bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photomodulation spectroscopy of thin Ge films formed by molecular beam epitaxy on Si (111)
Authors: Stoke K. L. , Deelman P. , Kang H. S. , Schowalter L. J. , Persans P. D. 
Published: April 2011

AbstractThe photomodulated transmission spectrum of a single Ge layer grown at 500°C on the Si(1 11) surface by molecular beam epitaxy is reported. The nominal Ge layer thickness was 50 nm. The modulation spectrum of thicker layers is dominated by a threelobed structure centered 70–80 meV above the bulk direct band edge. This structure is ascribed to excitation-induced broadening of the lowest direct exciton.
Sensitivity of Nanocrystalline Copper Sulfide/Cadmium Sulfide Heterojunction in Near-Ir Region
Authors: Artemyev M. V. , Sviridov D. V. , Gaponik N. P. , Maljarevich A. M. 
Published: April 2011

AbstractThe photovoltaic p-n heterojunction based on thin layer of 10 nim size copper sulfide nanocrystals and evaporated cadmium sulfide film was prepared. The partial oxidation of copper sulfide nanocrystals prior the fabrication of the heterostructure results in the formation of additional absorption band in near-IR region beyond the fundamental absorption of bulk copper sulfide and cadmium sulfide. This band can be attributed to the intervalence charge transfer between copper ions in the core and in the oxidized shell. The photovoltaic effect observed in the near-IR region at ITO/nano-CuS/CdS/Au heterojunction is due to the generation of the electron-hole pairs in the CuS nanocrystalline film followed by the separation of charge carriers at the CuS/CdS junction.
The Optical Properties of InGaAs(P)/InP Under Group V Sublattice Two-phase Interdiffusion
Authors: Li E. Herbert , Micallef Joseph , Shui W. C. 
Published: April 2011

AbstractUsing the fundamental transition state, we will investigate the two phase interdiffusion of group V sublattice in a strained lattice matched InGaAs/InP quantum well (QW) structures. The model employs three parameters namely the diffusion coefficients in the barrier (Db)and in the well (Dw)and the concentration ratio (k) of the diffused species at the heterstructure. The QW model includes the effects of strain and the exciton. A pseudo time dependent calculation is also considered and results are fitted to the reported experimental data. These parameters which characterize the diffusion mechanism can be measure to form a better understanding of the interdiffsion process for group V sublattice.
Selective Growth of GaP on Si by Metal Organic Vapor Phase Epitaxy
Authors: Lee J. S. , Salzman J. , Emerson D. , Shealy J. R. , Ballantyne J. M. 
Published: April 2011

AbstractExtremely flat layers of GaP were grown on 4° miscut (100) Si substrates by selective Metal- Organic Vapor Phase Epitaxy. An enhancement of Re@3 was measured at the growth edges, which corresponds to a Sherwood number of 12.5. Defect-free growth is obtained at the edge of the silicon nitride mask. A gradual transition to growth with a large defect density is observed with increasing distance from the mask edges. In the defect free areas, a recovery of the (100) crystal plane is consistently measured on top of the grown mesas. This seems to indicate a pure layer-bylayer homoepitaxial mode (Frank-van der Merve mode) after the island mode nucleation (Volmer- Weber mode) on Silicon is completed, forming a thin smooth seed layer. High Resolution TEM shows a uniform Si-GaP transition. Micro-Raman Spectroscopy with spatial resolution of ˜1 micrometer was performed to assess the crystal quality as a function of the distance from the growth edge.
Determination of the Order Parameter by Quantitative Tem Techniques
Authors: Bode Michael H. , Ahrenkiel S. P. , Kurtz S. R. , Bertness K. A. , Arent D. J. , Olson J. 
Published: April 2011

AbstractTo quantitatively measure the order parameter in ordered III-V materials we have developed two techniques based on electron microscopy. The first technique calculates the diffraction pattern of ordered material quantitatively and fits the calculated data to experimentally obtained data. A test sample, specifically grown for this technique, shows that the method can determine the average order parameter with high accuracy. We found an order parameter of 0.34, which coincides with the value found by piezo-reflectance measurements. To measure the order parameter on a smaller length scale, we use a technique based on image processing of high-resolution TEM images. By comparing ordered and disordered parts of the image, we calculate the relative order parameter on an atomic length scale. Analyzing the data provides information about the development of the ordering in the crystal.
Activation Energy of Electromigration in Copper Thin Film Conductor Lines
Authors: Gladkikh A. , Lereah Y. , Karpovski M. , Palevski A. , Kaganovskii Yu. S. 
Published: April 2011

