bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bioactivity Responses of Different Uhmwpe Particles from In-Vivo and In-Vitro Tests
Authors: Park YoungSoo , Yang ShangYou , Wooley Paul H. , Merritt Katharine , Hsu Stephen , McNallan Michael J. 
Published: April 2011

AbstractThis paper describes the results of bioactivity responses to different ultra high molecular weight polyethylene (UHMWPE) particles. Particles were produced by a wear tester using two different textures of steel counters, one with cross-hatched and the other with uni-hatched grooves. These two textured surfaces produced two distinct populations of wear particles. One is larger and more elongated (fibril shapes) than the other. The mean sizes and aspect ratios of the particles are in the ranges of 5 μm to 25 μm and about 1.5 to 3, respectively. These two distinct UHMWPE particles were examined through in-vitro and in-vivo tests. Macrophages RAW 264.7 and the murine air-pouch model of inflammation were employed to characterize the effect of the particle size and shape. Preliminary in-vivo tests results showed that more elongated and larger particles enhanced bio-reactions.
Crystal Morphology Control by Melt Phase Separation in Biodegradable Polymer Blends
Authors: Akpalu Y. A. , Meredith J. C. , Amis E. J. 
Published: April 2011

AbstractThe effect of lower critical solution temperature (LCST) phase separation on the crystallization of poly(ε-caprolactone) PCL in PCL/poly(D,L-lactide) (PDLA) blends is studied by simultaneous small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS). Phase separation is induced by controlled temperature jumps into the LCST (two-phase) region, which is above the melting temperature (60 °C) of PCL and the glass transition temperature (50 °C) of PDLA. We have followed the nanoscale structural changes (< 100 nm) during subsequent crystallization at 45 °C of critical (0.36 PCL) and off-critical (0.50 PCL) blend compositions in both one-phase and two-phase melts. The spherulite morphology (1-100 μm) is examined with optical microscopy. When crystallization follows LCST phase separation, the shape, size and distribution of the spherulites depends on the extent of melt phase separation. In our x-ray measurements, the WAXS crystallinity of PCL is less than 40 % for the temperature range of interest. We perform a correlation function and intensity model analysis of our SAXS data to obtain morphological variables that characterize the intraspherulitic morphology. These morphological variables are relatively constant during crystallization and are also independent of melt phase separation. On the other hand, the ultimate crystallinity and the crystallization rate depend on the extent of melt phase separation.
Adhesion of Pressure Sensitive Adhesives with Applications in Transdermal Drug Delivery
Authors: Taub Marc B. , Dauskardt Reinhold H. 
Published: April 2011

AbstractThe development and implementation of successful transdermal devices for drug delivery requires an understanding of the adhesion occurring between the device and the soft dermal layer. This study utilizes a mechanics approach to quantify the adhesive properties of representative pressure sensitive adhesives (PSAs) used as the adhesive layer in these systems. Debonding of PSAs is accompanied by cavitation in the PSA and the formation of an extensive cohesive zone behind the debond tip. The presence of such large-scale bridging provides significant energy dissipation and increased resistance to delamination. The strain energy release rate (G) during debonding of a cantilever-beam sample, containing at its midline a thin layer of PSA, was utilized to quantify the adhesion of the PSA. The analysis accounts for both the work of adhesion as well as the viscoelastic constitutive behavior of the soft adhesive layer. Effects of strain rate, physiological environment, and permeation-enhancement additions are considered. The resistance of human stratum corneum to debonding between corneocyte layers is also presented, as knowledge of this parameter is essential for developing techniques to test the fracture resistance of the PSA-stratum corneum interface present in the clinical use of these transdermal devices.
Effect of Interface and Crystallinity on the Ferroelectric Properties of Poly(Vinylidene Fluoride-Trifluoroethylene) Copolymer Thin Films
Authors: Xia Feng , Xu H.S. , Razavi Babak , Zhang Q. M. 
Published: April 2011

