bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fabrication of Polymer Light Emitting Diodes by Layer-by-Layer Complexation Technique
Authors: Kim Jaehyun , Chittibabu Kethinni G. , Cazeca Mario J. , Kim Woohong , Kumar Jayant , Tripathy Sukant K. 
Published: April 2011

AbstractMultilayer films were fabricated employing a new layer-by-layer complexation technique by alternatively dipping substrates in solutions of macromolecular ligands and Eu3+ ions. A luminescent poly[2-(3-thienyl)ethanol hydroxycarbonyl-methyl urethane] (H-PURET) was prepared by hydrolysis of thiophene polymer, poly[2-(3-thienyl)ethanol butoxycarbonyl-methyl urethane] (PURET), which was developed in our laboratory. H-PURET was used as macromolecular ligands. The multilayer deposition was monitored using UV-visible spectroscopy. As the number of bilayers increases, the absorption due to the polymer increases. The multilayer films were characterized by infrared and fluorescence spectroscopic techniques. Electroluminescence brightness easily obtained from the multilayer film of conjugated polymer-Eu3+ complex was measured to be about 40nW.
Light-Emitting Diodes with Voltage-Switchable Colors from Semiconducting Polymer/Polymer Heterojunctions
Authors: Zhang Xuejun , Jenekhe Samson A. 
Published: April 2011

AbstractReversible electroluminescence color changes with applied voltage have been observed in light-emitting diodes fabricated from semiconducting polymer heterojunctions consisting of an electron transporting polybenzobisthiazole and hole transporting poly(p-phenylene vinylene) when layer thicknesses are less than 60–100 nm. Enhanced device performances such as lower turn-on voltage and higher efficiency and luminance were also obtained compared to single-layer devices. The observed voltage-switchable emission colors in these nanoscale heterojunction light sources can be understood in terms of spatial confinement effects which are related to field-dependent charge transport and trapping processes in the materials. These results also demonstrate the use of new high temperature rigid-rod polymers as electron transport and emissive layers in electroluminescent devices.
Nanostructure of Electrically Conducting Polyaniline Prepared by a Novel Emulsion Polymerization Process
Authors: Liu J. , Kinlen P. J. , Graham C. R. 
Published: April 2011

AbstractA soluble polyaniline (PANI) salt with moderate conductivity was synthesized by a novel emulsion polymerization process. The conductivity of the processed PANI films can be substantially increased by treating the polymer films with surfactants or with low molecular weight alcohols. Transmission electron microscopy (TEM) images of thin polymer films revealed the existence of small islands of conducting PANI embedded in a non-conducting, dopant matrix. The conductivity of the PANI films is affected by the spatial distribution and the connectivity of these small islands. The conductivity enhancement observed upon treatment with surfactants is due to self-assembly of conducting PANI molecules into an interconnected network morphology. In the case of alcohol treatment the film conductivity is enhanced due to extraction of excess dopant phase and the subsequent densification of PANI islands to form highly conducting pathways.
New Polydiacetylenes with Visible Chromophoric Side Groups
Authors: Foley James L. , Shivshankar Venkataramani , Sandman Daniel J. 
Published: April 2011

AbstractIn the interest of obtaining crystalline polydiacetylene with absorption at longer wavelengths, new derivatives of 2,4-hexadiyne with planar, visible absorbing aromatic chromophores have been designed, synthesized, and thermally polymerized. The resulting polymers have a red shifted maximum with absorption extending to the infrared. Their Raman spectra show the usual polydiacetylene ene-yne structure, and X-ray powder diffraction reveals that the new polymers are crystalline.
Temperature Dependence of the Electrical Conductivity of Poly(Benzo[1,2-b:4,5-b'] Dithiophene-4,8-Diyl Vinylene) and Poly(Dodecylthiophene)
Authors: Hyer R. C , Pethe R. G. , Yogi T. , Sharma S. C. , Wang J. , Meline R. L. , Elsenbaumer R. L. , McCullough R. C. 
Published: April 2011

AbstractWe present results for the electrical conductivity (σ) of thin films of poly(benzo[1,2-b:4,5- b']dithiophene-4,8-diyl vinylene) (PBDV) and poly (dodecylthiophene) (PDDT) as a function of temperature in the range 15-295K. The polymers were doped with FeC13 and PF6 which resulted in electrical conductivities differing by two orders of magnitude at room temperature. We examine three sets of σ(T)-data by using the variable-range hopping (VRH) model that predicts a linear relationship between ln(T1/2σ) and T1/4. We observe a change in the slope of the ln(T1/2σ) vs T14 relationship in all three samples at low temperatures. We also analyze the temperature dependence of the resistivity of PBDV by using the thermal fluctuation-induced tunneling model.
UV Photoemission Study of Interfaces Related to Organic EL Devices
Authors: Sugiyama Kiyoshi , Seki Kazuhiko , Ito Eisuke , Ouchi Yukio , ISHII Hisao 
Published: April 2011

