bluuebunny/crossref_metadata_2025_split huggingface dataset:
Defect and Raman Spectroscopy of Chemical Vapor Deposition Grown Diamond Films
Authors: Perez J.M. , Stallcup R.E. , Akwani I.A. 
Published: April 2011

ABSTRACTUsing photoelectron emission and Raman spectroscopy, we characterize normally unoccupied states that have an energy 2.41-2.71 eV below the conduction band of polycrystalline diamond films. The films are grown using chemical vapor deposition with methane to hydrogen gas concentrations of 0.10%, 0.20%, 0.30%, 0.45%, 0.60% and 0.70%. Photoelectron emission is performed using visible light from an argon laser. The light is focussed on a 5-10 µm diameter area of the sample. The emitted electrons are collected with high efficiency using a microchannel plate detector. Raman spectroscopy is performed simultaneously with photoelectron emission to determine the morphology and diamond versus graphite content of the photoelectron emission area. The photoelectron emission rate is observed to have a quadratic dependence on the incident light power showing that the photoelectron emission process is a two-photon process involving the excitation of electrons from normally unoccupied states. The photoelectric yield versus incident photon energy, and the photoelectric yield as a function of methane concentration are presented.
Analysis of Measured I(V) Relations for Electron Emission from Insulating Diamond Films on Various SI Substrates
Authors: Jensen K. L. , Göhl A. , Müller G. 
Published: April 2011

ABSTRACTIn this work, we shall analyze the performance of a geometrical interface roughness model to estimate current from p-type silicon into insulating diamond and compare the performance of that model to experimental data. A minimum number of adjustable parameters are invoked. While the model qualitatively accounts for trends in the experimental data, in particular, the shift from negative to positive slope on a Fowler Nordheim plot of the I(V) data, it does so at the expense of demanding ellipsoid parameters that appear to be unreasonable. We therefore conclude that a simple geometrical field enhancement model of interface roughness is insufficient to account for the current observed, and thus the theory must be augmented by a more comprehensive electron transport model at the interface.
Intense UV-Visible-IR Adjustable Photoluminescence from Silicon-rich Oxynitride Layers Prepared by Plasma Enhanced Chemical Vapor Deposition
Authors: Pei Zingway , Chung Y.J. , Hsiao H.L. , Hwang H.L. 
Published: April 2011

ABSTRACTThe intense UV-visible-IR adjustable light emissions from silicon-rich oxynitride thin films without any thermal annealing were observed at room temperature under a 325 nm He-Cd laser excitation. The silicon-rich oxynitride thin films were deposited by plasma enhanced chemical vapor deposition (PECVD) with the mixture of 5% Ar diluted silane and nitrous oxide gases. The strong naked-eye recognizable photoluminescence (blue-white-red) could be adjusted by changing the process gas flow ratio τ =([SiH4]/[N20]). To the best of our knowledge, intense and adjustable UV-blue light emissions in the as-deposited thin films are first reported in this work. The Fourier Transform infrared (FTIR) spectroscopy was applied to investigate the microstructure-bonding configurations, in which silicon polysilane related bonding at 830-890 cm' present that silicon complex, exists along with the Si-O-Si bonding. X-ray photoelectron spectroscopy was used to investigate the binding configuration, the binding energy of Si 2p appearing at 99.3 eV was indicative of formation of the silicon clusters. As a consequence, we suppose that the visible-IR lights emissions might possible be strongly related to silicon clusters formation in the films and the intense UV emissions might come from the oxygen-related defects.
Photoconductivity and Luminescence Efficiency of Rare Earth Activated Insulating Materials
Authors: Yen William M. 
Published: April 2011

ABSTRACTIn this article, we discuss the nature of the high lying states in rare earth activated systems and their effect on the luminescence efficiency of these systems. We show that by comparing the optical spectra of these materials with complementary measurements such as photoconductivity (PC), the absolute energy level structure of the ions with respect ot the intrinsic bands of the host can be determined. We propose new measurements which will provide insight on the manner in which energy delocalizes in activated solids.
Cathodoluminescence of Quartz, Silica and Thin Amorphous SiO2 Layers
Authors: Barfels T. , Fitting H.-J. , von Czarnowski A. 
Published: April 2011

