| Processing of Interconnected Glass and Ceramic Composites for Electronic Packaging |
09 JUL 96 |
96 pages |
| Authors:
Prashant N. Kumta; CARNEGIE-MELLON UNIV PITTSBURGH PA DEPT OF MATERIALS SCIENCE AND ENGINEERING
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 | Glasses and glass-ceramics are well known for their low dielectric constant (epsilon approx. 3-5) at 1MHz which make them useful substrate materials for high speed electronic packaging. On the other hand, crystalline ceramics such as AlN have moderate dielectric constants (epsilon approx. 9-12) at 1MHz high thermal conductivity useful for high power packages. Porous and glass infiltrated ceramic composites with interconnected high thermal conductivity phases therefore, have the potential of ... |
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| Strain-Modulated Epitaxy: A Flexible Approach to 3-D Band Structure Engineering Without Surface Patterning |
08 JUL 1996 |
4 pages |
| Authors:
Carrier Carter-Coman; April S. Brown; Robert Bicknell-Tassius; Nan M. Jokerst; Mark Allen; GEORGIA INST OF TECH ATLANTA SCHOOL OF ELECTRICAL AND COMPUTER ENGINEERING
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| Thin compliant growth substrates have been used to reduce the strain in lattice-mismatched overlayers during epitaxial growth. This letter reports a new thin compliant substrate technology which allows these thin substrates to be patterned on the bottom, bonded surface. This lateral strain variation (inverted stressor) in the growing film can be combined with the additional effects of strain-dependent growth kinetics to realize the lateral control of composition and thickness without ... |
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| Nanocrystalline Processing and Interface Engineering of Si3N4-Based Nanocomposites |
01 JUL 96 |
6 pages |
| Authors:
Jackie Y. Ying; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMICAL ENGINEERING
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| The design and operation of a novel forced flow reactor for synthesizing nanocrystalline, high surface area (210 - 250 sq m/g) TiN powders is described. A key in tailoring the characteristics of the powder produced in the reactor is the use of a microwave-generated plasma. Sintering results demonstrate the tremendous potential for pressureless sintering of monodisperse, high surface area nitride powders as well as highlight the need for processing which ... |
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| Study of Surface Processes During Growth of Epitaxial Boron Nitride |
01 JUL 96 |
8 pages |
| Authors:
D. W. Greve; CARNEGIE-MELLON UNIV PITTSBURGH PA DEPT OF ELECTRICAL AND COMPUTER ENGINEERIN G
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| The surface reactions of diborane and ammonia with the Ni(100) substrate have been studied. Diborane decomposes to boron on the surface and upon annealing forms an Ni2B phase on the surface. Under appropriate conditions, BN can be formed when the surface is doped with both diborane and ammonia. The boron nitride so formed has been identified as the hexagonal phase of boron nitride. Additional studies on other substrates are planned ... |
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| Oxygen Diffusion through Ytterbium-Oxide/Yttrium-Barium-Cuprate Bilayers |
JUL 96 |
15 pages |
| Authors:
Steven C. Tidrow; Richard T. Lareau; William D. Wilber; Arthur Tauber; Donald W. Eckart; ARMY RESEARCH LAB FORT MONMOUTH NJ
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| We have studied the rate of oxygen diffusion through ytterbium oxide, a buffer and dielectric layer used in high critical temperature superconducting (HTSC) structures. An epitaxial bilayer film of ytterbium oxide on yttrium- barium-cuprate (YBCO) was deposited onto an (001) oriented single crystal MgO substrate using the pulsed laser deposition technique. The rate of oxygen diffusion through the bilayer was investigated from 365 to 655 deg C by post deposition ... |
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| Silicon Nitride Joining Using a Sr-Celsian-Based Glass Interlayer |
JUL 96 |
88 pages |
| Authors:
Brian G. Quillen; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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| Si3N4 was successfully joined to itself using a SiO2-SrO-Al2O3 glass composition. Two compositions were evaluated as joining agents, designated SAS-5 and SAS-10 with compositions of 51:44:5 and 49:41:10 weight % SiO2:SrO:Al2O3, respectively. Microstructure of the joint region was examined by electron microprobe and X-ray diffraction. Contact angle measurements and glass characterization, including differential thermal analysis (DTA), dilatometer thermal expansion measurements and crystallization experiments, were used to evaluate each glass composition. ... |