AbstractActivation energy of electromigration damage was determined as 1.2 eV for Cu lines, indicating grain boundary paths for electromigration. The surface diffusion was found to play a role during electromigration in Cu and impeded the failure process.
Chemical-Mechanical Polishing of Copper in Glycerol Based Slurries
Authors: Kumar K. S. , Murarka S. P. 
Published: April 2011

AbstractThe development of a reliable/reproducible chemical-mechanical polishing (CMP) process to planarize and define copper using a dual damascene approach is essential for introducing copper as the interconnection metal. In this paper we present results of a new polishing slurry containing glycerol and Al2O3 abrasive. The slurry is a near-neutral medium and does not have the effect of acidic or basic slurries on copper. The effect of glycerol concentration and the abrasive size on the CMP behavior is investigated. The changes in the slurry temperature, pH, viscosity, dielectric constant and surface tension were examined as a function of the glycerol concentration. The results, indicating a strong dependence on both the glycerol concentration and the abrasive size, are explained on the basis of viscosity and dielectric constant of the solution and the van der waal forces and the electrostatic repulsion between the particles.
Phase and Mechanical Stress in and Surrounding Tisi2 and Cosi2 Lines Studied by Micro-Raman Spectroscopy
Authors: Wolf I. De , Howard D. J. , Maex K. , Maes H. E. 
Published: April 2011

AbstractThe local mechanical stress induced in a silicon substrate by silicide lines (CoSi2, CoSi, C49 and C54 TiSi2) with different thicknesses, widths and spacings is studied using micro-Raman spectroscopy. The results show that the stress becomes larger with increasing line thickness and decreasing line spacing. For the different silicides, the stress increases according to: CoSi < CoSi2 < C49 TiSi2 < C54 TiSi2. By fitting a simple stress model to the Raman data, quantitative values for the stress components can be determined. The dependence of the TiSi2 phase on thickness and line width is studied for the same samples. These studies show that micro-Raman spectroscopy can provide local information (μm resolution) on the TiSi2 phase.
Effects of Size and Shape of Lateral Confinement on the Formation of NiSi2, CoSi2 and TiSi2 on Silicon Inside Miniature Size Oxide Openings
Authors: Chen L. J. , Yew J. Y. , Cheng S. L. , Chen K. M. , Nakamura K. , Tsui B. Y. 
Published: April 2011

AbstractThe effects of size and shape of lateral confinement on the formation of NiSi2, CoSi2 and TiSi2 on silicon inside miniature size oxide openings have been investigated. Epitaxial growth of NiSi2 of single orientation on (111)Si was found to occur at a temperature as low as 400 °C inside both contact holes and linear openings of 0.3 μm or smaller in size. Contact holes were found to be more effective in inducing the epitaxial growth of NiSi2 of single orientation than that of linear openings of the same size. The effects of size and shape of lateral confinement on the epitaxial growth of NiSi2 on (111)Si are correlated with the stress level inside oxide openings. The faceting of CoSi2 was found to occur at a lower temperature inside oxide openings of smaller size. C49-C54 TiSi2 transformation was observed to be more difficult on both blank and BF2+ implanted (001)Si inside smaller size oxide openings.
Structural Characteristics of CoGe2 Alloy Films Grown Heteroepitaxially on GaAs(100) Substrates Using the Partially Ionized Beam Deposition Technique
Authors: Mello K. E. , Murarkak S. P. , Lee S. L. , Lu T.-M. 
Published: April 2011

AbstractThe Partially ionized beam (PIB) deposition technique was used to deposit CoGe2 thin films heteroepitaxially on GaAs(100) substrates in a conventional vacuum. For the CoGe2(001)/GaAs(100) system, which leads to an Ohmic contact, a substrate temperature of 280°C and ∼1200 eV Ge+ ions are required. Reducing the ion energy or lowering the substrate temperature both produce a different orientation in the films. Films deposited at 280°C with a zero accelerating potential for the ions, and those deposited at 200°C with -1200 eV Ge+ ions result in a CoGe2(100)//GaAs(100) type orientation domination, leading to rectifying behavior.
A microstructural and electrical investigation of Pd/Ge/Ti/Au ohmic contact to n-type GaAs
Authors: Kwak J. S. , Baik H. K. , Kim H. , Lee J. -L. , Shin D. W. , Park C. G. 
Published: April 2011