ABSTRACTCathodoluminescence and its temperature-dose behaviour of different modifications of SiO2 are presented. The detected luminescence bands are attributed to three optical active luminescence centers: the twofold coordinated silicon center (=Si:), the non-bridging oxygen hole center (NBOHC) and the self-trapped exciton (STE). The experiments are correlated with infrared absorption measurements. Existing structural models are discussed with reference to our results.
Optical Properties and Characterization of Eu3+ Activated Pmma:Paac Copolymer Samples: Eu Concentration Effects
Authors: F. R. Sosa , Flores M. , Rodríguez T. R. , Munoz F. A. 
Published: April 2011

ABSTRACTSamples of Eu3+ -activated PMMA:PAAc copolymers were prepared in order to investigate their spectroscopic properties. The densities, refractive indices, UV-Visible absorption and emission spectra and fluorescence decay times were obtained experimentally. These data were used in conjunction with Judd-Ofelt theory to calculate the spontaneous emission probabilities and branching ratios, as a function of the europium content. The range of the concentration was 0.1 to 2.5 % mol. Our results are combined with previous information on the optical properties of rare-earth activated polymers in order to get a better understanding of the role played by the Eu3+ ions on the polymerization process in our samples.
Effect of Co-Doping on the Photoluminescent Behavior and Electronic Structure of Zinc Silicate Phosphors
Authors: Park H.D. , Sohn K.-S. , Cho B. , Chang H. 
Published: April 2011

ABSTRACTThe present study aims at investigating the effect of co-doping on the photoluminescence(PL) property of Zn2SiO4:Mn phosphor. Experimental data were interpreted by the first principles embedded-cluster discrete variational (DV)-Xα method.
Host Excitation and Luminescence in Large Band Gap Oxides
Authors: Schmidt P.C. , Sticht J. , Eyert V. , Mishra K.C. 
Published: April 2011

ABSTRACTA good understanding of the electronic states near the band gap of large gap materials is essential for designing phosphors when the energy of exciting radiation exceeds the band gap. This is particularly true when phosphors are designed for application in rare gas discharges with vacuum UV (VUV) radiation. Using density functional ab initio methods (augmented spherical waves and full potential linear muffin-tin orbitals), we have analyzed the nature of host excitations near the band gap energy for a number of complex oxides: LaPO4, AIPO4, BaB2O4, YBO3 and LuBO3 and the common trends in the optical transitions in borates and phosphates and the corresponding binary oxides La2O3, Lu2O3, Y2O3, BaO, B2O3 and P2O5. We have also studied the nature of impurity states of Eu3+ and Pr substituting y3+, in large gap oxides. The studies show how the relative ordering of the one-electron states of activator ions with respect to band states of the host lattice may affect their luminescence properties under host excitation.
Luminescence of Cds Nanoparticles Doped and Activated With Foreign Ions
Authors: Huang J. M. , Murphy C. J. 
Published: April 2011

ABSTRACTNanoparticles of CdS (5.0 nm diameter) are prepared in aqueous solution, and copper or silver ions are incorporated into the nanoparticle lattice (doped) or adsorbed to the nanoparticle surface (activated). The materials are characterized by ultraviolet-visible spectroscopy, photoluminescence spectroscopy, transmission electron microscopy and electron diffraction. The photoluminescence efficiency of the materials is affected by the concentration of the foreign ion. The effect of spatial location (doped vs. activated) on the spectral distribution of the emission are modest. Photodecomposition of copper-doped CdS is suppressed compared to CdS alone.
Theoretical Description of Luminescent Effects in β,β-Di(4'-formylphenylethynyl)-4-ethynylstyrene
Authors: Salcedo R. , Guadarrama P. , Sansores L.E. , Fomine S. , Fomina L. 
Published: April 2011

