bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anti-Corrosion Studies of Novel Conductive Polymer Coatings on Aluminum Alloys
Authors: Racicot R. J. , Clark R. L. , Liu H-B , Yang S. C. , Alias M. N. , Brown R. 
Published: April 2011

ABSTRACTWe report the corrosion protection properties of a novel conductive polymer coating on aluminum alloys. The conductive polymer coating is a double strand molecular complex of polyaniline and a polyelectrolyte. The double strand polyaniline offers advantages in stability and processability over other forms of conductive polymers. The coated aluminum alloys (AA7075- T6) were evaluated for corrosion protection in an aggressive salt environment of.5N NaCl solutions using cyclic polarization and electrochemical impedance spectroscopy. Corrosion current densities were calculated for uncoated alloy samples and alloys coated with the conductive and non-conductive derivative of the double strand polymer. The conductive form of the double strand polyaniline coating shows a two order of magnitude lowering of the corrosion current over the uncoated samples and a one order magnitude lowering over the non-conductive form of the polymer coated samples. The shape of the cyclic polarization data closely resembles results of sulfuric acid anodized aluminum. This data indicates that the conductive state of the polymer is required for improved corrosion protection and an anodized type protection is occurring.
Models of Electron-Hole Screening and Exciton Binding in Conjugated Polymers
Authors: Yaron David , Moore Eric , Gherman Benjamin 
Published: April 2011

ABSTRACTThe use of semi-empirical quantum chemistry to calculate the exciton binding energy of conjugated polymers is discussed. Both the Pariser-Parr-Pople (PPP) model with Ohno parameterization and the models present in the MOPAC program overestimate the exciton binding energy relative to that observed in solid-state materials. Inclusion of Coulomb screening from adjacent chains may correct this overestimation. The solvation energy of a point charge in polyacetylene is calculated as 0.9eV, using Hartree-Fock theory to describe the polarization induced in the solvent chains. It is argued that including screening by modifying the electron-electron interaction energy of the PPP model introduces physically unreasonable side effects and is not consistent with the 0.9eV solvation energy of a point charge. Electron-hole screening models are then discussed along with the need to consider the relative time scales of the electron-hole motion and the dielectric response.
Conductivity Tailoring Of Melt-Processible Polyaniline In Polyolefin Blends By Using Viscosity Ratio
Authors: Tanner J. O. , Ikkala O. T. , Laakso J. , Passiniemi P. 
Published: April 2011

ABSTRACTPolyaniline (PANI) is a semi-rigid polymer which does not melt and has only limited solubility. Protonation to yield electrical conductivity generally renders a polyelectrolyte which is still less processible. Even selection of the dopant to be bulky or “functionalized” does not render PANI-complex to become melt-processible unless additional additives are used. Neste Oy (Finland) in cooperation with Uniax (U.S.A.) has identified several proprietary additives to allow melt-processibility. We show that in this way PANI-complex starts rheologically to behave in many respects like a conventional polymer. For example, in blends of PANI-complex with polypropylene, their viscosity ratio can be used to render either the PANI-complex or PP continuous, completely analogically to the “classical” polymer blends.
Elastomeric Conductive Ipn From Polyaniline And Fullerene-Based Networks
Authors: Wang Lee Y. , Chiang Long Y. , Kuo C. S. , Lin J. G. , Huang C. Y. 
Published: April 2011

ABSTRACTPolyhydroxylated fullerenes were utilized as an efficient hyper cross-linking agent in the synthesis of polyurethane networks. The resultant elastomers exhibited greatly enhanced thermal stability in comparison with those of the corresponding linear polyurethane and analogous elastomers, which were cross-linked by 1,1,1- tris(hydroxymethyl)ethane. A synthetic method leading to the preparation of a thin layer of conductive polyaniline/polyurethane IPN at the near surface of a fullerenol- based elastomeric substrate was demonstrated, using aqueous ammonium persulfate as an oxidizing agent in the presence of HCI. This new material exhibits a conductivity of 2.0 S/cm at ambient temperatures with the retention of most bulk properties of the parent elastomer, such as elongation and tensile strength at break.
Electrical Properties of Ion Implanted and Chemically Doped Polyaniline Films
Authors: Aleshin Andrej N. , Mironkov Nikita B. , Suvorov Alexander V. , Conklint Jeanine A. , Su Timothy M , Kaner Richard B. 
Published: April 2011