ABSTRACTFerroelectric polymer thin films are attractive for a wide range of applications such as MEMS, IR sensors, and memory devices. We present the results of a recent investigation on the thickness dependence of the ferroelectric properties of poly(vinylidene fluoridetrifluoroethylene) copolymer spin cast films on electroded Si substrate. We show that as the film thickness is reduced, there exist two thickness regions. For films at thickness above 100 nm, the thickness dependence of the ferroelectric properties can be attributed to the interface effect. However, for thinner films, there is a large change in the ferroelectric properties such as the polarization level, the coercive field, and polarization switching speed, which is related to the large drop of the crystallinity in the ultrathin film region (below 100 nm). The results from Xray, dielectric measurement, and AFM all indicate that there is a threshold thickness at about 100 nm below which the crystallinity in the film reduces abruptly.
Statistical Method to Optimize the Efficiency of Multi-Layer Polymer LEDs
Authors: Cecchi Michele , Braun David , Smith Heather , Vanasupa Linda 
Published: April 2011

ABSTRACTResearch and development of displays and image sensors based on semiconducting polymers require design of new polymer materials and evaluation of film properties. Optimizing device performance using a one-factor-at-a-time (OFAT) requires screening the effect of several process parameters, running numerous samples, and may consume more scarce new material than desired. This paper investigates the effects of Indium-tin oxide (ITO), alkoxy-poly(pphenylene vinylene) (OC1C10-PPV) and poly(3,4-ethylene dioxythiophene) (PEDOT) layer preparation on polymer LED brightness and power efficiency by performing and analyzing a two-cubed full-factorial design experiment with 3 replicated center points. Full-factorial design evaluates all main factors and all interactions. Design of experiments (DOE) showed that correct selection of ITO anneal temperature can significantly improve brightness. Atomic Force Microscopy (AFM) measurements affirm that the increased brightness correlates with a reduction in ITO average surface roughness.
Stabilization of Optical Molecules Using Dendritic Boxes against Singlet Oxygen in Photobleaching
Authors: Otomo Sonoko , Otomo Akira , Mashiko Shinro 
Published: April 2011

ABSTRACTThe stabilizing effect of dendritic boxes (DBoxes) as a means to protect against photo- degradation of encapsulated dye molecules was experimentally investigated. We focused on photoinduced oxidation and studied the ability of DBoxes to protect dyes inside them from reactive singlet oxygen. Rubrene was captured in a DBox, and then the box was closed at the surface by other stable molecules. A singlet oxygen generator was added to a Rubrene solution to exaggerate photo-oxidation in the complicated total-photodegradation process, and then the solution was exposed to a laser beam to generate singlet oxygen. Bleaching of the encapsulated Rubrene in a DBox was 50 times slower than that of Rubrene alone. We also compared the dependence of surface molecules of a DBox with other kinds of molecules that have different efficiencies of quenching singlet oxygen. Further improved stability was observed by attaching singlet-oxygen-quencher molecules on the DBox surface.
Lateral and Vertical Phase Separation Control of Thin-film Structures for Photovoltaics
Authors: Arias A. C. , MacKenzie J. D. , Corcoran N. , Friend R. H. 
Published: April 2011

ABSTRACTInvestigations on microscopic and photovoltaic properties of polyfluorene blends are presented here. The length scale of lateral phase separation is manipulated by control of solvent evaporation conditions. Photoluminescence efficiency measurements show that charge transfer is more effective in blends phase separated on the nanometer scale. Vertically segregated structures are obtained by a combination of solution viscosity and spin coating conditions. The external quantum efficiency of photovoltaic devices fabricated with vertically segregated blend is found to be 4 times higher than that of devices made with laterally segregated blends.
High Performance Organic Field-Effect Transistors and Integrated Inverters
Authors: Ullmann A. , Ficker J. , Fix W. , Rost H. , Clemens W. , Mcculloch I. , Giles M. 
Published: April 2011

ABSTRACTIntegrated plastic circuits (IPCs) will become an integral component of future low cost electronics. For low cost processes IPCs have to be made of all-polymer Transistors. We present our recent results on fabrication of Organic Field-Effect Transistors (OFETs) and integrated inverters. Top-gate transistors were fabricated using polymer semiconductors and insulators. The source-drain structures were defined by standard lithography of Au on a flexible plastic film, and on top of these electrodes, poly(3-alkylthiophene) (P3AT) as semiconductor, and poly(4-hydroxystyrene) (PHS) as insulator were homogeneously deposited by spin-coating. The gate electrodes consist of metal contacts. With this simple set-up, the transistors exhibit excellent electric performance with a high source-drain current at source - drain and gate voltages below 30V. The characteristics show very good saturation behaviour for low biases and are comparable to results published for precursor pentacene. With this setup we obtain a mobility of 0.2cm2/Vs for P3AT. Furthermore, we discuss organic integrated inverters exhibiting logic capability. All devices show shelf-lives of several months without encapsulation.
Image Sensor Arrays with Organic Photoconductors
Authors: Street R. A. , Graham J. , Popovic Z. , Hor A. , Mulato M. , Lau R. , Ho J. 
Published: April 2011

