bluuebunny/crossref_metadata_2025_split huggingface dataset:
Control and Impact of Processing Ambient During Rapid Thermal Silicidation
Authors: Maex K. , Kondoh E. , Lauwers A. , Steegen A. , De Potter M. , Besser P. , Proost J. 
Published: April 2011

ABSTRACTThe introduction of rapid thermal processing for silicide formation has triggered a lot of research to temperature uniformity and reproducibility in RTP systems. In addition to the temperature, the ambient control is to be taken into account. Although gasses are specified to a low level of contaminants, the RTP step needs to be optimised for optimal contaminant reduction. Besides, the process wafer itself is a source of contamination.In this paper an overview will be given of the role of RTP ambient on the silicidation processes. The effect of the wafer on ambient purity will be highlighted. It will be shown that the use of a reactive capping layer during silicidation represents an adequate solution for both sources of contamination.
Development and Characterization of a Cvd System for Thin-Film Solar Cell Manufacturing
Authors: Faller F. R. , Hurrle A. , Schillinger N. 
Published: April 2011

ABSTRACTWith the development of crystalline-silicon thin-film solar cells (c-SiTFC) CVD has gained importance in a new field of application. In recent years research resulted in a large variety of different concepts of c-SiTFCs. Many of these concepts require the deposition of a silicon film of good quality. i.e., at high temperature. However, little effort has been made up to this point to develop a suitable apparatus for that purpose, especially for the case of mass production of such cells. In this paper we present a self-constructed CVD system that we believe has the potential to meet the goals of an economical production of c-SiTFCs. An extension of the existing apparatus into a system in which the substrates enter the reactor at one side and leave it at the other side in a continuous way is feasable.The present system is characterized according to its behavior when typical CVD parameters are changed, the silicon conversion yield was investigated, and solar cells with a maximum efficiency of 15.3% were fabricated from epitaxial layers deposited on various substrates
RTP Calibration Wafer using thin-film Thermocouples
Authors: Kreider K. G. , Dewitt D. P. , Tsai B. K. , Lovas F. J. , Allen D. W. 
Published: April 2011

ABSTRACTRapid thermal processing (RTP) is a key technology for the cluster tool, single wafer manufacturing approach that is used to produce integrated circuits at lower cost with reduced line widths and thermal budgets. However, various problems associated with wafer temperature measurements and dynamic temperature uniformity have hindered the widespread use of RTP in semiconductor device manufacturing. The current technology for calibrating the radiometers employs a thermocouple instrumented wafer. We have accomplished improvements in the accuracy of these measurements through the use of thin-film thermocouples and the new Pt/Pd thermocouple system. These new calibration wafers can reduce the uncertainty in wafer temperature measurement technology by (1) reducing the perturbation due to heat transfer at the thermocouple junctions and (2) replacing conventional thermocouples with the superior Pt/Pd system. The thin-film thermocouples were calibrated using proof specimens fabricated with the Si 200 mm wafers and evaluated in the NIST RTP sensor test bed.The commercial type K thermocouples yielded temperature measurements within 4 °C of the thin-film Rh/Pt and Pt/Pd thermocouples on the 200 mm calibration wafer between 725°C and 875 °C. The Pt/Pd thin-film thermocouples proved less durable than the Rh/Pt thin films and the limitations of these systems are discussed. We also present a comparison of the radiometric measurements with the thermocouple measurements using a model estimating the wafer temperature from its spectral radiance temperature.
On the Interaction of Insoluble Spherical Particles with a Solidifying Interface in the Presence of Morphological Instabilities
Authors: Hadji L. , Davis A.M.J. 
Published: April 2011

AbstractThe interaction of a dilute suspension of spherical particles with a moving solidifying front is investigated analytically. The front emerges during the unidirectional solidification of a dilute binary alloy. A linear stability analysis of the planar interface reveals that the presence of the particles has a destabilizing effect, i.e. the critical value of the control parameter, taken here to be the concentration faraway from the interface, for the onset of the Mullins-Sekerka instability is lowered due to the particles' presence.
The Microstructure of Portland Cement-Based Materials: Computer Simulation and Percolation Theory
Authors: Garboczi Edward J. , Bentz Dale P. 
Published: April 2011

