bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of Tie Electronic Structure By XPS f HTSC and Related Compounds
Authors: Myhrai S. , Bocquet A.E. , Dobsoni J.F. , Goodman P. , Healy P.C. , Stewart A.M. , Thompson J.G. , Vhite T.J. 
Published: March 2011

AbstractMeasurements by photoemission spectroscopy have shown that the chemical environments of alkaline earth cations in HTSC compounds are different from the environments of these ions in the prototype perovskite structures. A recently discovered HTSC compound (Pb2Sr2Ca0.5Y0.5Cu3O8) exhibits the exceptional feature of having a typical HTSC signature for Sr, while Ca shows a perovskite-like signature. The crystal-chemical features of the relevant compounds have been correlated with these observations. These correlations may be indicative of inter-layer electronic interactions.
Measurement of Grain Boundary Parameters by Laser-Spot Photoconductivity
Authors: Poon E. , Evans H.L. , Hwang W. , Osgood R.M. , Yang E.S. 
Published: March 2011

ABSTRACTAn experimental technique has been developed to study the electrical properties of semiconductor grain boundaries (GBs) by a focused laser beam. The laser beam is trained on a GB while the photoconductivity of the sample is measured. Both the steady-state and transient signals are recorded as functions of temperature. From these data, we obtain well-defined GB parameters, including the barrier height, interface charge density, trap energy and thermal capture cross-section. This technique allows us to examine localized regions of individual GBs in a semiconductor with multiple grains.
UV Laser-Initiated Formation of Si3N4
Authors: Deutsch T. F. , Silversmith D. J. , Mountain R. W. 
Published: March 2011

ABSTRACTSi3N4 films have been deposited on Si by using 193 nm ArF excimer laser radiation to initiate the reaction of SiH4 and NH3 at substrate temperatures between 200–600°C. Stoichiometric films having physical and optical properties comparable to those produced using low-pressure chemical vapor deposition (LPCVD) have been produced. The dielectric properties of the films are at present inferior to those of LPCVD material.
Evidence for Laser Induced Surface Silanol Formation
Authors: Muller D. F. , Rothschild M. , Rhodes C. K. 
Published: March 2011

ABSTRACTEvidence for the selective formation of surface silanol induced by ultraviolet irradiation in the intensity range between 3 × 107 W/cm2 and 108 W/cm2 is presented. Enhanced metallic deposition (Ti) on appropriately prepared samples is also reported.
Spectroscopy and Photoreactions of Organometallic Molecules on Surfaces
Authors: Chen C. J. , Osgood R. M. 
Published: March 2011

ABSTRACTA study of the UV photochemistry of organometallic molecules in the vapor and adsorbed phases is discussed. The gas-phase spectra is interpreted on the basis of molecular orbital theory and experimental data. The absorption spectra of the surface adlayers are determined by computer subtraction of the gas-phase spectra and an intepretation is provided. The influence of metalsubstrate microstructure on UV photochemical reactions of metal alkyls is briefly discussed.
The Spectroscopy and Photolysis of Metallo-Organic Precursors to III–V Compounds
Authors: Aylett Martin R , Haigh John 
Published: March 2011

ABSTRACTThis paper describes the deposition by light-stimulated breakdown of gallium and indium on borosilicate glass, gallium arsenide and indium phosphide substrates, from precursors whose ultraviolet (uv) spectra have recently been reported. Some preliminary work on the deposition of indium phosphide is also reported, using an indium-phosphorus complex whose uv spectrum is also given.
Production of Microstructures by Laser Pyrolysis
Authors: Bä;uerle Dieter 
Published: March 2011

ABSTRACTLaser pyrolysis at short wavelengths is a powerful tool for micron-sized one-step local deposition of insulating, semiconducting and metallic materials from the gas phase. Various structures, e.g. stripes on different substrates, and rods of various lengths and diameters, have been produced. The morphology of the deposited material, the deposition rate, and the dimensions (typically 1-300 μm) of the structures were investigated quantitatively as functions of laser irradiance local temperature, laser focus diameter, scanning velocity, and gas pressure.
Laser Stimulated Growth of Epitaxial Gaas
Authors: Roth Walter , Kräutle Herbert , Krings Annemarie , Beneking Heinz 
Published: March 2011

