bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transient Electroluminescence from PPV under Strong Voltage Pulses
Authors: Savvate'ev V. , Pogreb R. , Davidov D. , Chayet H. , Neumann R. , Avny Y. 
Published: April 2011

AbstractWe have studied the transient electroluminescence (EL) from poly(phenylenevinylene), PPV, as a function of electric field under strong electric pulses up to fields of E≈ 109 V/m with emphasis on (a) the time delay, τ, between the electric pulse and the onset of the EL emission pulse and (b) the EL intensity as a function of the field. A monotonic decrease of τ with increasing E is explained by an increase of the carriers mobility according to Frenkel- Poole model. The EL intensity at high fields is proportional to E3 suggesting that the contacts at the polymer-metal electrode interfaces are practically ohmic. We demonstrate significantly improved brightness, peak power and lifetimes for polymer-based light emitting diodes working under such a pulsed mode.
Passive Polarization Rotators for Nonlinear Optical Devices
Authors: Kowalczyk T. C. , Liu L-Y , Lackritz H. S. 
Published: April 2011

AbstractInitial experiments of a passive polymeric TE-to-TM polarization converter that utilizes laterally offset upper and lower poling electrodes to induce a 45° optical axis in the core of a nonlinear optical polymer waveguide are reported. By optimizing the device length, we have demonstrated polarization conversion efficiencies greater than 95% in devices as short as 240 um with negligible insertion loss.
Thermoreversible Gels of Polyaniline: Viscoelastic and Electrical Properties
Authors: Ikkala O. T. , Vikki T. , Ruokolainen J. , Hiekkataipale P. , Passiniemi P. , Mäkelä T. , Isotalo H. 
Published: April 2011

AbstractWe demonstrate that polyaniline (PANI) dissolved in dodecyl benzene sulphonic acid (DBSA) shows thermoreversible gelation. The dissolution has been performed in formic acid which allows particle-free complexes according to optical microscopy. Below the gelation temperature the materials are rubber-elastic in compression experiments, the storage modulus G' does not essentially depend on frequency, and the samples are electronically conductive. Above the gelation temperature, G' indicates flow-like behavior and drastically lower ionic conductivity is observed. These results suggest reversible, i.e. fusible, network formation. The properties are compared with gels consisting of camphor sulphonic acid (CSA) doped PANI dissolved in m-cresol which are poorly thermoreversible.
Electro-Optic Effects in Nanophase Polymer Dispersed Liquid-Crystal Systems
Authors: Blacker R. S. , Lewis K. L. , Mason I. , Sage I. , Webb K. 
Published: April 2011

AbstractResearch into electro-optic effects in nanophase polymer dispersed liquid crystal (PDLC) materials has highlighted their potential as materials for a new class of tuneable filters. The structures, based on UV cured phase separated composites, contain liquid crystal both as discrete nano-scale droplets, and as material dissolved in the polymeric host. The essential difference between these materials and more conventional PDLC's is the scale of the refractive index inhomogeneity which is considerably smaller than the wavelength of visible light. Based upon effective medium approximations, the composite thus acts as a single isotropic medium, whose average refractive index is dependant on the level of applied electric field. Tuneable filters have been fabricated using the composite material for use in the visible spectral band.
Functionalized Tetrathiafulvalene Derivatives and their Radical Cation Salts: Synthesis and X-Ray Crystal Structures
Authors: Bryce Martin R. , Moore Adrian J. , Batsanov Andrei S. , Chesney Antony , Wood Clare L. , Howard Judith A. K. 
Published: April 2011

AbstractWe report our investigations into tetrathiafulvalene (TTF) derivatives bearingN-methylthiocarbamoyl and halogen substituents which engage in intermolecular interactions in the solid state. The synthesis of new donors is presented, along with the X-ray crystal structures of some of these derivatives and their radical ion salts.
LECs Made of m-Lppp
Authors: Wenzl F. P. , Tasch S. , Gao J. , Holzer L. , Scherf U. , Heeger A.J. , Leising G. 
Published: April 2011

AbstractWe report the application of the blue light emitting conjugated polymer m-LPPP (methyl substituted laddertype poly(paraphenylene) ) in light emitting electrochemical cells. The active layer of the LEC consists of a blend of m-LPPP with the ionically conductive polymer PEO and LiCF3SO3 as ionic salt. Investigations of different concentrations of PEO and salt showed that the best LECs made of m-LPPP up to now where realised with an active layer consisting of a blend of m-LPPP:PEO:salt in the range of 20:10:3. In this case we are able to realise LECs with response times in the range of 30 μs. The I/U characteristics show low turn on voltages both for current and electroluminescence, but only in the case of ITO biased as a cathode. The initial electroluminescence spectra are quite the same as those for LEDs made of m-LPPP but turn into green after some time of operation.
Second-Order Nonlinear Optical Polymer by Directed Lithiation of Polyethersulfone
Authors: McCarron Harold E. , Walsh Christopher J. , Sen Rajashree , Mandal Braja K. 
Published: April 2011

