculate the deceleration of a solid steel billet when subjected to a drop or tip-over onto a concrete storage pad. The analysis approach described in NUREG/CR-6608 gives a good correlation of analysis and test results. The material model used for the concrete in the analyses in NUREG/CR-6608 is, however, somewhat troublesome to use, requiring a number of material constants which are difficult to obtain. Because of this a simpler approach, which adequately evaluates the impact of cylindrical containers onto concrete pads, is sought. Since finite element modeling of metals, and in particular carbon and stainless steel, is routinely and accurately accomplished with …
Date: February 25, 2000
Creator: Cowan, T.; Ditmire, T. & LeSage, G.
Object Type: Report
System: The UNT Digital Library
Predicted performance of neutron spectrometers using scintillating fibers (open access)

Predicted performance of neutron spectrometers using scintillating fibers

A variety of needs exists for knowing the energy spectral content of a neutron flux. Among these needs are arms-control and national-security applications, which arise because different neutron sources produce different neutron energy spectra. This work is primarily directed at these applications. The concept described herein is a spectrometer in the same sense as a Bonner sphere. The instrument response reflects a statistical average of the energy spectrum. The Bonner sphere is an early rendition of this class. In this, a neutron detector is placed at the center of a moderating (and absorbing) sphere (of varying thickness and composition). Spectral unfolding is required, and the resolution and efficiency are, typically, poor, although the potential bandwidth is very large. A recent variation on the Bonner-sphere approach uses {sup 3}He gas proportional counters with resistive wires to locate the position of the event (Toyokawa et al 1996). The spectrometer concept investigated here has the potential for better resolution and much improved neutron efficiency compared to Bonner spheres and similar devices. These improvements are possible because of the development of neutron-sensitive, scintillating-glass fibers. These fibers can be precisely located in space, which allows a corresponding precision in energy resolution. Also, they can be …
Date: February 14, 2000
Creator: Craig, RA & Bliss, M
Object Type: Report
System: The UNT Digital Library
Predicted Performance of Neutron Spectrometers Using Scintillating Fibers (open access)

Predicted Performance of Neutron Spectrometers Using Scintillating Fibers

One class of neutron spectrometers is devices that provide a measure of the neutron spectrum by using moderating and absorbing materials together with thermal-neutron detectors. Pacific Northwest National Laboratory has developed scintillating fibers that are sensitive to thermal neutrons. Because these fibers are thin, they present an enabling technology for several applications, including highly efficient neutron spectroscopy. The underlying concept is to arrange the fibers in an array of layers separated by materials whose characteristics have been chosen to optimize the instrument function for the application. Monte Carlo experiments have been performed to characterize the conceptual design and to determine the value of the concept as a tool for research and other applications.
Date: February 14, 2000
Creator: Craig, Richard A & Bliss, Mary
Object Type: Report
System: The UNT Digital Library
Design and performance of nitride-based UV LEDs (open access)

Design and performance of nitride-based UV LEDs

In this paper, the authors overview several of the critical materials growth, design and performance issues for nitride-based UV (< 400 nm) LEDs. The critical issue of optical efficiency is presented through temperature-dependent photoluminescence studies of various UV active regions. These studies demonstrate enhanced optical efficiencies for active regions with In-containing alloys (InGaN, AlInGaN). The authors discuss the trade-off between the challenging growth of high Al containing alloys (AlGaN, AlGaInN), and the need for sufficient carrier confinement in UV heterostructures. Carrier leakage for various composition AlGaN barriers is examined through a calculation of the total unconfined carrier density in the quantum well system. They compare the performance of two distinct UV LED structures: GaN/AlGaN quantum well LEDs for {lambda}< 360 nm emission, and InGaN/AlGaInN quantum well LEDs for 370 nm <{lambda}< 390 nm emission.
Date: February 16, 2000
Creator: Crawford, Mary H.; Han, Jung; Chow, Weng W.; Banas, Michael Anthony; Figiel, Jeffery J.; Zhang, Lei et al.
Object Type: Article
System: The UNT Digital Library
Characterization of electrical linewidth test structures patterned in (100) Silicon-on-Insulator for use as CD standards (open access)

Characterization of electrical linewidth test structures patterned in (100) Silicon-on-Insulator for use as CD standards

This paper describes the fabrication and measurement of the linewidths of the reference segments of cross-bridge resistors patterned in (100) Bonded and Etched Back Silicon-on-Insulator (BESOI) material. The critical dimensions (CD) of the reference segments of a selection of the cross-bridge resistor test structures were measured both electrically and by Scanning-Electron Microscopy (SEM) cross-section imaging. The reference-segment features were aligned with <110> directions in the BESOI surface material and had drawn linewidths ranging from 0.35 to 3.0 {micro}m. They were defined by a silicon micro-machining process which results in their sidewalls being atomically-planar and smooth and inclined at 54.737{degree} to the surface (100) plane of the substrate. This (100) implementation may usefully complement the attributes of the previously-reported vertical-sidewall one for selected reference-material applications. For example, the non-orthogonal intersection of the sidewalls and top-surface planes of the reference-segment features may alleviate difficulties encountered with atomic-force microscope measurements. In such applications it has been reported that it may be difficult to maintain probe-tip control at the sharp 90{degree} outside corner of the sidewalls and the upper surface. A second application is refining to-down image-processing algorithms and checking instrument performance. Novel aspects of the (100) SOI implementation that are reported here include …
Date: February 29, 2000
Creator: Cresswell, M. W.; Allen, R. A.; Ghoshtagore, R. N.; Guillaume, N. M. P.; Shea, Patrick J.; Everist, Sarah C. et al.
Object Type: Article
System: The UNT Digital Library