AbstractPortland cement-based materials are usually composites, where the matrix consists of portland cement paste. Cement paste is a material formed from the hydration reaction of portland cement, usually a calcium silicate material, with water. The microstructure of cement paste changes drastically over a time period of about one week, with slower changes occurring over subsequent weeks to months. The effect of this hydration process on the changing microstructure can be represented using computer simulation techniques applied to three dimensional digital image-based models. Percolation theory can be used to understand the evolving microstructure in terms of the three percolation thresholds that are of importance in the cement paste microstructure: the set point, capillary porosity percolation, and the percolation of the C-S-H phase.
High-Temperature Ageing of Modern Polymer-Coated Optical Fibres
Authors: Mauron P. , Nellen Ph. M. , Sennhauser U. 
Published: April 2011

AbstractReliability and durability are essential for optical fibres in both telecommunication networks and sensor applications. We report on stress-free accelerated ageing of modem telecommunication fibres in a temperature range from 60 °C to 150 °;C in dry air, relative humidity (rh) up to 85 %, and deionised water. Fibre fracture stress was measured by dynamic tensile testing according to IEC 60793-1-3 standard requirements. Ambient humidity effects on fibre fracture strength are shown. High temperature and relative humidity ageing behaviour of fibres and acrylate coatings is discussed. Fibre fracture strengths were fitted as functions of ageing time and ageing temperature using single process Arrhenius-based models. Acceleration factors can differ by several orders of magnitude, depending on the activation energy of the process. High temperatures damage acrylate coatings, which might deteriorate its adhesion to the fibre, thus introducing new ageing mechanisms not experienced under service conditions. Nevertheless, short time ageing at high temperature is useful for estimating relative lifetime of different products and for optimizing production process.
Effect of Mechanical Stripping and Arc-Fusion on the Strength and Aging of a Spliced Recoated Optical Fiber
Authors: Volotinen T. , Zimnol M. , Tomozawa M. , Lee Y.-K. , Raine K. 
Published: April 2011

AbstractMedian strength 4 GPa and Weibull slope 5 were obtained after stripping the coating from fibers with a mechanical stripping technique. However, the median strength was found to decrease to 1.6 GPa following fusion splicing. Most of the fractures in a tensile test occurred at a distance of 1 mm from the splice point. The internal axial tensile stress in the fiber cladding was found to be removed over a 2 mm section over the splice point. The surface fictive temperature was found to be decreased only at the zones where the fibers fracture. The reason for the fiber weakening during fusion is therefore thought to be due to the intrinsic structural changes in the silica indicated by the fictive temperature decrease. The magnitude of the decrease can be reduced by using a quicker fusion process. The corrosion velocity around a fusion splice point during aging in hot tap water was found to be significantly higher than along the fiber elsewhere. Silica layers with a thickness of hundreds nanometers were removed uniformly. However, the weakest points (roughest surface) after water aging were located in the ends of the recoated section.
Packaging of Fiber Sensors for Civil Engineering Applications
Authors: Brönnimann R. , Nellen Ph. M. , Anderegg P. , Sennhauser U. 
Published: April 2011

AbstractMany optical fiber sensor systems in outdoor applications are in operation and reliability aspects are a major concern. We installed multiplexed fiber optical Bragg grating sensor systems in a stay cable bridge and in a power dam both operational for about two years now. We report on design aspects of such systems which have several constraints: First, the sensing parts of a single multiplexed fiber had to be located at certain positions and in a specific orientation. Further, the sensors must be compensated for environmental influence, the fibers were not allowed to be bent too tightly, and the fibers had to be embedded and protected in a sensor body in a way to survive its installation in the monitored structure. Finally the sensor must be reliable to be a useful measurement device.We present long term monitoring data and test results concerning the reliability of our systems and discuss benefits and disadvantages of the various applied sensor designs.
Contact Issues of GaN Technology
Authors: Qiao D. , Yu L.S. , Lau S. S. , Sullivan G. J. , Ruvimov S. , Liliental-Weber Z. 
Published: April 2011

AbstractIn this paper, we discuss the issue of fabricating reliable and reproducible ohmic contacts on AlGaN HFET structures. During the course of our investigation of fabricating contacts to HFETs, we found that the contact properties could vary significantly from one sample to another, even though they were nominally the same. This problem was prominently manifested in the ohmic contact behavior. The origin of this problem was traced back to the variation of the HFET structure during growth. In this paper, we report an attempt to fabricate reproducible ohmic contacts of these structures.
Strong Piezoelectric Effects in Unstrained GaN Quantum Wells
Authors: Langer R. , Simon J. , Konovalov O. , Pelekanos N.T. , André R. , Barski A. , Godlewski M. 
Published: April 2011