ABSTRACTThe electronic transport mechanism for ion implanted and chemically doped polyanilinefilms was investigated through temperature dependent dc conductivity measurements over thetemperature range 1.8 – 300K. Chemically synthesized emeraldine base polyaniline free-standingfilms (∼40 µm thick) were irradiated by Ar ions at an energy of 90 keV and doses ranging from 1 ×1014 to 3 × 1017 cm-2 to an estimated thickness of 100 nm. Chemical modification of Polyanilinefilms consisted of doping with 1.0 M H2SO4.Ion implantation and chemical doping were found to considerably increase the roomtemperature dc conductivity of polyaniline films reaching values up to 800 S cm-1and 8 S cm-1, respectively. Both ion irradiated and chemically doped polyaniline films exhibit p-type conduction.An increase in the irradiation dose increases the stability of the conducting layer compared tochemical doping. In both cases the samples are on the insulator side of the metal-insulatortransition, where cr(T) exhibits a common temperature dependent characteristic of the variablerange hopping (VRH) transport mechanism:σ(T) = σ (0) exp[ - (To / T)m ] (1)where m = 0.5 and To = 103 to 104K. The influence of electron-electron Coulomb the low temperature VRH of ion implanted and chemically doped polyanilCinoeu floilmmbs iisn tperreascetniotend
Synthesis of A 1,1′-Binaphthyl Based Main Chain Chiral Conjugated Polymer
Authors: Hu Qiao-Sheng , Vitharana Dilrukshi , Pu Lin 
Published: April 2011

ABSTRACTThe synthesis and characterization of a 1,1′-binaphthyl based main chain chiral conjugated polymer, R-9, is described. The polymer is prepared from the palladium-catalyzed Suzuki coupling of an optically active binaphthyl molecule, (R)-2,2′-dihexyloxy-1,1′-binaphthyl-6,6′- diboronic acid, R-4 with 1,4-bis(p-bromostyryl)benzene (E:Z = 1:1.2), 8. The Suzuki coupling of 8 with 6-neopentyloxynaphthyl-2-boronic acid, 1 1, leads to the formation of a conjugated molecule 10. The structure of this molecule represents the repeat unit of R-9. The electronic absorption spectrum of 10 demonstrates that the degree of conjugation in the chiral conjugated polymer is almost the same as that of its repeat unit.
Structure-Electronic Properties Relationships in Conducting Polymers: CP-MAS NMR and MM Analysis
Authors: Bradamante S. , Berlin A. , Canavesi A. , Zotti G. 
Published: April 2011

ABSTRACTThe anodic oxidative polymerization of alkyl functionalized 4H-cyclopenta[2, 1-b:3,4-b']- dithiophene (CPDT) followed by undoping provides soluble and processable materials. We used CP MAS and high resolution NMR to analyze the monomers and polymers with the aim of correlating their structural features and conductivity. T1 relaxation values in solution and solid state were compared. Information about the preferred conformations of the polymers (backbone, distances, torsional angles) was deduced using the Molecular Modeling approach. The conclusions were derived by combining the indications obtained from both the spectroscopic and computational methods.
Electroluminescence with Laddertype Poly(paraphenylenes)
Authors: Tasch S. , Niko A. , Leising G. , Scherf U. 
Published: April 2011

ABSTRACTWe present the optical and electronic properties of a new laddertype poly(paraphenylene) (LPPP), the m-LPPP, having the highest intramolecular order and highest environmental stability in the familiy of the LPPPs up to now. The m-LPPP is an excellent candidate for the usage as an active layer in electroluminescence (EL) devices, due to its well defined structure and high purity, as the spectral behaviour of the absorption coefficient cc confirms. cx is very low (αmin <12 cm−1) in the subgap region with a steep onset to the interband transition leading to welir"resolved vibrationally split maxima (αmax ≈ 1.1×105 cm−1). Moreover, the high quantum efficiency of fluorescence (up to 30 % in films) makes the m-LPPP a promising material for high efficiency-EL devices.The polymer-light emitting diodes (PLEDs), which were fabricated in air stable sandwich structures ITO/m-LPPP/Al, are characterized by high quantum efficiencies up to 4% and cwoperation lifetimes around 170 h. The PLEDs produced homogeneous bright light in the blue and blue-yellow spectral range, with the dominant emission maximum located at 461 nm. The onset field significantly depends on the thickness of the m-LPPP layers (Emin ≈ 0.5 MV/cm; Emax ≈ 2.6 MV/cm) due to ordering effects in the cast polymer. In the blue-green spectral range, the shape of the EL spectra and hence the emission colour can be controlled, by varying the applied electric field.
Solid State Structure and Photoluminescence properties of poly(2,5-dialkoxy-p-phenyleneethynylene)s
Authors: Weder Christoph , Wagner Michael J. , Wrighton Mark S. 
Published: April 2011

