bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical and Electrical Characterization of Copper-and Chlorine-Doped Cadmium Zinc Telluride
Authors: Toney J. E. , Brunett B. A. , Schlesinger T. E. , Cross E. , Doty F. P. , James R. B. 
Published: April 2011

AbstractWe have used low-temperature photoluminescence spectroscopy and photo-induced current transient spectroscopy to study the properties of copper-doped Cd1−xZnxTe with x=0.1 and chlorine-doped Cd1−xZnxTe with x=0.2, 0.35 and 0.5. The current-voltage characteristics and detector response were also measured. We observed variations in charge collection and resistivity in the Cu-doped samples which was correlated with variations in PICTS spectra. The Cl-doped material was found to have insufficient resistivity for detector operation.
Growth, Characterization and Spectroscopic Investigations of InI Crystals for Optical and Radiation Detector Applications
Authors: Mandal K. C. , Klugerman M. , Cirignano L. J. , Moy L. P. , Shah K. S. , Squillante M. R. , Bhattacharyya R. N. 
Published: April 2011

AbstractSingle crystals of InI (Eg = 2.01 eV at 300K) have been grown by vertical Bridgman technique using zone refined (ZR) starting materials. The quality of the grown crystal has been evaluated by X-ray diffraction (XRD), Electron probe microanalysis (EPMA) and Photoelectron spectroscopy (XPS). Chemically etched crystal wafer has been used to fabricate optical and nuclear detectors. The results are presented in this paper.
Exciton Bandwidth and Coupling to Intramolecular Phonons in PTCDA
Authors: Hennessy M. H. , Soos Z. G. , Bulovic V. , Forrest S. R. 
Published: April 2011

abstractA Holstein model is introduced for PTCDA stacks forming a one-dimensional exciton system and analyzed using Merrifield's variational method. The bandwidth and hopping integral V = 0.15 eV are obtained by comparing the absorption, emission, and fluorescence excitation of PTCDA films to solution spectra.
Electronic Properties of a Novel Class of Conjugated Systems: Transition Metal Substituted Oligothiophenes
Authors: Lancellotti L. , Tubino R. , Luzzati S. , Licandro E. , Maiorana S. , Papagni A. 
Published: April 2011

AbstractWe report on a spectroscopical study of a novel class of push-pull molecules containing a Chromium or Tungsten atom connected to an oligothiophene through a carbenic bond. The electronic coupling between the π electrons of the conjugated system and the π electrons of the transition metal has been monitored through absorption and Raman spectra.This interaction between d and π electrons leads to a red shift of the thienylene π-π* absorption band and to the appearance of a new strong metal to ligand charge transfer band at lower energies. In this latter transition the electrical dipole reverses its direction upon photoexcitation from the ground to the first excited state, thus accounting for the enhanced non linear optical response of these molecules. Solvatochromic effect has been used to estimate the second order molecular hyperpolarizability.
Plastic Multilayered Molecular Organic Light Emitting Diodes
Authors: Daly George M. , Murata Hideyuki , Merritt Charles D. , Kafafi Zakya H. , Inada Hiroshi , Shirota Yasuhiko 
Published: April 2011

AbstractEnhanced performance has been observed for plastic molecular organic light emitting diodes (MOLEDs) consisting of two to four organic layers sequentially vacuum vapor deposited onto patterned indium-tin oxide (ITO) on polyester films. For all device structures studied, the performance of plastic diodes is comparable to or better than their analogs on glass substrates. At 100 A/m2, a luminous power efficiency of 4.4 lm/W and external quantum yield of 2.7% are measured for a device structure consisting of two hole transport layers, a doped emitting layer and an electron transport layer on a polyester substrate. The same device made on a silica substrate has a luminous power efficiency of 3.5 lm/W and external quantum yield of 2.3%. Electrical and optical performance for comparable device structures has been characterized by current-voltage-luminance measurements and electroluminescence spectra collected normal to the emitting surface. In addition, an integrating sphere was used to collect the total light emitted and to determine the optical output coupling on glass versus plastic substrates.
Multilayer Self-Assemblies as Electronic and Optical Materials
Authors: Li DeQuan , Lütt M. , Shi Xiaobo , Fitzsimmons M. R. 
Published: April 2011