ABSTRACTTheoretical calculations at HF/6-31G(d) level were carried out on a series of fully conjugated compounds (4-ethynylbenzaldehyde, β,β-dibromo-4-ethynylstyrene, β,β-Di(4'-formylphenylethynyl)-4-ethynylstyrene and its dimmer) to understand the source of blue emission observed in oligomers of the first and second generation in chloroform solutions. The frontier orbitals are distributed through the framework of the molecules (benzene rings, double and triple bonds and chromophores). Additionally, a configuration interaction approach was applied over β,β-Di(4'-formylphenylethynyl)-4-ethynylstyrene (compound 3) at CIS/6-31G(d) level to modeling excited states and simulate the UV-VIS spectrum experimentally obtained. Calculated transitions corresponded to S0→S1 which are, presumably, responsible for the fluorescence observed.
Design and Optimization of Chromophores for Liquid Crystal and Photorefractive Applications
Authors: Twieg R. J. , He M. , Sukhomlinova L. , You F. , Moerner W.E. , Diaz-Garcia M.A. , Wright D. , Casperson J.D. , Wortmann R. , Glania C. , Krämer P. , Lukaszuk K. , Matschiner R. , Singer K. D. , Ostoverkhov V. , Petschek R. 
Published: April 2011

ABSTRACTOrganic chromophores have been exploited for a wide range of discrete optical and electronic functions as well as a growing number of combined opto-electronic functions. We are pursuing development of organic and polymer materials for a range of applications that require properties including liquid crystallinity, second order optical nonlinearity, photorefractivity and, more recently, special nonlinear optical behavior involving molecular chirality.
Photorefractive Polymers With High Speed
Authors: Peyghambarian N. , Ferrio K. B. , Herlocker J. A. , Hendrick E. , Guenther B. D. , Mery S. , Zhang Y. , Kippelen B. 
Published: April 2011

ABSTRACTRapid progress in photorefractive polymers includes new materials with improved response rates. We briefly review recent developments in this rapidly evolving area and report grating formation with a 2-millisecond time-constant, the fastest reported to date in any photorefractive polymer.
1.5 νm Luminescence from ErQ based Organic Light Emitting Diodes
Authors: Curry R.J. , Gillin W.P. 
Published: April 2011

ABSTRACTOrganic light emitting diodes have been fabricated using erbium tris(8-hydroxy-quinoline) as the emitting layer and N, N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) as the hole transporting layer. Room temperature electroluminescence was observed at 1.5 νdue to intra-atomic transitions between the 4I13/2; and 4I15/2; levels in the Er3+, ion. These results make the possibility of producing silicon compatible 1.5 νm technology based on such devices a reality.
Frequency Resolved Photoluminescence (PL), Delayed Fluorescence and Triplet-Triplet Annihilation In 7Φ-Conjugated Polymers
Authors: Partee J. , Frankevich E. L. , Uhlhom B. , Shinar J. , Ding Y. , Barton T. J. 
Published: April 2011

ABSTRACTThe delayed fluorescence of poly(p-phenylene vinylene) (PPV) and poly(p-phenylene ethynylene) (PPE) derivative solids and frozen solutions at 20 K is described. It provides strong evidence for triplet-triplet annihilation to singlets excitons accounting for up to ∼3% of the total emission in PPV films and ∼1.5% in PPE powder. It also yields triplet lifetimes of 70 and 110 μs in PPV films and frozen solutions, and ∼200 and ∼500 μs in PPE powder and frozen solutions, respectively.
Second Order Nonlinear Optical Thin Films Fabricated from Electric Field-Assisted Electrostatic Self-Assembled Monolayer Method
Authors: Liu Y. , Claus R.O. , Marciu D. , Figura C. , Heflin J.R. 
Published: April 2011

ABSTRACTA new method for the build-up of non-centrosymmetric multilayer thin films has been developed for the first time using an electric field-assisted electrostatic self-assembled monolayer (EF-ESAM) technique. An increase by 116% of the second-harmonic intensity of the films has been observed in comparison with that of ESAM film.
Structure-Property Relationships in Organic Nonlinear Optical Materials
Authors: Breitung Eric M. , McMahon Robert J. 
Published: April 2011

ABSTRACTTuning the degree of bond-length alternation in organic nonlinear optical materials is a powerful paradigm for the design of organic materials with large molecular hyperpolarizabilities (β). Several research groups have employed this paradigm in the design and synthesis of NLO materials incorporating donor-acceptor polyenes. Increased bond-length alternation in polyenes leads to decreased barriers to rotation about C=C bonds and, hence, increased conformational flexibility. Since the degree of bond-length alternation is solvent dependent, so is the degree of conformational flexibility. In an effort to probe the influence of conformational flexibility on NLO response, we synthesized a series of simple donor-acceptor polyenes that are either conformationally flexible (la, 2a, 3a) or rigid (1b, 2b, 3b). For each pair of molecules ZINDO sum-over-states calculations predict a larger value of βμ, for the conformationally flexible isomer, but EFISH measurements (CHCl3) display mixed results. Various explanations for this behavior will be considered.
Optical Nonlinear Properties of Self-Assembled J-Aggregates Cyanine Molecules Doped in Spin-Casted Silicate Films
Authors: Honma I. , Watanabe T. , Zhou H.S. , Mito A. , Asai K. , Ishigure K. 
Published: April 2011

