bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of π-vi Semiconductor Nanocrystallites in a Glass
Matrix Using Chalcogenizing Agent: Application to cdse
Authors: Marc J.L. , Gramer W. , Pradel A. , Ribes M. , Richard T. , Allegre J. , Lefebvre P. 
Published: April 2011

ABSTRACTA new route for preparing CdX (X = S, Se, Te, S+Se) nanocrystallites
dispersed in a sodium borosilicate glass matrix from a hydrogel is proposed.
Chalcogenizing complexing molecules - for instance a mixture of
NH4SCN + H2SeO3 - introduced in the
starting solution allowed an in situ crystallite
preparation concomitant to gel densification. Prevention of crystallite
oxidation is thus obtained. Moreover, coalescence is minimized because of
the low gel-glass transition temperature. Low temperature absorption spectra
have been interpreted in terms of exciton and electron-hole confinements,
accounting for both an intrinsic broadening of energy states inside each
nanocrystal and a Gaussian size distribution. Crystallite sizes and size
dispersion can be adjusted by changing the initial Cd concentration. The
crystallinity of the nanoparticles without change in dispersion is strongly
improved by thermal treatment above the Tg of the glass
matrix.
A New Type of a Sol-Gel-Derived Inorganic-Organic
Nanocomposite
Authors: Kasemann Reiner , Schmidt Helmut K. , Wintrich Elisabeth 
Published: April 2011

ABSTRACTA new type of sol-gel-based transparent inorganic-organic nano composites
has been developed by increasing the inorganic phase dimension to values
just below the point, where scattering can be neglected. For this purpose,
nanosized boehmite particles ≤ 50 nm are homogeneously incorporated in a sol
based on tetraethoxysilane and an epoxysilane. The nano-scale boehmite
particles act as catalysts for the polymerization of the epoxy silane to
polyethylene oxide, as proved by 13C NMR, and are linked to the
matrix by Si-O-Al bridges, as proven by 27Al-NMR spectroscopy.
The synthesized sols can be applied by standard coating techniques on
transparent polymers and are cured thermally. The mechanical properties
(scratch resistance, hardness) have been substantially improved compared to
systems with molecular dimensions of the inorganic phase. The effect is
attributed to the special structure of flexibly suspended nano-scale
boehmite particles in an inorganic-organic network by a tailored
interface.
Fullerene-Based Catalysts for Methane Activation
Authors: Wu Hui-Jung , Hirschon Albert S. , Malhotra Ripudaman , Wilson Robert B. 
Published: April 2011

ABSTRACTWe investigated fullerene based catalysts for the conversion of methane into higher hydrocarbons. Fullerene soot, CO2 activated soot, and extracted soot as well as a Norit-A carbon were examined as catalysts for methane activation. The soot was found to easily activate the C-H bond of methane, allowing methane conversion at lower temperatures (lower by 250°C) than found under purely thermal conditions. Furthermore, soot catalysis appears to produce a minimal amount of aromatic hydrocarbons. Extracted soot was found to have a lower selectivity for C2 hydrocarbons than the non-extracted soot, and the CO2 activation of the soot did not appear to dramatically alter the catalytic activity.
Structural and Electronic Studies of C60 Films Deposited Using a New Technique of Neutral Cluster Beam Deposition
Authors: Ren Zhong-Min , Ying Zhi-Feng , Xiong Xia-Xing , He Mao-Qi , Du Yuan-Cheng , Li Yu-Fen , Li Fu-Ming 
Published: April 2011

ABSTRACTC50 films, are deposited on Si(111) substrates using neutral cluster beams of fullerenes generated from a crucible with a special nozzle. X-ray diffraction (XRD) have been used to investigate the structural properties of C50 films, which indicate highly textural films as close-packed structure with strong (110) XRD assignment and 400Å for correlation length. Raman spectrum indicates the existence of stable C60 films. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) measurements are carried out to analyze the electronic properties of the films. The resistivity to contamination of C50 film deposited here is better than that deposited by MBE. Different kinds of oxygen contamination on the surfaces of C50 films and HDPG are detected by the results of O 1s XPS analyses.
High-Density Production of Carbon Nanotubes in Contact Arc-Discharge at Low Helium Pressure
Authors: Zhou Dan , Wang Su , Seraphin Supapan , Withers James C. 
Published: April 2011