ABSTRACTTwo-dimensional image sensor arrays incorporating an organic light sensor are reported, with potential application to digital cameras and x-ray imaging. The 512×512 element array has pixel size of 100 micron, and operates with active matrix addressing using amorphous silicon thin film transistors. The array design allows the use of a continuous layer of the organic sensor material without the need for pixel-level patterning. The sensor is a bilayer comprising a thin generator layer and a thicker hole transport layer. Generator materials benzimidazole perylene (BZP) and hydroxy gallium phthalocyanine (HOGaPc) have been studied, with a tetraphenyldiamine (TPD) transport layer. Both sensors give excellent imaging properties with low leakage current, good charge collection and high spatial resolution.
Luminescent Polymer Fibers for Light Amplification and Lasing
Authors: Kobayashi Takeyuki , Blau Werner J. , Tillmann Hartwig , Härhold Hans-Heinrich 
Published: April 2011

ABSTRACTWe report on the fabrication of step index polymer optical fibers that use a novel conjugated polymer and fluorescent stilbenoid compounds for lasing and amplification applications in the blue-green regions. The green-emitting polymer, Thianthrene-MEH-PPV, and the blue-emitting compounds, 1,2-bis(4-diphenylaminophenyl)-ethylene and 1,4-bis(4-diphenylamino-styryl)-benzene, are designed for the blue-green region of the spectrum and have very high quantum yields and large Stokes shifts. Significant spectral narrowing and superlinear increase of output intensity are observed under photoexcitation at 355 nm, which are indicative of the occurrence of amplified spontaneous emission. By gain spectroscopy, a high gain coefficient of 36 cm−1 at 494 nm has been obtained for the 1,4-bis(4-diphenylamino-styryl)-benzene-doped fiber when it is transversely photoexcited at 12 mJ/cm2.
A Unified Model for the Space Charge Limited Currents in Organic Materials Combining Field Dependent Mobility and Poole-Frenkel Detrapping
Authors: Jain S. C. , Geens W. , Kumar V. , Kapoor A. , Mehra A. , Aernouts T. , Poortmans J. , Mertens R. , Willander M. 
Published: April 2011

ABSTRACTWe have calculated J-V characteristics of an organic conducting sample (containing traps) including the Poole-Frenkel Effect (PFE). Both shallow and exponentially distributed traps are considered. We show that our approach is equivalent to combining the effect of trapping and using the field dependent mobility in one unified model. For shallow single level or shallow Gaussian traps, inclusion of PFE or using the (well-known) field dependent mobility gives the same dependence of current on voltage at a given temperature. However the value of zero field mobility µ0 comes out to be different. We have fabricated and measured the J-V curves of the ITO/MEH-OPV5/Al diodes. An extremely fast rise with voltage V is observed at small voltages, which can be interpreted either by the Schottky contact limited Shockley like current or by bulk space charge limited current with PFE. The correct mechanism can be determined by making J-V measurements at different temperatures.
Synthesis and Characterization of Low Content of Structural Defects of Aryl-Substituted Electroluminescent Poly(p-phenylenevinylene)s
Authors: Chen Zhi-Kuan , Lee Nancy Hoi Sim , Huang Wei 
Published: April 2011

ABSTRACTWe report the synthesis and characterization of a novel series of aryl-substituted PPVs, which have shown excellent processability, good thermal stability, high photoluminescence quantum efficiency and low content of structural defects. The substituents of the polymers were designed with different degree of hindrance effect on the main chain. 1H NMR measurement indicates that the defect structure in the polymer main chain can be effectively depressed by introducing bulk and hindrance substituents.
Molecular Assemblies, Patterning, and Deposition of Conjugated Polymers: Ultrathin Films Prepared using the Layer-by-Layer and Precursor Polymer Electrodeposition Approach
Authors: Advincula Rigoberto , Park Mi-kyoung , Xia Chuanjun 
Published: April 2011