AbstractDirected lithiation of a polyethersulfone and the reactions of the lithiated species have been investigated. This method provides a new route to second-order nonlinear optical polymers.
Magnetic Properties of a Binary Mixture of Paramagnetic Metallomesogens
Authors: Shimizu Y. , Tantrawong S. , Yoshida M. , Sugino T. 
Published: April 2011

AbstractMagnetic properties of a binary mixture of mesogenic tetraphenylporphyrin Cu(II) and VO(IV) complexes are reported. These mesogens show two lamellar mesophases (DL and DLC) and a binary phase diagram revealed that each mesophase is miscible. The magnetic properties were investigated by magnetization measurements using SQUID. It was found that the magnetization of 1:1 mixture (mole% base) was larger than those of the pure compounds belowca. 190 K, whilst 1:3 and 3:1 mixtures showed the decrease of magnetization in the full range of temperature in which the measurements were carried out. It was shown that χ−1vs. T plots did not obey Curie-Weiss law. For the VO(IV) complex and 1:1 mixture, stepwise changes could be recognized at the temperatures corresponding to the phase transitions. 1:1 mixture as well as Cu(II) and VO(IV) complexes totally involve antiferromagnetic interaction. However, ferromagnetic behavior in χ−1vs. T plots was seen about DL- DLCphase transition.
New Luminescent PPV Derivatives for Led Applications
Authors: Chuah B.S. , Cacialli F. , Davies J. E. , Feeder N. , Friend R. H. , Holmes A. B. , Marseglia E. A. , Moratti S. C. , Brédas J.-L. , Santos D.A. dos 
Published: April 2011

AbstractA new poly(phenylenevinylene) [PPV] derivative 8 with dialkoxy substituents at the 2,3- positions of the phenylene ring of the polymer backbone has been prepared. This exhibited significantly different properties compared with the typical 2,5-dialkoxy substituted PPV derivatives. The polymer is not only significantly blue-shifted in its optical and luminescence properties but also has high photoluminescence (PL) and electroluminescence (EL) efficiencies. Investigation of the model oligomer 11 offers insight into this interesting behavior.
Thin Film of Conjugated Schiff-Base as Ultrahigh Density Data Storage Material
Authors: Yang W. J. , Yang Q. C. , Lu H. G. , Chen H. Y. , Hou S. M. , Ma L. P. , Zhang H. X. , Xue Z. Q. , Pang S. J. 
Published: April 2011

AbstractN-(3-nitrobenzylidene)-p-phenylenediamine (NBPDA) was used as ultrahigh density data storage medium by scanning tunneling microscope (STM) technique. Data marks of 1.4nm in diameter were written by applying voltage pulses between the STM tip and the substrate. Structures of single crystal and thin films were characterized by IR, UV–Vis, XRD, STM and verified by DFT quantum chemical calculation.
Polydomain Structure of Epitaxial PbTiO3 films on MgO
Authors: Alpay S. P. , Prakash A. S. , Aggarwal S. , Ramesh R. , Roytburd A. L. , Shuk P. , Greenblatt M. 
Published: April 2011

ABSTRACTA PbTiO3(001) film grown on MgO(001) by pulsed laser deposition is examined as an example to demonstrate the applications of the domain stability map for epitaxial perovskite films which shows regions of stable domains and fractions of domains in a polydomain structure. X-ray diffraction studies indicate that the film has a …c/a/c/a… domain structure in a temperature range of °C to 400°C with the fraction of c-domains decreasing with increasing temperature. These experimental results are in excellent agreement with theoretical predictions based on the stability map.
An Optimized Process and Characterization of Pb(Zr,Ti)O3 Ferroelectric Capacitor for 1T/1C Ferroelectric RAM
Authors: Shin Dong-Won , Shin Soo-Ho , Lee Jin-Woo , Park Hong-Bae , Chun Yoon-Soo , Lee Mi-Hyang , Jung Dong-Jin , Hwang Yoo-Sang , Koo Bon-Jae , Lee Sung-Young , Kim Kinam 
Published: April 2011

