| Nano-Structures via Diffusion Limited Crystallization from Solution Precursors: Synthesis and Properties |
15 JUN 95 |
95 pages |
| Authors:
Fred F. Lange; CALIFORNIA UNIV SANTA BARBARA COLL OF ENGINEERING
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 | This program has emphasized two topics: (1) the crystallization of metastable, solid-solution structures, their partitioning into equilibrium structures and compositions, and the role of the metastable phase and its partitioning on forming unique, nanometer microstructures important to the mechanics of structural ceramics and their composites, and (2) the formation of single crystal thin films via spin coating single crystal substrates with solution precursors. Results for the first topic are new, ... |
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| LEC Growth of Bulk In(x)Ga(1-x)As |
13 JUN 95 |
25 pages |
| Authors:
Rowland M. Ware; R. A. Puechner; Mark Tiernan; Mark Morris; WARE TECHNICAL SERVICES INC WESTWOOD MA
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| A Double Crucible Liquid Encapsulated Czochralski (DCLEC) process was developed for the growth of single crystals of In(x)Ga(1-x)As. The conditions for the flow of non-wetting liquids through capillaries were determined and applied to Hot Pressed Boron Nitride crucibles to achieve stable flow of InGaAs melts, without back-diffusion of In, and without interference from the boric oxide encapsulant. The problem of mixing int the inner crucible was solved by the use ... |
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| The First Example of an Aluminum-Phosphorus-Arsenic Mixed-Pnicogen Ring Compound: Et2A1p(SiMe3)2A1(Et)2As(SiMe3)2 |
10 JUN 95 |
19 pages |
| Authors:
Janeen A. Cooke; Richard L. Wells; Peter S. White; DUKE UNIV DURHAM NC DEPT OF CHEMISTRY
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| The aluminum mixed-pnicogen compound Et2 A1P(SiMe3)2A1(Et) 2As(SiMe3)2 (1) is the first structurally-characterized compound to contain a four membered ring with two aluminum centers bridged by two different heavier group 15 atoms. Compound 1 was synthesized by the equilibration of Et2A1P(SiMe3) 22 (2) and Et2A1As(SiMe3)22 (3) in a 1:1 mole ratio under ultrasonic conditions. Low-temperature X-ray crystallographic analysis revealed that crystals of 1 belong to the monoclinic system, space group C2/c ... |
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| Atomistic Calculations of Defects in ZnGeP2 |
09 JUN 95 |
24 pages |
| Authors:
Ravi Pandey; MICHIGAN TECHNOLOGICAL UNIV HOUGHTON DEPT OF PHYSICS
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| Atomistic calculations are performed to study defect energetics in ZnGeP2 were two- and three-body interatomic potentials are used to simulate the perfect lattice. Formation energies for native ionic defects and binding energies for some of the electronic defect-complexes are calculated. The dominance of antisite defect-pairs is predicted in the lattice. However, the defects controlling the spectroscopic properties would seem to be associated with vacancies. For the EPR-active acceptor center, the ... |
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| Crystal Structure and Magnetic Susceptibility of Ce8Pd24Sb |
01 JUN 95 |
23 pages |
| Authors:
Robert A. Gordon; Francis J. DiSalvo; CORNELL UNIV ITHACA NY DEPT OF CHEMISTRY
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| The ternary compound Ce8Pd24Sb is very close in composition to the intermediate valent binary Cepd3. A single crystal study yielded a cubic cell with a=8.461(1)A, Pm3m symmetry with wR2=0.0412 based on 1453 reflections (222 unique) and 16 parameters. This new structure type is composed of distorted perovskite and Cu3Au subcells arranged with the perovskite-like units centered on the corners of the cube. Fitting the magnetic susceptibility data above 100K to ... |
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| Pseudomorphic Semiconducting Heterostructures from Combinations of AlN, GaN and Selected SiC Polytypes: Theoretical Advancement and its Coordination with Experi mental Studies of Nucleation, Growth, Characterization and Device Development |
JUN 95 |
24 pages |
| Authors:
R. F. Davis; O. Aboelfotch; S. Kern; K. Linthicum; J. Sumakeris; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| The use of NH3 as an alternative to ECR in the gas source(GS) MBE of GaN has resulted in an increase in the growth rate and a sharp peak at 354 nm in the PL spectrum. The use of an ammonia cracker cell was investigated. Stoichiometric GaN films have also been deposited on Al2O3(0001), Si(001) and Si(111) substrates using an NH3 seeded free He jet and an effusive triethylgallium (TEG) ... |