AbstractThe layer-by-layer growth of film structures consisting of sequential depositions of oppositely charged polymers and macrocycles (ring-shaped molecules) have been constructed using molecular self-assembly techniques. These self-assembled thin films were characterized with X-ray reflectometry, which yielded (1) the average electron density, (2) the average thicknesses, and (3) the roughness of the growth surface of the self-assembled multilayer of macrocycles and polymers. These observations suggest that inorganic-organic interactions play an important role during the initial stages of thin-film growth, but less so as the thin film becomes thicker. Optical absorption techniques were also used to characterize the self-assembled multilayers. Phorphyrin and phthalocyanine derivatives were chosen as the building blocks of the self-assembled multilayers because of their interesting optical properties.
Structural and Electronic Properties of Self-Assembled Supramolecular Grid Structures: Doping of Supramolecular Thin Films
Authors: Hassmann J. , Hahn C. Y. , Waldmann O. , Volz E. , Schleemilch H-J. , Hallschmid N. , MÜller P. , Hanan G. S. , Volkmer D. , Schubert U. S. , Lehn J-M. , Mauser H. , Hirsch A. , Clark T. 
Published: April 2011

AbstractThin films of self-assembled supramolecular grid structures were prepared by electrochemical deposition. The surface structure of the films was determined by electrochemical insitu scanning tunneling microscopy (STM), revealing ordered monolayers of the grid molecules on a Au( 111) surface. The electronic structure of the films was studied by photoelectron spectroscopy. The thin films show semiconducting behavior with an insulating gap of ca. 2.5 eV. The size of insulating gap can be reduced to 0.5 eV by doping the films with additional Cd2+ ions, which is in agreement with molecular orbital calculations. Additionally, conductivity measurements were performed. By doping of the thin films, their conductivity could be increased by several orders of magnitude. This is due to additional electronic states in the insulating HOMO-LUMO gap, which is confirmed by UPS measurements.
Investigations on the Aluminum/Para-Hexaphenyl Interface in Light Emitting Devices
Authors: Koch N. , Yu L.-M. , Guyaux J.-L. , Morciaux Y. , Leising G. , Pireaux J.-J. , Demoustier G. 
Published: April 2011

AbstractBlue light emitting devices (LED) with para-hexaphenyl (PHP) as the active material and aluminum as cathode exhibit very high quantum efficiencies. To further optimize device performance it is crucial to understand the physical properties of the involved interfaces. We have performed Rutherford-Backscattering experiments on actual devices to show the importance of oxygen in the interface formation at the cathode as this leads to the formation of a layer of AlxOy between PHP and aluminum. In devices, where the organic film is exposed to air before the metal electrode is evaporated, an insulating layer on the metal-side therefore is inherent. It has been shown that the introduction of an intermediate layer between active material and electrodes results in a higher quantum efficiency of the LED, the most common concepts being charge-transport-layers, or insulators on the other hand. Our results underline the need for a better control of the LED processing. Ultraviolet- and X-ray photoelectron spectroscopy in situ growth studies of thin aluminum films on PHP have been made to reveal the change in the electronic structure of the active medium in a LED in the absence of oxygen. Also the direct interaction of oxygen with this organic material is investigated by photoelectron spectroscopy.
Electroactive and Photoactive Rod-Coil Block Copolymers: Self-Organization and Photophysical Properties
Authors: Chen X. Linda , Jenekhe Samson A. 
Published: April 2011

AbstractTwo series of new electroactive and photoactive coil-rod-coil and rod-coil-rod triblock copolymers, poly (pentadecamethylene carboxester)-block - poly(p-phenylene benzobisthiazole) - block - poly (pentadecamethylene carboxester) (1), and poly(2,6-benzoxazole)-block poly(benzobisthiazole decamethylene)-block-poly(2,6-benzoxazole) (2), were synthesized, characterized, and used to investigate the self-assembly properties of rod-coil block copolymers. The progressive band narrowing of the absorption spectrum of thin films of 1 confirmed the effects of spatial confinement with increasing coil block size. Photoluminescence studies of thin films of 1 and 2 showed the effects of self-organization, annealing at 110 °C, block lengths, and composition on photophysical properties. Bilayer photoreceptors consisting of a layer of block copolymer as the charge generation layer and a layer of tris(p-tolyl)amine dispersed in polycarbonate as a trap-free hole transport layer were oberved to have high quantum efficiency, good photosensitivity and good dark decay.
Cascade Connected Organic El Diodes for Multi-Color Emission
Authors: Ohmori Yutaka , Tada Norio , Kurosaka Yoshitaka , Fujii Akihiko , Yoshino Katsumi 
Published: April 2011

