bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Conductivity of N-Type Si-Ge
Authors: Klfmens Paul G.
Published: March 2011

The lattice thermal conductivity of 80-20 Si-Ge is treated theoretically for the case of the Fermi energy positioned for optimum figure of merit. The spectral distribution of the lattice conductivity is limited by anharmonic interactions, by the randomness of the Si-Ge lattice and, at low frequencies, by the interaction with free carriers and neutral donors. The two latter processes dominate over grain boundary scattering. The spectral conductivity is sharply peaked around 0.1 of the Debye frequency. A further reduction in lattice conductivity can be obtained by small insulating inclusions. This is partially offset by a reduction in electronic conductivity, but results in some improvement in the figure of merit.
A Model for the High Temperature Transport Properties of Heavily Doped P-Type Silicon-Germanium Alloys
Authors: Vining Cronin B.
Published: March 2011

A model is presented for the high temperature transport properties of large grain size, heavily doped p-type silicon-germanium alloys. Good agreement with experiment (±10%) is found by considering acoustic phonon and ionized impurity scattering for holes and phonon-phonon, point defect and hole-phonon scattering for phonons. Phonon scattering by holes is found to be substantially weaker than phonon scattering by electrons, which accounts for the larger thermal conductivity values of ptype silicon-germanium alloys compared to similarly doped n-type silicongermanium alloys. The relatively weak scattering of long-wavelength phonons by holes raises the possibility that p-type silicon-germanium alloys may be improved for thermoelectric applications by the addition of an additional phonon scattering mechanism which is effective on intermediate and long-wavelength phonons. Calculations indicate improvements in the thermoelectric figure of merit up to 40% may be possible by incorporating several volume percent of 20 Å radius inclusions into p-type silicon-germanium alloys.
Enhanced Third Order Nonlinearity in Macrocyclic Compounds
Authors: Hosoda Masahiro , Wada Tatsuo , Garito Anthony F. , Sasabe Hiroyuki
Published: March 2011

The third-order nonlinear optical susceptibilities χ(3)1111(-3ω; ω, ω, ω) of macrocyclic compounds such as phthalocyanines and porphyrins are determined for the vacuum deposited and spin coated thin films by optical third-harmonic generation measurements at a wavelength of 1907 nm. The enhancements of the χ(3) values are discussed in terms of the central metal substitution, molecular stacking, extended ring size and number of χ-electrons. We firstly describe the results of extended porphyrin systems with 26 delocalized π-electrons.
Poly(Vinyl Ethers) as Nonlinear Optical Materials, Shg in Corona Poled Polymer Films
Authors: S'heeren♦ Gert , Vanermen Guy , Samyn Celeste , Beylen Marcel Van , Persoons Andre
Published: March 2011

New poly(vinyl ethers) with pendant groups exhibiting nonlinear optical properties were synthesized: 4-cyano and 4-nitro-4'-(alkoxy) azobenzene substituted poly(vinyl ethyl ether), copolymers and 4-dicyano or 4-cyano-4-carbomethoxyvi-nyl-4'-(alkoxy)benzene substituted poly(vinyl ethyl ether). Films spincoated from these polymers were poled by a positive corona discharge just above their T9 (as measured by DSC). The second order susceptibilities of tne films were derived from full-angle Maker fringe patterns at 1064 nm. Susceptibilities x(2) zzz as high as 23×10−9 esu were measured.
The Nonlinear Optical Properties of Polyacetylene within the Intermediate Exciton Formalism
Authors: Yaron David , Silbey Robert
Published: March 2011

Within the Singles-CI approximation, the perturbation theory expression for γ (the non-resonant third-order nonlinear optical susceptibility) contains a class of terms which correspond to (i) the creation of an s-type exciton (ii) a transition to a p-type exciton, and (iii) a return to the ground state through an s-type exciton. The contribution of these terms to γ is considered in the limit of an infinite chain of polyacetylene. The infinite chain limit is obtained by considering a ring of polyacetylene and allowing the ring size to go to infinity. The limit is approached using three methods, each of which reveals a different characteristic length of the system. The form of the excitons is found to be independent of ring size for rings which are larger than the size of the exciton.
Linear and Nonlinear Optical Properties of Processable Polymeric Materials
Authors: Kaino Toshikuni , Tomaru Satoru , Kurihara Takashi , Amano Michiyuki
Published: March 2011

Linear and nonlinear optical (NLO) polymeric materials with good processabilities are discussed. An azo-dye substituted copolymer (3RNO2, nitro-terminated diazo dye) are investigated. The polymer film was found to be transparent and attenuation loss was less than 2 dB/cm. The χ(3) of 3RNo2 reaches 5×10−11 esu in the near-resonant region. With polymers where the dye molecules are introduced into the polymer backbone (a main chain polymer), a χ(3) larger than 10−11 esu is obtained even in a monoazo dye introduced polymer. A new molecular crystal, symmetrically substituted benzylidene-aniline compound, SBAC for short, are also successfully polymerized (introduced into a polymer main chain) and their χ(3) values are revealed to be around 1010 esu in the near-resonant wavelength region. The optical transmission of these polymers is also investigated and revealed to be around 2 dB/cm. With poly(arylene vinylene), a certain population of χ-conjugation length will induce enhancement of the resonant χ(3) of the polymers. The polymer can be used to fabricate channel waveguides with the photo-bleaching technique.
Synthesis, Characterization, and Processing of Organic Nlo Polymers
Authors: Druy Mark A. , Glatkowski Paul J. , Burzynski Ryszard
Published: March 2011

The research described in part in this manuscript is a multi disciplinary effort to target key applications and material and processing requirements for these third order nonlinear optical polymers. It discusses the synthesis, characterization, and processing of nonlinear optical properties of polyimides which have been tailored for nonlinear optical activity.
Third-Order Nonlinear Optical Properties of Phthalocyanines
Authors: Shirk James S. , Undle J. R. , Flom Steven R. , Bartoli F. J. , Snow Arthur W.
Published: March 2011