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| Atomic Layer Epitaxy of Group 4 Materials: Surface Processes, Thin Films, Devices and Their Characterization |
JUN 95 |
40 pages |
| Authors:
R. F. Davis; S. Bedair; N A. El-Masry; J. T. Glass; P. Goeller; NORTH CAROLINA STATE UNIV AT RALEIGH
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| The ALE technique has been employed to deposit monocrystalline 3C-SiC thin films at 860 + or - 10 deg C. Wafers containing heterojunction bipolar transistor structures have been completely processed and characterized. No transistor activity was detected in any of the HBT structures. Electrical characterization of the emitter-base and collector-base junctions revealed rudimentary rectifying behavior, indicating that the base region of the completed HBT structures was too thick for transistor ... |
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| Growth, Characterization and Device Development in Monocrystalline Diamond Films |
JUN 95 |
33 pages |
| Authors:
R. F. Davis; J. T. Glass; R. J. Nemanich; S. P. Bozeman; A. T. Sowers; NORTH CAROLINA STATE UNIV AT RALEIGH
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| Monocrystalline beta(3C)-SiC films were grown on alpha(6H)-SiC(0001) substrates using gas-source MBE, silane and ethylene precursors and a temperature range of 1050-l450 deg C. Cubic (3C)-SiC was achieved at all T1400 deg C when H2 diluent was present. The surface electronic states of clean 6H-SiC were investigated using ARUPS. Deposition and subsequent evaporation of Si and were used to clean the surface. LEED, AES and XPS showed that essentially all O ... |
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| Point-Charge Analysis of Symmetry-Preserving Charge Compensation and Vacancies in the Fluorapatites Ca5(PO4)3F and Sr5(PO4)3F |
JUN 95 |
20 pages |
| Authors:
Clyde A. Morrison; ARMY RESEARCH LAB ADELPHI MD
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| A single point-charge model was used to investigate four types of charge compensation and two types of vacancies for the M2 site in M5(PO4)3F (M = Ca, Sr). Two effective charges were chosen for the oxygen in the (PO4)(3-) complex. A set of crystal-field components, A(sub nm), was obtained for each assumed compensation or vacancy, and the crystal-field parameters, B(sub nm), for Nd(3+) were calculated for each type. The resulting ... |
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| Nitride Semiconductors for Ultraviolet Detection |
JUN 95 |
61 pages |
| Authors:
R. F. Davis; M. D. Bremser; K. Gruss; K. Linthicum; B. Ferry; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| Continued development and commercialization of optoelectronic devices, including light emitting diodes and semiconductor lasers produced from III-V gallium arsenide-based materials, has also generated interest in the much wider bandgap semiconductor mononitride materials containing aluminum, gallium, and indium. The majority of the studies have been conducted on pure gallium nitride thin films having the wurtzite structure, and this emphasis continues to the present day. The program objectives achieved in this reporting ... |
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| Interface Properties of Wide Bandgap Semiconductor Structures |
JUN 95 |
235 pages |
| Authors:
R. F. Davis; S. Bedair; J. Bernholc; J. T. Glass; R. J. Nemanich; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| Heteroepitaxy is the growth of a crystal (or a film) on a foreign crystalline substrate that determines its orientation. While the potential of heteroepitaxial deposition has been demonstrated, significant advances in theoretical understanding, experimental growth and control of this growth, and characterization are required to exploit the capabilities of this process route. The materials of concern in this report are classified as wide bandgap semiconductors and include diamond, SiC and ... |
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| High-Speed Machining of Materials with Low Machinability |
JUN 95 |
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| Authors:
Jukka Paro; Ilkka Nieminen; Veijo Kauppinen; HELSINKI UNIV (FINLAND)
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 | Materials with low machinability are often characterized by the difficulty of machining them by almost any cutting method. However, nowadays there are some advanced cutting methods and cutting tool materials available to make their machining possible. Classical high-speed milling tool materials, such as polychrystalline diamond (PCD) and cubic boron nitride (CBN) are famous for their resistivity against tool wear. PCD tool materials are used in the high- speed milling of ... |