ABSTRACTWe report here on the structural properties of carbon nanotubes prepared by contact arc-discharge at low helium pressure of 100 torr. In contrast to the conventional arcdischarge, the contact discharge reduces the gap between the electrodes to a minimum value while still maintaining a plasma. The resulting carbonaceous deposit on the cathode surface, with the contact discharge operating under 100 torr helium atmosphere, contains the columnar structures with high density carbon nanotubes. These columnar structures are several millimeters in length, much longer than those generated under the conventional arc-discharge. These experimental results reveal that reducing the gap adds greater stability to the arc-discharge and establishes conditions that favor high-density nanotube growth under a low helium pressure.
Residual Stress and Raman Spectra of Laser Deposited Highly Tetrahedral-Coordinated Amorphous Carbon Films
Authors: Friedmann T. A. , Siegal M. P. , Tallant D. R. , Simpson R. L. , Dominguez F. 
Published: April 2011

ABSTRACTWe are studying carbon thin films by using a pulsed excimer laser to ablate pyrolytic graphite targets to form highly tetrahedral coordinated amorphous carbon (at-C) films. These films have been grown on room temperature p-type Si (100) substrates without the intentional incorporation of hydrogen. In order to understand and optimize the growth of at-C films, parametric studies of the growth parameters have been performed. We have also introduced various background gases (H2, N2 and Ar) and varied the background gas pressure during deposition. The residual compressive stress levels in the films have been measured and correlated to changes in the Raman spectra of the at-C band near 1565 cm−1. The residual compressive stress falls with gas pressure, indicating a decreasing atomic sp3-bonded carbon fraction. We find that reactive gases such as hydrogen and nitrogen significantly alter the Raman spectra at higher pressures. These effects are due to a combination of chemical incorporation of nitrogen and hydrogen into the film as well as collisional cooling of the ablation plume. In contrast, films grown in non-reactive Ar background gases show much less dramatic changes in the Raman spectra at similar pressures.
Studying the Technology of Renaissance Bronzes
Authors: Bewer Francesca G. 
Published: April 2011

ABSTRACTLate fifteenth- and sixteenth-century freestanding bronze statuary presents evidence that the artists drew from both Experimentation sad divrcse, technological traditions prevalent at the time. The indirect lost wax casting technique was refined for the manufacture of statuettes by the end of the sixteenth century in the Florentine workshop of the Flemish sculptor Giambologna. Combining art historical and scientific analysis with an understanding of materials and techniques provides an integrated method of study which helps art historians and conservators to clarify the manufacturing process of these works. This can serve to construct a broad historical picture of techniques in different workshops and regions and to date and authenticate particular bronzes. X-radiography is the most informative tool for identifying technological features in this kind of work. Surface examination, analyses of the metal (by x-ray fluorescence spectroscopy and atomic absorption spectrometry) and refractory molding materials (by polarized light microscopy and microprobe analysis) complement this information.
Lattice Properties of Ge and GaAs Strained-Layers on Si
Authors: Eryigit Resul , Sui Zhifeng , Herman Irving P. 
Published: April 2011

AbstractA phenomenological lattice dynamics model has been developed that describes how strain affects phonon frequencies and elastic constants in Group IV and III-V semiconductor thin films and strained layers. Using this model, the phonon dispersion relations for strained-layer heterostructures of Ge and GaAs on Si have been obtained in the quasiharmonic approximation. This model uses available experimental data and can predict the effect of arbitrary strains on thin films.
A Numerical Study of Stress Controlled Surface Diffusion During Epitaxial Film Growth
Authors: Chiu Cheng-Hsin , Gao Huajian 
Published: April 2011

AbstractA two-dimensional numerical simulation is performed to model the morphological evolution of a strained film growing heteroepitaxially on a substrate under simultaneous action of vapor deposition and surface diffusion. To facilitate numerical implementation, a continuum boundary layer model is proposed to account for the influence of film/substrate interface on the film growth pattern. Discussions are focused on the Stranski-Krastanow growth mode, although our model is capable of explaining Frank-van der Merwe and Volmer-Weber growth modes as well. Both first-order perturbation and numerical results are developed to demonstrate that the film surface tends to remain flat during the initial stage of growth and that surface roughening occurs once the film thickness exceeds a critical value, in consistency with experimentally observed patterns of S-K growth. Numerical results further show that, depending on the deposition rate, the surface evolution could lead to a steady state morphology, unstable cusp formation, or growing islands with flattened valleys.
Dependence of Hardness on Modulation Amplitude in Compositionally Modulated Cu-Ni Thin Films
Authors: Oberle R.R. , Cammarata R.C. 
Published: April 2011

