bluuebunny/crossref_metadata_2025_split huggingface dataset:
Er3+ Doped Silica Glass by Sol-Gel Processing with Organic Complexation
Authors: Han Xiuhong , Cao Guozhong , Pratum Tom 
Published: April 2011

ABSTRACTEr3+-doped silica glass (up to 10 wt%) was synthesized by sol-gel processing with the addition of 3- aminopropyl trimethoxysilane (APS) as a complexing agent. Er3+ ions reacted with amino groups and, thus, linked to the silica network during the sol preparation. As a result, the motion of Er3+ ions was restricted and the formation of Er3+ clusters was inhibited. Both fluorescence spectra and magic-angle spinning (MAS) nuclear magnetic resonance (NMR) indicated that the addition of the complexing agent APS resulted in a homogeneous dispersion of high-level Er+3 doping in the resultant gels. After the removal of organic components, however, Er+3 clustering occurs when firing at a high temperature for a long period of time, e.g. at 1000°C for 10 hrs, due to enhanced Er3+ diffusion.
The Effect of Post-Anodization Chemical Etching on Porous Silicon Investigated by Means of Photoluminescence and Ir Spectroscopy
Authors: Uehara Nobutomo , Yamazaki Tetsuya , Kobayashi Akiharu , Fujihara Shinji , Ohmukai Masato , Tsutsumi Yasuo 
Published: April 2011

ABSTRACTWe studied the effect of post-anodization chemical etching on porous silicon by means of photoluminescence (PL), Fourier transform infrared (FTIR) absorption and Raman spectroscopy. We performed these measurements with repeating etching and then observed the variation of the spectra. On the basis of the correlation between PL and FTIR spectral changes, the PL emission at 660 and 730 nm in PL spectra stems from Si-H2, and Si-H clusters at surface, respectively. Raman spectra show a close relation between PL emission at 850 nm and nanocrystallites in porous silicon. In addition, chemical etching contributes to the promotion of nanocrystallites and to dissolving them.
Photoluminescent Polymer Films for Display Applications
Authors: Palmans Anja , Montali Andrea , Weder Christoph , Smith Paul 
Published: April 2011

ABSTRACTNovel poly(ρ-phenylene ethynylene) polymers, ANT-OPPE and COU-OPPE, have been prepared, in which anthracene and coumarin sensitizer molecules are covalently attached to the conjugated polymer backbone via a flexible spacer. These polymers show efficient energy transfer from the pendent sensitizer molecule to the PPE backbone, both in dilute solution as well as in an oriented polyethylene matrix. In case of ANT-OPPE, we found that the PPE backbone adapts the orientation of the matrix and is efficiently oriented, while the anthracene moiety remains essentially isotropic, resulting in a state-of-the-art polarizing energy transfer for this system.
From a Reaction Mechanism to New Ppv's for High Performance Polymer-Leds
Authors: Spreitzer H. , Becker H. , Kreuder W. , Kluge E. , Schenk H. 
Published: April 2011

ABSTRACTPoly(ρ-phenylene vinylene)s (PPVs) are very promising materials for optoelectronic applications, especially for displays based on polymer light emitting diodes (PLEDs). We report here our findings concerning defect structures in this materials and the influence of the discovered irregularities on an important property of the materials, i.e. the operational life in a PLED. Recent improvements, which were deviated from this findings are presented: optimized PPVs with a lower amount of defects result in a strong increase of operational lifetime.
Optical Activity and Order in Luminescent Langmuir-Blodgett Poly(ρ-Phenylene Vinylene) Films
Authors: Marletta A. , Guimãraes F.E.G. , Gonçalves D. , Campana P.T. , Nascimento O.R. , Oliveira O.N. , Faria R.M. 
Published: April 2011

ABSTRACTLangmuir-Blodgett (LB) PPV films of poly(ρ-phenylene vinylene) (PPV) have been obtained using a mixture of a PPV precursor, poly(xylylidene tetrahydrothiophenium chloride) (PTHT), with the sodium salt of dodecylsulfonic acid (DBSA) as the spreading solution. Spincoated films were prepared in order to compare their properties with those of LB films. A large circular dichroism was observed for LB films but not for spin-coated ones. Optical activity of PPV films was characterized by circular dichroism technique, while optical properties were evaluated by optical absorption and luminescence measurements at various temperatures. Overall, the results obtained allowed us to conclude that the layer-by-layer LB process yields a high degree of molecular order in the PPV films with low interchain interaction. Polarized absorption and circular dichroism measurements demonstrate a preferential chain orientation along the dipping direction in the LB processing. The origin of the CD in the PPV-LB can be ascribed to convenient packing of individual monolayers given by the Z-type deposition.
Thermal Shift and Broadening of Spectral Lines in Neodymium Doped Garnets
Authors: Chen Xuesheng , Bartolo Baldassare Di 
Published: April 2011