ABSTRACTJ aggregates cyanine dyes have been successfully doped directly in sol-gel derived silicate thin films. The films are transparent, homogeneous and stable at room temperature. The J aggregates successfully incorporated in rigid SiO2 framework were characterized by absorption spectroscopy and fluorescence microscopy. The films are expected to be useful for non-linear optical devices, multiple photon recording and photoelectric cell.
Electromigration Reliability Study of a GMR Spin Valve Device
Authors: Shingubara S. , Takeda Y. , Sakue H. , Takahagi T. , Verbruggen A. H. 
Published: April 2011

AbstractElectromigration reliability of a GMR spin valve device has been investigated at elevated temperatures at various DC current densities. Significant degradation of the magnetoresistance was observed when the current density was higher than 20 MA/cm2. Either the electromigration induced damage or the rotation of the magnetization vector of the Mnlr anti-ferromagnetic layer are possible mechanisms of degradation. Furthermore, significant voiding caused by electromigration and thermal gradient induced atomic motion was observed at current densities higher than 35 MA/cm2. High-resolution temperature distribution measurements by scanning thermal probe microscopy revealed the existence of a huge temperature gradient of 106°C/cm, which is a strong driving force for atomic diffusion.
Fracture of a Lead-Tin and a Tin-Silver Solder Under Combined Tensile Shear Loading
Authors: Manoharan M. , Siow K. S. 
Published: April 2011

AbstractThe increasing demands on solder joints have made it imperative that they perform not only their traditional role of electrical connection but also possess good mechanical integrity. One such key mechanical property is the shear strength of the solder. A number of specimen geometries can be used to evaluate the shear strength of solders, each with its advantages and limitations. However, these geometries do not provide information about the notched fracture strength of the solder under shear. Studies on a number of ductile materials have indicated that in many of these materials shear is the preferential mode of fracture even when the imposed load is a combination of tensile and shear. This study, which is part of a larger project on the failure of materials under combined tensile-shear loading, uses a modified compact tension specimen to measure the appropriate failure criterion. It is shown that the fracture of solders under these conditions follows the general principles of a mixedmode fracture mechanism map and shear is the preferred mode of failure.
Effects of Thickness and Oxygen Content on Thermomechanical Behavior of Thin Cu Films Passivated with Ain
Authors: Shu J. , Clyburn S. , Mates T. , Baker S. P. 
Published: April 2011

AbstractThe thermomechanical behavior of a Cu thin film can be dramatically influenced (“oxygen effect”) by exposing the film to a small amount of air or oxygen prior to passivation. Film exposure is accomplished by breaking vacuum at some point prior to passivation. When the top surface is exposed immediately before passivation, the oxygen effect is produced when the passivation material is Si3N4, but no effect is seen with AIN passivations. However, the effect is seen in AIN passivated films when the Cu film surface is exposed to air or O2 and additional Cu is deposited before passivation. This suggests that conditions at the film/passivation interface are an important factor in this anomalous plasticity effect. We have investigated the effects of film thickness and oxygen concentration on these behaviors by preparing films with different thicknesses and oxygen contents for thermomechanical analysis. The thermomechanical behavior is correlated with secondary ion mass spectrometry (SIMS) data that shows oxygen concentration vs. film depth. The presence of the “oxygen effect” in thermomechanical behavior is found to be correlated with an increased oxygen concentration near the film/passivation and film/barrier interfaces.
Environmental Effects on Cu/SiO2 and Cu/Ti/SiO2Thin Film Adhesion
Authors: Tymiak N. I. , Li M. , Volinsky A. A. , Katz Y. , Gerberich W. W. 
Published: April 2011