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| High Temperature Stability of Binary Microstructures Derived from Liquid Precursors |
JUL 96 |
12 pages |
| Authors:
Fred F. Lange; A. D. Polli; CALIFORNIA UNIV SANTA BARBARA DEPT OF MATERIALS
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| Chemical routes to synthesize inorganics start with solutions containing different metal-organic molecules that remain well mixed during evaporation to a solid precursor. The solid precursor decomposes and crystallizes during heating. Because decomposition (pyrolysis) occurs at very low temperatures relative to the melting temperature of the inorganic, a large free energy change exists for crystallization. This large free energy change is responsible or two very interesting phenomena. First, the size of ... |
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| Selected Energy Epitaxial Deposition and Low Energy Electron Microscopy of AlN, GaN, and SiC Thin Films |
30 JUN 96 |
20 pages |
| Authors:
R. F. Davis; H. H. Lamb; I. S. Tsong; E. Bauer; E. Chen; NORTH CAROLINA STATE UNIV AT RALEIGH
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| The ionicity of the III-V nitrides requires going beyond the original approach of the multicenter tight-binding method based on the Harris functional for the total energy. By including a self-consistent treatment of the electronic charge density in the formalism, a significant improvement of the static and dynamical properties calculated for GaN and AlN can be achieved. The extension of the generalized ab initio tight-binding scheme to slab calculations makes it ... |
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| Liquid Crystals for Advanced Technologies |
30 JUN 96 |
4 pages |
| Authors:
Robert Pachavis; MATERIALS RESEARCH SOCIETY PITTSBURGH PA
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| Liquid crystalline (LC) materials have found use in many areas of technology and their scope has been extended with the development of liquid crystalline polymers, elastomers, and composite systems. Considerable basic and applied research is being carried out in these areas as was recognized in Symposium I, 'Liquid Crystals for Advanced Technologies,' which presented an opportunity for researchers in different areas to come together, pool resources, and discuss common problems. ... |
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| Electrochemical Digital Etching: Atomic Level Studies of CdTe(100) |
25 JUN 96 |
19 pages |
| Authors:
Tom A. Sorenson; Belinda K. Wilmer; John L. Stickney; GEORGIA UNIV ATHENS DEPT OF CHEMISTRY
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| Atomic level control in the etching of CdTe(100) is being investigated, in an attempt to develop an electrochemical digital etching procedure. In principle, surface atoms on the crystal should show higher reactivity than those contained on the interior, due to their decreased coordination. Electrochemical oxidation in 50 mM K2SO4, resulted in removal of the surface Cd atoms and a tellurium enriched surface, as observed by Auger electron spectroscopy. Subsequent reduction ... |
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| Room Temperature Cyclopentadiene Elimination Reaction for the Synthesis of Diethylgallium-Amides, -Phosphides and -Thiolates, Crystal and Molecular Structures of Et2GaP(t-Bu)22 and Et2GaS(SiPh3)2 |
24 JUN 96 |
25 pages |
| Authors:
O. T. Beachley Jr.; Daniel B. Rosenblum; Melvyn R. Churchill; Charles H. Lake; Laurence M. Toomey; STATE UNIV OF NEW YORK AT BUFFALO DEPT OF CHEMISTRY
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| The compounds Et2GaNEt22, Et2GaN(H)(Me)2, Et2GaN(H)(t-Bu)2, Et2GaP(i- Pr)22, Et2GaP(t-Bu)22, and Et2GaS(SiPh3)2 have been prepared in high yields at room temperature by the elimination of cyclopentadiene from Et2Ga(C5H5) and the corresponding amine, phosphine or thiol. The three diethylgallium amides and Et2GaP(i-Pr)22 are liquids whereas the other phosphide and the thiolate are crystalline solids at room temperature. All compounds were fully characterized by elemental analyses, (1)H and (31)P NMR spectroscopy and cryoscopic molecular ... |
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| International Liquid Crystal Conference (16th) Held in Kent State University, Kent, Ohio ,USA on June 24-28, 1996 |
23 JUN 96 |
440 pages |
| Authors:
Satyendra Kumar; John L. West; KENT STATE UNIV OH LIQUID CRYSTAL INST
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| The International Liquid Crystal Conference provides a forum for the exchange of scientific ideas and technological advances in every aspect of liquid crystal research. The conference program consists of plenary, invited, and contributed talks and poster presentations. The first International Liquid Crystal Conference (ILCC), which attracted about 50 scientists, was organized by Professor Glenn H. Brown at Kent State University in 1965. It has since been held in ten countries ... |