AbstractMulticolor electroluminescent (EL) device which emits red (R), green (G) and blue (B) light has been realized by stacking a two-color emission part and a single-color emission part. The former part consists of two emissive layers of red and blue light, which can be selected by changing the polarity of applied field. The latter part consists of a single emissive layer of green light. The emission color from the R-G-B emission device can be modulated by the combination of applying various voltages to the two-color and to the single-color emission parts, separately.
Photolithographic Patterning of Vacuum–Deposited Organic Light Emitting Devices
Authors: Tian P. F. , Burrows P. E. , Bulovic V. , Forrest S. R. 
Published: April 2011

AbstractA photolithographic technique to fabricate vacuum-deposited organic light emitting devices has been demonstrated. The photolithographically patterned, yet unpackaged devices show no sign of deterioration in room ambient when compared with devices fabricated using shadow masks. Furthermore, the environmental robustness of the encapsulated devices makes them particularly useful in fabricating high resolution, full color displays.
Observation of the Temperature Dependence of the Dynamics of Photoexcited States in Pristine Tris(8-Hydroxyquinoline) Aluminum (Alq3)
Authors: Priestleya Richard , Walsera Ardie D. , Dorsinville Roger 
Published: April 2011

AbstractWe have investigated the temperature dependence of the dynamics of radiative excited states in pristine thin films of tris(8-hydroxyquinoline) aluminum (Alq3). By measuring the transient photoluminescence (PL) response with subnanosecond resolution, our results revealed an increase in the radiative excited state lifetime and fluorescence quantum yield with decreasing temperature from 300K to 77K. At low temperature we observed a decrease in the bimolecular recombination rate constant, singlet exciton diffusion coefficient and diffusion length. A singlet exciton trapping model is used to explain these results.
The Dielectric Response Of 8-Hydroxyquinoline Aluminum used in Multilayer Organic Devices
Authors: Niko A. , Hochfilzer C. , Jost T. , Graupner W. , Leising G. 
Published: April 2011

AbstractWe present optical measurements of 8-hydroxyquinoline aluminum (Alq3) a metal-chelate complex which is an important material used for multilayer light emitting diodes. Thin films of Alq3 produced by vacuum deposition were investigated by transmission and reflectance spectroscopy, and the dielectric coefficients in the near IR to UV-Vis energy range were calculated. Kramers-Kronig analysis was used to determine the real and imaginary dielectric spectral dependence of the thin films. Values obtained by internal field distribution measurements in organic double layer LED's are compared to those determined from optical data. A near-IR value of epsilon (real component) close to 3 was obtained from optical measurements.
Characterizing the NLO Chromophore Orientation of Polymeric Film by Electroabsorption Spectroscopy
Authors: Yang Ke , Wang Xiaogong , Kim Woohong , Jain Aloke , Li Lian , Kumar Jayant , Tripathy Sukant 
Published: April 2011

AbstractThe dispersion of third-order nonlinear coefficients and of three different NLO(nonlinear optical) polymer films were determined by electroabsorption spectroscopy. The first material investigated is an epoxy-based polymer BP-2A-NT, with azobenzene NLO chromophore 4-[((4-nitrophenyl)(azo)phenyl)azo)]aniline in its side chain. The other materials are two polydiacetylenes, poly(BPOD) and poly(4-BCMU), in which the( 3de)localized polymer chains contribute to the third-order nonlinearity. The complex spectrum of of each material is very similar in shape to corresponding spectrum. The ratio of to is 3.2 for BP-2ANT, 1.5 for both poly(BPOD) and poly(4-BCMU). These ratios indicate that the distribution of the side-chain NLO chromophores of BP-2A-NT is very close to three-dimensional isotropy, and the distribution of the main-chain chromophores of poly(BPOD) and poly(4-BCMU) is concentrated on the film plane.
Investigation of Dielectric Constant and Dispersion in Barium Strontium Titanate Capacitors
Authors: Zafar Sufi , Chu Peir , Remmel T. , Jones Robert E. , White Bruce , Gentile David , Jiang Bo , Melnick Bradley , Taylor Deborah , Zurcher Peter , Gillespie Sherry 
Published: April 2011

ABSTRACTThe correlation between the dielectric constant and dispersion is investigated for barium strontium titanate (BST) capacitors with platinum and iridium electrodes. For platinum electrode capacitors, dispersion decreases with increasing dielectric constant. In contrast, capacitors with iridium electrodes exhibit the reverse correlation. A simple model is proposed to provide a quantitative explanation for the observed correlation for both platinum and iridium electrodes. In addition, the dependence of the dielectric constant and dispersion on varying ratios of (Ba+Sr)/Ti is also reported.
PZT Electro-Optic Waveguide Devices Fabricated by Solid-Phase Epitaxy
Authors: Nashimoto Keiichi , Nakamura Shigetoshi , Moriyama Hiroaki , Watanabe Masao , Osakabe Eisuke 
Published: April 2011