ABSTRACTIn an effort to better understand the relationship between molecular structure and photophysical properties, we have prepared and investigated a series of novel poly(2,5-dialkoxy-p-phenyleneethynylene)s. Wide angle X-ray diffraction measurements show that the supramolecular structure can be easily and significantly influenced by the nature of substituents covalently linked to the rigid-rod polymer main chains. Polymers which have sterically hindered side chains are essentially amorphous, while those with only linear side chains can form lamellar structures with a significant degree of long-range order. High photoluminescence quantum yields, up to 0.86 in solution and 0.36 in the solid state, have been measured. While the solution quantum yields are independent of the functionalization, solid state quantum efficiencies were found to be related to the degree of long-range order in the samples. In samples with a high degree of long-range order, the close proximity of the coplanar oriented polymer backbones is assumed to lead to the formation of eximer complexes which provide non emissive decay channels and, hence, result in comparable low photoluminescence quantum yields. In samples that adopt only a small extent of long-range order, the rigid-rod conjugated polymer backbones behave as if they were ‘dissolved’ in a hydrocarbon solvent and consequently high quantum efficiencies are obtained. Preliminary results indicate the suitability of these polymers as the emitting layer in electroluminescent devices.
Excited-State Intramolecular Proton Transfer in Polymers
Authors: Tarkka Richard M. , Jenekhe Samson A. 
Published: April 2011

ABSTRACTExcited state intramolecular proton transfer (ESIPT) has been demonstrated in new intramoleculary hydrogen bonded (IHB) polymers of interest as photostabilizers, triplet quenchers, photochromic materials, laser dyes and electroluminescent materials. The new IHB polymers containing the 2-(2-hydroxyphenyl)benzoxazole moiety in the main chain were used to explore the effects of polymer structure, extended conjugation and competition with excimer formation on the ESIPT process. It was found that polymer structure, and particularly extent of conjugation, affects an IHB polymer's ability to exhibit ESIPT.
BaTiO3 Thin Films for Electro-optic and Non-linear Optical Applications
Authors: Block B. A. , Wessels B. W. 
Published: April 2011

ABSTRACTEr-doped BaTiO3 thin films have been investigated as a candidate for an optically active waveguide medium. Epitaxial layers were prepared by metal-organic chemical vapor deposition at low pressure. The properties of the characteristic Er3+ luminescence transition at 0.8 eV have been investigated for epitaxial Er doped BaTiO3 thin films for various Er concentrations. The photoluminescent intensity was found to increase by a factor greater than 500 when the doping level was increased from 1 × 1020 cm−3 to 2.2 × 1021cm−3, indicating that concentration quenching was not significant at the highest doping levels. A complex emission spectra was observed and was attributed to the multi-site substitution of Er in BaTiO3. Transient decay measurements revealed a 7 ms radiative lifetime for the 0.80 eV transition that was independent of concentration.
Dielectric Behavior of CVD (Ba,Sr)TiO3 thin Films on Pt/Si
Authors: Streiffer S.K. , Basceri C. , Kingon A.I. , Lipa S. , Bilodeau S. , Carl R. , Van Buskirk P.C. 
Published: April 2011

ABSTRACTWe have investigated the dielectric behavior of polycrystalline (Ba,Sr)TiO3 thin films deposited by liquid-source metalorganic chemical vapor deposition. The time-domain polarization current, the frequency dependence of the permittivity, and the dielectric loss for these CVD films are all described by a single set of parameters via the phenomenology of Curie - von Schweidler behavior. No change in the general form of the permittivity is found out to 1.5 GHz, suggesting that this description of the response is valid into the frequency range of interest for many applications. Low-frequency dispersion is found to be controllable, leading to films with very low dissipation factors and almost frequency-independent dielectric response. Finally, a non-zero intercept of the inverse of capacitance versus film thickness suggests the existence of a series interfacial capacitance, arising from either microstructural inhomogeneity or energy barriers to carrier transport at the film-electrode interfaces.
MOCVD OF SnO2 on Silicon Microhotplate Arrays for use un Gas Sensing Applications
Authors: Dimeo F. , Semancik S. , Cavicchi R.E. , Suehle J.S. , Chaparala P. , Tea N.H. 
Published: April 2011

