bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth and Photoluminescence of Strained < 110 > Si/SilxGex/Si Quantum Wells Grown by Rapid Thermal Chemical Vapor Deposition
Authors: Liu C. W. , Sturm J.C. , Lacroix Y. R. J. , Thewalt M. L. W. , Perovic D. D. 
Published: April 2011

ABSTRACTWe report the first chemical vapor deposition growth and systematic photoluminescence study of strained Si1–xGex alloy layers on < 110 > Si substrates. Compared to < 100 > Si substrates, the same growth conditions yielded a slightly lower Ge composition, but a much lower growth rate. For thick layers, the relaxation along [110] direction is insufficient and lead to predominantly uniaxial strain in the the films. From the photoluminescence, the bandgap of strained Si1–x.Gex on < 110 > Si for 0.16 ≤ x ≤ 0.43 is determined and compared to theory. A strong “no-phonon” emission process in photoluminescence spectra of strained < 110 > Si/Si1–x.Gex/Si was observed as compared with that observed in < 100 > layers. Finally, quantum confinement shift of Si/Si0.71 Ge0.29/Si wells with a confinement energy up to 110 meV has been observed by varying the well width from 133 Å to 17 Å.
Three-Dimensional Asymmetrical Modeling of Rapid Thermal Annealing of Silicon Wafers
Authors: Nagabushnam V. , Singh R.K. 
Published: April 2011

ABSTRACTWe have developed an analytical tool to predict temperature variations occuring both across the wafer and down the thermal cycles, based on very simple 3-dimensional physical models depicting the heat transfer processes taking place during a typical rapid thermal processing (RTP) step. This model takes into account the convective and the radiative heat losses along with the thermal conduction within the wafer. An hybrid control volume formulation has been used to solve the heat conduction equation to yield numerical solutions of temperature variation, both on and within the wafer. The effect of ambient gas flow direction and the related asymmetric convective heat loss on the temperature non-uniformity across the wafer at different stages of the thermal cycle is well analyzed. Finally, the temperature non-uniformity across a wafer patterned with oxide is examined.
Analysis of Critical Parameters Affecting the Temperature Uniformity During Rapid Thermal Processing
Authors: Nagabushnam V. , Sing R.K. , Thakur R.P.S. 
Published: April 2011

ABSTRACTIn this work we examine the effect of various system and wafer parameters such as the flowing ambient, the spatial distribution of incident energy flux, the slip-free ring and doping density on temperature non-uniformity occurring during rapid thermal processing (RTP). The effect of using two inert ambients, i.e. argon and nitrogen, on temperature non-uniformity occurring during RTP cycle is studied in detail. The importance of dynamic lamp power control in providing time dependent spatial variation of incident energy flux as a measure to improve the temperature uniformity is also examined. Finally the simulation studies are also done in the presence of a slip-free ring. The nature of photon capture by the silicon wafer and the correlation between doping density and the steady state temperature for any given open loop condition is discussed in detail. This analysis has been done using an analytical tool developed by us based on simple 3-dimensional physical models depicting a typical rapid thermal cycle[1].
Transition Metal-Promoted Oxygen Ion Conductors as Oxidation Catalyst
Authors: Liu Wei , Sarofim Adel , Flytzani-Stephanopoulos Maria 
Published: April 2011

AbstractA novel metal oxide composite catalyst for the complete oxidation of carbon monoxide and hydrocarbons was prepared by combining oxygen ion conducting materials with active transition metals. The oxygen ion conductors used were typical fluorite-type oxides, such as ceria, zirconia, and others. Active base metal catalysts, such as copper, were used as additives to promote the catalytic properties of oxygen ion conductors. The intimate contact of the two kinds of materials gave rise to a highly active oxidation catalyst. On Cu-Ce-O composite catalysts, 95% of carbon monoxide was oxidized by air at ∼100 °C. Complete methane oxidation on the same catalyst took place at ∼550 °C. When the stoichiometric amount of sulfur dioxide was used to oxidize carbon monoxide, 96% of sulfur dioxide was reduced to elemental sulfur at temperatures above 460 °C with 99% of sulfur dioxide conversion. This type of composite catalyst also showed excellent resistance to water poisoning.
Deactivation of Alumina Supported Catalysts Due to Spinel Formation
Authors: Bolt P. H. , Van Ipenburg M. E. , Geus J. W. , Habraken F. H. P. M. 
Published: April 2011