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| Thin-Layer Electrochemical Studies in the Development of a Cycle for the Formation of CdInSe2 by Electrochemical ALE |
22 JUN 96 |
14 pages |
| Authors:
Robert D. Herrick Ii; John L. Stickney; GEORGIA UNIV ATHENS DEPT OF CHEMISTRY
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| A thin-layer electrochemical cell (TLEC) was used in the development of a method for the electrodeposition of CuInSe2. Underpotential deposition (UPD) of atomic layers of Cu, In, and Se, as well as layers of Cu2Se, InSe and InSe2 was performed. However, extension of layers of CuInSe2 proved significantly more difficult due to differences in stability of Cu and In. A complexing agent was used to adjust the activity of the ... |
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| Electrochemical Formation of ZnS Screens |
22 JUN 96 |
28 pages |
| Authors:
Robert Nowak; Lisa P. Colletti; Reed Slaughter; John L. Stickney; GEORGIA UNIV ATHENS DEPT OF CHEMISTRY
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| This paper is a preliminary report on the formation of ZnS thin films thicker than 5 monolayers using electrochemical atomic layer epitaxy (ECALE). This films were electro-deposited on Au coated Si wafers and ITO coated borosilicate glass slides. The deposit's morphology was examined by scanning electron microscopy and composition was determined by electron probe microanalysis. Grazing angle X-ray diffraction showed cubic (111) ZnS films. |
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| Chemistry Involving the Preparation, Isolation, and Immobilization of III-V Compound Semiconductor Nanocrystals and Quantum Dots |
17 JUN 96 |
10 pages |
| Authors:
Richard L. Wells; Louis A. Coury; DUKE UNIV DURHAM NC DEPT OF CHEMISTRY
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| Dehalosilylation reactions have afforded the unique III-V (13-15) dimers X2GaP(SiMe3)22 (X = Cl, Br, I) and a stable substance having the empirical formula Cl3Ga2P is isolable, all of which have been thermally decomposed to yield nanocrystalline GaP; thus, they are new single-source precursors to GaP. Also, Cl3Ga2(As,P)n has been synthesized and shown to be a single-source precursor to the ternary semiconductor GaAsP. In addition, a new, low temperature solution phase ... |
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| Influence of Surface Defects on Chlorine Chemisorption on Si(100)-(2 x 1) |
12 JUN 96 |
30 pages |
| Authors:
W. Yang; Z. Dohnalek; W. J. Choyke; J. T. Yates Jr; PITTSBURGH UNIV PA DEPT OF CHEMISTRY
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| The influence on chlorine chemisorption of surface defects created by low fluence Ar(+) sputtering of the Si(100)-(2x1) surface has been studied. A distinctly different type of Cl bonding is observed on defect sites compared to Cl bonding on Si-Si dimers, as judged by electron stimulated desorption ion angular distribution (ESDIAD) measurements. On the ordered Si(100) surface only terminally bonded Si-Cl species are observed (producing four off-normal Cl(+) beams); on the ... |
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| Influence of the Proton Concentration on the Properties of the LiNbO3 and LiTaO3 Crystals |
12 JUN 96 |
3 pages |
| Authors:
De Mitcheli M. P.; ECOLE POLYTECHNIQUE PALAISEAU (FRANCE) LAB DE PHYSIQUE DE LA MATIERE CONDENS EE
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| In the proposal we wrote one year ago, the work plan for the first year was to compare between as exchanged waveguides and annealed waveguides presenting the same index profiles in order to determine if the proton concentration in a given phase is fixed or depends on the fabrication conditions, extra protons, sometimes called 'interstitial protons' being introduced in some cases. We planned to do this on LiTaO3 where we ... |
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| Method for Intrinsically Doped III-A and V-A Compounds. |
11 JUN 1996 |
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| Authors:
Mark E. Twigg; Mohammad Fatemi; Bijan Tadayon; DEPARTMENT OF THE NAVY WASHINGTON DC
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 | An amorphous compound is changed to single crystal structure by heating at an elevated temperature in an inert atmosphere or in an atmosphere of a forming gas, the amorphous compound is composed of at least one Group III-A element of the Periodic Table and at least one Group V-A element, the amorphous compound having an excess over stoichiometric amount of at least one Group V-A element. The single crystal phase ... |