ABSTRACTAn optimized process of Pb(Zr,Ti)O3(PZT) ferroelectric capacitor has been investigated in order to develop a highly scaleable 1T/1C ferroelectric random access memory. The PZT ferroelectric capacitor, Pt/PZT/Pt stack, was formed on the TiO2/SiO2/Si substrate. The PZT thin films were prepared by conventional sol-gel multi-coating method. Physical and electrical properties of the PZT ferroelectric capacitors were characterized by XRD, SEM, TEM and RT6000S, respectively.It was revealed that the microstructure of PZT thin film is strongly influenced by sol-gel coating process, especially depending on coating methods of the first PZT layer. The second phase was observed in the PZT thin films, which is found to be pyrochlore phase. The size and density of pyrochlore phase were significantly reduced by modifying the coating methods of first PZT layer. Microstructure of PZT thin film capacitors was evaluated in detail along with electrical properties such as remnant polarization, coercive electric field, and dielectric leakage. The sensing Pr window was also introduced for proper sensing margin in IT/1C ferroelectric random access memory. This concept is well verified by 64Kb 1T/1C ferroelectric random access memory.
Electrical Properties of MFS-FETs using SrBi2 Ta2O9 Films Directly Grown on Si Substrates by Sol-Gel Method
Authors: Tokumitsu E , Fujii G. , Ishiwara H. 
Published: April 2011

ABSTRACTSrBi2Ta2O9(SBT) films have been prepared by the sol-gel technique on n-Si(100) substrates and nonvolatile memory operation of a metal-ferroelectric-semiconductor field effect transistor (MFSFET) using the SBT/Si structure has been demonstrated. Ploy-crystalline SBT films can be obtained on Si substrates and it is shown by the secondary ion mass spectrometry (SIMS) that the inter-diffusion between SBT and Si is suppressed even though high annealing temperature is required for the SBT film growth. Then the SBT/Si MFSFETs have been fabricated. Drain current - gate voltage characteristics clearly show hysteresis loops due to the ferroelectric nature of the SBT film. It is demonstrated that the drain current can be controlled by the “write” pulse, which was applied before the measurements, even at the same “read” gate voltage. Memory retention characteristics of SBT/Si MFSFETs are also presented.
Kinetics of Reactions Relevant to the Chemical Vapor Deposition of Indium Compounds
Authors: Allendorf M. D. , McDaniel A. H. 
Published: April 2011

ABSTRACTThe kinetics of trimethylindium pyrolysis are investigated in a flow reactor equipped with a molecular-beam mass-spectrometric sampling system. Data are analyzed using a new computational approach that accounts for heat and mass transport in the reactor. The measured activation energy, 46.2 kcal mol−1, is in good agreement with previously reported values.
Effects of Reaction Conditions on Deposition of Ferrites from Alkaline Metal Hydroxide Gels
Authors: Schoch Karl F. , Vasilow Theodore R. 
Published: April 2011

ABSTRACTFormation of ferrites from aqueous solution of metal salts is a well known process involving precipitation of metal hydroxides followed by oxidation of the resulting gel. The purpose of the present work was to determine the effects oxygen flow rate on the progress of the reaction and on the structure and properties of the resulting precipitate. The reaction was carried out at 70°C with pH of 10.5 and oxygen flow rate of 2,4, or 8 standard liters per hour. The progress of the reaction was monitored by following the oxidation-reduction potential of the solution, which changes dramatically after the Fe(II) is consumed. The reaction rate increased with increasing oxygen flow rate. The Mg content of the precipitate was lower than that of the reaction mixture, possibly because of the pH of the reaction mixture. X-ray diffraction and infrared spectroscopy confirmed formation of a ferrite under these conditions.
Synthesis and Electro-Optical Properties of Potassium Titanyl Phosphate thin Films by Sol-Gel Method
Authors: Zhang Jianping , Lee Burtrand I. , Wang Feiling , Leitheiser Melvin A. 
Published: April 2011

ABSTRACTPotassium titanyl phosphate, KTiOPO4 (KTP), thin films were prepared by sol-gel process. The structural evolution of KTP thin films was investigated by means of DTA/TGA, XRD, and FT-IR. The electro-optical results show that KTP thin films have a refractive index of 1.8 and large quadratic electro-optical coefficient of R=2.50643*10−16 and have potential applications for electro-optical devices.
Removal of Titanium Oxide Grown on Titanium Nitride and Reduction of VIA Contact Resistance using a Modern Plasma Asher
Authors: Boumerzoug Mohamed , Xu Han , Bersin Richard , Mascher Peter , Balcaitis Ginutis 
Published: April 2011

