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Inductively Coupled Plasma Etching of III-V Semiconductors in BCl(3)-Based Chemistries: Part II: InP, InGaAs, InGaAsP, InAs and AllnAs
A parametric study of etch rates and surface morphologies of In-containing compound semiconductors (InP, InGaAs, InGaAsP, InAs and AlInAs) obtained by BClj-based Inductively Coupled Plasmas is reported. Etch rates in the range 1,500-3,000 &min. are obtained for all the materials at moderate source powers (500 W), with the rates being a strong function of discharge composition, rf chuck power and pressure. Typical root-mean-square surface roughness of-5 nm were obtained for InP, which is worse than the values obtained for Ga-based materials under the same conditions (-1 run). The near surface of etched samples is typically slightly deficient in the group V element, but the depth of this deficiency is small (a few tens of angstroms).
Date:
December 2, 1998
Creator:
Abernathy, C.R.; Han, J.; Hobson, W.S.; Hong, J.; Lambers, E.S.; Lee, J.W. et al.
Object Type:
Article
System:
The UNT Digital Library
Characterization and Prediction of Subsurface Pneumatic PressureVariations at Yucca Mountain, Nevada
Yucca Mountain, Nevada is being investigated as the proposed site for geologic disposal of high level nuclear waste. A massive data collection effort for characterization of the unsaturated zone is being carried out at the site. The USGS is monitoring the subsurface pressure variations due to barometric pumping in several boreholes. Numerical models are used to simulate the observed subsurface pressure variations. Data inversion is used to characterize the unsaturated system and estimate the pneumatic diffusivity of important geologic features. Blind predictions of subsurface response and subsequent comparison to recorded data have built confidence in the models of Yucca Mountain.
Date:
January 2, 1998
Creator:
Ahlers, C. Fredrik; Finsterle, Stefan & Bodvarsson, Gudmundur S.
Object Type:
Article
System:
The UNT Digital Library
Ash & Pulverized Coal Deposition in Combustors & Gasifiers
Further progress in achieving the objectives of the project was made in the period of October 1 to December 31, 1996. In particular, the sublayer model for evaluating the particle deposition in turbulent flows was extended to include the effect of particle rebound. A new more advance flow model for the near wall vortices is also used in these analysis. The computational model for simulating particle transport in turbulent flows was used to analyze the dispersion and deposition of particles in a recirculating flow region. The predictions of the particle resuspension model is compared with the experimental data. It is shown that when the effects of the near wall flow structure, as we as the surface roughness are included the model agrees with the available experimental data. Considerable progress was also made in the direct numerical simulation of particle removal process in turbulent gas flows. Experimental data for transport and deposition of glass fiber in the aerosol wind tunnel was also obtained.
Date:
December 2, 1998
Creator:
Ahmadi, Goodarz
Object Type:
Report
System:
The UNT Digital Library
Ash & Pulverized Coal Deposition in Combustors & Gasifiers
Further progress in achieving the objectives of the project was made in the period of October I to December 31, 1997. The direct numerical simulation of particle removal process in turbulent gas flows was continued. Variations of vorticity contours which are averaged over a short time duration are studied. It is shown that the near wall vortices profoundly affect the particle removal process in turbulent boundary layer flows. The sublayer model for evaluating the particle deposition in turbulent flows was extended to include the effect of particle rebound. A new more advance flow model for the near wall vortices is also used in these analysis. Sample particle trajectories are obtained and discussed. Experimental data for transport and deposition of fibrous particles in the aerosol wind tunnel was obtained. The measured deposition velocity is compared with the empirical correlation and the available data and discussed. Particle resuspension process in turbulent flows are studied. The model is compared with the experimental data. It is shown that when the effects of the near wall flow structure, as well as the surface roughness are included the model agrees with the available experimental data.
Date:
December 2, 1998
Creator:
Ahmadi, Goodarz
Object Type:
Report
System:
The UNT Digital Library
Ash & Pulverized Coal Deposition in Combustors & Gasifiers
Further progress in achieving the objectives of the project was made in the period of January I to March 31, 1998. The direct numerical simulation of particle removal process in turbulent gas flows was completed. Variations of particle trajectories are studied. It is shown that the near wall vortices profoundly affect the particle removal process in turbulent boundary layer flows. Experimental data for transport and deposition of fibrous particles in the aerosol wind tunnel was obtained. The measured deposition velocity for irregular fibrous particles is compared with the empirical correlation and the available data for glass fibers and discussed. Additional progress on the sublayer model for evaluating the particle deposition and resuspension in turbulent flows was made.