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| Low Temperature Epitaxial Growth of Rare Earth Doped Si |
05 JUN 96 |
22 pages |
| Authors:
Walter Varhue; VERMONT UNIV BURLINGTON DEPT OF COMPUTER SCIENCE AND ELECTRICAL ENGINEERING
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| Epitaxial Si films doped with high concentrations (10(exp 19)/cu cm) of the rare earth element Er have been deposited. The deposition technique used was low temperature plasma enhanced chemical vapor deposition with an electron cyclotron resonance source. The deposition temperatures were below 500 deg C to avoid formation of erbium silicide which is optically inactive. The growth process for undoped samples was developed to the point that good quality epitaxial ... |
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| Crystallization of Silver Halides from Non-Aqueous Gels |
04 JUN 96 |
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| Authors:
Kenneth M. Doxsee; Roger C. Chang; Eddy Chen; OREGON UNIV EUGENE DEPT OF CHEMISTRY
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| Crystallization of silver halides through salt metathesis reactions of silver nitrate and sodium halides within organic solvent-swollen polymer 'gels' allows the systematic exploration of solvent effects on crystal form. These effects are often dramatic, as typified by the crystallization of octahedral AgBr from dimethylsulfoxide/poly(vinyl chloride) gels and cubic AgBr from N,N- dimethylformamide/poly(vinyl chloride) gels. Other experimental variables in this gel growth approach (e.g., experimental apparatus, presence of chelating agents, type ... |
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| Controlled Synthesis of Calcium Carbonate Polymorphs from a Nonaqueous Solvent |
04 JUN 96 |
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| Authors:
Kenneth M. Doxsee; Robin L. Saulsbery; OREGON UNIV EUGENE DEPT OF CHEMISTRY
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| In order to exploit the often dramatic effects of solvent on crystal form, well-known in the organic chemical realm, in the crystallization of inorganic materials, we have developed the technique of complexation mediated crystallization, wherein use of chelating agents allows the preparation of solid-state materials through simple salt metathesis reactions in nonaqueous solvents. As we report here, this technique, when applied to the crystallization of calcium carbonate through the reaction ... |
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| Modeling for Microstructural Control in Spray Forming |
JUN 96 |
170 pages |
| Authors:
Roger D. Doherty; P. Mathur; S. Annavarapu; Cheng Cai; DREXEL UNIV PHILADELPHIA PA DEPT OF MATERIALS ENGINEERING
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| The earlier 'Drexel' model of Spray Forming was modified with improved measurements of the atomization process: particle size distribution, radial mass flux and gas velocity field as a function of process parameters. The model was also extended to predict, successfully, the droplet undercoolings, the deposit shapes and, in a two dimensional model, the temperatures in the deposit. (A three dimensional thermal model was started but not completed under this funding) ... |
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| Electrical Characterization of GaSb Based Semiconductors for 2-4 micrometers Diode Laser Applications |
JUN 96 |
263 pages |
| Authors:
Daniel K. Johnstone; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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| Deep Level Transient Spectroscopy (DLTS) was used to characterize the band offsets and deep levels in MBE grown GaSb-based semiconductors that are used in 2-4 micrometers laser diode structures. One of several deep level traps found in Al(x)Ga(1-x)As(y)Sb(1-y) (x=0, 0.5, 0.6, 1.0) is a GaSb double acceptor trap. Progress is also made in establishing the model for the DX center in this material. The degree of compensation of the donor ... |
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| Growth, Characterization and Device Development in Monocrystalline Diamond Films |
JUN 96 |
67 pages |
| Authors:
R. F. Davis; R. J. Nemanich; Z. Sitar; L. Bergman; S. P. Bozeman; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| Nuclear transmutation of boron to lithium is being investigated for donor doping of diamond Homoepitaxial (10)B enriched diamond films have been grown and characterized using Hall measurements and Raman and photoluminescence spectroscopies. The films have been neutron-irradiated at a dose of 3xl0(exp 20) n/sq cm. Gamma ray spectroscopy of the samples indicates an activity of 5microns Ci of (110)Ag. The samples are now being cleaned to remove this contaminant. The ... |
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| Low Temperature Deposition and Characterization of N- and P-Type Silicon Carbide Thin Films and Associated Ohmic and Schottky Contacts |