AbstractAn important cause of deactivation of alumina supported transition metal (oxide) catalysts is a solid state reaction between the active component and the support. We therefore studied the hightemperature behavior of Me layers (Me = Co, Ni, Cu and Fe) on polycrystalline α-A12O3 and γ- Al2O3 substrates. The samples were first oxidized at moderate temperatures and then annealed at high temperatures (up to 1000 °C) in O2, N2, or N2/O2 mixtures. The interfacial reaction to MeA12O4 was assessed using Rutherford Backscattering Spectrometry and X-ray diffraction. The reaction rate strongly depends on the transition metal element Me: Fe < Ni < Co < Cu. Low oxygen pressures favour spinel formation. γ-A12O3 shows a much higher reactivity towards the MeOx overlayers than α-Al2O3.
Biodegradation of Polymer Coatings
Authors: Jones William R. , Walch Marianne , Jones-Meehan Joanne 
Published: April 2011

AbstractConventional paint removal methods include chemical stripping with VOCs, blasting with plastic media, and delamination with high pressure water. These methods have many limitations, in that they are labor intensive, pose human health risks, are relatively expensive and pose significant waste disposal problems. However, polymeric coatings are known to contain structural components, such as ester, amide and urea linkages, that can be degraded biologically. We are working to develop a stable, enzyme-based, non-toxic paint stripping strategy that will be environmentally safe and cost effective.The specific objectives are to identify and characterize microbial systems capable of degrading polymeric coatings, to develop a quantitative degradation assay and to optimize activity levels for subsequent purification and concentration of the biological products required for rapid degradation of coatings.A water-dispersed colloid of an ester-based polyurethane polymer has been used in solid growth medium to screen about 100 different bacteria for microbial degradation activity. Those with demonstrable activity have been grown in the presence of epoxypolyamide paint- and polyester polyurethane paint-coated aluminum coupons. We have demonstrated delamination under certain conditions and have developed a spectrophotometric method for quantitating degradation activity as a function of dye release.
Plasma Enhanced Chemical Vapor Deposition of Silicon Nitride from Novel Organosilanes
Authors: Grow J. M. , Levy R. A. , Yu Y. , Shih K. T. 
Published: April 2011

AbstractThe environmentally benign precursors diethylsilane and di-t-butylsilane were used with NH3 to synthesize silicon nitride films by plasma enhanced chemical vapor deposition. The growth kinetics and film properties were examined as a function of deposition temperature, total pressure, and NH3/organosilane ratio. The growth rate was observed to decrease with higher temperature and higher NH3/organosilane ratio while increasing with higher total pressure. Values of index of refraction, film stress, hardness, and Young's modulus were measured as a function of processing variables and related to film density and resulting film composition. Oxidation of the films was noted to occur at high pressures, low temperatures, and low NH3/organosilane ratios. Carbon incorporation was present for all deposits and appeared not to be dependent on processing conditions.
Characterization of Sol-Gel Derived Composite Silica Carbon
Electrodes
Authors: Gun Genia , Tsionsky Michael , Lev Ovadia 
Published: April 2011

ABSTRACTSol-gel derived composite silica-carbon electrodes exhibit favorable
electrochemical characteristics. The electrodes benefit from the
conductivity and electrochemical advantages of the carbon powder, from the
favorable properties of the ceramic network and from the versatility of the
sol-gel process. Hydrophobie composite electrodes reject water, only their
outermost surface is wetted and they exhibit good signal to background
currents. A comparison of several types of carbon powders reveals that
higher carbon loading and larger surface area electrodes can be attained by
incorporation of dense graphite powder. When high surface area, small size
carbon-black powder is used, a homogeneous distribution of microelectrodes,
separated by insulating modified silica is formed. This ensemble of
microelectrodes increases the sensitivity of the CCEs by more than two
orders of magnitude as compared to glassy carbon electrode and graphite
CCEs.
Sol-Gel Glasses as New Waveguides for Optical
Immunosensors
Authors: Collino R. , Therasse J. , Chaput F. , Boilot J-P. , Levy Y. 
Published: April 2011

