bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of Nanocrystalline Titania Powder by Aerosol Pyrolysis of Titanium Alkoxide
Authors: Ahonen P.P. , Kauppinen E.I. , Deschanvres J.L. , Joubert J.C. , Van Tendeloo G. 
Published: April 2011

ABSTRACTNanocrystalline titania powders were prepared via aerosol pyrolysis of titanium tetrabutoxide precursor. As-received and annealed powders were characterized by XRD, SEM and TEM (+EDS), thermogravimetry, Raman- and IR-spectrometry, surface area analysis and XRF. In addition, gas-phase mass size distributions were obtained by low-pressure impactor aerosol measurements. Powders consisted of micrometer sized spherical particles. Amorphous titanium oxide powders were obtained at lower pyrolysis temperatures and only after subsequent thermal annealings crystallized titania was formed. Not until at 500°C in nitrogen and 580°C in air did pyrolysis synthesis form nanocrystalline anatase phase in-situ. During the annealing at 900°C for one hour rutile phase was usually approached, but phase pure anatase was obtained when powder had been synthesized in nitrogen atmosphere at 500°C. The proposed reason for the thermally stable anatase formation is the formation of oxygen deficient anatase phase which has a high thermal barrier to convert to rutile. Titanium tetrabutoxide evaporation and subsequent gas-to-particle formation of additional 30-80 nm particles was observed in nitrogen atmosphere at temperatures higher than precursor boiling point.
Fabrication of Agglomerate-Free Nanopowders by Hydrothermal Chemical Processing
Authors: Schmidt H.K. , Nass R. , Burgard D. , Nonninger R. 
Published: April 2011

ABSTRACTA chemical processing technique for the fabrication of nanopowders has been developed. The route is based on precipitation processes in solutions, either within aqueous droplets in micro-emulsions in the presence of surface modifiers like surfactants or by direct precipitation in solutions in the presence of these surface modifiers or small organic molecules directly bonded to the particle surface. In order to obtain well crystallized or densified particles, a continuous flow hydrothermal process has been developed which allows the fabrication of agglomerate-free surface modified nanopowders. The surface modification provides a full redispersibility after drying and permits a water-based processing. Nanoparticles preparation for ZrO2, ITO and ATO by this route are described.
Joining of Aluminium Structures with Aluminium Foams
Authors: Burzer J. , Bernard T. , Bergmann H. W. 
Published: April 2011

ABSTRACTThe aim of this work is the evaluation of new construction elements for applications in transportation industry which are based on new designs incorporating commonly applied aluminium structures and aluminium foams. The work includes the characterisation of the joining process, the joining mechanism and the mechanical properties of the joining zone. A testing method for the joints is developed which is based on a common tensile test in order to evaluate the influence of the main laser welding parameters on the toughness of the joints and to afford a comparison between laser beam welding and gluing process. The analysis of the joining mechanism is investigated with the help of metallographic studies. In addition, the energy absorption properties of aluminium hollows filled and joined with foam structures are characterised.
Shear Properties on Aluminum Metal Foams Prepared by the Melt Route
Authors: Saenz E. , Baranda P. S. , Bonhomme J. 
Published: April 2011

ABSTRACTThe shear modulus and shear strength of AISi7Mg aluminum foam with 15% (vol) of 13tm SiC particles were determined through shear testing. A foam slab with a density of 0.31 g/cm3 was supplied by Hydro Aluminium.Four samples were tested according to ASTM C 273–61. The specimens were bonded to steel load plates. The relative displacement of the plates was measured using two extensometers. In order to evaluate the effect of the cell size distribution on shear properties, cell size and material distribution analyses were carried out for the metal foam slab in areas close to those from which the shear specimens were extracted.A fast failure was observed after the maximum shear load. The failure in the samples were located in the central section of the slab mainly because the lower density was located there.
Emissivity Of Coated Silicon At Elevated Temperatures
Authors: Rogne H. , Ahmed H. 
Published: April 2011