JUN 96 |
39 pages |
| Authors:
R. F. Davis; R. J. Nemanich; M. C. Benjamin; S. Kern; S. W. King; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF PHYSICS
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| Epitaxial, undoped films of 6H-SiC(0001) and 3C-SiC(111) have been grown by gas source (GS) MBE on 6H-SiC((0001) substrates and 2H-AlN(0001) layers between 1050-1250 deg C using SiH4 and C2H4 for Si and C, respectively. Controlled n- and p-type doping was achieved via NH3 and evaporated Al. REED and HRTEM showed the films to be monocrystalline and of either the 6H or 3C polytype. As-deposited (at RT) NiAl, Au, and Ni ... |
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| Atomic Layer Epitaxy of Group IV Materials: Surface Processes, Thin Films, Devices and Their Characterization |
JUN 96 |
25 pages |
| Authors:
Robert F. Davis; S. Bedair; N. A. El-Masry; Z. Sitar; S. K. Han; NORTH CAROLINA STATE UNIV AT RALEIGH
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| The growth parameter, alpha, the ratio of the growth rates on (100) and (111) facets for diamond films deposited on Si and Ti by microwave plasma CVD has been studied using SEM micrographs. Different morphologies were generated on Si under different deposition conditions. The value of alpha increased with increasing temperature and increasing methane concentration, as expected. A value of alpha for Ti was not obtained due to the heavily ... |
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| Defects and Impurities in 4H- and 6H-SiC Homoepitaxial Layers: Identification, Origin, Effect on Properties of Ohmic Contacts and Insulating Layers and Reduction |
JUN 96 |
30 pages |
| Authors:
R. F. Davis; M. O. Aboelfotoh; B. J. Baliga; R. J. Nemanich; M. C. Benjamin; NORTH CAROLINA STATE UNIV AT RALEIGH
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| A chemical vapor deposition system has been designed and is being constructed for the purpose of depositing 4H- and 6H-SiC and AlN thin films. The design incorporates a separate load lock from which the growth chamber and a RHEED chamber are attached. Comparisons between the wetting characteristics of 6H-SiC(0001)Si and Si(111) surfaces in various acids and bases were conducted. The 10:1 HF dipped Si(111) surfaces were hydrophobic; the (0001)Si 6H-SiC ... |
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| Interface Properties of Wide Bandgap Semiconductor Structures |
JUN 96 |
172 pages |
| Authors:
Robert F. Davis; S. Bedair; J. Bernholc; R. J. Nemanich; Z. Sitar; NORTH CAROLINA STATE UNIV AT RALEIGH
|
| Nuclear transmutation of B to Li is being investigated for donor doping of diamond. Homoepitaxial (10)B enriched diamond films have been grown, characterized using Hall measurements and Raman and PL spectroscopies and neutron-irradiated at a dose of 3x10(exp 20)/sq cm. The field emission energy distribution was measured from a Mo field emitter before and after diamond coating. After coating, the Mo needle had a lower turn on voltage that WM ... |
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| Symposium Proceedings Decomposition, Combustion, and Detonation Chemistry of Energetic Materials Held in Boston, Massachusetts on 27-30 November 1995. Volume 418 |
JUN 96 |
453 pages |
| Authors:
Robert H. Pachavis; MATERIALS RESEARCH SOCIETY PITTSBURGH PA
|
| Progress in the understanding of energetic materials from the initial synthesis, in the nonreacting state, and finally during decomposition on timescales from hours to picoseconds has markedly advanced in recent years, A major factor has been the incorporation of advanced diagnostics, such as AFM, broadband time-resolved spectroscopy, laser methods, high-level theory, and high-speed computing. New and unusual compounds, which have been sought on the basis of theoretically optimized properties, are ... |
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| Symposium Proceedings Defect and Impurity Engineered Semiconductors and Devices Held in San Francisco, California on 17-21 April 1995. Volume 378 |
JUN 96 |
1052 pages |
| Authors:
John B. Ballance; MATERIALS RESEARCH SOCIETY PITTSBURGH PA
|
| This volume results from a symposium held at the 1995 MRS Spring Meeting, April 17-21, in San Francisco. The symposium, bearing the title of this volume, followed upon a highly successful earlier symposium entitled 'Defect Engineering in Semiconductor Growth. Processing and Device Technology,' held at the 1992 MRS Spring Meeting. The intent of the present symposium was to go beyond defect control and explore deliberate introduction and manipulation of defects ... |
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| Numerical Modeling for Crystal Growth |
25 MAY 96 |
12 pages |
| Authors:
John Strain; CALIFORNIA UNIV BERKELEY DEPT OF MATHEMATICS
|
| (1) Objectives: Our research on moving boundary problems in crystal growth aims to develop and implement new numerical methods which produce better accuracy for a given cost. (2) Status of effort: We have developed efficient and accurate new methods in several subareas of crystal growth. These include spectral methods for phase field models, new vortex methods for convection in the melt, and related quadrature and interpolation techniques. (3) Accomplishments/New Findings: ... |
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| Diamond Deposition by Controlled Nucleation and Growth |
25 MAY 96 |
45 pages |
| Authors:
Y. Tzeng; AUBURN UNIV AL
|
| Nucleation and growth of diamond were studied using microwave plasma, hot filament, and oxy-acetylene flame assisted CVD techniques. High quality as indicated by IR absorption and Raman spectra,diamond was achieved for optical applications. Sequential deposition and etching was applied to achieve high growth rate while maintaining good diamond quality. By the use of a high power density microwave plasma high rate, up to 50 micrometers/h, growth of diamond was achieved ... |
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| Single Crystal Films and Waveguides of Organic Materials: Preparation and Nonlinear Optical Properties |
24 MAY 96 |
8 pages |
| Authors:
M. Thakur; AUBURN UNIV AL
|
| The objective of this program includes establishment of a generic method for the growth of single crystal films of important organic materials and measurement of their nonlinear optical properties. In the last three years we have developed a method which is a modification of the 'shear method' to prepare single crystal films of specific organic materials having very large second order nonlinearities. This is the first time that single crystal ... |
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| New Substrate/Buffer Layer Compounds for High Temperature Superconductor Epitaxial Film Growth |
MAY 96 |
12 pages |
| Authors:
Arthur Tauber; Steven C. Tidrow; William D. Wilber; Robert D. Finnegan; ARMY RESEARCH LAB FORT MONMOUTH NJ
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| A series of compounds in the system A4MeSbO12, where A=Ba,Sr and ME=Li,Na and K, were prepared by solid state reaction at elevated temperature. A new form of strontium sodium antimonate (Sr4NaSb3Ol2) was prepared. The compounds that were prepared were characterized with regard to their lattice parameter, density and dielectric properties. Thin films were prepared by pulsed laser ablation deposition from dense targets, and epitaxial relationships identified between YBCO and these ... |
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| Crystal Structure, Reactivity, and Photochemical Properties of Tungsten(0) Zwitterionic Amido Complex (CO)5 WNPhNPhC(OMe)Ph |
MAY 96 |
32 pages |
| Authors:
Scott T. Massey; Nicholas D. Barnett; Khalil A. Abboud; Lisa McElwee-White; FLORIDA UNIV GAINESVILLE DEPT OF CHEMISTRY
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| The crystal structure of the zwitterionic complex (CO)5WNPhNPhC(Ph) OMe (1) shows that it is best described as an amido complex in which the 'imidate' fragment PhN=C(Ph)OMe serves as a substituent on the amide nitrogen. The structural information allows the previously reported conversion of 1 to an isomeric zwitterion to be assigned as simple rotation about the N-C double bond. The twisted intermediate for such a rotation also offers a pathway ... |
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| Electrochemistry of Sulfur Adlayers on the Low-Index Faces of Silver |
MAY 96 |
21 pages |
| Authors:
David W. Hatchett; Henry S. White; UTAH UNIV SALT LAKE CITY DEPT OF CHEMISTRY
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| The formation and reactivity of sulfur adlayers on single-crystal Ag electrodes ((111), (110), and (100) orientations) in aqueous solutions (pH = 13) containing HS(-) is reported. Oxidative adsorption of HS(-) (Ag + HS(-) (right arrow) AgSH + e(-)) occurs on all three low-index surfaces at potentials ranging between -0.5 and -0.7V of the thermodynamic value for bulk Ag2S formation. Voltammetric and electrochemical quartz crystal measurements demonstrate that the resulting AgSH ... |
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| Preparation and Characterization of Arsine Derivatives: X-Ray Crystal Structures of As(Si(t)BuMe2)3, As(SiMe3)2,(SiPh3), Et3Ga.As(SiMe3)2(SiPh3), and As(SePh)3 |
MAY 96 |
30 pages |
| Authors:
Ryan A. Baldwin; Hamid Rahbarnoohi; Leonidas J. Jones Iii.; Andrew T. McPhail; Richard L. Wells; DUKE UNIV DURHAM NC DEPT OF CHEMISTRY
|