This paper discusses the third-order nonlinear optical (NLO) properties of substituted phthalocyanines measured by time-resolved degenerate four-wave mixing at 1064 nm. The study explores optical pumping as a mechanism contributing to a large third-order optical nonlinearity in one member of this interesting class of NLO materials, PbPc(CP)4.
Third Order Nonlinear Optical Responses of Metallophthalocyanines in Films and Solutions
Authors: Reeves Roger J. , Powell Richard C. , Ford Warren T. , Chang Young H. , Zhu Weiming
Published: March 2011

Dihydrogen, copper, platinum, and lead octakis(2-ethylhexyloxy)phthalocyanines (Pc's) were studied in polystyrene films at 532 nm and in chloroform solutions at 1064 nm by picosecond degenerate four wave mixing. Resonant χ(3) values of Pc's at 532 nm (a local minimum in the absorption spectrum) at a time coincident with the 20 psec pump pulses were as high as 104 times that of CS2 by extrapolation of the response from 1 wt % PtPc in polystyrene film to a value for pure PtPc. Delay of the probe pulse as long as 3 nsec revealed acoustic responses stronger than the fast electronic responses. The films showed the expected quadratic dependence of the instantaneous reflectivity on incident intensity only for a decade of magnitude of intensity, 100–1000 MW/cm2, with the output saturating at higher intensities. Excited state absorption at 532 nm was detected in the film samples by pulse-probe spectroscopy and was shown to be a factor in the saturation observed in the NLO signals. Nonresonant χ(3) values at 1064 nm were as high as 120 times that of CS2 from measured responses of 1 wt % chloroform solutions of Pc's. Time delay of the probe revealed both fast electronic and slower acoustic responses at 1064 nm too.
Third-Order Nonlinear Optical Properties of a Series of Systematically Designed Conjugated Rigid-Rod Polyquinolines
Authors: Agrawal Ashwini K. , Jenekhe Samson A. , Vanherzeele Herman , Meth Jeffrey S.
Published: March 2011

The third-order nonlinear optical properties of thin films of two series of conjugated rigid-rod polyquinolines, exemplified by poly(2, 2'-(l, 4-phenylene)-6, 6'-bis(4-phenyl quinoline)) (PPPQ, 2d) and poly(2, 7-(l, 4-phenylene)-4, 9-diphenyl-l, 6-anthrazoline) (PPDA, 3d), were investigated by third harmonic generation spectroscopy. Of the nine polyquinolines with diverse backbone structures, PPPQ has the largest optical nonlinearity with a χ(3) (-3ω; ω, ω, ω) value of 3.2 × 10−12 esu and 3.3 × 10−11 esu in the off-resonant and three-photon resonant regions, respectively. A comparison of the nonresonant χ(3) of the series of nine systematically derived polyquinolines showed that a scaling law of the form χ(3) ∼ (λmax)v ∼ Eg-v does not hold; in fact, the nonresonant χ(3) was essentially independent of the optical bandgap. These results suggest that structure-χ(3) propeny relationships in polymers cannot be inferred from those of oligomers and model compounds.
A New Organic Crystal---MHBA for Potential Diode Laser Second-Harmonic Generation
Authors: Jiang Minhua , Tao Xutang , Yuan Duorong , Zhang Nan , Shao Zongshu
Published: March 2011

This paper reports a potential new organic crystal materials MHBA whose cut-off wavelength is 370nm and powder SHG intensity is 30 times higher than that of Urea. The crystal structure, single crystal growth, linear and nonlinear optical properties of MHBA are reported in detail. MHBA crystal belongs to monoclinic system; space group is P21, and the unit cell parameters are: a=14.057Å, b=7.875Å, c=15.037Å and β=115.45°. The nonlinear susceptibilities are: d11=25.0d36KDP, d12=10d36KDP, d13=33.3d36KDP and d14=8.3d36KDP.
Quadratic Nonlinear Optical Properties of Polymeric Organic Materials.
Authors: Cheng L.-T. , Foss R. P. , Meredith G. R. , Tam W. , Zumsteg F. C.
Published: March 2011

We discuss our rational approach to incorporate optically nonlinear molecules into polymeric and cross-linked materials through the use of isocyanate-hydroxy coupling chemistry. Thin film fabrication, optical loss, poling, second harmonic generation, and electro-optic properties are discussed.
Synthesis of Fullerols as Polyhydroxylated Fullerene Derivatives
Authors: Chiang Long Y. , Upasani Ravi , Swirczewski John W. , Creegan Kathy
Published: March 2011

we outline three methods for the preparation of fullerols as polyhydroxylated fullerene derivatives through the reaction of fullerenes with electrophilic reagents. The synthetic methodology includes a sequence of reactions using an aqueous acid chemistry, the epoxidation reaction, or the interesting nitronium chemistry as an key approach for the conversion of fullerenes to fullerols. The structure of fullerols was characterized and proposed to consist of at least 13 hydroxy functional moieties incorporating both hydroxy and hemi-ketal as parts of the structural components.
Functionalizing Fullerenes Through Cycloaddition Reactions
Authors: Malhotra Ripudaman , Narang Subhash C. , Nigam Asutosh , Ganapathiappan S. , Ventura Susanna , Satyam Apparao , Bhardawaj Tilak , Lorents Donald C.
Published: March 2011

