bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemistry and Characterization Of Polyimides Derived from Poly(Amic Alkyl Esters)
Authors: Volksen Willi , Yoon D. Y. , Hedrick J. L. , Hofer D. 
Published: March 2011

ABSTRACTThe modification of the pendant acid groups along the poly(amic acid) backbone in the form of alkyl ester groups leads to greatly improved polyimide precursors. These poly(amic alkyl esters) are characterized by the absence of hydrolytic instability due to elimimation of the “monomer-polymer” equilibrium associated with poly(amic acids), a broad imidization temperature regime, improved solubility characteristics, and enhanced mechanical properties. In the absence of hydrolytic instability, it is now possible to use an aqueous work-up of the polyimide precursor. This presents an attractive synthetic pathway for the preparation of well-defined, amine-terminated oligomers. Such oligomers can then be utilized both in the preparation of low molecular weight, chain-extendable polyimide precursors as well as polyimide block copolymers. The higher imidization temperatures offered by the “amic ester” chemistry allows for more efficient chain extension prior to imidization. Alternatively, the lack of the “monomer-polymer” equilibrium and accompanying propensity for monomer randomization reactions presents a potential pathway for the preparation of polyimide blends.
Spin Coating Planarization Of Integrated Circuit Topography On A Rotating Disk
Authors: Yonkoski Roger K. , Soane David S. 
Published: March 2011

ABSTRACTPolyimide is commonly used in the microelectronic industry for interconnection applications because of its ability to planarize features typically found on an IC chip. A mathematical model is developed to describe fluid flow on a rotating disk based on the principles of mass and momentum conservation. Constitutive relationships necessary for this model are proposed. Experimental data for polyimide precursor solutions are presented which enable the determination of parameters for the constitutive equations. This model is used to describe the film profiles over flat surfaces and near micron-sized features. Attention is focused on the coupling between mass transport and fluid flow as well as the effects of surface tension on film profiles over topographical features.
Protonation Effects On PPQ Polymer During HF Lift-Off Process Used In Multichip Module Fabrication.
Authors: Templier François , Torres J. , Clarisse C. , Palleau J. 
Published: March 2011

ABSTRACTThe reactions between PPQ and several acidic solutions have been studied. Protonation reactions have been evidenced using U.V.- Visible spectroscopy. PPQ revealed three different states concerning these completely reversible reactions. Each state exhibits a specific colour: Pale yellow (as deposited PPQ), and gold yellow and purple red for, respectively, the first and the second protonation states. Using IR spectroscopy, it has been shown that the protons are fixed at the nitrogen sites of the polymer. A possible degradation of the PPQ related to the protonation reactions is also studied, and thus technological solutions are proposed.
Thermotropic Polyesters Containing Carbonyl Or Ether Linkages
Authors: Irwin Robert S. 
Published: March 2011

ABSTRACTIn an assembly of aligned, thermotropic polyester macromolecules, such as a fiber, the flexibility and deviations from rectilinearity occasioned by in-chain ArCOAr or ArOAr units are reflected sensitively by overall stiffness (initial modulus) and elasticity (elongation at break). The influence of frequency and placement of these units, as well as the effect of ring substituents, is discussed.In a few cases where carbonyl or other units are regularly placed at suitable intervals along the chain, the latter apparently is extended as a low amplitude, regular helix which, in terms of physical properties, approximates to a straight, rod-like conformation. In situations where the angulation created by a carbonyl unit is immediately cancelled by an adjacentm-phenylene ring, the extended macromolecule is virtually rectilinear and, though marginally liquid crystalline, may provide some of the strongest organic fibers known.
Structure And Properties Of Binary Rodlike/Flexible Polyimide mixtures.
Authors: Rojstaczer S. , Ree M. , Yoon D Y. , Volksen W. 
Published: March 2011