| For the last decade, our laboratory has had great interest in the chemistry of silylarsines 1. These compounds, in combination with Group 13 alkyl or halogen derivatives, have been shown to be excellent starting reagents for preparing compounds which contain the Group 13 element-arsenic bond. Although the reactivity of silylarsines is well documented (vide supra), structural characterization data for these species has been limited to solution- and gas- phase measurements ... |
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| Strength Degrading Mechanisms for CVD SCS-6 SiC Fibers in Argon Environments |
MAY 96 |
20 pages |
| Authors:
Ramakrishna T. Bhatt; David R. Hull; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER
|
| The room temperature tensile strengths of chemically vapor deposited SCS-6 silicon carbide fibers were measured after 1 to 400 hr heat-treatments in 0.1 MPa argon at temperatures to 2100 deg C. The fibers heat treated for 1 hr above 1400 deg C and those heat treated for 400 hr above 1300 deg C showed strength degradation. Scanning and transmission electron microscopic examination of the degraded fibers showed formation of a ... |
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| Arsenic Cluster Engineering |
MAY 96 |
27 pages |
| Authors:
Michael R. Melloch; PURDUE UNIV LAFAYETTE IN
|
| During this project we have refined our ability to 'arsenic cluster engineer.' We have demonstrated the ability to routinely control the density and diameters of the As clusters using the substrate temperature during MBE to set the excess As concentration and the subsequent coarsening anneal. We have shown that one can vary the incorporation of excess As in GaAs and AlGaAs epilayers by growing at low substrate temperatures using As4 ... |
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| Molecular Structure of a New Potential Propellant Oxidizer 4,5- Dinitroimidazole (45DNI) |
MAY 96 |
19 pages |
| Authors:
A. J. Bracuti; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER PICATINNY ARSENAL N J ARMAMENT ENGINEERING DIRECTORATE
|
| A single crystal x-ray diffraction study verified that the target oxidizer molecule 4,5-dinitroimidazole (45DNI) had, indeed, been synthesized. Some structural features of 45DNI are compared with those of 1,4- dinitroimidazole (14DNI) and 2,4-dinitroimidazole (24DNI). 45DNI, in not planar, but the aromatic imidazole moiety is planar and the nitro groups twisted out the plane. The ring C-C and C-N bonds are all partial double bonds. 45DNI crystallizes with two crystallographically unique ... |
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| Effect of Metalloid Impurities on Grain Boundary Stability in Tantalum |
MAY 96 |
27 pages |
| Authors:
Genrich L. Krasko; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| Metalloid impurities have a very low solubility in tantalum and, therefore, prefer to segregate at the grain boundaries (GBs). In order to analyze the energetics of the impurities on the tantalum GB, the first- principles calculations were performed on a simple eight-atom supercell emulating a typical (capped trigonal prism) GB environment. The 'environment- sensitive' embedding energies were calculated for hydrogen, boron, carbon, nitrogen, oxygen, phosphorus, and sulphur, as a function ... |
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| Optoelectronic III-V Heterostructures by Gas-Source MBE |
30 APR 96 |
81 pages |
| Authors:
Gary Y. Robinson; COLORADO STATE UNIV FORT COLLINS DEPT OF ELECTRICAL ENGINEERING
|
| The objective of this research program was to grow by molecular beam epitaxy (MBE) quantum well heterostructures of the alloy InGaAsP and related materials for use in high performance devices. The first task was to grow InGaAsP/GaAs and InGaAsP/InP structures for shallow quantum well (QW) optical modulators and other optoelectronics devices. The second task was to develop selective-area regrowth techniques for lateral definition of complex optoelectronic integrated devices. The method ... |
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| Numerical Modelling of Crystal Growth |
30 APR 96 |
|
| Authors:
John Strain; CALIFORNIA UNIV BERKELEY CENTER FOR PURE AND APPLIED MATHEMATICS
|
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| Design and Construction of Smart Materials Based on Piezoresistive Sensors and Multilayer Actuators |
26 APR 96 |
6 pages |
| Authors:
Walter A. Schulze; William B. Carlson; ALFRED UNIV NY
|
| PTCR (positive temperature coefficient of resistance) barium titanate was the active material for a ceramic sensor which employed piezoresistivity to detect changes in applied stress. High purity, chemically prepared barium titanate was donor-doped at an optimum level of 0.30 at% lanthanum to provide semiconductivity. A transition metal counterdopant was added at a level of less than 0.10 at% in some cases, to enhance the PTCR effect. The donor dopant and ... |