AbstractInterfacial electronic structures related to organic electroluminescent (EL) devices were studied by UV photoemission spectroscopy (UPS). The two classes of interfaces studied were: (1) interfaces in a typical multilayer device AI/AIq3TPD/ITO, where Alq3 is tris(8-hydroxyquinolino)- aluminum, TPD is N,N×-diphenyl-NN×-(3-methylphenyl)- 1, 1‘-biphenyl-4,4’-diamine, and ITO is indium tin oxide, and (2) TTN/metals and TCNQ/metals interfaces, where TTN is tetrathianaphthacene and TCNQ is tetracyanoquinodimethane. The UPS studies of the specimen formed by the successive deposition of TPD, Alq3, and Al on ITO revealed interfacial energy diagrams, with the vacuum level shift of - 0.25 eV (downward) and - 0.1 eV (downward) at the TPD / ITO and the Alq3 / TPD interfaces, respectively. The deposition of TTN and TCNQ on metals showed opposite direction of the shift of the vacuum level, with the positive and negative charge at the vacuum side. This can be explained by considering the chargetransfer between the metal and the organic molecule, with these directions being consistent with the electron donating and accepting ability of these molecules.
Control of Light-Emitting Polymer Devices Using Polymer/Polymer Interfaces
Authors: Epstein A. J. , Wang Y. Z. , Gebler D. D. , Fu D. K. , Swager T. M. 
Published: April 2011

AbstractWe present the use of polymer/polymer interfaces to control light-emitting polymer devices. Bilayer devices utilizing poly(9-vinyl carbazole) (PVK) as a hole transporting/electron blocking polymer together with a pyridine containing electron transporting layer show dramatically improved efficiency and brightness as compared to single layer devices. This is attributed to charge confinement and exciplex emission at the PVK/emitting polymer interface. The introduction of emeraldine base (EB) form of polyaniline (PAN) on both side of the emitting layer enables the device to work under both forward and reverse bias, as well as in AC modes. Interfaces play an important role in the operation of these devices. Furthermore, when the EB is replaced by sulfonated polyaniline (SPAN) on the cathode side and the emitting layer is properly modified to balance electron and hole transport, the device generates different colors of light, red under forward bias and green under reverse bias.
New Base-Dopable Well-Defined Poly-2,7-Fluorene Derivatives
Authors: Ranger M. , Leclerc M. 
Published: April 2011

AbstractWell-defined poly(2,7-fluorene) derivatives have been prepared through palladium-catalyzed couplings; using this versatile synthetic method, processable polyfluorenes have been obtained in good yields. In solution, these yellow polymers exhibit blue emission around 410 nm with high quantum yields. Moreover, novel acidic polyfluorene derivatives have been synthesized (e.g. poly(2,7'-(pentyl 9,9-dioctyl-7,2'-bifluorene-9'-carbonyl))) which show, upon base-doping, electrical conductivities of 10−2 − 10−3 S/cm. This new doping method for conjugated polymers could open the way to the preparation of air-stable electron-injecting electrodes. Polyfluorene derivatives show their potential to play a double function in the fabrication of LEDs, i.e. as ntype electrode and luminescent polymeric materials.
Electronic Properties of Poly(Para-Phenylenes) Under High Pressure
Authors: Graupner W. , Guha S. , Yang S. , Chandrasekhar M. , Chandrasekhar H. R. , Leising G. , Scherf U. , Müllen K. 
Published: April 2011

AbstractWe have studied the photoluminescence emission spectra of polycrystalline and amorphous powder samples of phenylene-type polymers and oligomers. In order to modulate both intrachain and interchain interactions these investigations were performed at hydrostatic pressures up to 70 kbar and in a tOmperature range of 20 to 300 K. We report characteristic changes of the emission spectrum which depend on both the molecular environment as well as the intramolecular bond configuration.
Structure and Physical Properties of EDT-TTF Salts
Authors: Kondo Tetsuo , Kushch Lyudmila A. , Yamochi Hideki , Saito Gunzi 
Published: April 2011