ABSTRACTThermal shift and broadening of sharp luminescence lines in three Nd-doped laser garnet crystals, GGG, GSGG, and CYMGG, are investigated in a temperature range of 78 to 600K. These lines are due to the 4F3/2 → 4I9/2 (∼0.94μ) and 4F3/2 → 4I11/2 (∼lμ) transitions. Line widths and positions at different temperatures are reported for the lines of RI→Yl, RI→Y2, R2→Y3, RI→Z5 in GGG:Nd, RI→Y1, RI→Y2, R2→Y1, R2→Y3, RI→Y6, R2→Y6, RI→Z5 in GSGG:Nd,Cr, and R2→Y1, RI→Z5 in CYMGG:Nd,Cr. We observed that all the lines shift to longer wavelengths (red shift) with increasing temperature except for the R1,2 →Z5 lines that shift to shorter wavelength (blue shift) in all the three garnet crystals. For the widths, all the lines become broader with increasing temperature. It was also observed that the line width in the germanium garnet CYMGG is much broader than in GGG and GSGG.
Understanding the Photoluminescence of Copper Aluminum Halide Phosphors
Authors: Sullivan Roger M. , Martin James D. 
Published: April 2011

ABSTRACTAmbient temperature blue luminescence was observed under both UV and X-ray excitation during our investigation of the chemisorption of small molecules into both α- and β CuAIC14. The optical properties of the CuAIX4 (X=CI, Br) indicate a copper centered phosphorescence mechanism. The thermal history of the sample influences both which polymorph is formed and the color of the luminescence. The sorption of small molecules into the framework quenches the blue photoluminescence, which provides a useful probe of the interaction between the metal-halide framework and sorbed gases.
Sputtering Luminescent Ta2Zn3O8 Thin Films
Authors: Rack Philip D. , Potter Michael D. , Woodard Andrew , Kurinec Santosh 
Published: April 2011

ABSTRACTThin films have been deposited by rf magnetron sputtering from a stoichiometric Ta2Zn3O8 ceramic target (3ZnO + 1Ta2O5). Negative ion re-sputtering effects have been observed in the stoichiometric Ta2Zn3O8 target and have been attributed to O ion formation from primarily Ta-O bonds. Zinc deficient thin films were deposited as a result of the preferential re- sputtering of Zn versus Ta. The negative ion re-sputtering effects are exacerbated at higher powers and lower pressure. This observation is correlated to the oxygen ion transport through the dark space and the plasma, which ultimately controls the energy distribution of the oxygen particles that arrive at the substrate. To circumvent the negative ion re-sputtering, a mosaic ZnO-Ta target was sputtered, which resulted in stoichiometric and luminescent thin films.
Modeling of Cathodoluminescence and Photoluminescence Properties of Pulsed Laser-Deposited Europium-Activated Yttrium Oxide thin Film Phosphors
Authors: Cho K.G. , Kumar D. , Chen Z. , Holloway P. H. , Singh R. K. 
Published: April 2011

ABSTRACTEuropium-activated yttrium oxide (Eu:Y2O3) thin films were deposited on (100) silicon and (0001) sapphire substrates using 248 nm KrF pulsed laser. To investigate the effect of the Eu:Y2O3 film roughness on cathodoluminescence (CL) and photoluminescence (PL) properties, the substrate surfaces with various roughnesses were used. The roughness was found to play an important role in determining CL and PL brightness of the Eu:Y2O3 films. The improvement in brightness by increasing the film roughness is due to increase in total portion of light that escapes from the surface of the phosphor film. A model has been proposed which supports strongly this explanation. Our results show that depositions with slower growth rate and lower laser energy are more important parameters than increasing the roughness to improve CL brightness of the Eu:Y2O3 thin film phosphors.
Electrostatic Self-Assembly of Multilayer Noncentrosymmetric Thin Films and Devices
Authors: Lenahan K. M. , Zenga T. , Liu Y. , Wang Y.-X. , Zhao W. , Claus R.O. 
Published: April 2011