ABSTRACTStimulated growth of single crystalline GaAs has been obtained by irradiation of (100) oriented GaAs substrates inside an MOCVD reactor with a pulsed Nd-YAG laser.Process temperatures have been varied between 540°C and 360°C. In the non-irradiated areas, below 480°C substrate temperature the growth rate decreases rapidly, whereas in the irradiated part of the substrate epitaxial layers could be grown in the whole temperature range investigated. Below 450°C, the growth is reaction limited.
Laser Induced Chemical Vapor Deposition of Hydrogenated Amorphous Silicon
Authors: Bilenchi Renzo , Gianinoni Iva , Musci Mirella , Murri Roberto 
Published: March 2011

ABSTRACTSome results on hydrogenated amorphous silicon growth by CO2 laser photodissociation of silane are reported. A 100 W CW CO2 laser was used as the excitation source. A horizontal configuration was adopted, where the laser beam is sent parallel to the substrate surface inside a flux reactor, and its energy is used to excite and dissociate the silane molecules flowing near the solid surface. The laser has no direct heating effect on the substrate, which is independently heated by an oven.The photoproduced radicals by interacting with the surface grow a film at a rate strongly depending on silane pressure, substrate temperature and laser intensity. This experimental configuration allows depositions on large areas, owing to the large number of reactant molecules involved in the photochemical process. Moreover, material can be produced with a continuously variable hydrogen content, since the substrate temperature required for obtaining depositions can be as low as room temperature and adjusted independently of the other process parameters.The film properties are similar to those of the glow discharge deposited material. The film amorphousness and the hydrogen presence either in monohydride and dihydride groups are evidenced by x-ray patterns and ir spectra. Results on the electrical and optical properties are also reported.
Direct Writing Using Laser Chemical Vapor Deposition
Authors: Allen S. D. , Trigubo A. B. , Jan R. Y. 
Published: March 2011

ABSTRACTMetal, dielectric and semiconductor films have been deposited by laser chemical vapor deposition (LCVD) using both pulsed and cw laser sources on a variety of substrates. For LCVD on substrates such as quartz, the deposition was monitored optically in both transmission and reflection using a collinear visible laser and the depositing CO2 laser. Deposition initiation and rate were correlated with irradiation conditions, the laser generated surface temperature, and the changing optical properties of the filmpsubstrate during deposition. Single crystallites of W greater than 100 pm tall were deposited using a Kr laser on Si substrates.
Using Optical Fibers in Laser Processing
Authors: Laude L.D. , Baufay L. , Pigeolet A. 
Published: March 2011

ABSTRACTPhase transformation occuring upon CW laser irradiating through optical fiber polymetallic, multilayered films deposited on insulating substrates is shown to provide a simple and versatile way to optically micro-print predetermined patterns. The technique allows both further reduction to the Rayleigh limit and simultaneous multiplication of the patterns.
Laser-Initiated Ga-Deposition on Quartz Substrates
Authors: Rytz-Froidevaux Y. , Salathe R.P. , Gilgen H.H. 
Published: March 2011

ABSTRACTThe deposition of Ga on quartz substrates by photodissociation of trimethylgallium has been investigated. Light from a frequency doubled Ar-ion laser beam (257.2 nm) was focused onto quartz substrates. The Ar-ion laser was operated under cw or mode-locking conditions. The deposition rate has been investigated as a function of averaged UV power densities in the range of 1.8 – 1750 w/cm2 and is shown to depend critically on the laser operating mode. For cw operation, the maximum growth rate within the focal zone is limited to 17 Å/s whereas under mode-locking conditions, no saturation is observed and the growth rate increases linearly with the laser power up to 70 Å/s at 1.75 kW/cm2.
High Resolution Etching of Gaas and Cds Crystals
Authors: Podlesnik D. V. , Gilgen H.H. , Osgood R.M. , Sanchez A. , Daneu V. 
Published: March 2011

ABSTRACTSubmicrometer gratings have been etched in GaAs and CdS crystals which have been immersed in an oxidizing etch and illuminated with interferring laser beams. A resolution of 170 nm was obtained. At high laser intensity and with prolonged etching time the surface properties of the material are degraded. The use of in-situ optical measurements of grating parameters allows ready optimization of the grating fabrication process.
Laser-Controlled Etching Of Chromium-Doped and N-Doped <100> Gaas
Authors: Tisone Gary C. , Wayne Johnson A. 
Published: March 2011

