bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of the Crack Propagation in the API X-52 and API X-65 Steels into Cathodic Protection
Authors: Aguilar A. , Esparza R. , Gil M.A. , Cuahutitla L.F. , Rubio-Rosas E. , Rodríguez-Lugo V. , Perez R. 
Published: April 2011

ABSTRACTCathodic protection has been applied for many years as the best method to prevent the corrosion in systems which transported hydrocarbon pipelines. However, it has found the presence of stress corrosion cracking (SCC) in steel pipelines with high concentrations of carbonates and bicarbonates with pH final (9 to 11). The resistance to the stress corrosion cracking of the API X-52 and API X-65 steels was evaluated on compact modified wedge opening specimens (WOL). The specimens were loaded of 95% of the yield strength. The resistance of crack propagation and the corrosion rate were evaluated with different applied potentials (-850 and -650 mV), this with respect to a saturated copper/copper sulfate reference electrode. The used electrolytes were simulated soils (carbonate-bicarbonate solution). Evidence of crack propagation of the API X-52 and API X-65 steels were carried out by scanning electron microscopy. The obtained result showed susceptibility to SCC on specimens with cathodic protection. The cathodic protection applied (-850 mV vs Cu/CuSO4 electrode) decreases considerably the corrosion rate on the evaluated steels. In this work the loaded stress showed to be a very important variable on the susceptibility to SCC.
Critical Indicator of Slip-Prone Clayey Soils Due Rainfall in Teziutlán-Puebla-México Zone: Yield Stress Determination by Slump Tests
Authors: Méndez-Sánchez Arturo. F. , Nieto Zepeda Karen E. , Pérez-Trejo Leonor , Paniagua-Mercado Ana M. 
Published: April 2011

ABSTRACTThe yield stress evaluation as a function of water content for slip-prone clayey soils due to rainfall is studied in this work, particularly, the clayey soil from the region Teziutlán-Puebla-México. Yield stress was calculated as a function of water content using the slump test in cylindrical geometry. Results show a critical point of water content where yield stress decreases dramatically, and those values were related to the historical daily rain data. It was found a maximum precipitation millimeters that triggers the landslide, but still is low compared with the historical reported data.
Phase-separation in ZnxCd1-xSe/C Core/shell nanocrystals studied with cathodoluminescence spectroscopy
Authors: Estrin Yevgeni , Rich Daniel H , Moshe Ofer , Bhattacharyya Sayan , Gedanken Aharon 
Published: April 2011

AbstractZnxCd1-xSe/C core/shellnanocrystals with 31-39 nm diameter semiconductor cores and 11-25 nm-thick carbon shells were synthesized from solid state precursors. Transmission electron microscopy showed striations on a scale of ˜1 – 5 nm in the nanocrystals that are indicative of a composition modulation, and reveal a chemical phase separation and possible spinodal decomposition within the nanocrystals. Such a composition modulation within the ternary nanocrystals represents a rarely reported phenomenon that could lead to additional applications. The optical properties and carrier relaxation kinetics of the nanocrystals were examined with variable excitation cathodoluminescence (CL). As the excitation level is increased, carrier filling in two-dimensional (2D) phase-separated Cd-rich regions leads to a partial saturation of states before the onset of carrier filling in the higher bandgap homogenous Zn0.47Cd0.53Se regions. In order to model the state filling using Fermi-Dirac statistics for non-interacting carriers, a random quantum well model was used to determine the electron and hole eigensates in the Cd-rich regions of the nanocrystals.
Acetaldehyde Photocatalytic Decomposition over Nanostructured TiO2 Sol-Gel Catalysts
Authors: Castillo S. , Camposeco R. , Carrera R. , Mujica M. , Ángel P.Del , Montoya J.A. , Vázquez A.L. , Morán-Pineda M. , Goméz R. 
Published: April 2011

AbstractTiO2nanoparticles were synthesized by the Sol-Gel method by using 2-propanol as solvent in acid medium (pH1). The samples were annealed at 200 and 500°C and were characterized by BET, XRD-Rietveld refinements, TEM and FTIR. The activity was evaluated by the acetaldehyde photodecomposition in an isolated chamber with an initial concentration of contaminant of 300 ppmv with oxygen (2%) assisted with a 365-nm UV lamp. The test results were compared with those obtained with a commercial catalyst (P25). Improved photoactivity (≍100 % of acetaldehyde in 150 min) was obtained with catalysts annealed at 200°C (TiO2-P-200°C), that showed nanoparticles (≍7 nm) and abundant anatase phase (≍ 63 %) coexist with the brookite phase (≍ 37 %), as well as irregular equiaxial morphology. The samples annealed at 500°C (TiO2-P-500°C), showed an increment in nanoparticles (≍22 nm), different ratio and phase composition (anatase-brookite-rutile), and therefore less activity (≍80 %). This high activity could be explained by the special ratio of anatase-brookite and the dimension of nanometric crystal size. The aforementioned characteristics could be useful in the degradation of reactive organic gases like acetaldehyde either in confined spaces or in the open air.
Improved Quality of Bulk II-VI Substrates for HgcdTe and HgZnTe Epitaxy
Authors: Sen Sanghamitra , Stannard John E. 
Published: April 2011