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| Research on Nucleation of II-VI/III-V Semiconductor Heterojunctions |
31 MAY 95 |
3 pages |
| Authors:
N. Otsuka; R. L. Gunshor; PURDUE RESEARCH FOUNDATION LAFAYETTE IN
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| Two studies were carried out in this program. The first one is molecular dynamics (MD) simulations of MBE growth of ZnSe, and the second one is the analysis of phase separation of ZnSe based alloy epilayers. One study involved molecular dynamics simulations based on the Lennard-Jones- Axilrod- Teller (LJAT) potential model I. Using a set of interatomic potentials based on thermodynamic data and crystal structure data, the atomic configurations in ... |
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| Silicon-Germanium-Carbon Alloys for Optoelectronic Devices (FY91 AASERT) |
31 MAY 95 |
132 pages |
| Authors:
James Kolodzey; DELAWARE UNIV NEWARK DEPT OF ELECTRICAL ENGINEERING
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| This research resulted the growth on the growth of this new semiconductor alloys, silicon-germanium carbon, by the technique of molecular beam epitaxy (MBE). The alloys have been characterized by several techniques including Rutherford backscattering spectronietry (RBS) for composition, and Fourier transform infrared spectrometry (FTIR) for optical absorption. The Si%%%%%Ge%C% alloys were successfully grown using all solid sources for the Si, Ge and C. Substrates were 75 mm diameter (100) - ... |
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| Process for Forming Epitaxial BaF2 on GaAs |
31 MAY 1995 |
13 pages |
| Authors:
Tak-Kin Chu; Francisco Santiago; Michael Stumborg; DEPARTMENT OF THE NAVY WASHINGTON DC
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| A process for growing single crystal epitaxial BaF2 layers on gallium arsenide substrates by slowly reacting Ba, BaCl2, BaI2, BaBr2, BaF2.BaCl2, BaF2.BaBr2, BaF2.BaI2, BaC12.BaBr2 , Ba3(GaF6)2, BaH2, or BaO2 vapor with a clean, hot GaAs substrate at 500 to 700 deg C in high vacuum until a uniform, thin (tilde 12A) layer of reaction product is formed and then vapor depositing BaF2 onto the reaction layer at room temperature to ... |
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| Development of Process Technology for the Fabrication of Mesoscopic Devices |
30 MAY 95 |
100 pages |
| Authors:
Thomas W. Sigmon; Jane A. Alexander; Gerald Witt; OREGON GRADUATE INST BEAVERTON
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| The development of the processes necessary for fabrication of sub- 100nm heteroepitaxial Si(x)G3e(1 -x) structures in Si (100) substrates is described. The structures are required to be planar and definable by available patterning techniques (e.g. X-ray, e-beam, ion beam, or optical lithography). The report describes the investigation of two candidate patterning processes, enhanced ion beam etching, and standard e-beam lift off. The formation of the heteroepitaxial structures, in the form ... |
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| Intrinsically Doped III-A and V-A Compounds Having Precipitates of V-A Element. |
30 MAY 1995 |
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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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| A SNIFTIRS Study of the Diffuse Double Layer at Single Crystal Platinum Electrodes in Acetonitrile |
26 MAY 95 |
39 pages |
| Authors:
Nebojsa S. Marinkovic; Mathias Hecht; John S. Loring; W. R. Fawcett; CALIFORNIA UNIV DAVIS DEPT OF CHEMISTRY
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| In situ reflection infrared spectroscopy with electrochemical modulation has been used to investigate the structure of the double layer for the system: Pt(hkl)/acetonitrile. The electrolytes used were tetraethylammonium perchlorate and sodium perchlorate. It has been found that acetonitrile is preferentially chemisorbed on the surface either through the non-bonding electrons on the nitrogen atom at potentials positive of the point of zero charge, or on its side in a rehybridized form ... |
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| Mechanisms of Quasi-Brittle Failure in Metals and Intermetallic Compounds |
24 MAY 95 |
26 pages |
| Authors:
David P. Pope; Vaclav Vitek; PENNSYLVANIA UNIV PHILADELPHIA