Date:
December 2, 1998
Creator:
Ahmadi, Goodarz
Object Type:
Report
System:
The UNT Digital Library
Ash & Pulverized Coal Deposition in Combustors & Gasifiers
Further progress in achieving the objectives of the project was made in the period of July 1 to September 30, 1997. The direct numerical simulation of particle removal process in turbulent gas flows was continued. Variations of vorticity contours which are averaged over a short time duration are studied. It is shown that the near wall vortices profoundly affect the particle removal process in turbulent boundary layer flows. The sublayer model for evaluating the particle deposition in turbulent flows was extended to include the effect of particle rebound. A new more advance flow model for the near wall vortices is also used in these analysis. Sample particle trajectories are obtained and discussed. Experimental data for transport and deposition of fibrous particles in the aerosol wind tunnel was obtained. The measured deposition velocity is compared with the empirical correlation and the available data and discussed. Particle resuspension process in turbulent flows are studied. The model is compared with the experimental data. It is shown that when the effects of the near wall flow structure, as well as the surface roughness are included the model agrees with the available experimental data.
Date:
December 2, 1998
Creator:
Ahmadi, Goodarz
Object Type:
Report
System:
The UNT Digital Library
Quarterly Technical Progress Report
This report presents the work done on " Investigation of Syngas Interaction in Alcohol Synthesis Catalysts" during the last quarter. FTIR absorption studies on Cu/Co/Cr catalysts using CO as a probe molecule are presented in this report. A comprehensive FTIR investigation on the catalysts was undertaken to unfold the picture of the gas - metal interactions. Our magnetization studies have provided valuable information on the changes in the magnetic character of the ferromagnetic metal due to CO adsorption. The FTIR results showing the effect of the adsorbate-adsorbent interactions on the stretching frequencies of the CO vibrational modes are presented in this report.
Date:
December 2, 1998
Creator:
Akundi, Murty A.
Object Type:
Report
System:
The UNT Digital Library
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 16, Ed. 1 Wednesday, September 2, 1998
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
September 2, 1998
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 37, Ed. 1 Friday, October 2, 1998
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
October 2, 1998
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 57, Ed. 1 Monday, November 2, 1998
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
November 2, 1998
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
The Oklahoma Daily (Norman, Okla.), Vol. 83, No. 76, Ed. 1 Wednesday, December 2, 1998
Student newspaper of the University of Oklahoma in Norman, Oklahoma that includes national, local, and campus news along with advertising.
Date:
December 2, 1998
Creator:
Allam, Heather
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Optical sensors for process control and emissions monitoring in industry
Sandia National Laboratories has a number of ongoing projects developing optical sensors for industrial environments. Laser-based sensors can be attractive for relatively harsh environments where extractive sampling is difficult, inaccurate, or impractical. Tools developed primarily for laboratory research can often be adapted for the real world and applied to problems far from their original uses. Spectroscopic techniques, appropriately selected, have the potential to impact the bottom of line of a number of industries and industrial processes. In this paper the authors discuss three such applications: a laser-based instrument for process control in steelmaking, a laser-induced breakdown method for hazardous metal detection in process streams, and a laser-based imaging sensor for evaluating surface cleanliness. Each has the potential to provide critical, process-related information in a real-time, continuous manner. These sensor techniques encompass process control applications and emissions monitoring for pollution prevention. They also span the range from a field-tested pre-commercial prototype to laboratory instrumentation. Finally, these sensors employ a wide range of sophistication in both the laser source and associated analytical spectroscopy. In the ultimate applications, however, many attributes of the sensors are in common, such as the need for robust operation and hardening for harsh industrial environments.
Date:
November 2, 1998
Creator:
Allendorf, S. W.; Ottesen, D. K.; Hahn, D. W.; Kulp, T. J. & Goers, U. B.
Object Type:
Article
System:
The UNT Digital Library
[Letter from State Auditor to Legislative Audit Committee, February 2, 1998]
Letter detailing the audit of General Revenue fund distribution to three universities.
Date:
February 2, 1998
Creator:
Alwin, Lawrence F.
Object Type:
Letter
System:
The Portal to Texas History
Synthesis of Pu-Doped Ceramic
Plutonium-doped zircon containing about 10 wt% Pu was synthesized in this cooperative project between Russia and the United States conducted at the V. G. Khlopin Radium Institute. The sol-gel method was used for starting precursor preparation to provide complete mixing of initial components and to avoid dust formation inside the glove-box. The sol-gel process also gives interim Pu stabilization in the form of amorphous zirconium hydrosilicate (AZHS), which is a result of gel solidification. AZHS is a solid and relatively durable material that can be easy converted into crystalline zircon by pressureless sintering, thus avoiding significant radioactive contamination of laboratory equipment. A methanol-aqueous solution of tetraethoxysilane Si(OC2H5)4, Pu-nitrate, and zirconil oxynitrate was prepared in final stoichiometry of zircon (Zr,Pu)SiO4 80 wt% + zirconia (Zr,Pu)O2 20 wt%. Gelation occurred after 90 hours at room temperature. AZHS with excess of zirconia 20 wt% was obtained as an interim calcine product and then it was converted into zircon/zirconia ceramic by sintering at 1490 to 1500°C in air for different time periods. The samples obtained were studied by SRD and ESEM methods. It was found that both zircon yield and zircon cell parameters that are correlated with Pu incorporation depend on sintering time.