ABSTRACTIn this paper we present a combined protocol for ultrathin film formation and assembly of Φ- conjugated polymer materials using the layer-by-layer (LbL) technique and a precursor polymer approach to electrodeposition. While much work has been done on investigating the chemistry (synthesis) and properties (physics) of these materials, little focus has been given on the multilayer and ordering issues associated with ultrathin film formation especially using novel “wet-processing” approaches. This work details our molecular assembly approaches on conjugated polymer systems for polyfluorene and polythiophene derivatives. This was demonstrated in the following systems: a) ionene precursor polyfluorene polymers deposited as ultrathin films using the LbL technique from an aqueous solution and b) electrodeposition of polysiloxane modified precursor polymers. Important strategies are outlined for combining the two techniques as a novel method for preparing ultrathin films and patterning.
Ionic Self Assembly and Low Conversion Temperature (P-Phenylene Vinylene)
Authors: Marletta A. , Castro F. A. , Borges C. A. M. , Faria R. M. , Guimarães F. E. G. 
Published: April 2011

ABSTRACTWe developed an alternative approach to produce self-assembled (SA) thin films of poly(p-phenylene vinylene) (PPV) by controlled substitution of the chloride counterion of the precursor poly(xylylidene tetrahydrothiophenium chloride) (PTHT) by a long chain dodecylbenzenesulfonate (DBS) anion. The main advantage of this novel procedure is that thermal conversion through the elimination of DBS may be performed at considerably lower temperatures (80-100 °C) in few minutes. In addition it provides PPV films with better optical properties and low incorporation of structural defects, like carbonyl groups. An important feature of these SA-PPV films is the well resolved vibronic structures in the photoluminescence and absorption spectra. We observe a dramatic improvement in quantum efficiency of PPV when the conversion temperature is decreased from 230 to 80 °C. This effect may be explained by the decrease of extrinsic defect incorporations (carbonyl groups) detected by infrared (IR) measurements. This improvement in the optical properties at low temperatures may help us to understand basic phenomena, such as the nature of excitons in PPVs.
Electrical, Optical, and Structural Properties of Fluorine-Doped CdO
Authors: Barnes Teresa M. , Li Xiaonan , Dehart Clay , Moutinho Helio , Asher Sally , Yan Yanfa , Gessert Timothy A. 
Published: April 2011

ABSTRACTWe have investigated the effects of fluorine doping and deposition temperature on CdO grown by metal-organic chemical vapor deposition (MOCVD). Fluorine doping increases the carrier concentration of the films by about one order of magnitude at a deposition temperature of 300°C. The increased carrier concentration increases the optical bandgap from 2.4 eV to 2.85 eV. On the other hand, the higher deposition temperatures enabled by fluorine doping improve the crystal structure of the films. Therefore a higher mobility has been reached. The polycrystalline thin film CdO deposited at 450°C has the Hall mobility of 262 cm2/V-s and a carrier concentration of 3.8×1019/cm3.
Thermochromic VO2 Films Heteroepitaxially Grown on ZnO Coated Glass by RF Sputtering
Authors: Kato Kazuhiro , Keun Song Pung , Shigesato Yuzo , Odaka Hidehumi 
Published: April 2011

ABSTRACTVanadium dioxide (VO2) is one of the most attractive thermochromic materials, which shows large changes in optical and electrical properties at around 68°C, nearly room temperature. This thermochromic behavior has been explained in terms of the Mott-Hubbard transition from a high-temperature rutile structure (metal phase) to a low-temperature monoclinic structure (semiconductor phase). We already reported that rf magnetron sputtering using V2O3 or V2O5 targets enable us to deposit polycrystalline thermochromic VO2 films with high reproducibility by introduction of oxygen gas (O2/(Ar+O2)=1∼1.5%) or hydrogen gas (H2/(Ar+H2)=2.5∼10%), respectively, as reactive gases [see ref.1]. In this study, ZnO polycrystalline films were deposited as a buffer layer between the VO2 film and glass substrate also by rf magnetron sputtering, which have been known to exhibit <001> preferred orientation in the wide range of the deposition conditions. Very thin thermochromic VO2 films with thickness of 50nm were successfully deposited on the ZnO coated glass substrate because of the heteroepitaxial relationship of VO2(010)[100]//ZnO(001)[100],[010],[110].
Ion-beam Assisted Deposition of MgO with in situ RHEED Monitoring to Control Bi-axial Texture
Authors: Groves James R. , Arendt Paul N. , Foltyn Stephen R , Jia Quanxi , DePaula Raymond F. , Dowden Paul C. , Kung Harriet , Holesinger Terry G. , Stan Liliana , Emmert Luke A. , Peterson Eric J. 
Published: April 2011