ABSTRACTIsothermal electron beam heating has been combined with in situ optical measurements in order to measure the emissivity of coated silicon samples at elevated temperatures. The coatings include a number of oxide, nitride, and silicon films. Infrared emission spectra were recorded from I to 9 μm for temperatures between 750 and 1200°C. The experimental results were compared with calculated theoretical values, which were predicted from the theory of thin film coatings, using a matrix model incorporating the optical constants for the materials. A good match between experimental and theoretical values validates the use of the infrared optical constants for theoretical modelling related to control and temperature measurements in rapid thermal processing systems.
Residual Gases and Their Influence on Processes in the Atmospheric Rapid Thermal Processing Equipment
Authors: Hu Yao Zhi , Tay Sing Pin 
Published: April 2011

ABSTRACTThe residual impurity gases in the atmospheric rapid thermal processing (RTP) equipment are becoming an important factor in sub-micron ULSI industry. For example, 1% nitrogen in oxygen decreases the RT oxide thickness, and a small amount of moisture or oxygen in nitrogen may strongly affect the RT titanium silicidation. The effective method to reduce the residual gases is to use process gas to purge the chamber. In the present paper the gas purging mechanisms were in-situ investigated in the flow rate range of 10 to 60 slpm using a Quadrapole Residual Gas Analyser (RGA) and gas sensors. The gases for purging studies are N2, O2, He and Ar. It has been found that there are two regimes in the dependence of the residual gas concentration on purging time. Based on the results of systematic experiments, a purging equation, called Pseudo-PST (“perfectly stirred tank) model, has been developed and was used to give the interpretation of the purging process in the atmospheric RTP system. The limitation of the RGA and the oxygen analyzer used to atmospheric RTP system was also discussed.
The Growth of Strained Thin Films of Gadolinium
Authors: Waldfried C. , Zeybek O. , Bertrams T. , Barrett S. D. , Dowben P.A. 
Published: April 2011

AbstractThe growth of strained thin films of gadolinium has been investigated with low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) and compared to the film growth of unstrained gadolinium. Strained thin films of gadolinium are distinct from the unstrained films by a substrate induced preferential domain growth direction, which is also reflected in the electronic structure.
The Effect of Deposition Method on Growth Morphology - Comparison of Molecular Beam Epitaxy, Ion Beam Assisted Deposition and Sputter Deposition
Authors: Michely Th. , Kalff M. , Comsa G. 
Published: April 2011

AbstractThin films created by the deposition or under influence of atoms with hyperthermal energies (E = 100 -104eV) exhibit properties which differ in many respects from those of films created by deposition of atoms with thermal energy. The morphologies of thin Pt-films deposited on Pt(111) under otherwise identical deposition conditions by molecular beam epitaxy (MBE), ion beam assisted deposition (IBAD) and sputter deposition (SD) differ in film structure size, island shapes and film roughness. The different film structure sizes are unambiguously traced back to two different island formation mechanisms inherent to these deposition methods. While in MBE the islands result from nucleation in a supersaturated adatom gas, in IBAD and SD they result by direct or indirect creation of adatom clusters as a consequence of single impacts of energetic atoms present in the depositing particle flux. The differences in film roughness are not only due to the different island formation mechanisms, but seem to be closely related to the different step edge structures at the growth front.
Epitaxial Growth of Nb Films and Nb/Cu Bilayers on A12O3 Substrates by DC Magnetron Sputtering
Authors: Loloee R. , Crimp M.A. , Zhu W. , Pratt W.P. 
Published: April 2011

AbstractEpitaxial single crystal Nb films have been grown by sputter deposition on (1 1 2 0) sapphire substrates. Subsequently, high quality epitaxial Cu films, with two orientation variants, have been grown onto the epitaxial Nb films. The sputtered films have been characterized using atomic force microscopy, electron backscattered patterns, and conventional transmission electron microscopy.
Role of Oxygen Adatoms in Homoepitaxial Growth of Cu(001)
Authors: Yata Masanori , Rouch Herve , Nakamura Keikichi 
Published: April 2011