Date:
September 2, 1998
Creator:
Anderson, E. B.
Object Type:
Article
System:
The UNT Digital Library
Stand-alone microprobe at Livermore
Lawrence Livermore National Laboratory (LLNL) and Sandia National Laboratories/California have jointly constructed a new stand-alone microprobe facility. Although the facility was built to develop a method to rapidly locate and determine elemental concentrations of micron scale particulates on various media using PIXE, the facility has found numerous applications in biology and materials science. The facility is located at LLNL and uses a General Ionex Corporation Model 358 duoplasmatron negative ion source, a National Electrostatics Corporation 5SDH-2 tandem accelerator, and an Oxford triplet lens. Features of the system include complete computer control of the beam transport using LabVIEW<sup>TM</sup> for Macintosh, computer controlled beam collimating and divergence limiting slits, automated sample positioning to micron resolution, and video optics for beam positioning and sample observation. Data collection is accomplished with the simultaneous use of as many as four EG&G Ortec IGLET-X<sup>TM</sup> X-Ray detectors, digital amplifiers made by X-Ray Instruments and Associates (XIA), and LabVIEW<sup>TM</sup> for Macintosh acquisition software.
Date:
October 2, 1998
Creator:
Antolak, A. J.; Bench, G. S.; Brown, T. A.; Frantz, B. R.; Grant, P. G.; Morse, D. H. et al.
Object Type:
Article
System:
The UNT Digital Library
Archer County News (Archer City, Tex.), No. 14, Ed. 1 Thursday, April 2, 1998
Weekly newspaper from Archer City, Texas that includes local, state and national news along with advertising.
Date:
April 2, 1998
Creator:
Armstrong, Sonny
Object Type:
Newspaper
System:
The Portal to Texas History
Archer County News (Archer City, Tex.), No. 27, Ed. 1 Thursday, July 2, 1998
Weekly newspaper from Archer City, Texas that includes local, state and national news along with advertising.
Date:
July 2, 1998
Creator:
Armstrong, Sonny
Object Type:
Newspaper
System:
The Portal to Texas History
Self-Aligned GaAs JFETs for Low-Power Microwave Amplifiers and RFICs at 2.4 GHz
Self-aligned GaAs JFET narrowband amplifiers operating at 2.4 GHz were designed and fabricated with both discrete WETS as a hybrid amplifier and as RFICS. Enhancement-mode JFETs were used in order to be compatible with complementary digital logic. Hybrid amplifiers achieved 8-10 dB of gain at 2.4 GHz and 1 mW DC bias level. The RFIC achieved 10 dB of gain at 24 GHz and 2 mW DC bias level.
Date:
November 2, 1998
Creator:
Baca, A. G.; Dubbert, D. F.; Greenway, D.; Hietala, V. M.; Shul, R. J.; Sloan, L. R. et al.
Object Type:
Article
System:
The UNT Digital Library
A Combustion Model for the TWA 800 Center-Wing Fuel Tank Explosion
In support of the National Transportation Safety Board investigation of the TWA Flight 800 accident, a combined experimental/computational effort was conducted that focused on quarter-scale testing and simulation of the fuel-air explosion in the Boeing 747 center wing fuel tank. This report summarizes the modeling approach used at Sandia National Laboratories. In this approach approximations are introduced that capture the essential physics associated with turbulent flame propagation in multiple compartment fuel tanks. This model efficiently defines the pressure loading conditions during a jet-fuel air explosion in a fuel tank confinement. Modeling calculations compare favorably with a variety of experimental quarter-scale tests conducted in rigid confinement. The modeling describes well the overpressure history in several geometry configurations. Upon demonstrating a reasonable comparison to experimental observations, a parametric study of eight possible ignition sources is then discussed. Model calculations demonstrate that different loading conditions arise as the location of the ignition event is varied. By comparing the inferred damage and calculated impulses to that seen in the recovered tank, it maybe possible to reduce the number of likely sources. A possible extension of this work to better define tank damage includes coupling the combustion model as a pressure loading routine for structural …
Date:
October 2, 1998
Creator:
Baer, M.R. & Gross, R.J.