ABSTRACTHigh quality epitaxial PZT optical waveguides have been grown by solid-phase epitaxy based on metal alkoxide solution process. Optical propagation loss was 4 dB/cm in epitaxial PZT thin film optical waveguides grown on SrTiO3 substrates. Epitaxial PZT optical waveguides were grown on Nb doped conductive SrTiO3 substrates, since considerable reduction in drive voltage will be expected when top electrode / optical waveguide / conductive substrate structures are realized. Propagation loss was relatively large, as compared with the structure using non-dope insulative substrates. Preliminary electrooptic deflection devices were fabricated by preparing prism electrodes on the surface of the PZT optical waveguides. Efficient deflection/switching of coupled laser beam in the PZT optical waveguides as large as 26 mrad was observed by applying 70 volts between prism electrode and Nb doped SrTiO3 substrates.
Sol-Gel Derived Ferroelectric YMnO3 Films
Authors: Teowee G. , McCarthy K. C. , McCarthy F. S. , Dietz B. H. , Davis D. G. , Uhlmann D. R. 
Published: April 2011

ABSTRACTSol-gel derived YMnO3 films have been prepared on platinized Si wafers. Crystallization took place at firing temperatures above about 750C. The crystallized films were very conductive. YMnO3 films exhibited a dielectric constant of 23, a remanent polarization of 1.0 μC/cm2 and a coercive field of 12 kV/cm, all measured at -33C The FE loop was lossy and elliptical at room temperature but became more distinct at lower measuring temperatures or at higher measuring frequencies.
Design of Catalysts with Artificially Controllable Functions Using Surface Acoustic Waves and Resonance Oscillations Generated on Ferroelectric Materials
Authors: Saito N. , Ohkawara Y. , Sato K. , Inoue Y. 
Published: April 2011

ABSTRACTA poled ferroelectric material of a LiNbO3 single crystal and a polycrystalline lead strontium zirconium titanate(PSZT) disc were employed as a catalyst substrate, on which various metals such as Pd, Ag, Ni and Pt and a WO3 oxide were deposited as a thin film catalyst. The effects of acoustic waves generated by rf power upon catalyst activation and reaction selectivity have been examined. The activity for CO oxidation of a Pt/PSZT catalyst increased by a factor of 3.9 with a thickness-extensional(TE) mode of resonance oscillation(RO) and 2.9 with a radial-extensional (RE) mode. The activation energy of the reaction was larger for the TE mode( 38 kJmol−1) than that for the RE mode(24 kJmol−1). The polarization axis-dependent changes in surface potential occurred with the TE mode, but not with the RE mode. With the TE mode, the activation energy of ethanol oxidation over a Ni/LiNbO3 and a Ag/LiNbO3 catalyst decreased from 36 to 19 kJmol−1 and from 76 to 30 kJmol−1, respectively, and the TE mode had a larger effect on the reaction with a higher activation energy. In ethanol dehydrogenation and dehydration on a WO3 / LiNbO3 catalyst, the TE mode increased remarkably the selectivity for ethylene production without giving a significant change to acetaldehyde production. The effects of acoustic wave excitations on the catalysts are discussed.
Molecular Modeling of Selective Adsorption from Mixtures
Authors: Bandosz T. J. , Blas F. J. , Gubbins K. E. , McCallum C. L. , McGrother S. C. , Sowers S. L. , Vega L. F. 
Published: April 2011

ABSTRACTMolecular simulation methods provide a means for carrying out systematic studies of the factors affecting adsorption phenomena. For selective adsorption, the selectivity is strongly affected by the interaction energy with the pore walls, molecular size and shape, site specific interactions, entropie effects, differences in diffusion rates, and networking effects. Two recent studies of site specific selectivity will be described. The first is an investigation of the effect of oxygenated surface sites on the adsorption of water vapor on activated carbons. Hydrogen-bonding sites are modeled using off-center square well interactions for both water and wall sites; wall sites are placed at the edges of the graphite micro-crystals. New experimental results for water adsorption at low pressures on carefully characterized activated carbons are reported, and are found to be in good agreement with the simulations. In the second application, we consider the separation of alkene/alkane mixtures using aluminas whose surfaces have been doped with metal ions, π-complexation between these metal ions and the alkenes can produce a highly selective separation. The simulations are found to be in good agreement with the available experimental data, and have been used to predict separations for other conditions not yet studied in the laboratory.
Characterization of Carbon Nitride Films Prepared by Magnetic Filtered Plasma Deposition
Authors: Wei Aixiang , Chen Dihu , Ke N. , Peng Shaoqi , Wong S. P. 
Published: April 2011