AbstractCharge-transfer salts of EDT-TTF with tetrahedral anions MX4 (M=Fe, Ga ; X=Cl, Br) were prepared. They are isostructural to each other (monoclinic P21/m) with the stoichiometry of 2:1. All of them are semiconductors having the conductivity at room temperature of 5 to 9 Scm−1 and activation energy of 40 to 170 meV. Since the calculated band structure of them indicate that they should be quasi one-dimensional metals, they were discussed from the point of structural deformation and strong electron correlation.
The Effect of RuO2/Pt Hybrid Bottom Electrode Structure on The Microstructure and Ferroelectric Properties of Sol-Gel Derived PZT Thin Films
Authors: Kim Seung-Hyun , Hong J. G. , Gunter J. C. , Lee H. Y. , Streiffer S. K. , Kingon Angus I. 
Published: April 2011

ABSTRACTFerroelectric PZT thin films on thin RuO2 (10, 30, 50nm)/Pt hybrid bottom electrodes were successfully prepared by using a modified chemical solution deposition method. It was observed that the use of a lOnm RuO2Pt bottom electrode reduced leakage current, and gave more reliable capacitors with good microstructure compare to the use of thicker RuO2/Pt bottom electrodes. Typical P-E hysteresis behavior was observed even at an applied voltage of 3V, demonstrating greatly improved remanence and coercivity. Fatigue and breakdown characteristics, measured at 5V, showed stable behavior, and only below 13-15% degradation was observed up to 1010 cycles. Thicker RuO2 layers resulted in high leakage current density due to conducting lead ruthenate or PZT pyrochlore-ruthenate and a rosette-type microstructure.
A Thickness Dependent Study of SrBi2Nb2O9 Thin Films
Authors: Pérez W. , Ching-Prado E. , Reynés-Figueroa A. , Katiyar R. S. , Ravichandran D. , Bhalla A. S. 
Published: April 2011

ABSTRACTThin films of SrBi2Nb2O9 (SBN) with thickness of 0.1, 0.2, 0.3 and 0.4 μm were grown by sol-gel technique on platinum/silicon substrates, and annealed at 800°C. Raman spectra of the samples present bands around 170,210, 272, 300,430, 580, 717, and 839 cm−1 which correspond to the SBN formation. The prominent Raman band around 839 cm−1, which is the Alg mode of the orthorhombic symmetry, is assigned to the symmetric stretching of the NbO6 octahedrals. The frequency of this band is found to shift at different places in the same sample, as well as from sample to sample. The frequency and width variations of the Raman bands are discussed in term of ions in non-equilibrium positions, which seem to be related with the crystallization degree in the SBN samples. Also, the Raman study indicates the presence of foreign sharp peaks, which are associated with the coexistence of phases other than SBN. The thickness dependence of the Raman spectra and the X-ray diffraction are also discussed. Finally, the experimental results of the SBN/Pt/Si films grown at 800°C are compared with those obtained at 650°C.
Retention Studies on Ferroelectric Media for High Data Storage Application
Authors: Yoo I. K. , Kim B. M. , Kim D. S. , Park S. J. 
Published: April 2011

ABSTRACTData retention may be affected by depolarization, domain stabilization (ageing or imprint), and fuzzy electric field among neighboring bits in relation to microstructures of ferroelectric media. In this paper, the smearing effect due to electric field between two adjacent bits was demonstrated. In order to minimize the smearing effect, ferroelectric media with the top electrode is proposed by which fuzzy electric field can be screened by bound charges in the electrode. Bit on electrode (BOE) technique was suggested for “Write” (local polarization) and “Read” on ferroelectric media with the top electrode (ferroelectric capacitor). It is noticed that a highly sensitive device such as single electron transistor is indispensable for measuring potential variation in the top electrode of the ferroelectric capacitor media.
Frequency Spectra of Fatigue of PZT and other Ferroelectric Thin Films
Authors: Du Xiaofeng , Chen I-Wei 
Published: April 2011

ABSTRACTPolarization and polarization fatigue of PZT and other ferroelectric thin films have been studied via the frequency spectra of D-E hysteresis. The coercive field (Ec) of PZT thin films has been found strongly dependent on the measuring frequency, while a relatively flat frequency response is observed with SrBi2Nb2O9 thin films. The different fatigue behavior can be attributed to such a difference in the frequency response. Physical models have been suggested to for domain wall movement in PZT and SrBi2Nb2O9 thin films. Based on these observations, a methodology has been proposed to evaluate the high frequency and fatigue properties of ferroelectric thin films.
Deposition and Electrical Characterization of Epitaxial Pb(Mg1/3Nb2/3)O3-PbTiO3 (70/30) Thin Films
Authors: Maria J-P. , Hackenberger Wes , Trolier-McKinstry S. 
Published: April 2011