ABSTRACTIn making multi-level interconnects, a via layer is generally made of a dielectric layer grown on a TiN/AlSiCu/TiN metal stack. The via contact hole to the lower level metal is first etched after metal patterning and intermetal oxide deposition, then the resist mask for via etch is stripped in an oxygen plasma at high temperature before filling the via with tungsten or aluminum. However, during the resist stripping process, the titanium nitride (TiN) is exposed to oxygen radicals and becomes oxidized. This oxidized surface leads to high via resistance and may cause yield loss and poor adhesion of the subsequently deposited metal. Thus, the oxide layer must be removed completely before filling the via hole.Utilizing a modern asher and combining microwave downstream plasma and low damage RIE we have successfully developed an integral process to strip the resist and to remove any oxidized TiN film. This process also gives clean vias that are free of polymer residues from the etching process.Samples were characterized using Auger electron spectroscopy (AES), scanning electron microscopy (SEM), ellipsometry and via resistance measurements. The AES depth profile measurements and ellipsometry show clearly that a titanium oxide has grown onto TiN during the oxygen downstream ashing and is completely removed when adding the RIE step. The electrical measurements show that the resistance of vias cleaned with this two step process in a single tool is comparable to that of vias cleaned with Ar sputtering using a separate tool after the oxygen ashing process.
Epitaxial ZnO Piezoelectric Films for RF Filters
Authors: Emanetoglu Nuri W. , Lu Yicheng , Gorla Chandrasekhar , Liu Ying , Liang Shaohua , Mayo William 
Published: April 2011

ABSTRACTZnO has high piezoelectric coupling coefficient and acoustic velocity; therefore, it is an attractive material candidate for high frequency and low loss filters. Piezoelectric ZnO thin film based RF devices offer the advantages such as low power consumption, circuit miniaturization and cost reduction through integration with main stream MMIC technology. We report CVD growth of epitaxial ZnO thin films on R-sapphire substrates. X-ray diffraction techniques have been used to study the crystallinity and orientation of the films, as well as the epitaxial relationship between the films and the substrate. High-resolution cross-sectional TEM reveals the atomically sharp interface structure. As grown ZnO films exhibit dominant n-type conductivity due to the oxygen vacancies. Excellent piezoelectricity has been achieved through a multi-step Li diffusion under oxygen ambient. Surface Acoustic Wave (SAW) filters with 10-micron wavelength have been fabricated. Low insertion loss and high piezoelectric coupling coefficient have been observed.
Microstructural and Photoluminescence Studies on Europium Doped Yttrium Oxide Films Synthesized by Metallorganic Vapor Deposition
Authors: Hirata G. A. , McKittrick J. , Yi J. , Pattillo S. G. , Salazar K. V. , Trkula M. 
Published: April 2011

ABSTRACTThe microstructural and luminescence properties of europium doped yttrium oxide (Y2O3:Eu) thin films deposited by metallorganic chemical vapor deposition are presented in this work. It was found that surface morphology, crystallinity and photoluminescent emission properties are strongly dependent on substrate temperature during deposition. The depositions were carried out in a stainless steel chamber using yttrium and europium 2,2,6,6,-tetramethyl–3,5-heptanedionates as volatile precursors and O2 as the reactant gas. Post-annealing increased the crystallite size and decreased the lattice parameter, resulting in an increased photoluminescent emission intensity.
Mechanically Alloyed Nickel-Zirconium as a Heterogeneous Catalyst and a Catalyst Precursor
Authors: Brower W. E. , Montes A. J. , Pradlow K. A. , Bakker H. , Moleman A. C. , Yang H. 
Published: April 2011

ABSTRACTNiZr powders produced by mechanical alloying become active NO decomposition catalysts after an activation period in reaction conditions. Although the initially glassy structure exhibits a high activity, the NiZr powder becomes temporarily inactive. After about 10 hours in reaction conditions at 673 K, the powder again becomes active with a lower, but still substantial turnover frequency for NO decomposition. Oxygen produced by the reaction appears to be consumed by the catalyst during this second period of activity.
Field Emission From Tetrahedrally Bonded Amorphous Carbon as a Function of Surface Treatment and Contact Material
Authors: Milne W. I. , Robertson J. , Satyanarayana B. S. , Hart A. , Kleinsorge B. 
Published: April 2011