ABSTRACTThe photochemical etching of chromium-doped and n-doped <100> GaAs in HNO3 and KOH is examined in the wavelength region of 334 to 514 nm from an argon-ion laser. The etching process is found to be not thermally controlled. The etch rates of chromium-doped GaAs agree with a diffusion-controlled model of the photochemically produced holes. For both types of GaAs, HNO3 is found to produce morphologically superior results.
Raman Scattering as a Temperature Frobe for Laser Heating of Si
Authors: Kirillov Dimitry , Merz James L. 
Published: March 2011

ABSTRACTThe frequency of the phonon line in the Raman scattering spectrum recorded during CW laser-beam heating of Si was used as a characteristic of the lattice temperature inside the laser spot. It is shown that Raman scattering is a good temperature probe up to the laser power approaching optical damage of Si.
Synthesis and Properties of Copolymers of Diphenylsiloxane with Other Organosiloxanes
Authors: Ibemesi J. , Gvozdic N. , Kuemin M. , Tarshiani Y. , Meier D. J. 
Published: March 2011

ABSTRACTWe describe the synthesis, characterization and properties of various types of siloxane polymers containing diphenylsiloxane (P) as a component. The polymer types include di-and tri-block copolymers with dimethylsiloxane (M) as the second component, and random and statistical copolymers with dimethylsiloxane or methylphenylsiloxane (P/M) as the second component. Such copolymers combine siloxane units whose polymers have very different properties. The polydiphenylsiloxane chain is rigid and inflexible, and the polymer is a highly crystalline solid with a liquid crystalline or condis crystalline state and a very high melting (clearing) temperature. In contrast, the polydimethylsiloxane or polymethylphenylsiloxane chains are very flexible and the polymers have very low glass transition temperatures.Polymers of controlled molecular composition, size and architecture were prepared by anionic polymerization of the ‘cyclic trimers’, using lithium-based initiators.The physical properties of the copolymers vary dramatically with composition and architecture. Two types of ‘random’ copolymers can be prepared. In one type, siloxane units of a given type are randomly placed in the chain in groups of three, i.e., the minimum sequence length of a given siloxane type is three siloxane units. In the other type of random copolymer, individual siloxane units are randomly distributed so that the minimum sequence length is a single siloxane unit. The properties of the two types are quite different, showing that subtle changes in sequence distribution can have major effects on physical properties. At molar ratios near 1/1 and with molecular weights of ∼105, the first type of ‘random’ copolymer is an elastic solid with appreciable mechanical properties, whereas the latter type is a sticky gum.Diblock copolymer (P-M) with dimethylsiloxane as the major component are paste-like, whereas the triblock (P-M-P) and star-block copolymers of the same composition are tough elastomers. The block copolymers are molecular composites, in which the polydiphenylsiloxane component separates into crystalline microphases with very uniform fibrillar or lamellar morphologies, and with widths or thicknesses comparable to the length of the polydiphenylsiloxane block, i.e, typically of the order of 100 Å.
Pbzt/Polyamide Thermoplastic Micro-Composites - An Outgrowth of Molecular Composites Development
Authors: Uy William C. , Perusich E. R. 
Published: March 2011

ABSTRACTMolecular composites are dispersions of rigid-rod polymer molecules in a matrix of flexible coil polymers, formed by the coagulation of a solution containing these components. Where there is aggregation of the rigid-rod molecules, such composites are called micro-composites (MC's). These composites offer the potential for better economics and improvements in composite processing, and possibly performance, over conventional ‘string and glue’ composites. This paper describes work performed under contract to the U. S. Air Force to develop PBZT/thermoplastic molecular composites into a viable technology.A commercially viable MC spinning and heat-treatment process has been defined based on a novel mixed solvent/quaternary solution technology developed by Du Pont. Advantages of this process include better economics, superior processing performance, and improved MC fiber tensile properties versus prior art. PBZT/polyamide MC fibers with strength/modulus of 332 ksi/29 Msi have been produced using this process. Adhesion equivalent to that obtained in conventional composites has been demonstrated. Uni-axial properties achieved to date compare favorably with conventional ‘string and glue’ PBZT/epoxy composites although compressive and shear strengths may be limiting factors in MC applications.
Equilibrium and Non-Equilibrium Phases and Phase Diagrams in Blends of Polymer Liquid Crystals with Enoineerino Polymers
Authors: Brostow Witold , Dziemianowicz Theodore S. , Hess Michael , Kosfeld Robert 
Published: March 2011