Object Type:
Report
System:
The UNT Digital Library
Development of mixed-conducting ceramics for gas separation applications.
Mixed-conducting oxides are used in many applications, including fuel cells, gas separation membranes, sensors, and electrocatalysis. This paper describes mixed-conducting ceramic membranes that are being developed to selectively remove oxygen and hydrogen from gas streams in a nongalvanic mode of operation (i.e., with no electrodes or external power supply). Because of its high combined electronic/ionic conductivity and significant oxygen permeability, the mixed-conducting Sr-Fe-Co oxide (SFC) has been developed for high-purity oxygen separation and/or partial oxidation of methane to synthesis gas, i.e., syngas, a mixture of carbon monoxide and hydrogen. The electronic and ionic conductivities of SFC were found to be comparable in magnitude and are presented as a function of temperature. The oxygen flux through dense SFC tubes during separation of oxygen from air is compared with the oxygen flux during methane conversion. Unlike SFC, in which the ionic and electronic conductivities are nearly equivalent, BaCe{sub 0.80}Y{sub 0.20}O{sub 3} (BCY) exhibits protonic conductivity that is significantly higher than its electronic conductivity. To enhance the electronic conductivity and increase hydrogen permeation, metal powder was combined with the BCY to form a cermet membrane. Nongalvanic permeation of hydrogen through the cermet membrane was demonstrated and characterized as a function of membrane thickness. …
Date:
December 2, 1998
Creator:
Balachandran, U.
Object Type:
Article
System:
The UNT Digital Library
X-ray absorption spectroscopy studies of electrochemically deposited thin oxide films.
We have utilized ''in situ'' X-ray Absorption Fine Structure Spectroscopy to investigate the structure and composition of thin oxide films of nickel and iron that have been prepared by electrodeposition on a graphite substrate from aqueous solutions. The films are generally disordered. Structural information has been obtained from the analysis of the data. We also present initial findings on the local structure of heavy metal ions, e.g. Sr and Ce, incorporated into the electrodeposited nickel oxide films. Our results are of importance in a number of technological applications, among them, batteries, fuel cells, electrochromic and ferroelectric materials, corrosion protection, as well as environmental speciation and remediation.
Date:
June 2, 1998
Creator:
Balasubramanian, M.
Object Type:
Article
System:
The UNT Digital Library
Endangered Species Act Amendments: An Analysis of S. 1180 and H.R. 2351
Because of wide-spread interest in possible amendments to the Endangered Species Act (ESA), CRS has received numerous requests for an analysis and critique of S.1180 and H.R. 2351. This report analyzes those bills. HR. 2351 was introduced on July 31, 1997 and S. 1180 on September 16, 1997. Each bill is discussed under various topic headings. The Senate bill will be described first, since it has been reported.
Date:
March 2, 1998
Creator:
Baldwin, Pamela & Corn, M. Lynne
Object Type:
Report
System:
The UNT Digital Library
An integrated systems model for heavy ion drivers
A source-to-target computer model for an induction linac driver for heavy ion fusion has been developed and used to define a reference case driver that meets the requirements of one current target design. Key features of the model are discussed, and the design parameters of the reference case design are described. Examples of the systems analyses leading to the point design are given, and directions for future work are noted.
Date:
September 2, 1998
Creator:
Bangerter, R. O.; Faltens, A. & Meier, W. R.
Object Type:
Article
System:
The UNT Digital Library
Safety equipment list for the light duty utility arm system
The initial issue (Revision 0) of this Safety Equipment List (SEL) for the Light Duty Utility Arm (LDUA) requires an explanation for both its existence and its being what it is. All LDUA documentation leading up to creation of this SEL, and the SEL itself, is predicated on the LDUA only being approved for use in waste tanks designated as Facility Group 3, i.e., it is not approved for use in Facility Group 1 or 2 waste tanks. Facility Group 3 tanks are those in which a spontaneous or induced hydrogen gas release would be small, localized, and would not exceed 25% of the LFL when mixed with the remaining air volume in the dome space; exceeding these parameters is considered unlikely. Thus, from a NFPA flammable gas environment perspective the waste tank interior is not classified as a hazardous location. Furthermore, a hazards identification and evaluation (HNF-SD-WM-HIE-010, REV 0) performed for the LDUA system concluded that the consequences of actual LDUA system postulated accidents in Flammable Gas Facility Group 3 waste tanks would have either NO IMPACT or LOW IMPACT on the offsite public and onsite worker. Therefore, from a flammable gas perspective, there is not a rationale for …
Date:
March 2, 1998
Creator:
Barnes, G. A.
Object Type:
Report
System:
The UNT Digital Library