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| This is the final report for this program. Progress was made both on the experimental and theoretical aspects of the program. The experimental results demonstrate that single- and polycrystalline Al3Ti in the Ll2 form (by adding Fe or Cr) is intrinsically brittle; although second phase particles can make it even more brittle. The theoretical portion of the program has produced a new theory of the brittle-to-ductile transition temperature involving dislocation-screening ... |
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| Proceedings of NATO Advanced Research Workshop on Spatio-Temporal Patterns in Nonequilibrium Complex Systems Held in Santa Fe, New Mexico on 13-17 April 1993. Volume 21 |
23 MAY 95 |
677 pages |
| Authors:
L. M. Simmons; SANTA FE INST NM
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| This workshop brought together experimentalists working with pattern forming systems in complex materials, such as liquid crystals, polymers, and biological systems, and theorists knowledgeable and interested in a physical understanding of the many, sometimes startlingly beautiful, patterns exhibited by these complex materials. Pattern formation in complex systems is important because it stimulates the growth of new physics and therefore new technologies. The technological relevance touched on at the workshop ranged ... |
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| Low Temperature Epitaxial Growth of Rare Earth Doped Silicon and Silicon Germanium Alloys |
21 MAY 95 |
36 pages |
| Authors:
Walter J. Vrahue; VETERANS ADMINISTRATION WASHINGTON DC
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| This document reports on the progress towards the growth of rare earth dope Si by low temperature plasma enhanced chemical vapor deposition (PECVD). The goal of this investigation is to develop a commercially compatible technique to deposit thick, high concentration, precipitation free, rare earth doped Si films. The low temperature growth technique used is plasma enhanced chemical vapor deposition with an electron cyclotron resonance(ECR) source. Low temperature processing is needed ... |
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| The Role of Nickel in Si(001) Roughening |
10 MAY 95 |
31 pages |
| Authors:
V. A. Ukraintsev; John T. Yates Jr; PITTSBURGH UNIV PA SURFACE SCIENCE CENTER
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| The role of Ni impurities on the structure of the Si(001)-(2x1) surface has been investigated by statistically comparing STM patterns with Auger spectra. Characteristic reconstructed local structures (split off dimers' and vacancy channels') are observed for different surface concentrations of Ni as measured by Auger electron spectroscopy, and it is shown that the STM image provides a high sensitivity to Ni. For high levels of Ni contamination, long range roughening ... |
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| From Liquid Crystal Polymers Containing Crown Ethers to Tapered Building Blocks Containing Crown Ethers Which Self-Assemble into Tubular Supermolecules |
09 MAY 95 |
14 pages |
| Authors:
V. Percec; G. Johansson; CASE WESTERN RESERVE UNIV CLEVELAND OH
|
| Molecular recognition directed self-assembly of supramolecular architectures or noncovalent synthesis, and molecular recognition directed self- assembly of transition states or self-synthesis, are two of the most active topics of research in the area of supramolecular chemistry. We are concerned with the use of the simplest endo-receptor i.e., crown ether in the design of two classes of systems. The first one is a system which is externally regulated by molecular recognition ... |
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| Uncompensated Garnets: A Magnetic Semiconductor |
09 MAY 95 |
38 pages |
| Authors:
Philips E. Wigen; OHIO STATE UNIV COLUMBUS DEPT OF PHYSICS
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| Yttrium iron garnet (YIG) is a ferrimagnetic oxide, Y3Fe5O12 and a good insulator. When five to ten percent of the Y(3+) is replaced by Ca(2+), an uncompensated state exists. The resulting material has perturbed magnetic properties, semiconducting electrical properties with activation energies from 0.2 to 0.4 eV and resistivities as low as 300 ohms cm at room temperature, and modified optical properties. In the past year the conductivity studies have ... |
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| Surface Characterization of Cu-ion Implanted Single Crystal and Thin Film ZnO for Catalytic Applications |
MAY 95 |
31 pages |
| Authors:
J. S. Brodkin; D. Chadwick; ARMY RESEARCH LAB WATERTOWN MA MATERIALS DIRECTORATE