AbstractFor several microelectronics applications, Cu/dielectric adhesion is a key reliability issue. Either electroplating or local galvanic coupling under moist operating conditions may result in hydrogen induced interface weakening. The present study compared hydrogen effects on Cu/SiO2 adhesion for sputter deposited f'dms with and without Ti underlayers. Thin Cu and Cu/Ti films ranging from 80–3000 nm have been evaluated. Direct observations of the surface during electrolytic charging have shown no evidence of film/substrate debonding for Cu/Ti systems. In contrast, extensive delaminations have been observed for Cu films. Indentation testing immediately after charging indicated up to 100% decrease in the practical adhesion for Ti/Cu films. The observed effect resulted from a true interfacialfracture energy reduction from 4 to 2 J/m2, Plastic energy dissipation was assumed unaffected as no yield stress changes were detected after charging. Even with the deleterious effect of hydrogen, adhesion strength of Cu/Ti films remained higher than that of non-charged Cu films.
Reliability of Electroless Processed Thin Layered Solder Joints
Authors: Wang L. C. , Mei Z. , Dauskardt R. H. 
Published: April 2011

AbstractThere has recently been an increasing interest in using electroless processes to produce the metal thin film stacks that make up the bond pads in solder ball grid array (BGA) packages. Electroless processes produce a more uniform and better controlled film thickness, but the resulting metal stacks have exhibited less mechanical reliability than that of traditional electrolytic stacks. This paper addresses a layered system consisting of a eutectic Sn-Pb solder sandwiched between stacks of Cu, Ni, and Au thin films. The samples were tested to determine cyclic fatigue behavior and fracture toughness values using traditional linear elastic fracture mechanics techniques. Surprisingly, fatigue crack propagation occurred in the middle of the solder layer even though the electroless interface was expected to be very weak. In contrast, fracture tests did appear to cause failure near an interface, but not necessarily at the electroless interface. Fracture toughness values measured for these samples were much lower than those reported for bulk metals. These results are discussed in terms of the microstructures present in order to determine possible relationships between the microstructure of the solder joint and its fracture behavior.
Interconnect Failure Mechanism Maps for Different Metallization Materials and Processes
Authors: Andleigh V. K. , Park Y. J. , Thompson C. V. 
Published: April 2011

AbstractA tool for simulation of electromigration and electromigration-induced damage, MIT/EmSim, has been used to investigate interconnect reliability, focusing on transitions in failure mechanisms associated with void nucleation, growth, and growth saturation. Conventional scaling of electromigration test results assume that the median time to electromigration-induced failure scales with the current density j to the power −n. The effects of transitions in failure mechanisms have been studied by characterizing the apparent current density exponent. When failure is limited by void nucleation, n=2 scaling is observed, and when failure requires substantial void growth, n=1 scaling is observed. When lines end at diffusion barriers such as W or liner-filled vias, void growth saturates in short lines at low current densities, and, depending on the failure criterion, lines under these conditions can be ‘immortal’. As growth saturates, apparent current density exponents increase above 2. Failure mechanism maps can be constructed to illustrate the failure mechanisms and scaling behavior as a function of line length and current density. Failure maps can be used in accurately scaling test results to service conditions, to suggest layout strategies for optimized circuit reliability, and to assess the reliability of new interconnect materials and structures.
Simulation of Electromigration Induced Atomic Transport in Al-Cu Alloys
Authors: Dekker J. P. , Elsässer C. , Gumbsch P. 
Published: April 2011

AbstractTo improve the fundamental understanding of alloying effects in electromigration, in particular of Cu addition to Al conductor lines, the electromigration process in the grain boundary of an Al-Cu alloy is simulated using a 2D kinetic Monte Carlo method. These simulations give the fluxes of Al and Cu from microscopic parameters, which determine the probability of each atomic jump. The parameters used in these simulations are the diffusion barriers, the attempt frequencies, the electromigration driving force, the temperature, the Cu concentration, and the binding energy of a Cu-vacancy pair. Values for the electromigration driving force on Al and Cu atoms are calculated ab initio. A very interesting result of the kinetic Monte Carlo studies is that the Al flux is reversed due to the addition of a small amount of Cu if the binding energy for the Cu-vacancy pair is larger than 0.12 eV. Such an Al back flux can explain the strongly inhibiting effect of Cu on electromigration damage initiation and transport in Al.