We have explored several cycloaddition reactions as a general approach for preparing fullerene derivatives. In view of their electron-deficient nature, they are expected to participate as dienophiles rather than dienes in cycloadditions. This behavior is exemplified in their reactions with sulfur trioxide, diphenylisobenzofuran, and the nitrone from cyclohexanone and N-methyl-hydroxylamine. Fullerenes also formed adducts with maleic anhydride, although in this case the nature of the adduct is not clear. While changes in physical properties such as solubility or IR spectra clearly indicated formation of adducts, mass spectral analysis of diese and many other fullerene derivatives often showed ions due to fullerenes; thus confirmatory evidence for the derivatives was not available from mass spectrometry.
Structures and Properties of C60 & C70 Thin Films Fabricated by Organic MBE
Authors: Tanigaki K. , Ichihsdhi T. , Ebbesen T. W. , Kuroshima S. , Iijima S. , Hiura H. , Takahashi H.
Published: March 2011

The C60/C70 thin film crystals have been fabricated on the (001) surface of alkali halide substrates, KC1, KBr, and NaCl, and their structures have been studied. The crystal structure analyses by TEM show that the hexagonal closed packing (hep) with lattice parameters of a=10.0 Å and c=16.3 Å and the face-centered cubic (fee) with a=14.2 Å coexist in the C60 thin film crystals. The C70 thin film crystals show an expanded lattice constant of a=10.5 Å from the view perpendicular to the stacking plane. The ratio of hep to fee is dependent on the kind of the substrates and on the substrate temperatures during the crystal growth. The observed reversible change in the Raman spectrum of the C60 thin films implies a rotational molecular motion in the thin film crystals.
Electronic Structure of Carbon Fibers based on C60
Authors: Saito Riichiro , Fujita Mitsutaka , Dresselhaus G. , Dresselhaus M. S.
Published: March 2011

The electronic structures of some possible carbon fibers nucleated from the hemisphere of a bucky ball are presented. A one-dimensional electronic energy band structure model of such carbon fibers, having not only a principal rotational axis but also fibers with screw axes, can be derived by folding the two-dimensional energy bands of graphite. By considering the variation of the fiber diameter and helicity within a simple tight binding model calculation, we show that 1/3 of the fibers are metallic and 2/3 are semiconducting. The effect of adding multiple tubule layers is considered.
Electronic Structure of Fullerene Tubules
Authors: Mintmire J. W. , Robertson D. H. , Dunlap B. I. , Mowrey R. C. , Brenner D. W. , White C. T.
Published: March 2011

Recent reports suggest that graphitic tubules with diameters on the order of fullerene diameters have been synthesized. Such small-diameter tubules should have electronic properties related to those of two-dimensional graphite. We demonstrate by comparison with results from a first-principles, self-consistent, all-electron Gaussian-orbital based local-density functional approach that an all-valence tight-binding model can be expected to give a reasonable description of the electronic states of these tubules. In analyzing both high-symmetry tubules and lower-symmetry chiral tubules, we see that a relatively high carrier density could be expected for many of these structures.
Photoelectron Spectra of C60H36 and C60H60
Authors: Dunlap B. I. , Mintmire J. W. , Robertson D. H. , Brenner D. W. , Mowrey R. C. , White C. T.
Published: March 2011

We have calculated the electronic structure of icosahedrai C60H60 and tetrahedral C60H60 via an all-electron Gaussian-orbital based local-density functional approach. The one-electron wavefunctions and eigenvalues have been used in a first-order time-dependent perturbation theoretic calculation of the spherically averaged X-ray and ultraviolet pho-toemission cross-sections for these molecules.
Synthesis of AC60-Para-Xylylene Copolymer
Authors: Loy Douglas A. , Assink Roger A.
Published: March 2011

The preparation and purification of macroscopic quantities of buckminsterfullerenes [1] or buckyballs has ignited an explosion of research into their physical and chemical properties, and a variety of strategies for preparing new fullerene-based materials. Free radical synthesis is an appealing approach for forming polymeric fullerene materials. We report a polymeric fullerene material prepared by reacting pure C60 with xylylene from the thermolysis of paracyclophane. Addition of xylylene to a purple solution of C60 in toluene solution at -78 °C resulted in an olive-green solution from which an insoluble brown powder precipitated upon warming to room temperature. Analyses of the powder by solid state 13C MAS NMR, IR, and thermal gravimetric analysis are consistent with C60-xylylene copolymer.
Nonlinear Optical Properties of Buckminsterfullerene Solutions
Authors: Brandelik Donna , McLean Daniel , Schmitt Mark , Epling Bob , Colclasure Chris , Tondiglia Vince , Pachter Ruth , Obermeier Keith , Crane Robert L.
Published: March 2011

Results on the nonlinear properties of solutions of Buckminsterfullerene in toluene are reported. Optical limiting thresholds are as low as 15 mJ/cm2 with multiple pulse stability. Evidence for a different mechanism than that applicable in graphitic carbon black suspensions is presented. The calculated second hyperpolarizability agrees with experimentally reported values.
Interesting Electronic Properties Generated by Metal-Ion Linked C60 Chains
Authors: Singh D. J. , Fann Y. C. , Jansen S. A.
Published: March 2011

Recently it has been shown that buckminsterfullerene can be made to crystallize in a fee lattice when doped with various alkali metals eg. K, Rb, etc. Preliminary studies have shown the high propensity of C60 to be reduced without loss of stability. This may lead to interesting conductive pathways if a suitable dopant can be found which would act as an electronic “bridge” between adjacent “buckyballs” Out theoretical analyses have been geared towards a greater understanding of the reductive tendencies of C60, to discover how hypothetical metal-ion/C60, complexes differ from their corresponding simple, well characterized organometallic analogs. We demonstrate that the “metallocenium” link perturbs the electronic states of the C6 moiety including the frontier molecular Orbitals. Consequently, the metal ion plays an important role in establishing the electronic characteristics of metal-ion linked C60, chains and can be used to achieve desired properties.
Synthesis and Nonlinear Optical Characteristics of Chromophore-Functionalized Polymers Having Chromophore-Centered Hydrogen-Bonding and Crosslinking Groups
Authors: Jin Y. , Carr S. H. , Marks T. J. , Lin W. , Wong G. K.
Published: March 2011