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| Single crystals and thin films of zinc oxide were implanted with copper ions in order to study the catalytic properties of a mixed Cu-ZnO system. ZnO is widely used as a catalyst in the methanol synthesis reaction, and copper has been noted to have a synergistic effect on the rates and yields of reaction. The samples were characterized by x-ray photoelectron spectroscopy (XPS) before and after implantation, and surface copper ... |
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| Rapid Thermal Processing of Semiconductors at High Vapor Density |
25 APR 95 |
7 pages |
| Authors:
H. T. Banks; NORTH CAROLINA STATE UNIV AT RALEIGH CENTER FOR RESEARCH IN SCIENTIFIC COMPUTA TION
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| The fluid dynamics in a vertical reactor for high pressure vapor transport (HPVT) of compound semiconductors is modeled. The modeling is for the growth of II-IV-V2 chalcopyrite ZnGeP2 and addresses the flow of dense phosphorus gas at 3.42 x 10(exp 5) Pascals pressure. Effects of density variations on p-polarized reflectance spectroscopy are also examined. The mathematical model for transport processes is described by the full gasdynamic equations (Navier Stokes equations ... |
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| Surface Chemistry of Diamond Single Crystals |
21 APR 95 |
21 pages |
| Authors:
John T. Tates Jr; PITTSBURGH UNIV PA
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| Diamond(100) was studied as a substrate for the adsorption of atomic hydrogen and fluorine. Both surface C-H bonds and surface C-F bonds are of importance in the tribological use of diamond film coating. A new and facile method for depositing surface fluorine on diamond has been developed. The method involves the photochemical dissociation of perfluoroalkyl iodide molecules depositing C(n)F(2n+1) groups on the diamond. These groups, upon thermal dissociation, produce surface ... |
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| On the Jahn-Teller Effect of Mn(2+) in Zinc-Blende ZnS Crystal |
18 APR 95 |
26 pages |
| Authors:
Krassimir K. Stavrev; Michael C. Zerner; FLORIDA UNIV GAINESVILLE DEPT OF CHEMISTRY
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| The excited states of Mn(2+) in zinc-blende ZnS crystal have been studied by the Intermediate Neglect of Differential Overlap model parameterized for spectroscopy (INDO/S) within the Restricted Open-Shell Hartree-Fock (ROHF)- Configuration Interaction (CI) approximation. The effect of the Jahn-Teller (JT) active e-mode on the first excited state (a(4)T1) has been examined with respect to energy barriers and geometric distortions. The dynamical JT effect has been studied and the excited state ... |
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| A New Diamond Emitter Device |
10 APR 95 |
17 pages |
| Authors:
John C. Driscoll; PTS CO RALEIGH NC
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| The goal of the program is to produce and evaluate more efficient emitters using diamond semiconductor technology; and to propose use of electronic diamond technology in a phase II EBS (Electron Beam Semiconductor) device application. Accordingly, several samples of the rugged, type 6H SiC, high voltage EBS diode targets were obtained from Cree research. The SiC p-n junction diodes (20X2O mils) were evaluated on the PTS tektronix 576 curve tracer ... |
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| Materials for Adaptive Structural Acoustic Control. Volume 1 |
06 APR 95 |
214 pages |
| Authors:
L E. Cross; PENNSYLVANIA STATE UNIV UNIVERSITY PARK MATERIALS RESEARCH LAB
|
| The objectives of this ONR sponsored University Research Initiative (URI) entitled "Materials for Adaptive Structural Acoustic Control" concern both basic fundamental studies and highly applied development of the piezoelectric and electrostrictive ferroelectric ceramics which carry both the sensing and actuation functions for adaptive control. The report documents work over the third year of this five year program. For convenience and continuity, the activities are grouped under the headings General Summary ... |
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| Materials for Adaptive Structural Acoustic Control. Volume 2 |
06 APR 95 |
208 pages |
| Authors:
L. E. Cross; PENNSYLVANIA STATE UNIV UNIVERSITY PARK MATERIALS RESEARCH LAB
|
| The objectives of this ONR sponsored University Research Initiative (URI) entitled "Materials for Adaptive Structural Acoustic Control" concern both basic fundamental studies and highly applied development of the piezoelectric and electrostrictive ferroelectric ceramics which carry both the sensing and actuation functions for adaptive control. The report documents work over the third year of this five year program. For convenience and continuity, the activities are grouped under the headings (General Summary ... |