AbstractThe hardness dependence on the composition modulation amplitude of electrodeposited Cu-Ni multilayered thin films was investigated. The composition modulation amplitude was reduced by annealing the films, resulting in interdiffusion between the Cu and Ni layers. The hardness enhancement ΔH over that for a completely intermixed film was measured as a function of composition modulation amplitude A. It was found that for films with a sine wave composition profile, the hardness enhancement ΔH varied as A1.1±0.1, in good agreement with the model given by Krzanowski [1].
Effect of Copper Film Thickness on Stress and Strain in Grains of Different Orientation
Authors: Vinci R. P. , Zielinski E. M. , Bravman J. C. 
Published: April 2011

AbstractModels describing the effect of grain orientation on dislocation glide in a thin film are reviewed; it is predicted that differences in stress-temperature behavior should exist between grains of different orientation in a polycrystalline copper film. Direct x-ray evaluation of strains in {111} and {100| grains within primarily {111} textured copper films shows that these stresses are film thickness or grain size dependent. The {111} oriented grains behave as expected, with room temperature flow stress increasing linearly with 1/film thickness. The flow stress of grains of {100} orientation, however, is approximately constant with film thickness and is not well represented by the models. It is proposed that simplifying assumptions about orientation dependent yield may only be appropriate for the majority grain orientation population in a textured film.
Stress That Counteracts Electromigration: Threshold Versus Kinetic Approach
Authors: Glickman E. , Osipov N. , Ivanov A. 
Published: April 2011

AbstractThe paper analyzes electromigration (EM) conditions and material properties that determine the maximum EM induced stress, σa, and stress gradient, ∇σ, which counteract EM flow in interconnects.The first systematic data on the drift velocity vs. stripe length, L, current density, j, and temperature are presented for Al lines. In contrast to the conventional approach to the Blech problem with σa taken to be a material constant (“yield strength”), the observations suggest that σa increases with j. The stress adjustment is shown to result from the imperative coupling of the net flux of material directed to the downwind end of the stripe with the flux of plastic flow (creep) responsible for stress relaxation. The effect of parameters of the constitutive equation assumed to describe the plastic flow kinetics, namely that of strain rate exponent, threshold stress, and creep, effective viscosity, on the stress cya is considered. To account for the creep viscosity, η, obtained unpassivated aluminum stripes from EM experiments, a model for the attachment-controlled Coble creep is suggested.
Stress behavior of CVD-PSG Films Depending on Deposition Methods and Hillock Suppression
Authors: Kim Eungsoo , Kang Suk-Hee , Lim Soon-Kwon 
Published: April 2011

AbstractIn multilevel metallization processes, stress induced void and hillock formations cause serious problems with respect to the reliability of metal line, such as pitting corrosion of metal during the pad etching step, mask misalignment due to surface roughness, and open or short failure of metal line. It is generally known that these types of metal-film related problems are due to stress relaxation process in the metal line stress-induced by thermal expansion mismatch between metal and over/underlayer oxide film or compressive stress of overlayered passivation dielectric film.In this study, the stress behavior of phosphosilicate glass (PSG) film on the Al-l%Si film, deposited by different CVD methods, is investigated. Here we found that the degree of PSG film stress is related with the suppression of hillock growth, void formation, and cracking of passivation layer, depending on the heat treatment and heat treatment. Using stress measurement, surface profilometer, and SEM, the relation between passivated PSG film stress on metal line and the metal line failures is analyzed. In addition, an effective method of hillock suppression is suggested, which is the use of PECVD-PSG film on the metal line before heat treatment of 400°C or that of any type of PSG film before 350°C.
Morphology of Damage in Al Films Tested Under Electromigration Conditions Using the Drift Velocity Method
Authors: Kononenko Oleg V , Matveev V.N. 
Published: April 2011