ABSTRACT(001)-oriented heterostructures consisting of LaAlCO3 substrates, SrRuO3 bottom electrodes, and Pb(Mg1/3Nb2/3) O3-PbTiO3 (PMN-PT) piezoelectric actuators were deposited by pulsed laser deposition (PLD). 4-circle x-ray diffraction analysis confirmed the epitaxial growth of each layer. In general, the electrical properties were found to be very sensitive to the processing conditions, in particular, the growth temperature. At growth temperatures below ∼620°C, the temperature dependence of the dielectric constant and the onset of a hysteritic polarization were found to be depressed by as much as 80 °C. When growth temperatures were increased above 660°C, electrical properties with temperature dependencies more consistent with those of single crystals were observed.
Structural Characterization of a Series of New Ternary η-Nitride Compounds
Authors: Weil K. S. , Kumta P. N. 
Published: April 2011

ABSTRACTThe structures of four new tungsten based, ternary nitride compounds, Fe3W3N, Ni6W6N, Ni2W4N, and Fe4W2N, each prepared using a complexed precursor synthesis route, have been determined by Rietveld analyses of the respective powder x-ray diffraction (PXRD) data. Each compound crystallizes in a relatively complex cubic structure which is in general isostructural with the η-carbide structure. However, subtle structural differences which are compositionally dependent do exist between each nitride and these will be examined in detail in this paper.
A Comparison of Ferroelectric thin Films Prepared by Sol-Gel, Metalorganic Deposition and Photochemical Methods
Authors: Shi Y. , Blair S. L. , Yaroslavsky I. , Hill R. H. 
Published: April 2011

ABSTRACTThe process for generating films of Ba0.5Sr0.5TiO3, and PbZr0.48Ti0.52O3 by photochemical deposition from metal-organic thin films has been investigated. Films have also been prepared by metal-organic and sol-gel deposition for comparison with the photochemical method. All three methods could produce crystalline films of the target materials. Studies of the heating of the amorphous films prepared by each of the methods indicated that similar crystalline films could be prepared by the different methods. Under some conditions the photochemical methods gave the highest degree of orientation of the crystalline films.
Effect of Precursors and Stacking Structures on Crystallization of Multi-Layered Lead Zirconate Tit Anate Thin Films by Sol-Gel Method
Authors: Suzuki H. , Kondo Y. , Kaneko S. , Tsutsumi T. , Miura T. , Hayashii T. 
Published: April 2011

ABSTRACTFerroelectric tead zirconate titanate, Pb(Zrx Tibx)O3 (hereafter abbreviated as PZT), thin films were prepared by annealing precursor films of multilayered structures composed of alternating layers of PZT aiKL lead titanate (hereafter abbreviated as PT). This method (which we refer to as multi-seeding) was used in order to lower the processing temperature of PZT. The precursor films were prepared from alkoxide precursor solutions. Effects of zirconium to titanium ratios and stacking structures of the multi-layered precursor films on crystallization behavior were studied to improve the electrical properties of the resultant PZT thin films. Layers of PT were inserted between every PZT layer in order to seed the crystallization of the desired perovskite phase. PT has previously been shown to crystallize with a pure perovskite structure at temperatures as low as 450 °C. Precursor layers of PZT with different compositions, ranging from x = 1 to x = 0.53 were prepared. In this process, the compositions of the PZT precursors and/or the stacking structure, as well as the heating schedule, had a large effect on the crystallization behavior. Nucleation control of the PT seeding layer by changing the heating schedules played an important role in preparing perovskite PZT thin films at low temperatures. Dielectric properties of the resultant films depended on the compositions and annealing temperatures. It was demonstrated that the composition of the resultant PZT film was controllable in the multi-seeding process, and that dielectric properties of the resultant films were improved.
Electrodeposited CuInSe2 Thin Film Junctions
Authors: Raffaelle R. P. , Mantovani J. G. , Bailey S. G. , Hepp A. F. , Gordon E. M. , Haraway R. 
Published: April 2011

ABSTRACTWe have investigated thin films and junctions based on copper indium diselenide (CIS) which have been grown by electrochemical deposition. CIS is a leading candidate for use in polycrystalline thin film photovoltaic solar cells. Electrodeposition is a cost-effective method for producing thin-film CIS. We have produced both p and n type CIS thin films from the same aqueous solution by simply varying the deposition potential. A CIS pn junction was deposited using a step-function potential. Stoichiometry of the single layer films was determined by energy dispersive spectroscopy. Carrier densities of these films increased with deviation from stoichiometry, as determined by the capacitance versus voltage dependence of Schottky contacts. Optical bandgaps for the single layer films as determined by transmission spectrocopy were also found to increase with deviation from stoichiometry. Rectifying current versus voltage characteristics were demonstrated for the Schottky barriers and for the pn junction.
Microstructures in thin BaTiO3 Films by Hydrothermal Method
Authors: Hoffmann T. , Fuenzalida V. M. 
Published: April 2011