Abbstract:Binary mixtures of a rodlike poly(p-phenylene pyromellitimide) (PMDA-PDA) and a flexible 6F-BDAF polyimide synthesized from hexafluoroisopropylidene diphthalic anhydride and 2,2-bis(4-aminophenoxy-p-phenylene) hexafluoropropane were prepared by solution-blending of the meta-PMDA-PDA poly(amic ethyl ester) and 6F-BDAF poly(amic acid) precursors, followed by solvent evaporation and thermal imidization. The size scale of the phase separation, as measured by light scattering, is ca. I μm or smaller in most cases. Dynamical mechanical thermal analysis measurements indicate that the glass transition temperature of 6F-BDAF is unaffected in all of the mixtures studied, indicating complete demixing of rodlike and flexible polyimides in agreement with theory. X-ray photoelectron spectroscopy results show a strong surface segregation of 6F-BDAF in mixtures containing as low as 10% by weight of the 6F-BDAF component in the bulk. The mixtures with PMDA-PDA as the major matrix component therefore maintain excellent bulk properties of rodlike polymers, i.e., high modulus to 500°C, and low coefficients of thermal expansion (< ca. 10 ppm/°C). On the other hand, the surface properties of the mixtures are dominated by the flexible 6F-BDAF, resulting in excellent polymer/polymer self-adhesion (lamination) properties between fully imidized films.
Growth Of Polyimide Films By Chemical Vapor Deposition And Their Characterization
Authors: Kowalczyk Steven P. , Dimitrakopoulos Christos D. , Molis Steven E. 
Published: March 2011

ABSTRACTA dry ultra high vacuum technique for the preparation of polyimide films is investigated as an alternative to standard wet processing techniques involving the use of solvents. This technique is based on the co-deposition of monomers (pyromellitic dianhydride and oxydianaline in this study) to form polyimide (poly (4,4′-oxydiphenylenepyromellitimide)). Various parameters to optimize film growth are investigated and the properties of the films are compared to films prepared by spin casting from solution. Films from 10Å to 15 μ were grown. Uniform films over 3 inch wafers were successfully grown. Many properties such as adhesion, dielectric constant and stress were similar to spun films. H-lowever, these films did exhibit more crystalinity but less orientation than the spun films. Finally, being a vapor phase process the rdms were conformal rather than planar.
Imide-Aryl Ether Ketone Block Copolymers
Authors: Hedrick J. L. , Volksen W. , Moiianty D. K. 
Published: March 2011

ABSTRACTImide-aryl ether ketone block copolymers were prepared and their morphology and thermal and mechanical properties investigated. The key feature of this copolymerization is the preparation of soluble aryl ether ketimine oliogmers which may be subsequently hydrolized to the aryl ether ether ketone form. A bis(amino) aryl ether ketimine oligomer was prepared via a nucleophilic aromatic substitution reaction with a molecular weight of 6,000 g/mol. The oligomer was co-reacted with 4,4′-oxydianiline (OI)A) and pyromellitic dianhydride (PMDA) diethyl ester diacyl chloride in N-methyl-2-pyrrolidone (NMP) in the presence of N-methylmorpholine. The copolymer compositions, determined by II-NMR, of the resulting amic ester based copolymers ranged from 8 to 20 wt% aryl ether ketimine content. Prior to imide formation, the ketimine moiety of the aryl ether ketimine block was hydrolyzed (p-toluene sulfonic acid) to the ketone form producing the aryl ether ether ketone block. Solutions of the copolymers were cast and cured to effect imidization, producing clear films. The copolymers displayed good thermal stability with decomposition temperatures in excess of 450°C. Multiphase morphologies were observed irrespective of the co-block type or composition.
Photorefractive Properties of Cobalt-Doped Barium
Titanate
Authors: Chang J. Y. , Garrett M. H. , Jenssen H. P. , Warde C. , Tayebati P. 
Published: March 2011

ABSTRACTA series of cobalt-doped barium titanate crystals were grown that have high
beam-coupling gain. Our photorefractive characterization shows that with
increasing cobalt concentration in the crystal a deep level is formed and
the relative effect of shallow levels on the space-charge field amplitude
diminishes. This gives the crystal a long dark storage time. We find that
cobalt-doping in barium titanate increases the two-beam coupling gain by
reducing the dark conductivity and increasing the total effective trap
density.
Low Temperature Growth of Gaas Quantum Well Lasers by Modulated
Beam Epitaxy
Authors: Xin S. , Longenbach K. F. , Schwartz C. , Jiang Y. , Wang W. I. 
Published: March 2011

ABSTRACTGaAs single quantum well lasers have been successfully grown at low
temperatures by a modulated beam epitaxy process in which the Al/Ga flux is
held constant while the As flux is periodically shut off to produce a
metal-rich surface. Devices grown at a substrate temperature of 500 °C
exhibit threshold current densities below 1 kA/cm2. This value is
lower than normally grown low temperature lasers and is the lowest achieved
by any low substrate temperature growth technique. In addition, low
temperature (10 K) photoluminescence of single quantum wells grown with this
technique exhibit full-width half maximum values, comparable to that
attainable by higher temperature growth techniques. The improved quality of
these low temperature grown quantum structures is attributed to both a
smoothing of the growth front and a reduction of excess As during the
modulated beam epitaxy process. The high growth rates and less frequent
shutter operation of this technique make it a more practical than migration
enhanced epitaxy or atomic layer epitaxy for low temperature growth.
Strained InGaAs/GaAs Multiple Quantum Wells Grown on Planar and
Pre-Patterned GaAs(100) Substrates VIA Molecular Beam Epitaxy: Applications
to Light Modulators and Detectors
Authors: Chen Li , Hu Kezhong , Rajkumar K. C. , Guhae S. , Kapre R. , Madhukar A. 
Published: March 2011