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| Measurement and Analysis of Properties of Several Types of Films Doped with Oxides |
05 APR 95 |
16 pages |
| Authors:
Chen Yuming; Tang Jinfa; Gu Peifu; NATIONAL AIR INTELLIGENCE CENTER WRIGHT-PATTERSON AFB OH
|
| This article introduces several types of experimental equipment associated with the measurement of stress, absorption, and scattering in thin films. It makes use of these systems to carry out measurements and tests on such characteristics as stress, absorption, scattering, focusing density, and so on, in a number of common oxides and their doping films. At the same time, with the help of Auger energy spectra techniques and X-ray diffraction technology, ... |
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| Ultra-High Vacuum/Chemical Vapor Deposition of Epitaxial Silicon-on-Sapphire. |
04 APR 1995 |
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| Authors:
Douglas A. Sexton; Howard W. Walker; DEPARTMENT OF THE NAVY WASHINGTON DC
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| A method of fabricating epitaxial thin films, such as doped films or silicon-on-sapphire films, relies upon ultrahigh vacuum vapor deposition. The method calls for a preparing of an ultrahigh vacuum chamber to reduce water and oxygen pressure to below 10(exp -10) Torr. At at least one sapphire substrate is placed in the ultra high vacuum chamber and is purged in the chamber with about 600 sccm hydrogen for about 5 ... |
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| Molecular Engineering of Liquid Crystalline Polymers by 'Living' Polymerization 30. Synthesis and 'Living' Cationic Polymerization of (2R, 3S)-2- Fluoro-3-Methylpentyl 4'-(8-Vinyloxyoctyloxy) Biphenyl-4 Carboxylate and Its Copolymerization with (2R, 3S)-2 |
03 APR 95 |
28 pages |
| Authors:
V. Percec; H. Oda; CASE WESTERN RESERVE UNIV CLEVELAND OH DEPT OF MACROMOLECULAR SCIENCE
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| The synthesis and 'living' cationic polymerization of (2R, 3S)-2- fluoro-3-methylpentyl 4'-(8-vinyloxyoctyloxy)biphenyl-4-carboxylate (11-8) are described. Poly(11-8)s with degrees of polymerization from 4.3 to 15.7 and polydispersities less than or equal to 1.19 were synthesized and characterized by differential scanning calorimetry (DSC) and thermal optical polarized microscopy. All poly(11-8)s exhibit an enantiotropic S(sub c*) and an unidentified smectic (S(sub 1) phase. Poly(11-8)s with DP less than or equal 11.5 exhibit an additional ... |
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| From Molecular to Macromolecular Liquid Crystals |
03 APR 95 |
248 pages |
| Authors:
V. Percec; CASE WESTERN RESERVE UNIV CLEVELAND OH DEPT OF MACROMOLECULAR SCIENCE
|
| The goal of this chapter is to discuss the dependence between various molecular parameters including structure, molecular weight, architecture, etc., and phase behavior. An attempt will be made to follow this trend on passing from a molecular to a macromolecular liquid crystal. The main goal is to provide the reader with the presently available tools which can be used to tailor-make liquid crystalline polymers. A brief and general introduction to ... |
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| Surface Electrical Conductivity of Single Crystal Spinel in Cesium Vapour |
02 APR 1995 |
15 pages |
| Authors:
P. Agnew; J. L. Ing; AEA TECHNOLOGY PLC DIDCOT (UNITED KINGDOM) MATERIALS AND CHEMISTRY DIV
|
| The operation of a thermionic fuel element (TFE) requires the maintenance of good electrical resistance between the anode and cathode, and between the electrodes and the TFE body. A program of research was established as part of the TOPAZ International Program (TIP) with the purpose of investigating the degradation of TFE electrical insulators. The major emphasis of this research has been on the interactions of ... |
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| Predictions of the Spectra of the Rare-Earth Ions Ce(3+) Through Yb(3+) in the Two Sites of Ca5(PO4)3F |
APR 95 |
72 pages |
| Authors:
Clyde A. Morrison; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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| The results of fitting the experimental data on Er(3+) in the two Ca2+ sites of Ca5(PO4)3F are used to predict the crystal-field parameters for the entire rare-earth series. These crystal-field parameters are then used along with the free-ion wavefunctions determined with aqueous parameters to determine a set of energy levels of the rare-earth ions Ce(3+) through Yb(3+) for both Ca(2+) sites (Cal with C(sub 3) symmetry and Ca2 with C(sub ... |