AbstractSingle crystals of CdTe or dilute alloys of Cd1−yZnyTe (y≤0.04) and CdTe1−zSez (z ≤0.04) with low defect density, high purity and large single-crystal area (>30 cm2) are required as substrates for high-quality epitaxial Hg1−xCdxTe thin films in the infrared (IR) detector industry. Bridgman or gradient freeze is the most common technique used for commercial production of these materials because of its success in producing large area substrates of good quality and reproducibility. For epitaxial growth of Hg1−xZnxTe, which has been of considerable interest in recent years as an IR detector material, the substrate of choice has been Cd0.80Zn0.20Te, for lattice matching with long wavelength Hg1−xZnxTe epitaxial layers (x = 0.13–0.14). The primary focus of this paper is on CdZnTe which is currently the preferred substrate material and most widely used for both HgCdTe and HgZnTe epitaxy. This paper reviews the current status of bulk substrate technology for IR detector applications, highlighting critical issues and essential research areas for further improvement of these materials.
Twinning Effects in Hg1−xCdxTe(x˜0.2) Grown by THM in the 〈111〉 Direction
Authors: Weiss Efiezer , Kedar Ehud , Mainzer Nili 
Published: April 2011

AbstractHg1−xCdxTe crystals with x˜0.2 were grown by the traveling heater method (THM), in either the [111]A or [111]B directions, using oriented CdTe seeds. Twins are sometimes formed during the growth of these crystals. In crystals grown in the [111]A direction the twins, of orientation [511]B, are constantly growing at the expense of the original [111]A oriented grain. Growth in the [111]B direction, on the other hand, suppresses the growth of the twin domain. Photodiodes and capacitors realized on the (111)A plane are markedly superior to those on the twin plane, [511]B. The difference is due to higher fixed charge and larger fast surface state densities in the case of the [511]B plane. These effects are explained by the lattice structures in the {111} and {511} planes and their possible influence on surface reactivity.
Buffer Layers for Ferroelectric-Based Infra-Red Detectors on Si Grown by a Novel CVD Method
Authors: Stauf Gregory T. , VanBuskirk Peter C. , Kirlin Peter S. , Kosar Walter P. 
Published: April 2011

AbstractFerroelectrics such as PbTiO3 and BaSrTiO3 are promising candidates for pyroelectric infrared detector materials. Integration of ferroelectric thin films on Si will permit fabrication of low-cost infrared detector arrays, but a buffer layer will be required to reduce interactions with the substrate. For this reason we have investigated MOCVD of MgAl2O4 and yttria-stabilized zirconia (YSZ) buffer layers on both Si and MgO. A single source molecule, magnesium dialuminum isopropoxide (Mg[Al(OCH(CH3)2)4]2), was used for deposition of the MgAl2O4, the first time to our knowledge that well characterized multi-metal oxide films have been deposited by CVD from a single-source compound. Both EDAX and RBS showed film stoichiometries consistent with the elemental ratio in the source. A novel liquid solution-based flash vaporization technique was used to transport the organometallic sources into the reactor, providing both excellent reproducibility and ease of stoichiometry control and deposition rate. Highly oriented [100] MgAl2O4 was grown on MgO, and [100] YSZ was grown on MgO and Si. Degree of preferred orientation of the YSZ was found to be dependent on oxygen partial pressure, both for the MgO and Si substrates.
Structural Relaxation and Structural Memory at Amorphous Silicon Dangling Bonds
Authors: Branz Howard M. , Fedders Peter A. 
Published: April 2011

ABSTRACTWe examine the energy and time scales of configurational relaxation around the dangling bond defect, D, in hydrogenated Amorphous silicon (a-Si:H). After D captures or emits charge, its bond angle, electron energy eigenvalues and local structural environment all change. This determines the measured electronic energy levels; we use previous theoretical results and experimental data to estimate the density of gap states in the different atomic configurations of D. We also describe D relaxation effects observed in experiments, including the very slow relaxations found in recent transient capacitance measurements. To explain the unusual T-independent kinetics of transient capacitance carrier emission, we propose a model of “structural memory” in a-Si:H. After carrier capture, neighbors of D retain memory of their pre-capture configuration for seconds at 300K. The rate-limiting step to carrier emission is an effectively one-dimensional random walk of these neighbors through their configuration space and back to the pre-capture configuration. The final, activated, step of emission is very rapid. We describe analytic and monte Carlo calculations that support the structural memory Model and propose possible microscopic Mechanisms.
New Approaches to Molecular Dynamics Simulations of a-Si:H
Authors: Li Qiming , Biswas R. , Soukoulis C.M. 
Published: April 2011