In this study, we report the synthesis and characterization of a new, systematically designed class of second-order NLO polymers in which the appended chromophoric substituent is modified (hydroxylated) to allow direct chromophore involvement in hydrogen-bonding and crosslinking. Thus, the glassy polymer poly(p-hydroxystyrene) has been functionalized to varying levels with the N-(3-hydroxy-4-nitrophenyl)-(S)-prolinoxy (HNPP) high-β chromophore. The time-dependent second harmonic generation characteristics of thin films of this material have been studied at λ = 1.064 μm as a function of chromophore functionalization level, hydrogen-bonding capacity, and thermal crosslinking. These materials are found to possess high d33 values (up to 34 × 10−9 esu) and long characteristic SHG decay times (longer than a year). Analysis of the decay of the second harmonic signal shows that increasing hydrogen-bonding density substantially increases relaxation times; it is further shown that introduction of crosslinks is yet more effective in imparting SHG temporal stability to these polymeric nonlinear optical materials.
Approaches from High-Spin Organic Molecules to Organic Ferromagnets
Authors: Ishida Takayuki , Inoue Katsuya , Koga Noboru , Nakamura Nobuo , Iwamura Hiizu
Published: March 2011

Pseudo-two dimensional branched polycarbenes 1, 3, 5-[H(m-C6H4C:)n/3]3C6H3 (2)(n = 6, 9) were prepared. The measurement of their magnetization on a Faraday balance equipped with a light guide has revealed that 2(n = 6) has a tridecet ground state (S = 6.0). The m-phenylene skeleton as a dependable ferromagnetic coupling unit has also been applied with success to the synthesis of persistent systems, i.e., 5, by replacing each carbene center in linear polycarbenes 1 with a nitroxide. A necessary degree of steric protection of the radical centers was disclosed. Extension to real polymers 4 gave an only partly successful result.
Synthesis and Magnetic Characterization of Poly(2, 4-Bis(4, 4, 5, 5-Tetramethyl-4, 5-Dihydro-1H-Imidazolyl-1-OXY-3-Oxide-2-Phenoxy))Hexadiiyne
Authors: Zhang Deqing , Wu Peigi , Zhu Daoben
Published: March 2011

The title monomer diacetylene with α-nitronyl nitroxide as pendants was synthesized and polymerized by heating in vacuum. The magnetic properties of the polymer were studied, and it was found that this organic polymer showed weak ferromagnetism.
Metallomesogens and Amorphous Metallopolymers: Magnetic Properties
Authors: Haase W. , Griesar K. , Erasmus-Buhr C.
Published: March 2011

The magnetic susceptibility data in the temperature range of 4.2 K up to 300 K in the crystalline state of a metal lomesogen containing a Cu(II)-center are reported and discussed. Also magnetic properties of a Cu(II) containing chemically modified polymethylmethacrylate are presented. The interpretation of data, based on the Curie-Weiss-equation, shows a negative Weiss constant in the range up to θ = −27 K. An intermolecular long range antiferromagnetic exchange interaction at least in the solid or amorphous state has been discussed.
Syntheses and Properties of k-Phase Organic Superconductors
Authors: Hau Wang H. , Carlson K. D. , Geiser U. , Kini A. M. , Schultz A. J. , Williams J. M. , Welp U. , Darula K. E. , Hitsman V. M. , Lathrop M. W. , Megna L. A. , Mobley P. R. , Yaconi G. A. , Schirber J. E. , Overmyert D. L.
Published: March 2011

The syntheses and physical properties of K-(ET)2CU[N(CN)2]X (X = Br and Cl) are summarized. The K-(ET)2Cu [N(CN)2] Br salt is the highest Tc radical-cation based ambient pressure organic superconductor (Tc = 11.6 K), and the K-(ET)2CU [N(CN)2] C1 salt becomes a superconductor at even higher Tc under 0.3 kbar hydrostatic pressure (Tc = 12.8 K). The similarities and differences between K-(ET)2Cu[N(CN)2]Br and K-(ET)2CU(NCS)2 (TC = 10.4 K) are presented. The X-ray structures at 127 K reveal that the S-S contacts shorten between ET dimers in the former compound while the S-S contacts shorten within dimers in the latter. The differences in their ESR linewidth behavior is also explained in terms of the structural differences. A semiconducting compound, (ET)Cu[N(CN)2]2, isolated during K-(ET)2Cu[N(CN)2]Cl synthesis is also reported. The ESR measurements of the K-(ET)2Cu[N(CN)2]Cl salt indicate that the phase transition near 40 K is similar to the spin density wave transition in (TMTSF)2SbF6. A new class of organic superconductors, K-(ET)2CU2(CN)3 and K-(ET)2Cu2(CN)3.δBrδ, is reported with Tc's of 2.8 K (1.5 kbar) and 2.6 K (1 kbar), respectively.
Superconducting Transition in к-Bedt-TTF Salts Under Magnetic Field
Authors: Ito Hiroshi , Nogami Yoshio , Watanabe Masashi , Ishiguro Takehiko , Komatsu Tokutaro , Saito Gunzi , Hosoito Nobuyoshi
Published: March 2011

The superconducting transition under magnetic field for organic superconductors к-(BEDT-TTF)2 Cu(NCS)2 and к-(BEDT-TTFh)2 Cu[N(CN)2]Br has been analyzed by employing fluctuation renormal-ization theory. From magnetization measurements the interlayer and intralayer Ginzburg-Landau coherence lengths are determined. The effect of the isotope substitution to BEDT-TTF molecules has been studied. The result for resistive measurements is also described.
Tetraheterafulvalenes as Precursors of Conducting Materials
Authors: Papavassiliou George C.
Published: March 2011