ABSTRACTThe quantitative detection of gas concentrations in mixed atmospheres is becoming increasingly important in manufacturing processing, environmental monitoring, and medical diagnostics. Several conductive oxides, such as SnO2, ZnO, and TiO2, are well known to exhibit changes in resistivity when exposed to various gases at temperatures ranging from 200–500°C. Current discrete devices based on resistive changes such as the Taguchi sensor, however, suffer from certain performance problems, including poor gas detection specificity. Integrated arrays of sensors, fabricated using planar technology, offer a promising solution to these problems, as well as other benefits such as low power consumption and low cost.In this paper, we report the results of using Metalorganic Chemical Vapor Deposition (MOCVD) to fabricate thin films of SnO2 on microhotplate arrays. The studied arrays contain 4 micromachined, suspended elements, each having an integrated resistive heater that produces a rapid thermal rise time ∼3 msec. By separately heating individual elements, we can take advantage of the thermally selective nature of the MOCVD process to limit deposition to these areas, resulting in a maskless deposition process. In addition, these array elements have surface electrical contacts that permit the measurement of the resistance of the thin films during deposition, as well as when they are operated in a gas sensing mode. In situ growth measurements will be reported.
Study of Microstructure and Gas Sensing Properties of tin Oxide thin Films Prepared by Metal Organic Chemical Vapor Deposition
Authors: Lee Sang Woo , Liu Donihang , Tsai Ping P. , Chen Haydn 
Published: April 2011

ABSTRACTTin oxide (SnO2) thin films were deposited on polycrystalline alumina (A12O3) substrates using metal organic chemical vapor deposition (MOCVD) technique at the growth temperature of 600°C. X-ray diffraction, scanning electron microscopy, and Auger electron spectroscopy were applied for the microstructure characterization of the films. The films were subjected to sensing tests under 1% H2 environment by monitoring changes in the electrical resistance of the films at elevated temperatures. There is a trend to exhibit sensor temperature characteristic in the deposited thin films which show a local maximum in the electrical resistance curve as a function of ambient temperature. The local maximum occurred at a relatively higher temperature than found in bulk sintered ceramics.
Silicon Nitride Tools Coated With Tic Or Tin Composite Diamond Structures
Authors: Fan W.D. , Jagannadham K. , Narayan J. 
Published: April 2011

ABSTRACTComposite diamond coatings on Si3N4 substrates have been developed to minimize stresses/strains and improve wear and adhesion properties. The coatings consist of a first layer of discontinuous diamond crystallites which are anchored to the Si3N4 substrate by a second interposing layer of TiC or TiN film. A top third layer of continuous diamond film is grown epitaxially on the first layer. The diamond films and TiC or TiN films were deposited using hot filament chemical vapor deposition and laser physical vapor deposition, respectively. The TiC and TiN films were examined by X-ray diffraction. The diamond films were characterized by scanning electron microscopy and Raman spectroscopy. Adhesion of the diamond coatings was investigated using overlap polishing with diamond paste, wear against Al-12.5%Si alloy, and pull-test. The results show that after introducing an interposing layer of TiC or TiN, adhesion of diamond coatings on Si3N4 substrates is improved significantly. After polishing test against diamond paste for 4 hours, only 30% of diamond was retained with single diamond coating while 80% of diamond was found with TiN composite diamond coating. The mechanism of improvement of adhesion is discussed.
Characterization Of Amorphous Carbon Films Based On Carbon, Nitrogen, and hydrogen*.
Authors: Efstathiadis H. , Akkerman Z. , Smith F. W. 
Published: April 2011