ABSTRACTIn order to develop an optical immunosensor based on Surface Plasmon
Resonance (SPR) and guided waves propagation, the sol-gel process has
been used to prepare thin films of amorphous silica, deposited by spin
coating on a gold-coated glass slide, and possessing chemically active
functional groups (SH, NH2...). After activation of the sol-gel film in
aqueous buffers by a bifunctional coupling agent, biological molecules
such as antibodies could be covalently bonded on or inside the sol-gel
film. Therefore, the behaviour of the functionalized silica thin films in
aqueous solutions has been analyzed by SPR and guided waves propagation.
The matrix hydrophilicity has been studied with different mixtures of
functionalized silicon precursors forming organic-inorganic hybrid films.
Immunoassays outline the possibility of obtaining covalent binding of
antibodies to the sol-gel matrix with optimal stability and biological
activity.
Preparation of Stabilized Zirconia Using A Mixture of Rare Earth Oxides as Dopant
Authors: Santos Adelina P. , Fernandes Rosana Z. D. 
Published: April 2011

ABSTRACTThe present work deals with the effect of the rare earth nature and the content of the oxide dopants on the stabilization process of zirconia based ceramics. There are two main interests in our work. The first is to verify the possibility of stabilizing a cubic structure of zirconia using a natural mixture of rare earth elements as dopant, and second, to study and to characterize its basic physical-chemical properties such as phase diagrams, zirconia stabilization models and dopant distribution.
Mechanical and Microstructural Properties of Two-Step Acid-Base
Catalyzed Silica Gels
Authors: Meyers D. E. , Kirkbir F. , Murata H. , chaudhuri S. Ray , Sarkar A. 
Published: April 2011

ABSTRACTThe mechanical and microstructural properties of two-step acid-base
catalyzed silica gels were examined as functions of aging time, catalyst
concentration, and hydrolysis time. Cylindrical gels were prepared using
Si(OC2H5)4,
C2H5OH, and H2O, with HCl followed by
NH3 as catalysts. Mechanical properties were obtained from
three-point bend tests, and the microstructures of dried gels were analyzed
using nitrogen adsorption/desorption techniques. Gel strength initially
increased with aging time at 70 °C, then leveled off after about one week.
When the sol was hydrolyzed for less than two hours, there were significant
differences in the properties of gels catalyzed with relative molar amounts
of 0.0001 and 0.0002 HCl. However, as the hydrolysis time was increased, the
gels all had similar properties, independent of the amount of HC1. The
amount of NH3 influenced gelation time and to a lesser extent, the strength,
but had no observable effect on pore size. The two-step catalysis procedure
produced gels with strength and pore size combinations intermediate to those
of either single acid or base-catalyzed gels.
Spectroscopic Studies of Chemical Reactions and Dynamics in
Sol-Gel Matrices
Authors: Akbarian F. , Dunnt B. , Fuquat P.D. , Mckiernan J. , Simoni E. , Zink J.I. 
Published: April 2011

ABSTRACTThe synthesis of sol-gel glasses containing organic and organometallic
molecular dopants has been well established as an approach for creating new
optical materials. Some of these properties are dependent upon chemical
reactions which occur in porous xerogel matrices during the sol-gel process
or when encapsulated molecules are exposed to other molecules in solution.
In this paper, the study of two different types of chemical reactions in the
pores of xerogel matrices is reported. In one case copper phthalocyanine is
used to characterize dimerization within the pores. The results show that
dimer formation is most likely to occur towards the end of the drying stage
as the dye concentration in the pores increases from solvent evaporation. A
second example involves the use of a pump-probe technique to determine the
rate of proton recombination inside the pores of silica monoliths. The
behavior of sols and gels is similar to aqueous solution while recombination
of protons in the xerogel seems to be affected by the walls of the
pores.
Additive-Coated Si3N4 Powder Prepared By
The Sol-Gel Method
Authors: Ge Manzheng , Kan Honghua , Yang Hui , Qiao Jianmin , Jiang Zhonghua 
Published: April 2011

ABSTRACTThe Y2O3-La2O3 additive-coated
Si3N4 powders of about 1.5 μm in size were prepared
by the sol-gel method. X-ray diffraction, X-ray photoelectron spectroscopy,
differential thermal analysis, thermogravimetric analysis, electron
microscopies, and particle size analysis were used to study the coating on
the Si3N4 particles. The results show that properties
of the bulk Si3N4 powder are not affected by using the
sol-gel coating and the powders are homogeneously coated by a thin layer of
the Y2O3-La2O3 additives. The
structure of the Y2O3-La2O3
coating layer is amorphous or microcrystalline with a submicron thickness.
The coated powders are then more sinterable, and the mechanical properties
of the ceramics prepared from such powders are improved.
Electronic Properties and Formation Mechanism of Metallo-Carbohedrenes
Authors: Kawazoe Yoshiyuki , Gu Bing-Lin , van Schilfgaarde Mark , Yu Jing-Zhi , Ohno Kaoru 
Published: April 2011