ABSTRACTBarium titanate microstructures are fabricated on silicon(100)/platinum substrates coated with photoresist and titanium by a combination of hydrothermal and lift-off techniques. The microstructures of 10μm width are well defined. The barium titanate films grow in its cubic phase. Analysis by means of x-ray diffraction and scanning electron microscopy shows that only a part of the titanium layer is affected by the hydrothermal reaction. This limitation may be overcome by application of electrochemistry.
Investigation on the Growth Mechanism of Zinc Oxide Film Prepared by Electrochemical Method
Authors: Lee Jaeyoung , Tak Yongsug 
Published: April 2011

ABSTRACTZnO thin films were potentiostatically deposited on ITO electrode in 0.1 M Zn(NO3)2 and the film growth mechanism was investigated by using FTIR and electrochemical quartz crystal microbalance(EQCM). Intermediates formed in the initial stage were identified as soluble zinc hydroxides and a critical concentration of OH was required for the ZnO to be deposited. A rapid growth rate of ZnO film observed in the presence of O2 was attributed to the higher cathodic current which produces OH
Relationship Between Catalytic Activity and Electrical Conductivity in the Nonstoichiometric Nickel Manganite Spinels
Authors: Laberty Christel , Alphonse Pierre , Rousset Abel 
Published: April 2011

ABSTRACTNonstoichiometric nickel manganite spinels NixMn3-x □3δ/4O4+δ, have been synthesised by calcination of mixed oxalates in air at 350°C. The variation of the electrical conductivity σ with partial pressure of O2 shows that these oxides are n-type semiconductors; σ also varies with the nickel content and has a maximum at x = 0.6. The intrinsic catalytic activity of these oxides for CO/CO2 conversion varies with nickel content and the most active catalyst is at x=0.6 where the conversion starts at room temperature. The variation of the catalytic activity and the electrical conductivity and the nickel amount are correlated. Apparent activation energies are very low (less than 20 kJ/mol) and remain the same for all these mixed oxides. Similarly, the reaction order with respect to O2 and CO does not depend on the nickel content (order/O2 ≈ 0; order/CO ≈ 0.6). A reaction mechanism involving formation of oxygen ions adsorbed and carbonate species is discussed.
A Field Emission Study of the Critical Parameters of Amorphous Carbon Films Deposited on a Variety of Carbonaceous Substrates
Authors: Burden A. P. , Forrest R. , Silva S.R.P. , Sealy B. J. , Amaratunga G.A.J. 
Published: April 2011

ABSTRACTThe field emission properties of a variety of nitrogen-containing hydrogenated amorphous carbon films have been characterised as a function of film thickness and substrate type. Identified trends have been discussed in terms of the optical band-gap and refractive index of the films, and the surface roughness of the substrates. In addition, carbon-based materials have been considered as inexpensive film-compatible substrates, and an in-situ oxygen plasma pre-treatment has been investigated as a means of changing the field enhancement factor of the system. We have achieved field emission with threshold voltages as low as 8 V μm−1, and we present data that supports the view that the electron emission from amorphous carbon is dependent on the nature of the back contact, and possibly the ease at which the film can be fully depleted, i.e. film thickness.
LCVD of CNx Layers from NH3,/CCI4. Mixture using CuBr Vapor Laser
Authors: Ivanov B. , Popov C. , Dimitrov D. , Shanov Y , Zambov L. , Georgiev M. , Peev G. 
Published: April 2011

ABSTRACTAmorphous CNx films were obtained on monocrystalline silicon substrates by direct writing laser induced chemical vapor deposition from CCI4 and NH3 using CuBr vapor laser. The main process parameters (scanning speed, laser power, background temperature) were varied in wide ranges. The deposition rates in the laser spot were in the range of 1 – 10 μm/s. Scanning electron microscopy showed that the layers had rather rough surface. The deposited films were composed of carbon, nitrogen, silicon and oxygen, as detected by AES and EDX analyses. Chemical bonding structure was investigated by FTIR and showed absorption bands corresponding to different chemical groups - CH, CH2, CH3, C=C, C=N, C=O, Si-O, Si-C, Si-N and C-N. The electrical measurements of the deposited films showed that their resistivity varied from 0.15 to 1.40 MΩ.cm and it was very sensitive to the deposition conditions.