AbstractO atoms segregate to the surface during Cu homoepitaxial growth on Cu(001)-(2√2×√2)-O to retain the (2√2×√2) surface. The presence of an O adlayer on the Cu surface raises the barrier height for the surface diffusion of the Cu adatom and increases the transition temperature of the growth mode from step flow to layer by layer. The growth proceeds by site exchange between Cu adatoms and O atoms. The site-exchange rate competes with the Cu deposition rate. There exists a critical Cu deposition rate above which the O atoms can not exchange the sites with Cu adatoms. The critical Cu deposition rate obeys an Arrhenius relation and the active energy for the site-exchange is estimated at 0.66 eV.
Failure Mechanisms of Particulate Two-Phase Composites
Authors: Antretter T. , Fischer E D. 
Published: April 2011

AbstractIn many composites consisting of hard and brittle inclusions embedded in a ductile matrix failure can be attributed to particle cleavage followed by ductile crack growth in the matrix. Both mechanisms are significantly sensitive towards the presence of residual stresses.On the one hand particle failure depends on the stress distribution inside the inclusion, which, in turn, is a function of various geometrical parameters such as the aspect ratio and the position relative to adjacent particles as well as the external load. On the other hand it has been observed that the absolute size of each particle plays a role as well and will, therefore, be taken into account in this work by means of the Weibull theory. Unit cells containing a number of quasi-randomly oriented elliptical inclusions serve as the basis for the finite element calculations. The numerical results are then correlated to the geometrical parameters defining the inclusions. The probability of fracture has been evaluated for a large number of inclusions and plotted versus the particle size. The parameters of the fitting curves to the resulting data points depend on the choice of the Weibull parameters.A crack tip opening angle criterion (CTOA) is used to describe crack growth in the matrix emanating from a broken particle. It turns out that the crack resistance of the matrix largely depends on the distance from an adjacent particle. Residual stresses due to quenching of the material tend to reduce the risk of particle cleavage but promote crack propagation in the matrix.
Theoretical Analysis of Faceted Void Dynamics in Metallic Thin Films Under Electromigration Conditions
Authors: Ho Henry S. , Gungor M. Rauf , Maroudas Dimitrios 
Published: April 2011

AbstractA theoretical analysis is presented of the electromigration-induced dynamics of transgranular voids in metallic thin films. The analysis is based on self-consistent dynamical simulations of current-driven void surface propagation coupled with the distribution of the electric field in the metallic film. The simulation predictions highlight the rich nonlinear dynamics of current-driven evolution of voids that become faceted due to the strongly anisotropic nature of surface diffusion. The numerical results are analyzed based on approximate analytical solutions to faceted void migration and a linearized theory for the morphological stability of planar void facets.
The Role of the Diffusion Mechanism in Models of the Evolution of Microstructure During Phase Separation
Authors: Rautialnen T.T. , Sutton A.P. 
Published: April 2011

AbstractWe have studied phase separation and subsequent coarsening of the microstructure in a two-dimensional square lattice using a stochastic Monte Carlo model and a deterministic mean field model. The differences and similarities between these approaches are discussed. We have found that a realistic diffusion mechanism through a vacancy motion in Monte Carlo simulations is cruicial in producing different coarsening mechanisms over a range of temperatures. This cannot be captured by the mean field model, in which the transformation is governed by the minimization of a free energy functional.
Potts Model Simulation of Grain Size Distributions During Final Stage Sintering
Authors: Zeng P. , Tikare V. 
Published: April 2011

AbstractThe Potts Monte Carlo model was used to simulate microstructural evolution and characterize grain size distribution during the final stages of sintering. Simultaneous grain growth, pore migration and pore shrinkage were simulated in a system with an initial porosity of 10% with varying ratios of grain boundary mobility to pore shrinkage rates. This investigation shows that the presence of pores changes the grain size distribution and the topological characteristics due to pinning of grains by pores. As pores shrink away, their pinning effect decreases. Once pore shrinkage is complete, normal grain growth is achieved.
A Study of Self-Reinforcement Phenomenon in Silicon Nitride by Monte-Carlo Simulation
Authors: Okamoto Y. , Hirosaki N. , Matsubara H. 
Published: April 2011