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| Zinc Selenide Substrates for Blue Lasers |
APR 95 |
3 pages |
| Authors:
Brian J. Fitzpatrick; OPTICAL SEMICONDUCTORS INC PEEKSKILL NY
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| A new crucible was designed for the zone melting growth of zinc selenide (ZnSe). This is partially compatible with the old crucible, in that most of the parts are interchangeable. The seeding area has been reduced to 6 mm diameter at the bottom, but the full 25 mm boule diameter has been reached by 30 mm above the bottom. This allows a seeding neck of considerably smaller diameter than the ... |
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| Langasite Crystals Growth with Quality Factor Q, That Exceeds the Q of Quartz, and Which are Suitable for High-Precision Resonators |
31 MAR 95 |
24 pages |
| Authors:
A. N. Gotalskaja; D. I. Dresin; S. N. Schegolkova; N. I. Saveleva; V. V. Bezdelkin; LANTAN MOSCOW (RUSSIA)
|
| Processes of langasite crystal growth are considered. Distribution of temperature fields, heat assembly design, pulling and rotation rates are optimized. Composition of charge, impurity content and technology of its manufacture have been studied. Influence of annealing regimes and gaseous medium on crystal quality are discussed. The main defect types encountering in crystals are identified. Langasite resonator at 5 MHz, 3rd overtone has been developed. |
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| 'Nanocrystalline Processing and Interface Engineering of Si3N4-Based Ceramics' |
31 MAR 95 |
6 pages |
| Authors:
Jackie Y. Ying; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMICAL ENGINEERING
|
| Construction and modification of the novel tubular flow reactor for the synthesis of nanocrystalline materials by thermal evaporation in a forced flux of gas has been an ongoing process over the past year. The first version of the reactor was used to synthesize nanocrystalline silicon (Si). The incoming gas flow rate is set with a mass flow controller. Helium (He) enters at one end of the reactor and flows over ... |
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| Luminescence Properties of ZnWO4:Cr3+ Laser Crystals |
30 MAR 95 |
11 pages |
| Authors:
Zang Jingcun; Wu Shanhua; Ma Yue; NATIONAL AIR INTELLIGENCE CENTER WRIGHT-PATTERSON AFB OH
|
| Luminescence properties of Zn WO4 : Cr(3+) laser crystals were investigated. (4)T2 energy level of Cr(3+) splitted to three levels, 13550, 14205 and 14706/cm, and the Stokes shift of luminescence spectra is 236 nm. The best intensity peak of emission is at 912nm. If the excitation wavelength was selected as 608 nm and doping concentration was 0.01 wt%, a broad emission band would be observed at 532 nm excitation. jg ... |
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| A Molecular Beam Epitaxy Growth Technique for Quality 1.5 - 2.5 Micrometers near Infrared Sensing Devices |
30 MAR 95 |
37 pages |
| Authors:
Marshall J. Cohen; SENSORS UNLIMITED INC PRINCETON NJ
|
| The objective of this Program is to develop long wavelength, lattice mismatched InGaAs PIN diode structures grown using Molecular Beam Epitaxy (MBE). The overall goal is to generate structures sensitive to the entire near infrared (1.0 - 2.5 micrometers) which take advantage of the uniformity inherent to MBE but with a buffer structure practical for commercialization. The activity during Phase I was centered on an intermediate alloy, In(.74)Ga(.28)As, with optical ... |
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| Sum Frequency Generation of Dual-Wavelength Nd. YAP Laser in LiIO3 Crystal |
29 MAR 95 |
9 pages |
| Authors:
Yuping Zhou; Hongyuan Shen; NATIONAL AIR INTELLIGENCE CENTER WRIGHT-PATTERSON AFB OH
|
| Based on Sellmeier's equation for LiIO3 crystal, the phase-matched condition for sum-frequency generation of 1.0795 micrometers and 1.3414 micrometers dual wavelength Nd:YAP laser has been calculated. The calculated results agree well with the experimental ones. The CW and pulsed 0.5981 micrometers sum-frequency radiation have been achieved for the first time. jg p.4 ANNOTATION: Sum Frequency Generation of Dual-Wavelength Nd. YAP Laser in L1ID3 Crystal. --Translation. |
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| E-Beam Addressed Spatial Light Modulator Employing Electron Trapping Materials. Phase 1 |
29 MAR 95 |
31 pages |
| Authors:
Xiaojing Lu; Xiangyang Yang; Charles Y. Wrigley; Richard Bradley; Janos Meszaros; QUANTEX CORP ROCKVILLE MD
|