AbstractPure Al films deposited by the partially ionized beam technique at bias Iavels of 0, 3 and 6 kV onto TiN sublayers were patterned for measurement for direct drift velocities. Then films were annealed in a vacuum 10−4 Pa for 1 hour. Electromigration tests were performed in an air atmosphere at a temperature of 280°C. The current density during tests was 6·105 A/cm2. Examinations in the SEM showed that the morphology of the damage on cathode and anode ends of the Al stripes depends on the bias during deposition. In the case of 0 kV bias, voids nucleate on the back and side edges of the cathode end and propagate toward the anode end. Hillock and whisker formation was observed on the anode end. The height and diameter of the whiskers were about 50 and 1–2 μm, respectively. In the case of 3 and 6 kV bias the drifting edge was smooth. Only hillocks (no whiskers) grew on the anode edge. The morphological differences of these films are discussed on the basis of self-ion bombardment effects.
Measuring the Mechanical Properties of Thin Metal Films by Means of Bulge Testing of Micromachined Windows
Authors: Paviot V. M. , Vlassak J. J. , Nix W. D. 
Published: April 2011

AbstractFree-standing films of gold and aluminum have been fabricated using standard micro-machining techniques. LPCVD silicon nitride films are deposited onto (100) silicon wafers. Square and rectangular silicon nitride membranes are made by anisotropic etching of the silicon substrates. Then, metal films are deposited onto the silicon nitride membranes by means of evaporation. Finally, the sacrificial silicon nitride film is etched away by means of reactive plasma etching, resulting in well-defined, square and rectangular metal membranes.Bulge testing of square windows allows one to determine the biaxial modulus of the film as well as the residual stress in it. Testing rectangular windows yields the plane-strain elastic modulus and the residual stress. Since deformation in rectangular membranes approaches plane-strain deformation, this geometry is ideal for studying the plastic properties of the metal films. Stress-strain curves can be readily determined from the load-deflection curves of rectangular membranes. The gold films have a biaxial modulus of 161±3 GPa and a plane-strain modulus of 105±5 GPa, slightly lower than the literature values for a (111) textured film. The yield stress of these films is approximately 231±17 MPa at 10−4% plastic strain. The elastic moduli of the aluminum films are 105±3 GPa and 76.4±0.7 GPa, respectively; the yield stress of these films is 187±30MPa.
Blister Test Analysis Methods
Authors: Hohlfelder Robert J , Vlassak Joost J. , Nix William D. , Luo Huihong , Chidsey Christopher E.D. 
Published: April 2011

AbstractWe present a general mathematical model of the blister test describing the relation between adhesion energy and other test parameters, and discuss the assumptions made therein. We describe the effects of excessive compliance in the blister test apparatus and discuss the design of our apparatus. Preliminary results from adhesion tests of polymer films which use self-assembled monolayers as adhesion promoters are presented. Some features of the data can be explained by a simple model incorporating a rate-dependent adhesion energy.
Ferroelectric Domain Inversion in LiNbO3 and its Application to High-Precision Piezoelectric Actuators
Authors: Nakamura Kiyoshi , Yamada Ken 
Published: April 2011

AbstractHeat treatment of bare single-domain LiNbO3 plates near the Curie temperature induces a local polarization reversal, thereby yielding a ferroelectric inversion layer. For a sufficiently long heat treatment the inversion layer thickness becomes equal to one half of the plate thickness. Similar domain inversion is also induced by heat treatment of protonexchanged LiTaO3. These domain inversion phenomena and a model for explaining the mechanism are reviewed.The inversion layer has piezoelectric constants opposite in sign to those of the uninveiled domain. Therefore, a LiNbO3 plate with such an inversion layer can be used as a piezoelectric actuator similar to the bimorph, because bending motion or torsional motion can be piezoelectrically produced, depending on the plate orientation. The measured characteristics of these actuators are presented and demonstrated to exhibit excellent linearity and no hysteresis.
Deposition Parameters for Sputter-Deposited Thin Film TiNi
Authors: Jardine A.Peter 
Published: April 2011

AbstractSputter deposition of TiNi has been problematic due to the extreme reactivity of titanium. There are several advantages in depositing TiNi with other metals, such as Ti and Cu, as the Shape Memory Effect properties can be changed selectively, including coring of the thin film. Simultaneous co-deposition of cored material using sputter deposition becomes technically difficult as this implies that the sample to target distance increases. In this paper, we discuss a relationship developed so that a basic base vacuum pressure can be found with target-sample distance and correlated with the observed phases for both Ti and TiNi samples. Practical limitations imposed by the vacuum system on both devices and device quality are discussed
Composite Piezoelectric Sensors and Actuators
Authors: Newnham R. E. , Fernandez J. F. , Markowski K. A. , Fielding J. T. , Dogan A. , Wallis J. 
Published: April 2011