ABSTRACTA new tight-binding molecular dynamics approach for Si-H systems is developed using the valence orbitale of Si and H for calculation of atomic forces. Previous tight-binding models are not able to describe formation energies of different charge states of H in c-Si and new physics is introduced in our model to describe both effects of charge transfer and varying atomic environments. The Si-H Model was developed by fitting to silane, and ensuring that the formation energies of different charge states of H in c-Si were correctly described. This new model also describes well vibrational properties of SiHn configurations, and the structural and electronic properties of a-Si:H Models. The new molecular dynamics utilizes quantum mechanical forces, incorporating important electronic effects, and is robust enough to simulate hundreds of atoms as would be needed in realistic a-Si:H systems.
Comparison of Dark and Light-Induced Annealing of Metastable Defects in a-Si:H
Authors: Gleskova Helena , Nakata M. , Wagner S. 
Published: April 2011

ABSTRACTWe propose a rate law that unifies the dark and light-induced annealing of metastable defects in hydrogenated Amorphous silicon (a-Si:H). Its form is dN/dt ∼ - C Naf (T), where N is the defect density, C the concentration of free electrons (holes), f (T) a dispersive function, t the time, and T the temperature. Special dark and light-annealing experiments, designed to keep the free electron density constant, were conducted to eliminate C from the rate law. We find that f (T) for the dark annealing process differs from that for light-annealing. We calculated the thermal activation energies for the decay of N to 1/e of its initial value. They are 1.56±0.2 eV for dark annealing and 0.91±0.2 eV for light-induced annealing.
Metastability Under High-Intensity Light of Device-Quality He-Diluted, H2-Diluted and Standard a-Si:H Films Deposited Between 50°C and 350°C
Authors: Morin P. , Roca i Cabarrocas P. 
Published: April 2011

ABSTRACTWe report the results of a study of the metastability under illumination by high intensity red light of device quality a-Si:H thin films deposited using a wide range of deposition conditions. The process variables included substrate temperature, pressure, rf power, and dilution of silane by He or H2. In-situ Monitoring of the sample conductivity and defect density during light-soaking provides the kinetics of the degradation of the electronic properties of the films. We observe equilibration of the photoconductivity and of the defect density. The characteristic time of equilibration τse of the defect density varies by more than an order of magnitude, dividing the samples into two groups: one group with a τse on the order of 103 seconds, the other with a τse on the order of 104 seconds. Low steady state defect densities combined with high ημτ products are observed for “standard” a-Si:H deposited between 100°C and 250°C and He-diluted films deposited above 250°C.
Charge and Current Transient Measurements on N-Type Hydrogenated Amorphous Silicon in the Relaxation Regime
Authors: Paschen Uwe W. , Kwon Daewon , David Cohen J. 
Published: April 2011

ABSTRACTJunction capacitance measurements were employed to study the thermal emission of electrons after application of a voltage filling pulse on a 80 Vppm PH3 doped a-Si:H sample on p+ c-Si substrate. We show that these data can be explained in terms of the relaxation Model. In addition, the time dependence of the charge flow into the depletion region during the filling pulse is investigated by current transient Measurements. Finally, we present charge transient data for a 9 Vppm a-Si:H sample on n+ c-Si substrate and compare the results to those obtained on samples on p-type substrates.
Switching Effects, Current Fluctuations and Lateral Photovoltage - The Electrical Appearance of A-Si:H/Metal Multilayers
Authors: Panckow Andreas N. , Drüsedau T.P. , Schmidt U. 
Published: April 2011

ABSTRACTMultilayer systems (MLS) consisting of hydrogenated Amorphous silicon (a-Si:II) and a transition Metal (Mo, Ti) were prepared by alternating dual magnetron sputtering. In this study we investigate the electrical performance of multilayer films containing discontinuous metal sublayers separated by a-Si:H sublayers of 80 nm thickness. A voltage of typical 8 V applied to the coplanar electrodes switches the samples from a semiconducting to a metallic state. The switching effect, which is reversible by thermal annealing, is accompanied by chaotic current oscillations. The temperature dependence of the conductivity in the metallic state is described by Inσ α T−1/2. The asymmetric illumination of the interelectrode spacing in coplanar configuration resulted in a generation of a lateral photovoltage.
A Basic Study of the GeH4 + H2 RF Discharge
Authors: Wickboldt Paul , Pang Dawen , Paul William 
Published: April 2011