Methods for preparation of thetraheterafulvalenes containig O, S, Se, N as additional he-teroatoms and some of their conducting products are described. Also, results concerning stoichi-ometry, structures, and physical properteis are briefly discussed.
The Synthesis and Physical Studies of a new Synthetic Metal: The Charge-Transfer Salt of Dimethyltetrathiotetracene-Tetracyanoethylene
Authors: Kilgore K. J. , Rath N. P. , Jones M. T.
Published: March 2011

The 1:1 charge transfer salt of dimethyltetrathiotetracene (DMTTT) and of tetracyanoethylene (TCNE), C26H12N4S4 crystallizes from chlorobenzene in the monoclinic system, space group P2(l)/c with cell constants a = 11.136(2), b = 11.254(3), C = 17.280(4) A, beta = 96.56(2), V = 2151.4(9) A, Z = 4 and dcalc = 1.57 0 mg/nun. The structure is made up of dimers of DMTTT and TCNE, respectively. Polycrystalline samples of DMTTT/TCNE exhibit a weak paramagnetism which was studied by ESR techniques from 102 to 293 K. The ESR studies reveal anisotropie spectra which are best resolved in the temperature range 102 to 250 K. The spectra observed are those expected from a spin system which is described by an orthorhombic g-tensor. The isotropie g-value calculated from the observed anisotropie g-tensors falls between the isotropie g-values for DMTTT and TCNE. As the temperature is increased, the spectral width decreases suggesting motion of and/or an increase in the spin concentration. DMTTT/TCNE is a relatively poor electrical conductor which is consistent with its crystal structure.
Conducting and Superconducting Salts Based on Some Symmetrical and Unsymmetrical Donors
Authors: Papavassiliou George C. , Lagouvardos D. J. , Kakoussis V. C. , Terzis A. , Hountas A. , Hilti B. , Mayer C. , Zambounis J. S. , Pfeiffer J. , Whangbo M. -H. , Ren J. , Kang D. B.
Published: March 2011

Conducting and superconducting salts based on bis(ethylenedithio)tetrathiafulvalene, ehtylenedithioselenatrithiafulvalene, ethylenedioxyethylenedithiotetrathiafulvalene, and ethylenedioxyvinylenedithiotetrathiafulvalene were prepared and studied.
Studies on the Chemical Modifications of Metallo- Organic Charge-Transfer Complex Switching and Memory Storage Materials
Authors: Ddan Hailing , Cohan Dwaine O. , Poehler Theodore O.
Published: March 2011

In order to obtain desired switching and memory properties by carrying out chemical modifications on CuTCNQ-type charge-transfer complexes, systematic explorations on various donor and acceptor reactivities are necessary. Thus, the reactivities of thirty-three different metals with TCNQ and four organo-acceptors with Cu in an CH3CN solution were qualitatively studied, as well as the solvent effects on the complex film formation. Uniform coverage of Metallo-organic complex films were obtained (in the order of reactivities) on TCNQ complexes of Tl, Ca, Mg, Cu, Ag, Mn and Cd, as well as on Cu complexes of TCNQ(OET)2, BTCNQ and TCNQ(i-Pr)2. The donor reactivity is affected by its surface immunity (behavior) towards the acceptor attack and the solubility of the formed charge-transfer complex in the chosen solvent. The acceptor reactivity is affected mainly by a steric effect, followed by an inductive effect of the substituents. The complex film morphology and quality could be optimized by matching the relative reactivity of donor vs. acceptor and by choosing the appropriate solvent with proper solubility of the formed complex.
Polyaniline: Interrelationships Between Molecular Weight, Morphology, Donnan Potential and Conductivity
Authors: Macdiarmid Alan G. , Epstein Arthur J.
Published: March 2011

Methods for significantly increasing the molecular weight of polyaniline are described. The conductivity of doped polyaniline is shown to be more directly dependent on its degree of alignment/crystallinity than on its molecular weight. The tensile strength of polyanilines films and fibers increases with increasing stretch alignment. An interpenetrating polymer system involving polyaniline which shows greatly enhanced conductivity at pH values where polyaniline has negligible conductivity is described. The doping level of polyaniline is shown to be dependent not only on the pH of the dopant medium but also on the presence of dissolved neutral salts. This new phenomenon is explained in terms of Donnan equilibrium effects.
Novel Template Guided Synthesis of Poly Aniline
Authors: Liu Jia-Ming , Sun Linfeng , Hwang Jyun-Hwei , Yang Sze Cheng
Published: March 2011

In acidic medium, polyaniline has positive charges on its molecular backbone. These charges come from either protonation at the nitrogen atom sites or polarons in its β-electronic system [1]. Although polyaniline, due to its positive charges, is a polycation, yet its physical properties are quite different from the classical polyelectrolytes. For example, the polycation vinylbenzyltrimethylammonium chloride is soluble in water but polyaniline molecules (and other conducting polymers too) tends to aggregate into intractable solid. Conducting polymers aggregate into intractable solid because of their stiff molecular backbone and the strong short range attractive forces between βclouds of adjacent polyaniline chains. The insolubility of polyaniline poses problem for solution processing of polymers. There have been a heavy effort towards the resolution of this problem [2].
Diether Substituted Polyanilines: Novel Electrode Materials
Authors: Gopal J. , Vanhouten K. , Cowan D. O. , Poehler T. O. , Madsen P. V. , Searson P. C.
Published: March 2011

(2-Methoxy)ethoxy substituted anilines have been polymerized by chemical and electrochemical methods in hydrochloric acid (HC1) and p-toluenesulphonic acid(TsOH). Electrical conductivity, optical properties, solubility and charge capacity of these polymers are discussed.
Dynamics of Electrochromic Phenomena in Organic Conducting Polypyrrole Films
Authors: Amemiya T. , Hashimoto K. , Fujishima A.
Published: March 2011