ABSTRACTCarbon nitride films prepared by magnetic filtered plasma deposition were characterized using Fourier transform infrared (FTIR) absorption and X-ray photoelectron spectroscopy (XPS). Characteristic bands corresponding to C-N, C=N, C=N, and C=C bonds were observed in FTIR spectra. It was found that the XPS C 1s and N 1s signals could be deconvoluted into three and two gaussian peaks, respectively. A plausible suggestion on the assignments of the XPS peaks to C3N4, CNx and ta-C phases was discussed. The relative abundance of the various CN bonds, the relative abundance of the various bonding components from XPS results, and their dependence on the nitrogen partial pressure PN during deposition were analyzed. Assuming the assignments of the XPS peaks to the various phases, the XPS results suggested that there would be an optimal PN that would favor the growth of the C3N4 phase. The electrical conductivity, the optical band gap and the Vickers hardness of these films were measured and the effects of PN on these properties were studied.
Doping Mechanism in Tetrahedral Amorphous Carbon
Authors: Chen C W , Robertson J 
Published: April 2011

ABSTRACTDoping in hydrogenated amorphous silicon occurs by a process of an ionised donor atom partially compensated by a charged dangling bond. The total energies of various dopant and dopant/bonding combinations are calculated for tetrahedral amorphous carbon. It is found that charged dangling bonds are less favoured because of the stronger Coulombic repulsion in ta-C. Instead the dopants can be compensated by weak bond states in the lower gap associated with odd-membered π-rings or odd-numbered π-chains. The effect is that the doping efficiency is low but there are not charged midgap recombination centres, to reduce photoconductivity or photoluminescence with doping, as occurs in a-Si:H.
The Effect of Bonding Disorder on the Vibrational Features of Amorphous Carbon Based Binary Alloys
Authors: Compagnini G. , Foti G. 
Published: April 2011

ABSTRACTIn this work we report some results concerning Raman characterisation of covalently bonded amorphous carbon based thin films (∼ 100 nm) of binary alloys, obtained by ion implantation of carbon ions into silicon and germanium matrices. It will be shown that compositional disorder is present in our samples even below the stoichiometric concentration (∼50 carbon at.%) as deduced by the presence of three vibrational features in the Raman spectra. A quantitative measure of the compositional disorder will be also given by using either Raman or infrared spectroscopies in samples with different carbon content.
High Pressure Lattice Instabilities and Structural Phase Transformations in Solids from Ab-Initio Lattice Dynamics
Authors: Baroni Stefano , Giannozzi Paolo 
Published: April 2011

ABSTRACTThis paper is devoted to some recent applications of density-functional perturbation theory to the prediction of lattice instabilities occurring in ionic solids at high pressure. We first briefly review some work aimed at understanding the interplay between shear instabilities and phonon softening in the pressure-induced phase transformations of Cesium halides and hydride. We then report on preliminary results of an attempt of ours to apply similar techniques to the long-standing problem of the pressure-induced amorphization of quartz.
Studies on Materials Under Ultrahigh P-T at the Advanced Photon Source
Authors: Shen G. , Duffy T. , Wang Y. , Rivers M. , Sutton S. 
Published: April 2011

ABSTRACTThe Advanced Photon Source (APS) is a third-generation synchrotron now in operation at Ar-gonne National Laboratory. A national user facility for research in the Earth sciences is being constructed by the GeoSoilEnviro group of the Consortium for Advanced Radiation Sources (GSECARS). One component of this effort is the program for diamond anvil cell (DAC) research, to study materials at ultrahigh pressure and temperature conditions using a variety of techniques.In this paper, we describe the DAC facility that is being developed at the GSECARS. Recent progress in developing a laser heating system is presented.
A Study of Band Alignment in GaAs/GaInP(Partially Ordered) Heterostructures with High Pressure
Authors: Uchida K. , Yu P. Y. , Zeman J. , Kwok S. H. , Teo K. L. , Su Z. P. , Martinez G. , Arai T. , Matsumoto K. 
Published: April 2011

ABSTRACTIn this paper we review the use of high pressure techniques to investigate the optical properties of partially ordered GalnP epitaxial layers grown on GaAs substrates. In particular, we demonstrate the ability of high pressure to modify the band alignment at the GalnP/GaAs interface and hence to alter the optical properties of heterostructures fabricated from partially ordered GalnP on GaAs.