| Spatial light modulators (SLMs) play a critically important role in optical signal processing optical computing. A novel electron beam addressed emissive SLM which combines high performance polycrystalline electron trapping (ET) materials with an advanced field-emitter array is being developed. The proposed SLM combines high resolution (> 100 lplmm), high SBP (> 1000x1000), high frame rate (>- 1 KHz), high contrast ratio (> l03:l) and low drive voltage (< 15 V) ... |
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| Processing of Polymers Using Supercritical Fluids |
27 MAR 95 |
19 pages |
| Authors:
John J. Aklonis; Eric J. Amis; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES DEPT OF CHEMISTRY
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| In this project we seek to use this variability of solvating power to dissolve high molecular weight polymers, provide solution processing capacity for polymers which are typically difficult to process, and produce blends of normally incompatible polymers from cosolvated mixtures. This last area, polymer blends, this one of great potential and interest because traditional polymer blends are often phase separate into large domains. For example, we expect that by molecularly ... |
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| Study of Liquid Crystal Spatial Light Modulator Application to Hadamard Transform Spectrometer -- A Fast and Accurate Decoding Method |
27 MAR 95 |
12 pages |
| Authors:
Bingquan B. Zhang; Fengfei Bi; NATIONAL AIR INTELLIGENCE CENTER WRIGHT-PATTERSON AFB OH
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| A study is made on liquid crystal spatial light modulator (LC-SLM), used as a stationary encoding mask of Hadamard transform spectrometer (HTS), and thus a fast and accurate decoding method is proposed; the improvement is given in terms of root-mean-square of the signal-to-noise ratio produced by the LC-SLM mask. jg p.5 ANNOTATION: Study of Liquid Crystal Spatial Light Modulator Application to Hadamard Transform Spectrometer -- A Fast and Accurate Decoding ... |
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| Pseudomorphic Heterostructure Materials for High Performance Devices |
21 MAR 95 |
12 pages |
| Authors:
Wen I. Wang; COLUMBIA UNIV NEW YORK DEPT OF ELECTRICAL ENGINEERING
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| Using the planar-doping technique, Si has been shown to be amphoteric on (311)A InAlAs/InGaAs/InP grown by molecular beam epitaxy and excellent modulation-doped field effect transistors have been demonstrated. Through the use of an AlN/GaN strained superlattice buffer layer, high quality GaN layers were obtained. Crystalline SiC thin layers have been grown on 125 mm silicon-on- insulator (SOI) substrates. These two techniques have also been combined to synthesize the first GaN ... |
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| Properties of High-Tc Josephson Junctions with Y(0.7)Ca(0.3)Ba2Cu3O(7- delta) Barrier Layers |
20 MAR 95 |
33 pages |
| Authors:
L. Antognazza; B. H. Moeckly; T. H. Geballe; K. Char; CONDUCTUS INC SUNNYVALE CA
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| We report the use of Y(0.7)Ca(0.3)Ba2Cu3O(7-delta) as an epitaxial barrier between YBa2CuO(7-delta) (YBCO) electrodes in high-Tc SNS edge junctions. Ca-doped YBCO is an overdoped version of YBCO, and it has an excellent lattice and thermal expansion match with YBCO. We show that these junctions exhibit clean interfaces with resistances smaller than 10(exp -10) ohm sq cm. We present the temperature dependence of the critical current density J(sub c) and the ... |
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| Growth of GaN Single-Crystal Boules |
20 MAR 95 |
8 pages |
| Authors:
Moeljanto Leksono; Jaques I. Pankova; ASTRALUX BOULDER CO
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| The first step in growing a GaN boule was to demonstrate the possibility of growing GaN from elemental Ga and ammonia on a substrate. Although GaN crystals were obtained the diffusion rate of gas vapor was too high. A number of other problems was uncovered and their solution was conceived. Several changes to the deposition system were made, but to succeed, a more radical redesign is needed. This new design ... |
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| Novel Electric-Field Effects in Quantum Wells and Superlattices |
16 MAR 95 |
5 pages |
| Authors:
Emilio E. Mendez; IBM THOMAS J WATSON RESEARCH CENTER YORKTOWN HEIGHTS NY
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| This report summarizes the most important result obtained during the short span of this grant, namely, the (theoretical) possibility of electric- field induced TE to TM mode switching in semiconductor quantum well lasers under moderate tensile strain. jg |
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Crystallography