The electrochromic responses for two kinds of polypyrrole (PPy) films, PPy/inorganic anion and PPy/polyanion composite films, were studied by electromodulation technique. Analyses of electrical and optical responses show that electrochromic responses in conducting state were nearly the same for the both films, however, those in redox active state were characteristic of the two films. The differences in the responses of the two films seem to arise from the differences of both the morphologies of the films and charge transport properties in the films.
Towards Oriented Polymeric Structures for Cubic Nonlinear Optics
Authors: Lemoigne J. , Moroni M. , Coles H. , Thierry A. , Kajzar F.
Published: March 2011

Our approach consists of improving the molecular architecture of π-electron delocalization and orientations of the polymeric backbone of materials for cubic nonlinear optics. First, the syntheses of new polymers such as substituted polyacetylenes or polyphenyleneynylenes were done, in which the stiff conjugated chain and the flexible side-chains are well adapted to the orientation of the backbone. They have been studied for their third order susceptibility and their ability to give processable optical films. We have found liquid crystal properties with the rigid rod derivative of the poly(ethynylarylene). Unlike previous poly(ethynylarylene), we obtained a high molecular weight: , which allows films of good optical and mechanical properties. Second, in order to increase the third order response, we focused our attention on the orientational order of polydiacetylenes, which we obtained by epitaxial growth of the monomer on a single crystal substrate. From the proposed epitaxial model a possible extension of highly oriented thin films can be applied to a large class of materials.
Charge Carrier Generation by Exciton-Exciton Annihilation in Poly(Di-N-Hexylsilane)
Authors: Kepler R. G. , Soos Z. G.
Published: March 2011

We have studied charge carrier generation by photons in thin films of poly(di-n-hexylsilane) over the photon energy range 3.15 to 6 eV and find that it is nonlinear in light intensity to above 4.5 eV. We show that the generation mechanism is exciton-exciton annihilation.
Recent Studies of Raman Spectroscopy of Polydiacetylene Crystals: Poly-Ipudo
Authors: Hankin S. H. W. , Sandman D. J.
Published: March 2011

Using 632.8, 514.5, 488.0, and 457.9 nm as wavelengths of excitation, Raman spectra have been observed for single crystals of the polydiacetylene of - (CH2)4OCONHCH(CH3) 2 (Poly-IPUDO). The hysteresis effect observed for the thermochromic shift in the Raman spectra is supported by data from repetitive temperature cycling in differential scanning calorimetry.
Photoinduced Absorption Spectroscopy of Poly-3-Alkylthiophenes
Authors: Botta C. , Luzzati S. , Bolognesi A. , Tubino R. , Borghesi A.
Published: March 2011

We report a study of the near infrared photoinduced absorption of a series of poly -3-decylthiophene with different supermolecular organization as solution cast films, good solvent and aggregated bad solvent solutions.

Photoinduced subgap electronic states are detected both in the solid and in solutions independently from the presence of polymer aggregates. The study of the photoinduced activity Δ/T on the laser intensity I indicate a I0.6 dependence for the films and a I0.95 dependence for the solutions. This is the evidence that the photoinduced states are generated in the solid via an inter-chain mechanism while in the solution via an intra-chain mechanism.

A possible role of the solvent into the photoexcitation pathway is discussed.
Synthesis and Characterization of Soluble Alkyl Substituted Poly(2, 5-Thienylene Vinylenes)
Authors: Catellani M. , Porzio W. , Musco A. , Pontellini R.
Published: March 2011

Alkyl substituted poly(2, 5-thienylenevinylene)s were produced with a new synthesis. The polymers are soluble and processable and show a strong electrochromic effect in the visible spectral range.
Synthesis and Microwave Characterization of Polypyrrole-PVC Blends
Authors: Jousse F. , Hourquebie P. , Deleuze C. , Olmedo L.
Published: March 2011

ABSTRACT.: Thermoplastic blends have been created by in situ growth of polypyrrole in an insulating PVC matrix. This type of synthesis gives a level of conductivity of the order of 10−5 to 1 S/cm for concentrations of less than 15% (in weight). A study of the synthetic conditions shows that the reaction parameters (solvent, nature of oxidizing agent) control the eventual properties of the blend (structure, conductivity level). The microwave characterization of these materials has allowed us to establish a direct link between the method of processing and the radioelectric properties.
Defects in [1, 6-DI(N-Carbazolyl)-2, 4-Hexadiyne] Diacetylene Crystals
Authors: Liao Jun , Martin David C.
Published: March 2011

The effect of solution concentration on the morphology of [l, 6-di(N-carbazolyl)-2, 4-hexadiyne] (DCHD) diacetylene crystals has been studied by conventional TEM, SAED, and HREM. Crystals obtained by evaporating 0.1 wt% DCHD-chloroform solution on amorphous carbon films are fibrous (about 3 μm wide and 100 μm long) and have defects such as kinks, pores, cracks, and dislocations. Two characteristic single crystal textured morphologies are found in these crystals: (1) a microfibrillar structure consisting of highly-oriented crystallites, with greater axial sizes than lateral sizes, slightly misorienting with a standard deviation of 3°; and (2) a“cross-hatched”structure consisting of highly-oriented crystalline domains separated by two groups of obliquely oriented boundary planes which make (45+/-3)∘ and (37+/-3)∘ angles respectively with the [001] chain direction. Crystals obtained by evaporating more dilute (0.01 wt%) DCHD-chloroform solutions onto amorphous carbon films are about 0.1–0.2 μm long and 0.05–0.1 μm wide and have the chain axis oriented perpendicular to the carbon support film. For these crystals, lateral-chain-invariant (LCI) small angle grain boundaries have been found in HREM images of the [001] zone axis.
Polarization Dependent Photocurrent in Thin Film Polydiacetylene Single Crystals
Authors: Yang Y. , Lee J. Y. , Li L. , Kumar J. , Jain A. K. , Tripathy S. K. , Matsuda H. , Okada S. , Nakanishi H.
Published: March 2011