ABSTRACTThe electrostatic self-assembly of multilayer thin films by alternate adsorption from polyelectrolyte solutions spontaneously leads to the formation of noncentrosymmetric structures if the molecules themselves have net dipole moments. Significant second-order nonlinear optical susceptibility has been observed in such films, using both commercially available chromophores and molecules specifically designed to yield an enhanced net dipole moment. Recent results indicate the capability to fabricate piezoelectric films using the same method. The nature of the deposition process results in an alignment of the chromophores that is stable over time and to temperatures up to 150°C, in contrast with poled polymers. ESA films offer the additional major advantages of excellent homogeneity and low optical loss, high thermal and chemical stability, and low cost.
Towards the Synthesis of Mono- and Bi-Functional Amphiphilic Oligothiophenes: Organic Materials for Opto-Electronic Applications
Authors: Advincula R.C. , Inaoka S. , Park M. , Phillips D. , Shin D.M. 
Published: April 2011

ABSTRACTIn this report, we describe our initial synthesis and characterization of mono-functional and bi-functional dibromoalkyl oligothiophenes to achieve amphiphilicity and telechelic functionality. Oligothiophenes are an important class of organic materials for opto-electronic devices and display applications. We have mono-functionalized oligothiophenes by the synthesis of a quinquethiophene bromoalkyl derivative. A bi-functional sexithiophene was derived primarily by the symmetrical coupling of terthiophene derivatives. Both were synthesized using Grignard coupling and lithiation reaction methodologies. UV-Vis, IR, NMR, MALDI-TOF-MS, and DSC confirmed the structure and physical properties of the oligomers. In addition, we have also synthesized an amphiphilic diamine derivative from the reaction of hexamethylenediamine with a bromoalkyl terthiophene derivative. Using photoluminescence, the photophysical properties of the oligomers were found to be that of typical oligothiophenes. Processing as ultrathin films for devices is currently being investigated.
Two Photon Spectroscopy of Dithienyl Polyenes
Authors: Cooper Thomas M. , Fleitz Paul A. , Sowards Laura A. , Natarajan Lalgudi V. , Kirkpatricky Sean , Chandra Suresh , Spangler Charles W. 
Published: April 2011

ABSTRACTTo understand the properties of light-sensitive compounds used in optical limiters having photoinduced charge transfer mechanisms, we have investigated the photophysics of a series of di(2-thienyl-3,3'-butyl)polyenes. Spectroscopic measurements, including UV/Vis, fluorescence, fluorescence lifetimes, fluorescence quantum yields, triplet state lifetime, solvent effects and two-photon absorption coefficient were obtained as a function of the number of double bonds(n = 1-5). Trends in the data reflected the ordering, energy gap between and mixing of 1Bu* and 1Ag* excited state configurations.
Electromigration in Sputter Deposited Copper/Zirconium Alloys
Authors: McCusker N. D. , McCusker N. D. , Armstrong B. M. 
Published: April 2011

AbstractRF-magnetron sputter deposited copper/zirconium alloy films have been characterised in terms of resistivity, composition, microstructure, texture and stress. The properties and electromigration reliability of these alloys have been compared to those of pure sputtered copper films. The surface segregation of zirconium within the films after annealing has been studied. We have proposed a mechanism in which zirconium at the copper surface can influence the electromigration damage process, enhancing reliability.
In Situ Stem Technique for Characterization of Nanoscale Interconnects During Electromigration Testing
Authors: Gobulukoglu Ismail , Robertson Brian W. 
Published: April 2011

AbstractA technique for observing microstructure and morphology changes during annealing or electromigration of 100 nm-scale and smaller interconnects is presented. The technique is based on dynamic in situ characterization using a UHV field-emission scanning transmission electron microscope (STEM) and can enable full microstructural characterization (images, diffraction patterns and compositions) during electromigration testing. Initial steps in the validation of the approach include in situ electron-beam OMCVD of Al-containing wires and observation of these wires. Although the deposition conditions were not optimized, Al-containing wires, with high edge acuity, thickness uniformity, and with minimum interconnect widths as small as 15 nm have successfully been deposited. In situ imaging of the annealing of 100 nm Al films on 25 nm Si3N4 substrates at 350°C demonstrates that an image resolution of 10 nm should readily be attainable in passivated nanoscale interconnects during electromigration.
X-Ray Diffraction Determination of Texture and Stress in Damascene Fabricated Copper Interconnects
Authors: Winter Delrose , Besser Paul R. 
Published: April 2011