ABSTRACTWe report the realization of high quality strained InGaAs/GaAs multiple
quantum wells (MQW) grown on planar GaAs (100) substrates through
optimization of molecular beam epitaxical (MBE) growth conditions and
structure. Such MQWs containing ∼ 11% In have lead to the realization of an
asymmetric Fabry-Perot (ASFP) reflection modulator with a room temperature
contrast ratio of 66:1 and an on-state reflectivity of 30%. For In
composition ≥ 0.2, the improved optical quality for very thick (gt;2μm)
InGaAs/GaAs MQWs grown on pre-patterned substrates is demonstrated via
transmission electron microscopy (TEM) and micro-absorption
measurements.
Modulator Structure Using In(As, P)/lnP Strained Multiple
Quantum Wells Grown By Gas-Source MBE
Authors: Hou H. Q. , Chin T. P. , Liang B. W. , Tu C. W 
Published: March 2011

ABSTRACTIn(As, P)/InP strained multiple quantum wells (SMQW's) were grown with
gas-source molecular-beam epitaxy (GSMBE). A successful control of the As
composition was achieved over a wide range by using two techniques.
High-quality samples were characterized structurally and optically by x-ray
diffractometry, transmission electron microscopy (TEM), photoluminescence
(PL) and absorption measurements. Excitonic emission energy and the critical
layer thickness of In(As, P)/InP SMQW's are calculated as a function of the
As composition. The results show that 1.06, 1.3 and 1.55 μm excitonic
emission can be achieved at room temperature using this material system. We
also discuss the perspective of using In(As, P)/InP SMQW's for modulator
application.
On The Photoemission From Quantum Confined Compound
Semiconductors
Authors: Ghatak Kamakhya P. , De B. 
Published: March 2011

ABSTRACTIn this paper, we have studied the photoemission from quantum wells (QWs),
quantum well wires (QWWs) and quantum dots (QDs) of degenerate Kane-type
semiconductors, on the basis of a newly derived electron dispersion law
considering all types of anisotropies within the framework of k.p formalism.
It is found, taking n-Cd3 As2 as an example, that the
photoemission increases with increasing photon energy in a ladder-like
manner and also exhibits oscillatory dependences with changing electron
concentration and with film thickness, for all types of quantum confinement.
The photoemission current density is greatest in QDs and least in QWWs. In
addition, the theoretical results are in agreement with the experimental
observation as reported elsewhere.
Nonlinear optical devices: Relative Status of Polymeric
Materials
Authors: Stegeman George I. 
Published: March 2011

ABSTRACTNonlinear optical phenomena have been investigated over the last three
decades in many different materials and a great deal of progress has been
made in both the basic science and device applications.(1] Although interest
in nonlinear organic materials dates back to the early days of nonlinear
optics, it is only in the last five years that progress has been sustained
and rapid. The purpose of this paper is to examine progress in developing
new nonlinear organic materials and in their application to devices for
comparison with current state-of-the-art devices using other material
systems.
Molecular Beam Epitaxy of Znl-x Cdx
Se/ZnSe Heterostructures And Their Optical Properties
Authors: Luo H. , Samarth N. , Furdyna J. K. , Jeon H. , Ding J. , Pelekanos N. , Nurmikko A. V. 
Published: March 2011

ABSTRACTSuperlattices and quantum wells of Znl-xCdxSe/ZnSe,
and heterostructures based on ZnSe/CdSe digital alloys have been grown by
molecular beam epitaxy (MBE). Their optical properties were studied with
particular emphasis on excitonic absorption and photopumped stimulated
emission. Excitonic absorption is easily observable up to 400 K, and is
characterized by extremely large absorption coefficients (α =
2×105cm−1). Optically pumped lasing action is
obtained at room temperature with a typical threshold intensity of 100
kW/cm2. The lasing mechanism in these II-VI quantum wells
appears to be quite different from that in the better studied III-V
materials: in our case, the onset of stimulated emission occurs
before the saturation of the excitonic absorption, and
the stimulated emission occurs at an energy lower than that
of the excitonic absorption.
Photoluminescence Study of Li-implantation into ZnSe Epitaxial
Layers Grown by Molecular Beam Epitaxy
Authors: Yasuda T. , Jin M. K. , Gaines J. , Merz J. L. 
Published: March 2011