AbstractA grain growth model based on the results of Monte-Carlo simulations is proposed for silicon nitride. The model was derived from the Potts model; in addition, principal characteristics of silicon nitride such as presence of liquid phase and anisotropy of grain growth were introduced. Employing this model, microstructure development of silicon nitride was investigated.Under certain simulation conditions, several grains grew in preference to other grains, and consequently, a self-reinforced microstructure was produced similar to that of actual silicon nitride. In particular, liquid phase fraction was found to be dominant factor affecting microstructure development.
Fatigue Behavior of GeO2-SiO2 Glasses
Authors: Gulati Suresh T. , Helfinstine John D. 
Published: April 2011

AbstractThe fatigue behavior of binary oxide glasses in the germania-silica system is interesting since it influences the long-term mechanical reliability of products made of these glasses. Dynamic fatigue tests were carried out in four-point bending in 100% RH using tumble abraded rods. The fatigue data were obtained as a function of GeO2 content which ranged from 0 to 24 mole %. In addition, other physical properties of these glasses, such as the thermal expansion coefficient, were measured as a function of GeO2 content. The results of these tests and analyses are highlighted in this paper.
Current Advances in Development of Material in the Field of Wiring in Japan
Authors: Takagi S. , Ishii N. , Hashimoto D. 
Published: April 2011

AbstractThis paper presents the current advances in the development of materials in the field of telecommunication wiring together with the background which created the need for the new technologies. The background is somewhat unique to the current socio-economical situation of Japan. The key technical areas, which are addressed in this paper, are; (1) fibers for transmission of over 1 Tbps by utilizing WDM (wavelength division multiplexing), (2) fibers for fiber amplifiers to replace repeaters within trunk lines, (3) high density cables with over 1000 fiber counts, (4) ABF (air blown fiber) for access system, (5) plastic optical fibers wiring in premises or offices operating at the transmission speed of over 200 Mbps.
Telecommunications Technology for the First Decade of the 21st Century
Authors: Wyndrum R. W. 
Published: April 2011

AbstractToday I will focus on telecommunications technology for the first decade of the 21st century. Few things incite speculation about the future more than a year ending in the numeral “zero.” With the approaching millennium and its near-mystical three zeroes, everyone everywhere hungers for a glimpse into the future. My vision of the telecommunications future shows a collective of universal capabilities made possible by limitless digital networks with ubiquitous access and functionality. Mobile communications, the Internet, video, telephony and a broad array of end-user services will be the major drivers moving network providers to fuse capability with transparency. Integration of the full spectrum of communication possibilities will be the trend of the 21st century.
Long-Term Reliability of Silica-Based Planar Lightwave Circuit Devices
Authors: Hanafusa H. , Sumida S. , Takato N. 
Published: April 2011

AbstractWe describe the results of accelerated lifetests performed on silica-based planar lightwave circuit (PLC) devices. Specifically, we tested PLC splitter modules in damp heat environments with different temperatures and humidities. The time-to-failure data of the splitter samples were analyzed by using the Weibull distribution, and the shape parameter was derived as 1.77. Moreover, the temperature and humidity dependence of the median life e was analyzed by using the equationand the coefficients E and n were determined to be 1.49 eV and 3.70, respectively. The thirtyyear hazard rate is estimated to be less than 40 FIT for PLC splitter modules operating at 60°C/ 40% RH.
Life Testing and Reliability Behavior of Gan/Ingan/Aigan Light-Emitting Diodes
Authors: Osinski M. , Barton D. L. , Helms C. J. , Berg N. H. , Seager C. H. 
Published: April 2011