AbstractOptical properties of GaN/AIGaN single quantum well (SQW) and multi quantum well (MQW) structures grown by nitrogen plasma assisted MBE on MOCVD-grown GaN/sapphire have been characterised by low temperature photoluminescence. Photoluminescence (PL) peaks corresponding to emission from very narrow (10 Å wide) SQWs are blue shifted with respect to the bulk GaN emissions but reveal strong red shift for wider SQWs (40 and 60 Å wide). Structural properties of SQW and MQW structures have been characterised by X-ray reciprocal lattice mapping in order to determine the strain conditions and composition of ternary A1GaN alloys. The results clearly demonstrate that in all structures under investigation the ternary (barrier) alloys are fully strained to underlying MOCVD-grown GaN/sapphire substrates. Despite of the fact that GaN quantum wells (QW) are unstrained, photoluminescence experiments clearly reveal the presence of extremely strong electric fields in the QW regions, which can be attributed to the interplay of the piezoelectric-type polarisation in the well and barrier layers due to Fermi level alignment.
Pendeo-Epitaxy of Gallium Nitride and Aluminum Nitride Films and Heterostructures on Silicon Carbide Substrate
Authors: Gehrke T. , Linthicum K. J. , Thomson D. B. , Rajagopal P. , Batchelor A. D. , Davis R. F. 
Published: April 2011

AbstractPendeo-epitaxy of individual GaN and AlxGa,1-xN films and single- and multi-layer heterostructures of these materials have been achieved on a columnar GaN seed layer using metallorganic vapor phase epitaxy. These structures have been characterized using scanning electron microscopy and atomic force microscopy. The RMS roughness value of the grown side wall plane (1120) of these structures was 0.099 nm.
Comparative Growth of AIN on Singular and Off-Axis 6H and 4H-SiC by MOCVD
Authors: Wilson S. , Dickens C. S. , Griffin J. , Spencer M. G. 
Published: April 2011

AbstractA comparison study of the growth of aluminum nitride (AIN) single crystal epitaxy on 6H-SiC and 4H-SiC substrates has been performed. The material has been characterized using atomic force microscopy (AFM) and reflective high energy electron diffraction (RHEED). AIN crystals were deposited on the following 6H-SiC substrates: singular with and without an initial SiC epilayer, and 3.5° off-axis with and without an initial SIC epilayer. AIN crystals were deposited on 8.0° off-axis 4H-SiC with and without initial SIC epilayers. AFM shows that the deposition of AIN on 6H-SiC and 4H-SIC with an initial SiC epilayer displays high quality quasi-two dimensional growth as atomically flat or step flow epitaxy.
Optical Properties of Si-DOPED AlxGal-xN/AlyGal-yN (x=0.24-0.53, y=0.11) Multi-Quantum-Well Structures
Authors: Hirayama H. , Aoyagi Y. 
Published: April 2011

AbstractWe demonstrate strong ultraviolet (UV) (280-330nm) photoluminescence (PL) emission from multi-quantum-well (MQW) structures consisting of AlGaN active layers fabricated by metal-organic chemical-vapor-deposition (MOCVD). Si-doping is shown to be very effective in order to enhance the PL emission of AlGaN QWs. We found that the optimum values of well thickness and Si-doping concentration of AlxGal-xN/AlyGal-yN (x=0.24-0.53, y=0.11) MQW structure for efficient emission were approximately 3nm and 2×1019cm-3, respectively. In addition, the PL intensities of AlGaN, GaN and InGaN quantum well structures are compared. We have found that the PL emission at 77K from a Al0.53Ga0.47N/Al0.11Ga0.89N MQW is as strong as that of InGaN QWs.
Fast Lateral Epitaxial Overgrowth of Gallium Nitride by Metalorganic Chemical Vapor Deposition Using A Two-Step Process
Authors: Marchand H. , Ibbetson J.P. , Fini P.T. , Wu X.H. , Keller S. , DenBaars S.P. , Speck J.S. , Mishra U.K. 
Published: April 2011