AbstractInterfacial microstructure and elemental diffusion of Pd/Ge/Ti/Au ohmic contact to n-type GaAs have been investigated using x-ray diffraction(XRD), Auger electron spectroscopy(AES), and cross-sectional transmission electron microscopy(XTEM), and their results are used to interpret the electrical properties. The lowest contact resistance of 0.43 Ωmm is obtained after annealing at 380°C. The contact is thermally stable even after isothermal annealing for 5h at 400°C. The good Pd/Ge/Ti/Au ohmic contact is due to the formation of both AuGa and TiO compounds. The AuGa compound enhances the creation of more Ga vacancies, followed by incorporation of Ge into Ga vacancies and TiO compound suppresses As outdiffusion from GaAs substrate, respectively.
Comparison of pd/sn and pd/sn/au thin-film Systems for Device Metallization
Authors: Islam M. S. , Mcnally Patrick J. , Cameron D. C. , Herbert P. A. F. 
Published: April 2011

AbstractAn Ohmic contact system comprising of Pd/Sn metallization has been developed for n-GaAs and compared with Pd/Sn/Au metallization. Surface morphology of the contacts is investigated using surface profilometry measurements and Scanning Electron Microscopy (SEM). The contact depth profiles are analyzed by Secondary Ion Mass Spectrometry (SIMS). Contact resistivities, Pc, of the proposed metallizations are measured using a conventional Transmission Line Model (TLM) method. A lowest ρc, of ∼2.07×10−5 Ω-cm2 was obtained with a Pd(50 nm)/Sn(125 nm) contact on 2×1018 cm−3 n-GaAs after annealing at 400 °C for 30 min. A Au overlayer improves the characteristics of the Pd/Sn contacts. The Pd(50 nm)/Sn(125 nm)/Au(100 nm) contact shows a lowest ρc of ∼1.29×10−6 Ω-cm2 after annealing at 330 °C for 30 min. The Pd/Sn/Au contacts exhibit superior properties compared to those of alloyed five-layer Au/Ge/Au/Ni/Au contacts.
In-Situ UHV Electromigration In Cu Films
Authors: Vook R. W. , Jo B. H. 
Published: April 2011

AbstractCopper stripes, current stressed under UHV, clean surface conditions, have an activation energy Q for electromigration (EM) of 0.5 eV, significantly lower than the 0.8 eV reported when the surface has been exposed to air. Application of positive or negative potentials to the stripes during EM testing raises or lowers the clean surface Q in a linear relationship in the range of 0.2 to 1.0 eV. These results were obtained from in-situ electrical resistance measurements during which potentials up to +/− 800 volts were applied to the stripe. Thus the rate at which surface EM takes place is influenced by the sign and magnitude of the applied potential. The low Q for the in-situ clean surface studies also implies that surface diffusion is the dominant physical mechanism whereby EM damage occurs. Ex-situ SEM studies support this conclusion. This work has important implications for ULSI since numerous recent studies have indicated that surface and/or interface diffusion are present during current stressing of passivated and unpassivated fine line stripes.
Influence of the Synthesis Parameters on Textural and Structural Properties of MCM-41 Mesoporous Materials
Authors: Terrés E. , Ramírez S. S. , Domínguez J. M. , Montoya A. , Navarrete J. , Gómez-Cisneros M. 
Published: April 2011

AbstractMCM-41 mesoporous materials were synthesized under different hydrothermal conditions using organic templates, i.e. CTMA-Br, DTMA-Br. Reaction temperature (120 to 195 °C) and reaction time (24 to 120 hr) varied and their influence on the structure properties of MCM-41 was sought i.e. d = 36 to 41.6 Å for distinct micelles diameters. Also, insertion of polyaromatics into the surfactant micelles was determinant in the final pore diameter, i.e d = 35.4 to 48.6 Å.
Emission Control Catalyst Derived from Mesoporous Molecular Sieves
Authors: Paul Partha P. , Miller Michael A. , Heimrich Martin J. , Schwab Stuart T. 
Published: April 2011