AbstractX-Ray diffraction (XRD) provides an excellent tool for the measurement of both stress and texture (preferred orientation) on fabricated damascene interconnect structures. Since x-ray diffraction provides a direct measurement of lattice spacings, film strain can be measured directly. Also, since the intensity of diffracted x-rays is proportional to the density of lattice planes oriented in diffracting condition with respect to the incident beam, both the direction and extent of preferred orientation can be accurately measured. Special techniques and considerations are necessary when examining damascene interconnect structures with XRD which are not necessary with blanket films. These techniques are discussed and described in order to aid in obtaining meaningful XRD data and a correct interpretation of the results.
The Effect of Film Stress on Indentation Modulus/Hardness for Silicon Oxide Films
Authors: Sun Brad , Lee Jin , Kofron Patrick , Ma Qing 
Published: April 2011

AbstractA controlled experiment was performed to determine whether residual stresses in silicon oxide films affect the apparent modulus and hardness of the films measured using microindentation. A set of wafers, each with a SiO2 film of different residual stress, were produced by PECVD deposition using different RF power settings. Residual stresses, determined by curvature measurement, were shown to become more compressive with the increase of the RF power. Correlation between indentation modulus/hardness and residual stress was established because the modulus was also observed to be trending with the RF power. To determine whether the residual stress change is the cause for the change of indentation modulus/hardness, one of the wafers was cut to pieces and bonded to steel substrates of different thickness at elevated temperatures. Because of the thermal mismatch between silicon and steel, the silicon pieces were stressed by the steel substrates and therefore provided additional stresses to the SiO2 film on the top surface. The applied stresses were determined using Raman piezospectroscopy. Micro-indentation tests performed on these samples showed no appreciable change of modulus/hardness due to additional stresses. It was concluded that the material change, such as density, was behind the correlation between indentation modulus and residual stress.
Analytical Methodology and Design of Advanced Test Structure for the Mechanical Characteristics of Microactuator Materials
Authors: Lee Se-Ho , Park Byung Woo , Pak Yukeun , Kwon Dongil 
Published: April 2011

AbstractThe electrostatic test structure was presented to measure the micromechanical properties of micromaterials as thin films forming the microactuators. The test structure was fabricated by using the surface micromachining processes and driven by the electrostatic force. In order to measure the fracture toughness, the sharp notch in the test structure was introduced by using the etching process. The displacement and deflection of the test structure under the electrostatic force was on the basis of the beam bending theory. An analytical model was proposed to evaluate the fracture toughness by experimental determination of crack propagation from the variations of capacitance and voltage. Additionally, an acceleration test for evaluation of the long-term reliability of the microactuator device was performed to predict the lifetime of a gold micromirror plane used in DVD (Digital Video Disk) by analyzing the resonant frequency and capacitance.
On the Methodology of Numerical Etching
Authors: Wang X. H. , Shyu K. , Chang C.-T. , Zheng D. W. , Wen Weijia 
Published: April 2011

AbstractA methodology to study the stress distribution of a patterned thin film residing on a silicon wafer was developed. Si underlying the pattern was thinned down through etching so that the deformation caused by residual stress in the microstructure could be detected by a Twyman- Green interferometer. A procedure called "numerical etching" was implemented to simulate the etching process, which linked the stress state of the microstructure on a regular wafer to that on a Si diaphragm. An initial stress field on the pattern was assumed, and its effect on the deformation of the Si diaphragm beneath was calculated and compared with experimental results. The discrepancy between them was used to modify the initially assumed stress field and repeated until a satisfactory match was achieved. The stress field from numerical analysis accurately predicts the actual stress distribution in and around the patterned structure under investigation. The stress distribution in a Ti pad on a Si3N4/ SiO2/Si composite diaphragm is used as an example.
Interfacial Diffusivity of Moisture Along A SiO2/Tin Interface Measured Using Imaging Secondary Ion Mass Spectroscopy (SIMS)
Authors: Xu Guanghai , Mates T. E. , Clarke D. R. , Ma Qing , Fujimoto Harry 
Published: April 2011