AbstractComposite materials have found a number of structural applications, but their use in the electronics industry has been relatively limited. As the function of electroceramic composites are better understood, we can expect this picture to change. In this paper some of the piezoelectric composite sensor and actuator studies carried out in our laboratory during the past decade will be reviewed. The ideas that provide a basic understanding of functional composites have previously been discussed [1]. This paper describes recent advances in the processing and properties of composites possessing 0-3, 1-3, and 2-2 connectivity made of polymers, metals and ferroelectric ceramics. The introduction of open spaces in the previous connectivity patterns allows the development of new designs of several piezoelectric composites with connectivity patterns of 0(0)-3, 1(0)-3, 2(0)-2-2, and 2-0-2. As in most electronic systems that are developed with improved properties a push toward lower cost and smaller sizes of the piezoelectric ceramics, together with improved reliability and performance occurs. The piezocomposites with open spaces in their structures clearly demonstrate the growth of the functional ceramics into the field of the smart ceramics as the materials for the beginning of the next century.
Structure and Thermal Stability in Titanium-Nickel Thin Films Sputtered at Elevated-Temperature on Inorganic and Polymeric Substrates
Authors: Hou Ll , Pence T. J. , Grummon David S. 
Published: April 2011

AbstractDeposition of crystalline titanium-nickel shape-memory alloys on polymeric substrates is complicated by the elevated temperatures that must be withstood either during deposition or during post-deposition crystallization anneals. In this paper we report results on thin films of titanium-nickel, with Ni-rich compositions, which were prepared by dc magnetron sputtering onto quartz substrates, and onto thin polyimide membranes, at various elevated substrate temperatures between 623K and 703K. All of the as-deposited films possessed ordered bcc microstructures and had nano-scale grain sizes. Films deposited at the higher end of the temperature range displayed familiar two-step transformation behavior in electrical resistivity experiments, with transformation temperatures that were stable with respect to annealing for 22-hrs at 700K. Classic shape-memory was observed for a bilayer consisting of an 7.6 μm thick Kapton® polyimide sheet onto which 3 μm of near-equiatomic TiNi had been sputtered at 703K. By applying a pattern-etch technique to the metallized polymer we were able to fabricate a prototype electrically-excitable thin-film actuating element, potentially applicable to microelectromechanical and biomechanical systems.
Piezoelectric Fiber Coatings and Micro-Tubes
Authors: Fox G.R. , Damjanovic D. , Danai P.A. , Setter N. , Limberger H.G. , Ky N.H. 
Published: April 2011

AbstractAxially symmetric coatings of ZnO and PZT have been deposited onto fiber substrates by reactive dc magnetron sputtering. Multi-layer Cr/Au/ZnO/Cr/Au coating structures on optical fibers have been used to make integrated phase modulator devices. An analysis of the structural properties and piezoelectric response of the phase modulator devices will be presented. Microtubes of ZnO and Pt/ZnO/Pt multi-layers have been prepared by coating polyester fibers that act as a fugitive phase. After burning away the polyester fiber, up to 3 cm long micro-tubes with a 23 μm inside diameter and 3 to 9 μm wall thickness were obtained.
Ferroelectric Behavior and Microstructure of Calcium-Modified Lead Titanate Ceramics
Authors: Zhuang Zhiqiang , Kulesha G.A. , Du H. , Gallois B. 
Published: April 2011

AbstractCalcium-doped lead titanate ceramics exhibiting piezoelectric anisotropy were fabricated for applications in ultrasonic transducers, infrared detectors and surface acoustic wave devices. Transmission electron microscopy and X-ray diffraction techniques were used to characterize the development of the piezoelectric anisotropy and the dependence of the piezoelectric anisotropy on microstructure. Electron diffraction patterns indicated that most of the ferroelectric domains in samples with [CaA] up to 30 mole% were 90° domains. The size of the ferroelectric domains was not related to piezoelectric anisotropy. Ferroelectric domains could not be detected above this concentration. Measurements of the temperature dependence of dielectric properties at different frequencies did not show any ferroelectric relaxor behavior.