ABSTRACTWe have calculated the structure and electronic properties of several metallo-carbohedrenes within the local density-functional approximation, using both methods of a linear combination of atomic orbitals and full-potential muffin-tin orbitals. The calculated density of states and Mulliken population of double cage Ti14C21and triple cage Ti18C29are quite similar to that of single cage Ti8C12. There is no additional cohesion in multicage structure, which may explain why there is not a strong tendency to form larger, multi-cage structures. A new stable structure for Ti8C12is also proposed and structures Ti10C12+x(x=1, 2, 3, 4, 5) have also been discussed.
A Study on the Purification methods of Carbon Nanotubes and Stm Imaging of the Carbon Nanotubes
Authors: Yumura Motoo , Uchida Kunio , Niino Hiroyuki , Ohshima Satoshi , Kuriki Yasunori , Yase Kiyoshi , Ikazaki Fumikazu 
Published: April 2011

AbstractsPurification process to obtain nanotubes out of the cathode product mostly including fragments of graphitic sheet and/or amorphous carbon has been established. Structures and electronic properties of carbon nanotubes were studied. By the Raman scattering measurement, only one peak at 1581 cm−1 akin to that of graphite was found out. It was confirmed by STM observation of purified nanotubes. Purified nanotubes was semiconductor or semimetal.
Measurements of the Conductivity of Individual 10 Nm Carbon Nanotubes
Authors: Whitesides George M. , Weisbecker Carl S. 
Published: April 2011

ABSTRACTCatalytically grown carbon fibers approximately 10 nm in diameter and several microns long were characterized by transmission electron microscopy and determined to be multiple-walled nanotubes, and a technique was developed to measure the conductivity of an individual nanotube. Nanotubes were dispersed in solvents and precipitated onto lithographically defined gold contacts to make a ‘nano-wire’ circuit. Non-contact AFM was used to image the nano-wires, and a resistance of 11.4 (± 1.0) MΩ was measured through a single nanotube at 23°C. A resistivity of 9.5×10−5 Ω m was estimated for carbon conducting along the axis of a fiber. Local heating of nanotubes appeared to occur at high current densities. The nanotubes could sustain currents on the order of 10 μA per fiber, but application of currents on the order of 100 μA per fiber resulted in rapid decomposition in air and breaking of the circuit.
Optical Properties of Amorphous Carbon Doped with Copper
Authors: Ivanov-Omskii Vladimir I. , Abaev M.I. , Yastrebov S.G. 
Published: April 2011

ABSTRACTWe report the optical properties of amorphous C:Cu films produced by co-sputtering of graphite and copper targets in an argon plasma. Ellipsometric measurements at 632.8 nm were performed to evaluate dielectric permittivity vs copper content. We have observed a pronounced peculiarity of imaginary and real parts of the dielectric function at a copper content of about 14%. A correlation between the concentration dependence of the DC conductivity and that of the imaginary part of permittivity is clearly demonstrated. This correlation points to the existence of a less-conductive phase with the stoichiometric formula CuC6.
Aspects of the Mechanical Properties of Electrodeposits
Authors: Weil Rolf 
Published: April 2011

AbstractThe strengths and ductility of electrochemically deposited metals generally are different from those of the corresponding ones produced by other means. The difference is due to the growth mechanism of the deposits, that they can contain substances which are unstable at elevated temperature and the presence of various crystal defects. The effects on the mechanical properties of electrodeposits of dislocations, twins, voids, codeposited foreign materials, surface crevices, subgrain and grain boundaries, internal stresses and textures are discussed. The ways polarization, current form, solution temperature and agitation affect the mechanical properties of deposits are reviewed. A discussion of the relationships between hardness, the tensile and the fatigue properties is also included. Annealing effects and those of special structures on the properties are also considered.
W/Si Schottky Diodes: Effect of Metal Deposition Conditions on the Barrier Height
Authors: Mamor M. , Finkman E. , Meyer F. , Bouziane K. 
Published: April 2011