ABSTRACTIn order to test whether field emission from tetrahedrally bonded amorphous (ta-C) is affected by the back contact material we have carried out a series of emission experiments on Filtered Cathodic Vacuum Arc (FCVA) produced ta-C films. The measurements were made on identical films of approximately 25 nm thickness which have been grown simultaneously on various substrates of different work function. For these experiments the substrates used were p-type c-Si, n-type c-Si, SnO2, tungsten, gold, lead, aluminium, molybdenum, chromium and titanium. Threshold fields for emission were generally in the range of 5–15 V/micron and showed no direct dependence on back contact material work function. Films grown on Ti and W however had much higher threshold fields in the range 30–35 V/micron and this is thought to be associated with the native oxide which was present between the back contact and the ta-C film. As grown ta-C is also known to have a 1–2 nm thick sp2 rich layer on its surface and this layer may also have some effect on field emission. The layer was etched in either an O2 or H2 plasma and both etched surfaces led to improved emission efficiency.
Field Emission from Nitrogen-Doped Diamond Film
Authors: Park M. , Bergman L. , Choi W. B. , Sowers A. T. , Nemanich R. J. , Hren J. J. , Cuomo J. J. 
Published: April 2011

ABSTRACTNitrogen-doped diamond films were prepared for the first time using melamine (C3H6N6) as the nitrogen source. To explore the differences in the films produced with different precursors, nitrogen-doped films were also produced using pure nitrogen gas as the source. Since melamine has a ring structure with pre-existing C-N bonds, the incorporation of nitrogen on substitutional sites of diamond lattice are expected. Relatively large amounts of substitutional nitrogen were successfully doped into diamond without degrading its quality. However, when pure nitrogen gas was used as a doping source, the quality of the diamond was not as high as the sample doped with nitrogen by melamine. Raman spectroscopy, photoluminescence spectroscopy (PL), and field emission measurements were carried out to characterize the samples. Nitrogen-doped diamond samples did not exhibit any significant reduction in turn-on fields. It is suggested that nitrogen doping has only a minor effect on the field emission properties of the diamond films.
Raman Spectroscopy of Amorphous Carbon
Authors: Tallant D. R. , Friedmann T. A. , Missert N. A. , Siegal M. P. , Sullivan J. P. 
Published: April 2011

ABSTRACTAmorphous carbon is an elemental form of carbon with low hydrogen content, which may be deposited in thin films by the impact of high energy carbon atoms or ions. It is structurally distinct from the more well-known elemental forms of carbon, diamond and graphite. It is distinct in physical and chemical properties from the material known as diamond-like carbon, a form which is also amorphous but which has a higher hydrogen content, typically near 40 atomic percent. Amorphous carbon also has distinctive Raman spectra, whose patterns depend, through resonance enhancement effects, not only on deposition conditions but also on the wavelength selected for Raman excitation. This paper provides an overview of the Raman spectroscopy of amorphous carbon and describes how Raman spectral patterns correlate to film deposition conditions, physical properties and molecular level structure.
Structural Characterization of the Thermal Evolution of Tetrahedrally Coordinated Amorphous Carbon Films
Authors: Martinez-Miranda L. J. , Sullivan J. P. , Friedmann T. A. , Siegal M. P. , DiNardo N. J. 
Published: April 2011

ABSTRACTWe present the results of a post-deposition annealing structural study on amorphous tetrahedrally-coordinated carbon (a-tC) films on Si(100) prepared by pulsed-laser deposition. Films as-deposited and post-annealed at 200, 300, 400, 500 and 600 °C, respectively, are studied using combined x-ray reflectivity and low-angle scattering measurements. The scans are fit to the Fresnel equations to obtain values for average film density, film and interface thickness, and film and interface roughness. We observe a correlation between the evolution of film density, roughness and the spacing of quasi-periodic structures in the films as a function of annealing temperature. We relate the evolution of these structural features with previous measurements of the resistivity and the observed stress release in these films.
Lattice Strains in Gold and Rhenium Under Non-Hydrostatic Compression
Authors: Duffy T. S. , Shen G. , Heinz D. L. , Ma Y. , Hemley R. J. , Mao H. K. , Singh A. K. 
Published: April 2011

ABSTRACTLattice strains have been measured as a function of the angle, ψ, from the diamond cell stress axis in a sample of gold and rhenium at pressures of 15–37 GPa. Experiments were conducted using X-ray transparent gaskets made from beryllium. The differential stresses supported by gold and rhenium have been characterized to 37 GPa. It is also shown that proper choice of the diffraction geometry allows recovery of a quasi-hydrostatic compression curve under these highly non-hydrostatic conditions. X-ray elastic moduli have also been determined, and while good agreement with previous data is achieved for gold, there is a large discrepancy between the present results and extrapolated ultrasonic data for rhenium.