AbstractWe demonstrate a two-step process wherein the lateral epitaxial growth (LEO) of GaN from <1010>-oriented stripes is initiated at a low V/II1 ratio to produce smooth, vertical {1120} sidewalls, and where the V/III ratio is subsequently raised in order to increase the lateral growth rate. We find that the formation of the {1101} facets is inhibited using this two-step process, and that it is possible to maintain the {1120} sidewalls while achieving a large lateral growth rate. The ratio of lateral to vertical growth rate has been increased by up to factor of 2.6 using this approach relative to identical growth conditions without the initiation at low V/III ratio. The effect of lateral growth rate on the structural properties of the stripes is discussed.
The Behavior of Ion-Implanted Hydrogen in Gallium Nitride
Authors: Myers S. M. , Headley T.J. , Hills C.R. , Han J. , Petersen G.A. , Seager C.H. , Wampler W.R. 
Published: April 2011

AbstractHydrogen was ion-implanted into wurtzite-phase GaN, and its transport, bound states, and microstructural effects during annealing up to 980°C were investigated by nuclear-reaction profiling, ion-channeling analysis, transmission electron microscopy, and infrared (IR) vibrational spectroscopy. At implanted concentrations vl at.%, faceted H 2 bubbles formed, enabling identification of energetically preferred surfaces, examination of passivating N-H states on these surfaces, and determination of the diffusivity-solubility product of the H. Additionally, the formation and evolution of point and extended defects arising from implantation and bubble formation were characterized. At implanted H concentrations ^0.1 at.%, bubble formation was not observed, and ion-channeling analysis indicated a defect-related H site located within the [0001] channel.
Electrical Characterization of Sputter Deposition Induced Defects in n-GaN
Authors: Auret F. D. , Goodman S. A. , Koschnick F. K. , Spaeth J.-M. , Beaumont B. , Gibart P. 
Published: April 2011

AbstractWe have used current-voltage (I-V) measurements to assess and compare the electrical characteristics of resistively evaporated and sputter deposited Au Schottky contacts on epitaxially grown GaN. These I-V measurements revealed that resistively deposited Au contacts exhibited excellent rectification properties: high barrier height, low reverse current and good ideality factor (n = 1.04). In contrast, sputter deposited contacts had poor characteristics: low barrier height, high reverse current and non-linear forward I-V characteristics. The cause of this is thought to be defects introduced at and near the surface during sputter deposition. Deep level transient spectroscopy (DLTS) showed that at least four defects, with energy levels at 0.22±0.02 eV, 0.30±0.01 eV, 0.40±0.01 eV and 0.45±0.10 eV below the conduction band, were introduced in the GaN during sputter deposition. The first of these defects has similar electronic properties as a radiation induced defect in GaN, speculated to be the nitrogen vacancy, while the second appears to be the same as a defect in the as-grown material. The latter two defects have not previously been observed in as-grown or processed epitaxial GaN.
Electroluminescence Properties of InGaN/AlGaN/GaN Light Emitting Diodes with Quantum Wells
Authors: Yunovich A.E. , Kudryashov V.E. , Turkin A..N. , Kovalev A.N. , Manyakhin F.I. 
Published: April 2011

AbstractElectroluminescence spectra of light-emitting diodes based on InGaN/AlGaN/GaN heterostructures with single and multiple quantum wells (QWs) are analyzed by models of radiative recombination in 2D-structures with band tails. Equations of the model fit spectra quite good in a wide range of currents. Parameters of the fit are discussed and compared for single and multiple QWs. Tunnel effects play a sufficient role in blue LEDs with single QWs at low currents; they can be neglected in LEDs with multiple QWs. A new spectral band was detected at the high energy side of the spectra of green LEDs with multiple QWs; it is attributed with large scale inhomogenities of In distribution in InGaN QWs.)
Characterization of Hot-Electron Effects on Flicker Noise in III-V Nitride Based Heterojunctions
Authors: Ho W.Y. , Fong W.K. , Surya Charles , Tong K.Y. , Lu L.W. , Ge W.K. 
Published: April 2011