ABSTRACTThis work represents a continuation of earlier studies of blends of polymer liquid crystals (PLC) with ordinary engineering polymers (EP). We now focus on connections between mechanical and other properties and phase structures and phase diagrams. Pure PLC are already two-phase systems; in each case addition of an EP complicates the situation further. In particular, we are concerned with phases which we call quasi-liquids, at temperatures between the glass transition and the melting point. Quasi-liquids do not have the mobility usually associated with liquids - because of the presence of other constituents and also because of orientational effects produced by the mesogenic groups. In phase diagrams of PLC-containing systems one should also take into account non-equlibrium phases. We are trying to show how such diagrams make possible Intelligent processing and a better control of properties of the PLC + EP materials.
Structure and Properties of Blends of Polycarbonate and Poly(Ethylene-Terephthalate-Co-p-Hydroxybenzoate): Phase Diagram and Mechanical Behavior
Authors: Kosfeld Robert , Schubert Frank , Hess Michael , Brostow Witold 
Published: March 2011

ABSTRACTThe investigation of the thermal behavior of polymer blends leads to phase diagrams which involve Important information about the system. From these diagrams, equilibrium as well as non-equilibrium phases can be deduced and ranges of miscibility or partial miscibility of the polymers become obvious. Hence the diagrams are of a great value for processing of advanced polymer blends, especially If a polyphasic polymers such as a polymer liquid crystal is one of the constituents of the system.
“Dynamics of Phase Segrewation in Poly-P-Phenylene Terephtualamide and Amorphous Nylon Molfcular Composites”
Authors: Kyu Thein , Yang Jan Chang , Chen Tsuey Ing 
Published: March 2011

ABSTRACTTime-resolved light scattering has been employed to elucidate the dynamics of phase segregation of poly-p-phenylene terephthalamide (PPTA)/ amorphous nylon (AN) molecular composites. Miscible PPTA/AN blends can be prepared from sulfuric acid solution by rapidly coagulating the solution in distilled water. The composites, however, undergo phase segregation upon thermal treatment and exhibit a miscibility window reminiscent of a lower critical solution temperature (LCST). Several temperature-jump experiments were undertaken from ambient to a two-phase temperature region of 240, 250 and 260°C. Time-evolution of scattering profiles are analyzed in accordance with non-linear and dynamical scaling theories.
Dielectric Studies Of Polyester/Polycarbonate Blends
Authors: O'Reilly James K. , Sedita Joseph S. 
Published: March 2011

ABSTRACTDielectric and enthalpic relaxation times have been measured as a function of composition and temperature. A fractional exponential (W–W) distribution of relaxation times fits both the dielectric and enthalpic relaxation times with different values which are a function of composition. Free volume parameters calculated using the WLF equation are not simple functions of the composition. Concentration fluctuations are considered to be important in these phenomena.
Small Angle X-Ray Scattering on Poly(Ethylene-Methacrylic Acid) Lead and Lead Sulfide Ionomers
Authors: Chu Benjami , Wu Dan O. , Mahler Walter 
Published: March 2011

ABSTRACTThe morphology of ionomers, e.g., poly(ethylene-methacrylic acid) (EMA) lead salts (EMA/Pb) and lead sulfide compounds (EMA/PbS), has been studied by using the techniques of small angle x-ray scattering (SAXS), anomalous SAXS (ASAXS), wide angle x-ray scattering (WAXS), and differential scanning calorimetry (DSC). EMA/Pb containing less than 5 wt% of lead exhibited two characteristic SAXS peaks which corresponded to the lamellar structure of the partially crystalline polymer matrix and the ionic structure of the lead aggregates that were present in the amorphous regions. The lead aggregates were not distributed uniformly and increased in packing density with increasing lead content. Both DSC and WAXS showed that the crystalline phase was present for all EMA/Pb samples and that the crystallinity decreased slightly with increasing lead content. ASAXS near the L3 absorption edge of lead permitted the extraction of the scattered intensity of lead ions from the SAXS patterns of the superimposed crystalline and ionic structures. Correlation function analysis revealed that the ionic aggregates of the EMA/Pb containing 5 wt% of lead could be described by a liquid-like model with a short range order of 2-4 nm. EMA/PbS samples were made by a reaction of EMA/Pb ionomers with hydrogen sulfide. Instead of an ionic peak as shown by EMA/Pb samples, the SAXS patterns of EMA/PbS showed a broad diffraction peak located at the same q value as the lamellar peak of the EMA in acid form. The (lamellar) peak could be attributed to the interference between the PbS crystallites in the neighboring lamellae.
Synthetic Procedures for Preparing Cross-Linkable Acrylic Comb-Like Copolymers Via Macromonomers
Authors: Chen Gang-Fung , Jones Frank N. 
Published: March 2011