The photocurrent behavior in polydiacetylene (PDA) single crystals of PTS (poly-(2, 4-hexadiyne-1, 6-diol bis(p-toluenesulfonate)) and MADF (poly-(1-(3-(methylamino)phenyl)-4-(3, 5-bis (trifluoromethyl)-phenyl) butadiyne)) have been investigated by using steady state photoconductivity measurements. These measurements were carried out as a function of sample temperature and incident light polarization. PTS and MADF show completely different behavior in these measurements. These differences between PTS and MADF suggest that the side groups of PDA strongly influence the photocurrent behavior in PDA.
Mechanical and Electrical Properties of Heat-Treated Ladder Polymer Fiber
Authors: Wang C. S. , Lee C. Y-C , Arnold F. E.
Published: March 2011

The ladder polymer poly[(7-oxo-7H, 10H-benz(d, e)imidazo(4', 5':5, 6)-benzimidazo(2, l-a)isoquinoline-3, 4:10, ll-tetrayl)-10-carbonyl] (BBL) was synthesized in polyphosphoric acid (PPA) at a concentration of 15% by weight. The polymer had an intrinsic viscosity of 8.75 dl/g in methanesulfonic acid (MSA) at 30°C. Highly oriented BBL fiber was spun by a dry-jet wet-spin process with a spin-draw-ratio of 8 to 1. After neutralization, the fiber exhibited a phosphoms content below the detectable limit (0.04%) by elemental analysis. This fiber, after a heat treatment at 300°C for 30 seconds under tension, showed a Young's modulus of 120 GPa, a tensile strength of 830 MPa and a compressive strength of 410 MPa. The fiber was also heat-treated at temperatures from 100°C to 600°C at 50°C increments for electrical conductivity measurements. It was found that room temperature DC conductivity of the BBL fiber increased dramatically from 2×10−8 S/cm with 100°C heat treatment to 3×10−4 S/cm with 350°C heat treatment and then decreased to 6×10−7 S/cm with 600°C heat treatment. The enhanced conductivity of heat-treated BBL fiber is believed due to the improved structural order in the BBL fiber and the thermally excited charge carriers.
Molecular Engineering of Polymers and Polymer Systems for Photonics and Electronics
Authors: Wegner Gerhard , Mathauer Klemens
Published: March 2011

Rod-like polymers dressed with a skin of flexible short side-chains and overall cylindrical shape have been developed towards application in photonics and electronics. Layered structures which qualify as ‘molecular composites’ are obtained applying the Langmuir-Blodgett (LB) technique to these materials. The rod-like moieties are embedded in a continuous matrix formed by the side-chain segments. The orientation of the rods in the matrix is determined by the rheology of the LB-process. Photoreactive groups incorporated into the side-chain moieties allow photoresist patterns to be formed. The actual chemistry of the layer forming systems is based on poly(phthalocyaninatosiloxanes)s, helical poly(peptide)s, poly(silane)s or cellulose ethers. Some of the polymers have been designed to be chromophores for NLO processes or may serve as hosts for chromophores or ionophores.

More complex architectures arise by preparation of structures with alternating layers of different chemical composition. The preparation of stripe wave guide patterns and of Si-based ion sensors is described.
Graded-Index and Single-Mode Polymer Optical Fibers
Authors: Koike Yasuhiro
Published: March 2011

High-bandwidth graded-index (GI) polymer optical fiber (POF) and single-mode POF with good mechanical properties were successfully obtained by our interfacial-gel polymerization technique. The bandwidth of the GI POF is about 1 GHz · km which is two hundred times larger than that of the conventional step-index (SI) POF. The minimum attenuation of transmission is 56 dB/km at 688-nm wavelength and 94 dB/km at 780-nm wavelength. The single-mode POF in which the core diameter was 3–15 μ m and the attenuation of transmission was 200 dB/km at 652-nm wavelength was successfully obtained for the first time.
New Strategies for Preparing Electrically Conductive Langmuir-Blodgett Films
Authors: Cheung J. H. , Rosner R. B. , Rubner M. F.
Published: March 2011

The fabrication, structure and electrical properties of new electrically conductive Langmuir-Blodgett (LB) films of polyaniline and polypyrrole have been investigated. Polyaniline in its emeraldine-base form was mixed with stearic acid (PAN-B/SA) to produce stable films at the air-water interface (5/1 or 10/1 mole ratio of PAN-B/SA). These films were then transferred into multilayer films which were found to exhibit conductivities of about 1 S/cm upon doping with hydrochloric acid. The alkyl chains of the stearic acid molecules were found to be distributed randomly throughout the LB film thereby exerting a minimal influence on the electrical properties of the polyaniline phase. In addition to this mixed monolayer approach, a novel method of fabricating highly conductive polypyrrole LB films has been developed. This method is based on the sequential exposure of ferric stéarate LB films to hydrogen chloride (HC1) gas and pyrrole vapor. Each of these two solid state reactions was found to impart dramatic chemical and structural changes to the film. Polypyrrole LB films with conductivities as high as 5 S/cm were produced via this process. The electrical and optical properties of films made by both techniques were examined in order to elucidate their structure/property relationships.
Defect Studies of the Transparent/Translucent Plastic Products Ujith the Polarized Light
Authors: Rahman Miftahur , Schott N. R.
Published: March 2011