ABSTRACTLithium ion-implantation was performed on ZnSe layers which were grown on
GaAs substrates by MBE. Strong photoluminescence emission due to
acceptor-bound excitons was observed from samples implanted with lithium
doses of up to 1015cm−2 and annealed under optimized
conditions for rapid thermal annealing. Lithium implantation results in low
damage to the ZnSe as well as the formation of a shallow acceptor level.
Thermal degradation of both implanted and unimplanted epilayers caused by
the rapid thermal annealing was inviestigated at various annealing
temperatures. We find that, under certain annealing conditions, unimplanted
samples show greater thermal degradation than lithium implanted samples. The
photoluminescence spectrum of an unimplanted sample annealed at 800°C shows
considerable degradation; however, a lithium-implanted sample annealed at
the same temperature still shows strong luminescence in the excitonic
region.
Electroluminescence from p-n Junction Leds Consisting of N-Doped
and Cl-Doped ZnSe Layers
Authors: Ohkawa K. , Ueno A. , Mitsuyu T. 
Published: March 2011

ABSTRACTWe have fabricated ZnSe p-n junction LEDs with a new structure of
Pt/p-ZnSe/n-ZnSe/n-GaAs. The dopant used for n-type ZnSe was Cl, and p-type
ZnSe:N was formed by nitrogen radical doping. The LEDs exhibited good
rectification properties. We have found that electroluminescence at 77 K was
dominated by recombination emission between free electrons and acceptor
holes at 2.705 eV. Increasing the temperature, recombination emission
between donor electrons and free holes dominated blue bandedge emission
region.
Second and third order Nonlinear Optical Properties of
Crystalline Inorganic / Organic Complexes.
Authors: Marcy Henry O. , Warren Leslie. F. , Davis Laura E. , Webb Mark S. , Velsko Stephan P. 
Published: March 2011

ABSTRACTThe properties for members of a new class of nonlinear optical (NLO)
materials which stoichiometrically incorporate organic and inorganic
constituents into a single crystalline lattice are reported. Recent results
for our synthetic, crystal growth, and optical studies suggest that a number
of these relatively transparent “semiorganic” compounds have significant
second and/or third order NLO responses and often display favorable crystal
growth morphologies.The prototype material of this class, zinc tris(thiourea) sulfate, or ZTS,
has a UV cutoff at about 325 nm, can be readily grown to cm3
sizes, and has been shown to be a highly efficient Type II frequency doubler
for 1064 nm Nd:YAG laser radiation. ZTS also possesses a moderate third
order nonlinear optical response (ca. 0.1 × CS2) which occurs on
at least a picosecond time scale as determined by degenerate four-wave
mixing (DFWM) experiments at 532 nm.Refractive index, second harmonic generation, and DFWM data for a number of
these new compounds are presented.
Optical Second Harmonic Generation in
CdxZn1−xS and the
CdxZn1−xS:CdyZn1−yS
Superlattice System
Authors: Mullins J. T. , Taguchi T. 
Published: March 2011

ABSTRACTOptical second harmonic generation in epitaxial layers of
CdxZn1−xS and CdxZn1−xS:ZnS
and CdS:CdxZn1−xS strained layer superlattices which
had been removed from their substrates has been investigated. Some evidence
for resonant enhancement of the second order non-linear susceptibility has
been found for one sample where the onset of optical absorption was at
photon energies close to that of the second harmonic radiation.
Side Chain Polymers for Electro-Optic
Applications
Authors: DeMartino Ronald N. , Allen Diane E. , Keosian Richard , Khanarian Garo , Haas David R. 
Published: March 2011

ABSTRACTOrganic and polymeric materials have emerged in recent years as candidates
for advanced device and systems applications. This interest has arisen from
the promise of extraordinary optical, structural, and mechanical properties
of certain organic materials, and from the fundamental success of molecular
design performed to create new materials.Our approach to the problem is to develop an understanding of the molecular
basis of non-linear optical activity, incorporate the most promising
candidates into tractable polymers, and evaluate these materials in device
format. This paper will review some of the recent developments in the NLO
materials effort at Hoechst Celanese.
Magnetic and Transport Properties of Ag/Cr Metallic Superlattices
Authors: Kyuno Kentaro , Inoue Yasushi , Ogu Shinzo , Mae Kazuki , Kaneko Takeo , Yamamoto Ryoichi 
Published: March 2011