AbstractThe Schottky barrier heights (ΦB) for W/Si Schottky diodes have been determined from I–V measurements. The effects of the sputter deposition conditions of the W-films were studied. X-ray diffraction was used to examine the structure and the lattice parameters of the W-films while the stress was determined by using a profilometer from the measurement of the curvature of the substrate after metallization. The resistivity is determined by using a four-point probe. A compressive-to-tensile stress transition is associated with the transformation of the ±—W-phase into the (β—W-phase as the working gas pressure is increased. These effects, which are frequently observed, coïncide with a significant increase of the W-film resistivity and a change (△ΦB≈50 meV) in the Schottky barrier height on n-type. On the other hand, the barrier height on the p-type remains constant under all the experimental conditions investigated. These results are discussed in terms of effects of strain and structure of W-films on the work function of the W, as well as in terms of modification of the pinning position of the Fermi level or else change in the value of the Richardson constant.
Stress and Density of Thin TiO2 Films Produced by Different Methods
Authors: Ottermann C. R. , Heming M. , Bange K. 
Published: April 2011

AbstractStress, density and refractive behavior are analyzed for TiO2 layers deposited by reactive evaporation (RE), ion plating (IP), plasma impulse chemical vapour deposition (PICVD) and spin coating (SP) from bending of the substrate and by means of Rutherford Backscattering Spectroscopy (RBS), respectively. Densities between 2.7 gem-3 and 3.8 gem-3 are obtained depending on coating techniques and coating conditions. Refractive index depends linear on density. A correlation between film stress and density is observed which is independent from coating process, production parameters and crystal structure of the as-deposited films. Stress is tensile at low densities and compressive for films with densities of the order of the crystal phase of anatase (3.84 gem-3). The phase transition from amorphous to anatase due to annealing induces an increase in stress. Film density determines the transition temperature, and the magnitude of stress increase.
Structure and Mechanical Properties of Nitrogen Incorporated Diamond-Like Carbon Films
Authors: Lee Kwang-Ryeol , Eun Kwang Yong , Rhee Jae-Seong 
Published: April 2011

AbstractNitrogen incorporated diamond-like carbon (DLC) films were deposited by r.f. plasma assisted chemical vapor deposition (r.f.-PACVD) method. Mixtures of benzene and ammonia or nitrogen were used as the reaction gases for the deposition. Composition, atomic bond structure and mechanical properties of the film were investigated when the fraction of nitrogen source increases from 0 to 0.79. All films were deposited at fixed negative bias voltage of the cathode (-500 V) and the deposition pressure (10 mTorr). While ammonia addition reduces both residual stress and hardness of the film from 1.7 to 1 GPa and from 2750 to 1700 Kgf/mm2 respectively, the mechanical properties are not significantly varied by nitrogen addition. Deposition rate, composition and atomic bond structure are also dependent on the nitrogen source gases. Observed behavior of mechanical properties is discussed in terms of the content of inter-links of sp2 clusters. In addition to hydrogen, C≡N bonds in the film are also terminated sites of three dimensional atomic bond network. By considering the hydrogen concentration and the C≡N bonds, it can be shown that the mechanical properties of nitrogen incorporated DLC films are determined by the content of inter-links of sp2 clusters.
Role of Dislocation Interactions in Decreasing Mobile Threading Dislocation Density and Limiting Strain Relaxation in Si1-xGex Heteroepitaxial Films
Authors: Gillard Veronique T , Nix William D 
Published: April 2011

AbstractIn situ substrate curvature measurements obtained during isothermal annealing of Si1-xGex films grown on (001) Si substrates allow determination of the evolution of strain versus time in these films. By coupling the strain relaxation measurements with previous measurements of dislocation velocities in this system, the mobile threading dislocation density and its evolution in the course of strain relaxation can be determined. The results indicate that in the late stage of strain relaxation, the mobile threading dislocation density decreases significantly. Results obtained with samples of two different sizes show that this decrease in mobile dislocation density is not primarily associated with dislocations running out at the edges of the film but with dislocation interactions impeding their further motion. Furthermore, for films thinner than 500 nm the residual strains after annealing are significantly higher than the values predicted by the equilibrium theory of misfit dislocations. The measured residual strains are compared with predictions based on Freund’s treatment of the blocking of a moving threading segment by an orthogonal misfit dislocation in its path. We find that the blocking criterion gives a very good account of the residual strain in Si1-xGex films and that blocking of threading dislocations by other misfit dislocations appears to play an important role in the late stage of strain relaxation.