AbstractThe SiO2/TiN interface is prone to sub-critical decohesion by crack extension along the interface when exposed to moisture. As with conventional sub-critical crack growth in bulk silica, the rate of decohesion is dependent on both the relative humidity and the strain energy release rate. One of the unusual observations we have noted is that the decohesion velocity of narrow strips is highly sensitive to the exposure time in the humid environment, suggesting that the moisture diffuses into the interface ahead of the propagating decohesion crack, causing a form of hydrolytic weakening of the interface. In seeking to establish the origin of this behavior, we report measurements of moisture diffusion along the SiO2/TiN interface using Imaging Secondary Ion Mass Spectroscopy (SIMS) after immersion in water containing radioactive tracers, 2D and 18O. Analysis of images formed using 2D and 18O revealed that both diffuse along the interface with a diffusivity of (6 ±2)×10−13 cm2/sec, a value about 104 times faster than the bulk diffusion in the SiO2 dielectric.
Adhesion and Progressive Debonding of Polymer/Metal Interfaces: Effects of Temperature and Environment
Authors: Kook Seung-Yeop , Kirtikar Amol , Dauskardt Reinhold H. 
Published: April 2011

AbstractThe interfacial fracture properties of a representative polymer/metal interface commonly found in microelectronic applications are examined. The double cantilever beam (DCB) configuration was used to investigate the effects of environmental variables on interfacial adhesion and progressive delamination under monotonic and cyclic fatigue loading conditions. The steady-state interfacial fracture energy, Gss, taken from the plateau of the R-curve, of a representative silica-filled Phenol-Novolac epoxy on a Nielectroplated Cu substrate showed little sensitivity to the presence of moisture. On the other hand, both the initiation interfacial fracture energy, Gi, and the entire progressive debond curve under fatigue loading were remarkably sensitive to moisture and temperature, respectively. Debonding is modeled in terms of interface structure, chemistry using chemical reaction rate theory, and relaxation process at the debond tip. The activation energy for stage I debond growth is found to be 140 kJ/mol and 63 kJ/mol for stage II for the current polymer/metal interface.
Acoustic Emission Analysis of Fracture Events in Cu Films with W Overlayers
Authors: Volinsky Alex A. , Gerberich William W. 
Published: April 2011

AbstractIndentation-induced delamination of thin films provides the basis for adhesion calculations. In the case of ductile Cu films plastic deformation usually prevents a film from debonding from the substrate. Deadhesion is facilitated by the use of a hard W superlayer, which promotes indenter-induced Cu film failure, increasing the delamination area by an order of magnitude. Radial as well as annular cracking acts like a secondary mechanism in the strain energy release, and can be resolved from excursions on the load-displacement curves. For the thicker Cu films no excursions were observed, though radial cracking took place. It is important to identify fracture events as they occur in order to understand the system behavior and accurately apply the analysis. An acoustic emission signal is used to detect the magnitude of fracture events in thin Cu films. For the films of different thickness from 40 nm to 3 microns the corresponding interfacial fracture energy ranged from 0.2 to over 100 J/m2. Limits of plastic energy dissipation are determined with the lower limit, the true work of adhesion, being associated with a dislocation emission criterion. Crack arrest marks were found upon the blister removal, and are proposed to represent the shape of the crack tip. Total acoustic emission energy was found to be inversely proportional to the strain energy release rate.
Measurement of Bonding Stress in Silicon High Power Device Structures by Infrared Photoelasticity Method
Authors: Peng H. J. , Wong S. P. , Lau W. F. , Ke N. , Zhao Shounan 
Published: April 2011

AbstractSilicon high-power devices are commonly bonded to Mo electrodes using Al films. Bonding stress will inevitably be introduced into the Si substrate by such a process. In this work, the infrared (IR) photoelasticity (PE) method was employed to measure the stress distribution in the Si substrates induced by high temperature bonding process of Si/Al/Mo structures commonly used in the production of silicon thyristors. It is demonstrated that quantitative information on both the directions and magnitudes of the stress can be obtained. The dependence of the magnitude of the stress on the geometrical parameters of the structure has also been studied. The experimental results are shown to agree well with the calculated results derived from a theory of interlaminar stresses in composites.