ABSTRACTA series of amorphous hydrogenated carbon-nitrogen alloy films (a-CxNyHz) has been prepared via plasma-enhanced chemical vapor deposition from mixtures of nitrogen and acetylene. It is found that as the ratio R=N2/C2H2 is increased from zero to 100, the nitrogen incorporation into the films is increasing while the deposition rate is decreasing for 0<R<10 and is saturating at a value of about 1.0 A/sec for 10<R<100. The absorption associated with the N-H stretching mode increases while that of the C-H stretching mode decreases with increase of R. The optical constants and the energy gaps of these films have also been determined. A free energy model previously developed for the prediction of the bonding in amorphous a-CxHyalloys is extended and applied here to a-CxNyHz. Predictions are presented for the bonding of tetrahedral C(sp3), trigonal C(sp2), linear C(sp1), pyramidal N(sp 3), trigonal N(sp 2), and linear N(sp1) atoms in the alloy, and the bonding of H to these atoms.
From Proposal To Product: Scaling Up The Chemical Synthesis of MOCVD Oxide Precursors
Authors: Leedham T J 
Published: April 2011

ABSTRACTAn essential step in the commercialisation of the MOCVD technique is the prompt availability of reliable precursors such as volatile alkoxides and diketonates for oxide deposition. Synthesis methods must be scaled by three orders of magnitude from grams to kilos to manufacture precursors for commercial devices. Impurities determine whether an identified method is viable due to the way in which they affect yield, shelf life and performance. Deleterious contaminants include free radicals, moisture damage and raw material remnants. Such considerations dominate multi-kilo synthesis but their impact may not have been perceived at an earlier stage. By particular examples we show attention to methodology can overcome these problems.
Barium bis(β-Diketonate)•tetraglyme Complexes as Potential CVD Precursors for Electronic Materials
Authors: Luten Henry A. , Otway David J. , Rees William S. 
Published: April 2011

ABSTRACTMOCVD, one preferred technique of the present electronics industry, has not yet emerged as the thin film method of choice for group 2 element containing materials due to the demonstrable shortcomings of the available source compounds. Most specifically, the challenge presented by the group 2 element charge/ionic radius ratio must be overcome to meet the vapor pressure requirements for CVD. To date, development of group 2 precursors suitable for MOCVD has focused mainly on the use of substituted acetylacetonate (acac) complexes. Earlier, several series of somewhat volatile precursors were developed by the use of acetylacetonate complexes containing fluorinated sidegroups. These precursors, while elegantly designed for the thermal deposition of BaF2, are not ideal for the preparation of oxide thin films. This arises from their propensity to initially form MF2, which must be reacted further in situ, or in a post-deposition treatment to yield the ultimately sought metal oxide. It is of interest, therefore, to develop stable, volatile precursors lacking fluorinated ligands.
Optical Properties of Diamond-Like Carbon Films Deposited by Laser Ablation
Authors: Seager C. H. , Friedmann T. A. , Bliss D. E. 
Published: April 2011

ABSTRACTVarious optical techniques, including Photothermal Deflection Spectroscopy (PDS), ellipsometry, and transmission measurements, have been used to examine the optical properties of diamond like C films deposited at various laser power densities on Si and fused quartz. The absorption coefficients of these films are typically above 5 × 104 cm−1 throughout the visible part of the spectrum, decreasing quasi-exponentially in the infra-red. Larger sp2/sp3 bonding ratios caused by deposition at lower laser power settings noticeably increase film absorption coefficients. While Tauc plots of our absorption data yield bandgaps of 1.5-1.0 eV, the quality of these fits is unimpressive and the slopes are unphysically low. Rather than modelling these materials as narrow gap semiconductors, we have pursued another avenue: treating the films as a mixture of small graphitic particles embedded in a diamond, sp3-like matrix. We will discuss the results of this approach as well as the evolution of the optical properties after thermal anneals.
About Homogeneity of CVD Diamond Nuclear Particles Detectors
Authors: Manfredotti C. , Fizzotti F. , Polesello P. , Vittone E. , Jaksic M. , Bogdanovic I. , Fazinic S. 
Published: April 2011

ABSTRACTCVD diamond films show both at optical microscope and at SEM a quasi-columnar structure, not homogeneously distributed in the bulk which is agreed to be responsible for the relatively large charge collection lengths measured in the material. In this work, we present the first data on charge collection efficiency distributions as measured directly in the bulk by a 3 Meν proton microbeam. The results indicate that the material is really non-homogeneous, that only few columns are really connecting both electrodes and that, finally, a real connection exists between the morphological structure and the maps of collection efficiency distribution.