ABSTRACTWe have studied the growth of magnesium oxide using ion-beam assisted deposition (IBAD) to achieve (100) oriented, bi-axially textured films with low mosaic spread, for film thicknesses of 10 nm on silicon substrates. We have refined the process by using reflected high-energy electron diffraction (RHEED) to monitor the growth of IBAD MgO films and found that the diffracted intensity can be used to determine (and ultimately control) final in-plane texture of the film. Here we present results on our work to develop the use of real-time RHEED monitoring to deposit well-oriented IBAD MgO films. The results have been corroborated with extensive grazing-incidence X-ray diffraction (GID). Results of these analyses have allowed us to deposit films on metallic substrates with in-plane mosaic spread less than 7°.
Internal Stress of ITO, IZO and GZO Films Deposited by RF and DC Magnetron Sputtering
Authors: Sasabayashi T. , Song P. K. , Shigesato Y. , Utsumi K. , Kaijo A. , Mitsui A. 
Published: April 2011

ABSTRACTMechanical properties such as internal stress or adhesion of transparent conductive oxide (TCO) films are quite important to guarantee the patterning accuracy and the durability for various kinds of commercial applications. In this study, representative TCO films with the thickness of about 200 nm, such as tin-doped indium oxide (ITO), indium-zinc oxide (IZO), and gallium-doped zinc oxide (GZO) films were deposited on unheated glass substrate by rf and dc magnetron sputtering using corresponding oxide targets under various total gas pressure (Ptot) from 0.3 to 3.0 Pa. The internal stress of these TCO films was measured by cantilever method using 50 µ m thick 50mmx5mm micro-sheet glass substrates in relation to the Ptot during the deposition. The ITO films deposited at Ptot lower than 0.7 Pa were polycrystalline and showed large compressive stress, while the amorphous ITO films deposited at 1.5-3.0 Pa showed a very slight tensile stress. On the contrary, the all the IZO films with various thicknesses (50-750 nm) deposited at Ptot of 0.3-3.0 Pa showed entirely amorphous structure, where the compressive stress of IZO films was lower than that of ITO films. Whereas, all the GZO films deposited under Ptot from 0.3 to 5.0 Pa showed polycrystalline structure with <001> preferred orientation, where the compressive stress showed almost constant for all the films.
Mobility in SnO2:F Thin Polycrystalline Films: Grain Boundary Effect and Scattering in the Grain Bulk
Authors: Gilmore A. S. , Al-Kaoud A. , Kaydanov V. , Ohno T.R. 
Published: April 2011

ABSTRACTBasic electronic properties relevant to the carrier mobility were studied in tin oxide thin films doped with fluorine, prepared by atmospheric pressure chemical vapor deposition. Electrical resistivity, Hall and Seebeck effects, plasma and collision frequencies were measured (the last two by using multiangle spectral ellipsometry) and analyzed for films with carrier concentrations from 1.8×1020 to 5.6×1020 cm−3. Scanning over the sample area of resistivity (four-point probe method) and Seebeck coefficient (thermoprobe) monitored uniformity of electronic properties in plane. Ellipsometry was used to check uniformity over the film thickness. Films with a thickness above 400 nm demonstrated high spatial uniformity and were used for further studies.Effective mass was determined from combined Hall and plasma frequency measurements and was found to be independent of carrier concentration, which indicates a parabolic band spectrum. Its value was very close to the literature data. In films with carrier concentration ≥3×1020 cm−3 the Hall mobility was very close to the optical mobility calculated based on collision frequency and effective mass values. This indicates a very small contribution of grain boundaries to the total resistivity of films. Thus the measured mobility is close to the electron mobility in the grain bulk.The scattering parameter value derived from thermopower measurements along with the temperature independent mobility indicated that electron scattering by impurity ions screened by free carriers is the dominating scattering mechanism. Theoretical estimates of mobility are very close to the highest measured mobility values (≥ 30 cm2/Vs) if the spatial dispersion of the dielectric constant is taken into account. Comparison of differently processed films showed that compensation of donor dopant with uncontrolled acceptor centers significantly impacted mobility.