AbstractA lean NOx catalyst is needed to control NOx emissions generated by oxygen-rich combustion processes to obtain higher fuel economy. We have developed such a catalyst using modified mesoporous molecular sieves (MCM-41). An iron(II)-complex impregnated MCM-41 has been synthesized which has been further treated with [Pd(NH3)4]Cl2. This treatment resulted in further exchange of Na+ ions of the molecular sieves with Pd(NH3)42+ thus forming Catalyst A. The catalytic activity towards NOx, CO and HC was studied using simulated exhaust gas, as well as engine exhaust gas.
Preparation of Microporous Films with Sub Nanometer Pores and their Characterization Using Stress and FTIR Measurements
Authors: Samuel J. , Hurd A. J. , van Swol F. , Frink L. J. Douglas , Brinker C. J. , Contakes S. C. 
Published: April 2011

AbstractWe have used a novel technique, measurement of stress isotherms in microporous thin films, as a means of characterizing porosity. The stress measurement was carried out by applying sol-gel thin films on a thin silicon substrate and monitoring the curvature of the substrate under a controlled atmosphere of various vapors. The magnitude of macroscopic bending stress developed in microporous films depends on the relative pressure and molar volume of the adsorbate and reaches a value of 180 MPa for a relative vapor pressure, P/Po = 0.001, of methanol. By using a series of molecules, and observing both the magnitude and the kinetics of stress development while changing the relative pressure, we have determined the pore size of microporous thin films. FTIR measurements were used to acquire adsorption isotherms and to compare pore emptying to stress development, about 80% of the change in stress takes place with no measurable change in the amount adsorbed. We show that for sol-gel films, pore diameters can be controlled in the range of 5 – 8 Å by “solvent templating”.
Synthesis and Structural Studies of Microporous Yttria-Stabilized Zirconia Ceramics
Authors: Srinivasan R. , Sparks D. E. , Milburn D. R. , Davis B. H. 
Published: April 2011

AbstractYttria-stabilized zirconia was prepared by (i) coprecipitation and (ii) alkoxide hydrolysis. The thermal and X-ray diffraction data were compared. The coprecipitation method yields microporous materials after calcination at 500°C for 4 hours with a narrow pore size distribution at a radius of 2–2.5 nm. Similar results were also seen with the alkoxide hydrolysis.
Sol-Gel Process form Heterometallic Alkoxides to Incorporate Alkaline- and Rare Earths in Alumina for automotive Applications
Authors: Narula C. K. 
Published: April 2011

AbstractThe high cost of materials prepared by sol-gel processing and the loss of useful surface properties at elevated temperature has prevented the application of sol-gel processed materials in automotive exhaust reduction catalyst formulations. In this report, we briefly describe the important developments needed in the next generation automotive catalysts and the role of sol-gel processed materials. We will also discuss the application of heterometallic alkoxides as sol-gel precursors to achieve the molecular distribution of lanthanides and alkaline earths in alumina matrices needed for the stabilization of alumina based materials at elevated temperatures.
Colloidal Processing of Temperature Shock Resistant SiC with Tailored Porosity
Authors: Aslan Mesut , Nass Rüdiger , Schmidt Helmut 
Published: April 2011

AbstractFrom aqueous slurries containing SiC powder coated with nano-scaled carbon black, green bodies were prepared by slip casting. On slip cast green bodies the densification, microstructural development and mechanical properties were investigated. Depending on the sintering temperature and boron carbide content samples with different relative densities between 0.90 and 0.988 were obtained after pressureless sintering. In all samples a homogeneous microstructure (distribution of the residual pores and grain morphology) was observed. Due to this homogeneity the sintered samples showed high amount of fracture strength of about 500 MPa, even at large residual porosities of 10 %. The thermal shock resistance of samples with different porosities measured by water quenching revealed the critical temperature difference to be around 700 K.
Local Microstructural Organization in Carbogenic Molecular Sieves
Authors: Kane Michael S. , Foley Henry C. 
Published: April 2011