AbstractOur studies of device lifetime and the main degradation mechanisms in Nichia blue LEDs date back to Spring 1994. Following the initial studies of rapid failures under high current electrical pulses, where metal migration was identified as the cause of degradation, we have placed a number of Nichia NLPB-500 LEDs on a series of life tests. The first test ran for 1000 hours under normal operating conditions (20 mA at 23 °C). As no noticeable degradation was observed, the second room temperature test was performed with the same devices but with a range of currents between 20 and 70 mA. After 1600 hours, some degradation in output intensity was observed in devices driven at 60 and 70 mA, but it was still less than 20%. The subsequent tests included stepping up the temperature by 10 °C in 500 h intervals up to a final temperature of 95 °C using the same currents applied in the second test. This work reviews the failure analysis that was performed on the degraded devices and the degradation mechanisms that were identified.
Material Properties of GaN in the Context of Electron Devices
Authors: Morkoç H. , Cingolani R. , Lambrecht W. , Gil B. , Jiang H.-X , Lin J. , Pavlidis D. , Shenai K. 
Published: April 2011

AbstractWide bandgap nitride semiconductors have recently attracted a great level of attention owing to their direct bandgaps in the visible to ultraviolet regions of the spectrum as emitters and detectors. However, this material system with its favorable heterojunctions and transport properties began to produce very respectable power levels in microwave amplifiers. If and when the breakdown fields achieved experimentally approaches the predicted values, this material system may also be very attractive for switching power devices. In addition to the premature breakdown, a number of scientific challenges remain including a clear experimental investigation of polarization effects. In this paper, transport properties as pertained to electronic devices and potential switching devices, and polarization effects will be treated.
Etch Processing of III-V Nitrides
Authors: Eddy Charles R. 
Published: April 2011

AbstractAs III-V nitride devices advance in technological importance, a fundamental understanding of device processing techniques becomes essential. Recent works have exposed various aspects of etch processes. The most recent advances and the greatest remaining challenges in the etching of GaN, AIN, and InN are reviewed. A more detailed presentation is given with respect to GaN high density plasma etching. In particular, the results of parametric and fundamental studies of GaN etching in a high density plasma are described. The effect of ion energy and mass on surface electronic properties is reported. Experimental results identify preferential sputtering as the leading cause of observed surface non-stoichiometry. This mechanism provides excellent surfaces for ohmic contacts to n-type GaN, but presents a major obstacle for Schottky contacts or ohmic contacts to p-type GaN. Chlorine-based discharges minimize this stoichiometry problem by improving the rate of gallium removal from the surface. In an effort to better understand the high density plasma etching process for GaN, in-situ mass spectrometry is employed to study the chlorine-based high density plasma etching process. Gallium chloride mass peaks were monitored in a highly surface sensitive geometry as a function of microwave power (ion flux), total pressure (neutral flux), and ion energy. Microwave power and pressure dependencies clearly demonstrate the importance of reactive ions in the etching of wide band gap materials. The ion energy dependence demonstrates the importance of adequate ion energy to promote a reasonable etch rate (≥ 100-150 eV). The benefits of ion-assisted chemical etching are diminished for ion energies in excess of 350 V, placing an upper limit to the useful ion energy range for etching GaN. The impact of these results on device processing will be discussed and future needs identified.
Structure of Ain on Si (111) Deposited with Metal Organic Vapor Phase Epitaxy
Authors: Rehder Eric , Zhou M. , Zhang L. , Perkins N. R. , Babcock S. E. , Kuech T. F. 
Published: April 2011

AbstractThe surface morphology and structure of AIN deposited by metal organic vapor phase epitaxy (MOVPE) on Si (111) at growth temperatures ranging from 825 to 1175°C was investigated. Transmission electron microscopy (TEM), reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM), and secondary ion mass spectrometry (SIMS) techniques were used to study the resulting film structure. Growth at high temperatures but less than ∼1100°C, resulted in a wire texture with some degree of in-plane alignment with (0001)AIN //(111)si, <1010>AIN //<211>si, and <1120>AIN. // <110>si. Deposition at temperatures greater than 1100°C results in single crystal films consisting of domains 60 nm across with an aspect ratio near unity. Growth below 1100°C leads to degraded crystal quality with the grains developing random rotational misalignments around the AIN [0001] axis. Growth at lower temperatures produces islands elongated along the [1120] direction. At the growth temperature of 825°C, the aspect ratio of the islands increased to 3 and a width of 25 nm. Cross -sectional TEM reveals that these islands are faceted due to slow growth on the {1101} planes.