The applications of plastic products in the areas of medical science, computer technology and optics demand high quality and defect free products. The medical products such as implanted lenses to correct cataracts (opacity of the lens of the eye, causing partial or total blindness), contact lenses etc. need to be cmpletely defect free. The injection molded compact disc (CD) substrates of polycarbonate also require to be defect free as well as stress free. The retardation of the optical beam has to be less than 50 nm for single pass in the CD ROM and for erasable magneto-optical disk the retardation needs to be even lower in magnitude. Many optical components also require to be defect free and stress free. In this present investigation, a well known optical birefringence technique is used to study the stresses and microscopic defects such as foreign matter, voids, cracks, bubbles, inclusions, gels, etc. in these products using a commercially available polariscope.
Tunable Diode Laser Absorption Spectroscopy of the Pyrolysis of Methylsilazane
Authors: Sun H. C. , Bae Y. W. , Whittaker E. A. , Gallois B.
Published: March 2011

An understanding of the chemical processes occurring in the gas phase during metalorganic chemical vapor deposition is needed to design novel precursors and for the subsequent control of the composition and the microstructure of the solid product. Tunable diode laser absorption spectroscopy provides a means to precisely monitor specific bond rupture in the precursor during pyrolysis. Methylsilazane [CH3SiHNH]n,, a precursor to silicon-based ceramic thin films, was used to investigate the potential of this technique. Below the decomposition temperature, the intensity of the absorption line at 871.6±0.1 cm−1 corresponding to one of the harmonics from Si-CH3, increased linearly with the vapor pressure of methylsilazane up to 800 Pa and then decreased exponentially. The typical linewidths of the absorption line was approximately 0.006 cm−;1, orders of magnitude narrower than would be observable using conventional infrared techniques. The absorption line was detectable over a pressure range from less than 1 Pa to 10 kPa.
Laser Induced Fluorescence for Temperature Measurement in Reacting Flows
Authors: Joklik R. G.
Published: March 2011

OH vibrational Thermally Assisted Fluorescence (THAF) temperature measurements have been demonstrated in both premixed and diffusion flames. The accuracy of the measurements is generally better than 100 K over a wide range of flame conditions for which the collisional quenching rate varies considerably. Application of this technique for temperature measurement in Chemical Vapor Deposition (CVD) flows, for which the quenching rate is relatively constant, should exhibit greater accuracy. THAF measurements in these flows are limited by signal to noise considerations, and should be possible down to pressures of 103-104 Pa or less.
In-Situ Optical Emission Spectra of Ti, TiN and TiSi2 Plasma During Thin Film Growth by Pulsed Laser Evaporation
Authors: Pramanick S. , Narayan J.
Published: March 2011

The first optical emission spectra of Ti, TiN and TiSi2 plasma during growth of thin films by pulsed laser evaporation has been reported. A KrF excimer laser (248nm) with pulsewidth of 45ns operating on 5Hz repitition rate was used for deposition of refractory metal thin films using varying laser fluence of 4J/cm2 to 15J/cm2. Most of the radiative species seen in plasma belongs to atomic neutrals and ionic species such as Ti I, Ti II, Si I, Si II and N 11. Emission spectra was mostly dominated by neutral and ionic emission from Titanium (Ti I and Ti II).
Near-Room Temperature Deposition of W and WO3 Thin Films by Hydrogen Atom Assisted Chemical Vapor Deposition
Authors: Lee Wei William , Reeves Robert R.
Published: March 2011

A novel near-room temperature CVD process has been developed using H-atoms reaction with WF6 to produce tungsten and tungsten oxide films. The chemical, physical and electrical properties of these films were studied. Good adhesion and low resistivity of W films were measured. Conformal W03 films were obtained on columnar tungsten using a small amount of molecular oxygen in the gas stream. A reaction mechanism was evaluated on the basis of experimental results. The advantages of the method include deposition of adherent films in a plasma-free environment, near-room temperature, with a low level of impurity
Effect of Process Conditions and Chemical Composition on the Microstructure and Properties of Chemically Vapor Deposited SiC, Si, ZnSe, ZnS and ZnSxSe1-x
Authors: Pickering Michael A. , Taylor Raymond L. , Goela Jitendra S. , Desai Hemant D.
Published: March 2011

Sub-atmospheric pressure chemical vapor deposition (CVD) processes have been developed to produce theoretically dense, highly pure, void-free and large area bulk materials, SiC, Si, ZnSe, ZnS and ZnSxSe1-x. These materials are used for optical elements, such as mirrors, lenses and windows, over a wide spectral range from the vacuum ultraviolet (VUV) to the infrared (IR).

In this paper we discuss the effect of CVD process conditions on the microstructure and properties of these materials, with emphasis on optical performance. In addition, we discuss the effect of chemical composition on the properties of the composite material ZnSxSe1-x.

We first present a general overview of the bulk CVD process and the relationship between process conditions, such as temperature, pressure, reactant gas concentration and growth rate, and the microstructure, morphology and properties of CVD-grown materials. Then we discuss specific results for CVDgrown SiC, Si, ZnSe, ZnS and ZnSxSe1-x.
Effect of High Temperature Annealing on the Microstructure of SCS-6 SiC Fibers
Authors: Ning X. J. , Pirouz P. , Bhatt R. T.
Published: March 2011

The effect of annealing the SCS-6* SiC fiber for one hour at 2000°C in an argon atmosphere is reported. The SiC grains in the fiber coarsen appreciably and the intergranular carbon films segregate to the grain junctions. It would appear that grain growth in the outer part of the fiber is primarily responsible for the loss in fiber strength and improvement in fiber creep resistance.
Thin Film Properties of LPCVD TiN Barrier for Silicon Device Technology
Authors: Hegde Rama I. , Fiordalice Robert W. , Travis Edward O. , Tobin Philip J.
Published: March 2011

Thin film properties of LPCVD TiN barriers deposited on Si(100), using TiCl4 and NH3 as reactants, were investigated as a function of deposition temperature between 400 °C and 700 °C. The TiN film chemistry and film composition were studied by AES and RBS techniques, while the microstructural properties (grain size, lattice parameter and texture) were evaluated by XRD. The TiN deposition rates and film resistivities were also determined. Finally the film properties of the TiN barriers as determined by surface analysis were related to the process parameters.