AbstractWe report experiments on hot-electron stressing in commercial III-V nitride based heterojunction light-emitting diodes. Stressing currents ranging from 100 mA to 200 mA were used. Degradations in the device properties were investigated through detailed studies of the I-V characteristics, electroluminescence, Deep-Level Transient Fourier Spectroscopy and flicker noise. Our experimental data demonstrated significant distortions in the I-V characteristics. The room temperature electroluminescence of the devices exhibited 25% decrement in the peak emission intensity. Concentration of the deep-levels was examined by measuring the Deep-Level Transient Fourier Spectroscopy, which indicated an increase in the density of deep-traps from 2.7 × 1013 cm−3 to 4.21 × 1013 cm−3 at El = Ec – 1.1eV. The result is consistent with our study of I/f noise, which exhibited up to three orders of magnitude increase in the voltage noise power spectra. Our experiments show large increase in both the interface traps and deep-levels resulted from hot-carrier stressing.
Influence of Si-Doping on Carrier Localization of Mocvd-Grown InGaN/GaN Multiple Quantum Wells
Authors: Cho Yong-Hoon , Schmidt T. J. , Bidnyk S. , Song J.J. , Keller S. , Mishra U.K. , DenBaars S.P. 
Published: April 2011

AbstractWe have systematically studied the influence of Si doping on the optical characteristics of InGaN/GaN multiple quantum wells (MQWs) using photoluminescence (PL), PL excitation (PLE), and time-resolved PL spectroscopy combined with studies of optically pumped stimulated emission and structural properties from these materials. The MQWs were grown on 1.8-μm-thick GaN layers on c-plane sapphire films by metalorganic chemical vapor deposition. The structures consisted of 12 MQWs with 3-nm-thick InGaN wells, 4.5-nm-thick GaN barriers, and a 0.1 -μm-thick Al0.07Ga0.93N capping layer. The Si doping level in the GaN barriers was varied from 1 × 1017 to 3 × 1019 cm3. PL and PLE measurements show a decrease in the Stokes shift with increasing Si doping concentration. The 10 K radiative recombination lifetime was observed to decrease with increasing Si doping concentration (n), from ∼ 30 ns (for n < 1 × 1017 cm-3) to ∼4 ns (for n = 3 x 1019 cm-3). To elucidate whether non-radiative recombination processes affect the measured lifetime, the temperature-dependence of the measured lifetime was investigated. The reduced Stokes shift, the decrease in radiative recombination lifetime, and the increase in structural and interface quality with increasing Si doping indicate that the incorporation of Si in the GaN barriers results in a decrease in carrier localization at potential fluctuations in the InGaN active regions and the interfaces.
Theory of the Gain Characteristics of InGaN/AlGaN QD Lasers
Authors: Andreev A.D. , O'Reilly E.P. 
Published: April 2011

AbstractWe present a theoretical analysis of the gain characteristics of InGaN/AlGaN quantum dot (QD) lasers. We calculate the elastic strain distribution caused by the lattice mismatch between the QD and the barrier using an original method which takes into account the hexagonal symmetry of the structure's elastic properties. The method is based on an analytical derivation of the Fourier transform of the strain tensor. The proposed approach is combined with a plane-wave expansion method to calculate the carrier spectrum and wave functions. The many-body gain of a laser containing a periodic array of QDs is calculated using the Padé approximation. We show that band gap reduction and the Coulomb enhancement of the interband transition probability can significantly modify the gain spectrum in InGaN/AlGaN QD lasers.
Patterning III-N Semiconductors by Low Energy Electron Enhanced Etching (LE4)
Authors: Gillis H.P. , Christopher M.B. , Martin K.P. , Choutov D.A. 
Published: April 2011

AbstractFabricating device structures from the III-N wide ba-ndgap semiconductors requires anisotropoic dry etching processes that leave smooth surfaces with stoichiometric composition after transferring high-resolution patterns with vertical sidewalls. The purpose of this article is to describe results obtained by a new low-damage dry etching technique that provides an alternative to the standard ion-enhanced dry etching methods in meeting these demands for processing the HI-N materials.
Effect of Transition Temperature, Structure and Anisotropy on the Deformation and Failure of Polymers
Authors: Samuels Robert J. 
Published: April 2011

AbstractThe yield strength, the failure strength and strain behavior of Isotactic Polypropylene are all a function of the molecular orientation in the polymer. Further, although Isotactic Polypropylene and PMDA-ODA polyimide are very different polymers, they behave similarly when the strain rate is slow enough for the polymer to be at the low strain rate limit of its failure envelope. A master True Stress-Total True Strain curve is obtained for both polymers.