AbstractThe microstructure of nanoporous, carbogenic molecular sieves (CMS) was studied using high resolution electron microscopy and neutron diffraction. The narrow range of pore sizes observed in these complex materials suggests that although these materials are globally amorphous, the local microstructural features are more organized. Our work, focused on poly(furfuryl alcohol)-derived CMS, is aimed at characterizing the evolution of this microstructure. Microscopy results show that materials synthesized at low temperature have some degree of organization but that the microstructure is featureless and symmetric at longer length scales. This symmetry is broken at higher synthesis temperatures as thermodynamic driving forces lead to further organization of the carbon atoms into more ordered structures but the length scales remain short. Micrographs of high temperature CMS show a high degree of curvature and features reminiscent of fullerene. The connectivity of the carbon atoms in the CMS has been probed using powder neutron diffraction. This data suggests that the atoms in the CMS form ordered structures on the length scale of 15Å which are distinctly different from the structure of graphite. These observed changes in the microstructure directly impact the adsorptive and molecular sieving characteristics of the CMS as illustrated by the marked differences between the diffusivities of oxygen and nitrogen. This property is crucial for the very demanding separation of nitrogen from oxygen in air.
Raman Spectroscopy Studies of Reactions Between Sulfur Dioxide and Microparticles of Hydroxides
Authors: Aardahl C. L. , Davis E. J. 
Published: April 2011

AbstractGas-aerosol chemical reactions between dilute SO2 and alkali-metal hydroxides have been explored using elastic and inelastic (Raman) light scattering. Single charged particles of NaOH, KOH, and Ca(OH)2 were levitated electrodynamically in a reaction chamber and exposed to humid nitrogen. Particles that were not water soluble remained crystalline while water soluble compounds deliquesced into solution microdroplets. The resulting solids or solutions were reacted with dilute SO2 in humid N2. Elastic scattering measurements and Raman spectra were taken during the gas-aerosol reactions, and results indicate that reaction products and sorbent utilization are highly dependent on the water content of the particle.
Formal Charge Model for Predicting Structures, Acid-Base, and Ion Exchange Properties of Mixed Oxides
Authors: Bunker B. C. 
Published: April 2011

AbstractThe range of mixed-oxide materials used in ion exchange and catalytic materials is rapidly expanding from aluminosilicates such as zeolites and clays into materials whose structure and chemical properties are more difficult to predict and understand. A simple model based on local charge has been developed to predict distributions of local bonding configurations of both cations and anions in mixed oxides. The model, illustrated for the case of silicotitanates, provides qualitative predictions regarding both the acid-base and ion exchange properties of such materials as a function of composition.
Getting a Charge Out of Microporous Oxides: Building a Better Ultracapacitor
Authors: Liu Kuo-Chuan , Anderson Marc A. 
Published: April 2011

AbstractMicroporous nickel oxides consisting of nano-sized particles have been utilized as active electrode materials for ultracapacitors. Both the physical adsorption of ions near the charged surface of these particles and surface oxidation/reduction reactions play a role in the capacitative charge storing mechanism. These are therefore appropriately referred to as pseudo-capacitors since they rely on mechanisms in addition to double layer charging in order to store energy. In this study, it has been shown that surface hydration contributes to the formation of an initial compound which participates in the electrochemical reactions of ultracapacitors. The specific capacitance of this material is ranging from 60 to 120 F/g depending upon the types of electrolyte solution used in the ultracapacitor.
Silver Sorption by Manganese Oxide
Authors: Ravikumar R. , Fuerstenau D. W. 
Published: April 2011

AbstractSilver-manganese oxide ores are present in western United States, Mexico, South America, and Sumatra. The amount of silver varies between a few parts per million (ppm) to thousands of ppm. However, these ores are not compatible with conventional metallurgical treatment for the extraction of silver. This research is the study of the nature of silver binding with one model manganese oxide phase, cryptomelane. Cryptomelane is widely present in the United States and in parts of Colorado, with silver-bearing cryptomelane ore bodies containing up to a maximum of 1 wt% of silver. In order to better understand the nature of silver binding in cryptomelane, synthetic samples of cryptomelane were prepared and characterized, and then used for silver sorption experiments. The silver uptake appears to be a function of the solution chemistry conditions, pH and potassium nitrate concentration. The sorption of silver was found to increase with decreasing pH and at a fixed pH value, the sorption density was higher at a lower potassium nitrate concentration. Kinetics and equilibrium sorption data from lithium and sodium nitrate background electrolyte demonstrates three main results: firstly, most of the uptake of silver is compensated by release of potassium; secondly, the exchange for silver with protons and potassium ions is almost stoichiometric; and lastly, the importance of tunnel sites for the sorption reaction in cryptomelane. An ion-exchange model for the uptake of silver onto cryptomelane will also be discussed.