ABSTRACTA versatile procedure was developed for synthesis of acrylic comb-like copolymers in three steps: (1) Hydroxyl terminated oligomers were synthesized from methyl methacrylate, butyl acrylate and glycidyl acrylate by free-radical initiated addition polymerization using a functional chain transfer agent, 2-mercaptoethanol, and very low initiator levels. (2) The oligomers were converted to macromonomers by reaction with isocyanatoethyl methacrylate. (3) The macromonomers were polymerized by free-radical initiation. Conditions during the first stage must be carefully selected to minimize formation of difunctional material which could cause gelation in the third stage. A variety of structures can be made such as comb-like copolymers with homopolymer tines or comb-like homopolymers with copolymer tines. Functional groups can be introduced by copolymerizing glycidyl acrylate into the macromonomer. Assignment of comb-like structures is not rigorously proven but is strongly supported by the synthetic route and by DSC, FT-IR and chromatographic data.
Synthesis and Characterization of Segmented Copolymers of a Methylated Polyamide and a Thermotropic Liquid Crystalline Polyester
Authors: Pawlikowski Gregory T. , Weiss R. A. , Huang S. J. 
Published: March 2011

ABSTRACTA block copolymer consisting of liquid crystalline polyester segments and methylated polyamide segments has been synthesized. Solution polycondensation of acid chloride end-capped poly(terephthaloyl phenylhydroquinone) (LCP portion) with an amine terminated poly(N,N'-dimethylethylene sebacamide) was utilized to prepare the block copolymer. Characterization by differential scanning calorimetry, infrared spectroscopy, thermogravimetric analysis, optical microscopy and elemental analysis has been performed to verify the existence of the block copolymer that may have potential as a molecular composite material or self-reinforcing thermoplastic.
Aggregation Structure and Electro—Optical Properties of (Liquid Crystalline Polymer)/(Low Molecular Weight Liquid Crystal) Composite System
Authors: Kajiyama Tisato , Kikuchi Hirotsugu , Miyamoto Akira , Moritomi Satoru , Hwang Jenn—Chiu 
Published: March 2011

ABSTRACTA series of thin films composed of liquid crystalline polymer (LCP) and low molecular weight liquid crystal (LMWLC) was prepared by a solventcasting method or by a bar—coating method. LCPs were of mesogenic side chain type with strong or weak polar terminalgroups in the side chain portion. A mixture of smectic LCP (LCP with side chain of strong polar end) and nematic LMWLC formed a smectic phase in a LCP weight fraction range above 50 %. Also, a mixture of nematic LCP (LCP with side chain of weak polar end) and nematic LMWLC with strong polar group induced a new smectic phase in a LCP molar fraction range of 20–80 %. Reversible and bistable electro-optical effects based on light scattering were recognized for a smectic phase of a binary composite composed of LCP and LMWLC. A light scattering state caused by many fragmented smectic lamellae appeared in the case of application of an a.c. electric field below a threshold frequency (∼l Hz). Furthermore, application of a 100 Vp—p a.c. field of 1 kHz made the transmission light intensity increased to 94 % within a few seconds. The optical heterogeneity in asmectic layer composed of the side chain group of LCP was caused by the difference of twoforces based on both dielectric anisotropy of the side chain and electrohydrodynamic motion of the main chain. Since application of a low frequency electric field causes an ioniccurrent throughout the mixture film, it is reasonable to consider that an induced turbulent flow of main chains by an ionic current collapsed a fairly well organized large smectic layer into many small fragments, resulting in an increase in light scattering. The response speed of LCP upon application of an electric field increased remarkably by mixingLMWLC. In the case of a smectic mesophase, turbid and transparent states remained unchanged as it was, even though after removing an electric field.1Such abistable and reversiblelight switching driven by two different frequencies of electric field could be newly realized by both characteristics of turbulent effect of a wellorganized large smectic layer of LCP and rapid response of LMWLC. We believe that the LCP/LMWLC mixture system is promissing as a novel type of “light valve” exhibiting memory effect (bistable light switching).