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| Apparatus and Method for Achieving Growth-Etch Deposition of Diamond Using a Chopped Oxygen-Acetylene Flame. |
09 APR 1996 |
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| Authors:
Thomas P. Thorpe Jr.; Ronald A. Weimer; DEPARTMENT OF THE NAVY WASHINGTON DC
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| A novel apparatus and method for the cyclic growth-etch deposition of diamond on a substrate by flame chemical vapor deposition (CVD) is developed. The cyclic growth-etch diamond deposition is accomplished by placing a suitable substrate to be coated under a CVD flame and providing a disk or face plate or other shapes having one or more teeth (or holes) wherein upon rotation of the disk, or face plate or other ... |
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| Electrochemical Annealing and Friction Anisotropy of Domains in Epitaxial Molecular Films |
08 APR 96 |
18 pages |
| Authors:
Julie A. Last; Michael D. Ward; MINNESOTA UNIV MINNEAPOLIS DEPT OF CHEMICAL ENGINEERING AND MATERIALS SCIENCE
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| Electrochemical annealing of domain boundary defects in an epitaxial monolayer whose structure mimics the (001) layers of the organic superconductor Beta-bis(ethylenedithio)tetrathiafulvalene trioxide, (ET)2I3, has been visualized in situ using real-time atomic force microscopy. These defects are observed readily by lateral force imaging and high resolution contact mode imaging reveals that the domains are oriented at angles of +/-n6O because of epitaxy with the HOPG substrate. The frictional contrast between domains ... |
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| Microstrain and Defect Analysis of CL-20 Crystals by Novel X-Ray Methods |
03 APR 96 |
36 pages |
| Authors:
R. Yazici; D. Kalyon; STEVENS INST OF TECHNOLOGY HOBOKEN NJ HIGHLY FILLED MATERIALS INST
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| This project has demonstrated the capabilities of a new x-ray technique to detect and quantify microstrains and defects in semi-crystalline energetic materials. The technique is based on simultaneous rocking-curve analysis of individual particles. The technique was applied to the analysis of CL-20 particles to investigate the effects of synthesis, grinding and static loads on the extent of microstrain and defect development. Overall, these demonstrated capabilities can be employed by DoD ... |
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| Selective Etching of Silicon for Selective Area Epitaxial Growth |
APR 96 |
16 pages |
| Authors:
Donna J. Advena; John H. Dinan; ARMY RESEARCH LAB FORT BELVOIR VA
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| Process conditions are described for selectively etching silicon by wet and dry etching techniques. High etch rates are achieved and a selectivity (etch rate of silicon/etch rate of masking material) as high as 600 is obtained when thermal oxide is used as a mask and SF6 as the gas in a reactive ion etcher at high pressure. Dry etch process parameters are optimized to produce undercut edge profiles and smooth ... |
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| Ferroelectric and Piezoelectric Properties of a Quenched Poly(Vinylidene Fluoride-Trifluoroethylene) Copolymer |
APR 96 |
23 pages |
| Authors:
M. C. Christie; J. I. Scheinbeim; B. A. Newman; RUTGERS - THE STATE UNIV NEW BRUNSWICK NJ DEPT OF CHEMICAL AND BIOCHEMICAL E NGINEERING
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| The ferroelectric and piezoelectric properties of melt-quenched unoriented poly(vinylidene fluoride-trifluoroethylene) (73:27) copolymer films as a function of the number of poling cycles have been studied. The investigation revealed that quenched films exhibit a decrease in D-E hysteresis behavior as the number of poling cycles increases when the samples are poled at room temperature. Corresponding decreases in remanent polarization, Pr, as well as small increases in the coercive field, Ec, were ... |
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| Strain Characterization of AsH3 Induced Exchange Reactions in InP Grown by OMVPE |
APR 96 |
8 pages |
| Authors:
A. R. Clawson; C. M. Hanson; NAVAL COMMAND CONTROL AND OCEAN SURVEILLANCE CENTER RDT AND E DIV SAN DIEGO CA
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| Behavior of As-P intermixing in heterojunctions of As-compounds grown on InP (001) has been inferred from strain of very thin mis-matched layers inserted periodically in InP to form multilayer superlattice structures. Strain components are observed for both As-P exchange in the InP and from inserted layer growth. The data suggest that for As-compounds grown on an InP surface the availability of As for both layer growth and As-P exchange is ... |
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Crystallography