AbstractThe results of x-ray diffraction, resistivity and magnetization measurements of Ag/Cr metallic superlattices are presented. Dramatic changes in the interplanar distances of Ag and Cr were found as a function of the number of Cr monolayers in a period. The resistivities of the superlattices increased as the composition of Cr increased. Magnetization measurements show that the superlattice [Ag(10ML)/Cr(2ML)] exibits a maximum magnetic susceptibility.
On the Microstructure of a Ni3Al/SiC/TiB2 Intermetallic Matrix Composite Processed by Spray Atomization and Co-Deposition
Authors: Liang X. , Lavernia E. J. 
Published: March 2011

AbstractThis work reports on the microstructure of a particulate reinforced nickel aluminide composite synthesized by spray atomization and co-deposition. This synthesis methodology involved using high energy inert gas to disintegrate the nickel aluminide matrix (IC-396) into a Gaussian distribution of micrometer-sized, semi-solid droplets while simultaneously co-injecting SiC and TiB2 particulates, followed by deposition onto a water cooled substrate. The microstructure of the as-spray deposited composite material consisted of a mixture of the ordered γ (Ni3Al) and the disordered γ (Ni-rich) phase with a homogeneous distribution of SiC and TiB2 particulates. Scanning electron microscopy, combined with Energy Dispersive X-ray Spectroscopy were used to provide insight into the reactions taking place in the interfacial zone. The results of the present study show that a well defined reaction zone was formed at the Ni3Al/TiB2 interface; whereas extensive reaction occurred between the SiC particulates and matrix, resulting in complete transformation of almost all SiC particulates into other carbide phases.
Morphological Stability of Semicoherent Solid-Solid Interfaces: a Simple Model
Authors: Rottman Craig 
Published: March 2011

AbstractThe stability of semicoherent interfaces between two solids with small lattice mismatch is examined. I consider the cases in which the rotation θ between the two solids is both zero and small. The interface orientation, characterized by a single angle φ, is arbitrary. The interfaces are composed of regularly spaced misfit dislocations, steps, and lattice dislocations. For a wide range of φ, many flat interfaces are unstable with respect to breaking up into two interfaces of distinct orientations, one of which contains only one of the two types of dislocations possible.
Elastic Moduli of Metallic Multilayered Thin Films Ag/Cu, Al/Cu and Co/Cu Measured by Brillouin Scattering Method
Authors: Ito Toshiya , Yamamoto Ryoichi , Yoshihara Akira 
Published: March 2011

AbstractThe Rayleigh wave velocity of metallic superlattices Ag/Cu, Al/Cu and Co/Cu deposited by ion beam sputtering were measured as a function of layering period Λ using Brillouin scattering method. The VR-Λ relationship can be well interpreted using a phenomenological model consisting of three elastically different layers, i.e. two original and an intermediate layer. We have assumed in this model that the elastic modulus and the thickness of the intermediate layer are independent on the layering period.
Temperature Dependence of the Elastic Behavior of Structurally Disordered Metallic Superlattices
Authors: Jaszczak J. A. , Wolf D. 
Published: March 2011

AbstractThe structure and elastic properties of superlattices composed of high-angle twist grain boundaries on (100) planes of copper are investigated as a function of both the modulation wavelength and temperature via molecular dynamics simulations. Comparison is made with zero-temperature results, where a stiffening of the Young's modulus normal to the interfaces and a softening of the modulus for shear parallel to the interfaces has previously been observed. The differences between the effects of homogeneous (temperature-induced) and inhomogeneous (interface-induced) structural disorder on the elastic properties is explored.
Contamination Effects in Mo/Ni Superlattices
Authors: Hues Steven M. , Makous John L. 
Published: March 2011

AbstractA softening of the shear elastic constant c44 has been observed previously in Mo/Ni superlattices as a function of decreasing bilayer thickness below approximately 100 Å.[1] We have prepared a series of Mo/Ni superlattice films by ion beam sputtering doped with varying concentrations of either aluminum or oxygen. The chemical and structural properties of these films were then determined using x-ray diffraction (XRD) and Auger electron spectroscopy (AES). The shear elastic properties were characterized by measuring the surface acoustic wave (SAW) velocity of the deposited films. We demonstrate structural and elastic property effects resulting from Al and O impurity incorporation in Mo/Ni multilayers.