ABSTRACTExtensive studies were made of GeH4+H2 and SiH4+H2 rf discharges used in depositing a-Ge:H and a-Si:H films. Residual Gas Analysis (RGA) Measurements were made of the gaseous species generated by these discharges. Data from the measurements of SiH4 + H4 discharges were entirely consistent with the generally accepted models of silane discharge chemistry and a-Si:H film deposition. Identical experiments for GeH4 + H2 discharges show that the chemistry for these discharges cannot be interpreted using a model similar to that proposed for silane. A review of the literature reveals differences between the stability of GeH2 and SiH2 radicals. These differences, usually overlooked by other workers, can account for the observed differences in the RGA results, as well as offer an explanation as to why it is difficult to deposit structurally homogeneous a-Ge:H.Other RGA Measurements and electrode potential measurements are compared to the properties of a-Ge:H films that are deposited under different deposition conditions. Overall, the results strongly suggest that the chemistry which is beneficial for homogeneous film growth is promoted by a high electron temperature in the discharge. This conclusion is shown to be consistent with the results summarized above.
Influence of Substrate Temperature on the Properties of A-Si:H P-Layers Obtained from Trimethylboron
Authors: Puigdollers J. , Asensi J.M. , Bertomeu J. , Andreu J. , Delgado J.C. 
Published: April 2011

ABSTRACTa-Si:H p-layers doped by trimethylboron (TMB) were obtained by PECVD in a monochamber reactor with a rotating substrate holder. The influence of the substrate temperature (Ts) on the film properties was systematically studied for two different doping gas concentrations. The incorporation of boron, hydrogen and carbon was studied by Secondary Ion Mass Spectrometry (SIMS). Optical properties were determined by means of Photothermal Deplection Spectroscopy (PDS) and optical transmission. Dark conductivity (aj and activation energy (Eact) were measured electrically. Our results show that Σd has a marked dependence on substrate temperature, although boron atom concentration depends only slightly on Ts. The optical gap for samples obtained at the higher concentration also depends on Ts and its dependence is related to the hydrogen content, as boron content does not change. P-i-n diodes were obtained with the p-layer deposited from TMB.
1/f Noise Measurements of Hydrogenated Amorphous Silicon-Carbon Alloys
Authors: Dyalsingh H. M. , Khera G. M. , Kakalios J. , Tsai C. C. , Street R. A. 
Published: April 2011

ABSTRACTMeasurements of the optical, electronic and 1/f noise properties for a series of n-type doped hydrogenated amorphous silicon carbide thin films with varying gas phase concentrations of CH4 are described. The increase in the optical absorption edge of the n-type a-SiCx:H films with the addition of carbon is slower than in p-type films. Studies of the variation in the non-Gaussian statistics which characterize the 1/f noise indicate that the disorder at the mobility edge is greater for films with higher carbon concentrations.
Understanding of Thin Film Transistor Electrical Measurements in the Light of the Defect Pool Model
Authors: Deane S.C. , Powell M.J. 
Published: April 2011

ABSTRACTRecently we described a new computer program which used a defect pool model of the density of states in a thin film transistor. With this model we modelled the effects of thermal bias annealing on the field effect characteristics of amorphous silicon thin film transistors, and used these results to determine key defect pool parameters. Here we use this program to provide new insight into other features of thin film transistor properties, such as activation energies of conduction as a function of gate bias, details of the subthreshold slopes, Movement of the apparent flat band voltages, and contact effects including current crowding. These effects are all successfully modelled and explained with our first principles defect pool Model, and compared with experimental results on a variety of material systems. In particular we show how measurements of the apparent flat band voltage produce potentially misleading results, and explain the inconsistency between observations of much less current crowding in contacts compared to predictions based on observed bulk defect densities and conventional Models.
High Performance A-Si:H Thin Film Transistors, TFTs: The Importance of Nitride Dielectrics with no Detectable Si-Si Bonding
Authors: He S.S. , Lucovsky G. 
Published: April 2011

ABSTRACTThis research addresses silicon nitride dielectrics for a-Si:H TFTs. Si-Si bonds in these films detected by AES have been identified as the major factor that degrades the performance of the TFTs. With no detected Si-Si bonds in the silicon nitride and a relatively low concentration of Si-NH bonds, the TFTs show optimized performance.
Dependence of Field-Effect Mobility on Deposition Conditions in a-Si:H TFT
Authors: Chida Y. , Kondo M. , Ganguly G. , Matsuda A. 
Published: April 2011

ABSTRACTHigh electron Mobility (over 3 cm2/Vs) thin film transistors (TFTs) have been fabricated using a-Si:H on thermally oxidized crystalline Si substrate. The procedures for fabricating the high performance TFTs are presented and the possible reasons for the high mobility are discussed.
Improvement of Brightness & Threshold-Current in Visible-Light a-Sic:H Thin Film Led by Using Metal Sheet Substrate
Authors: Boonkosum Wirote , Kruangam Dusit , Panyakeow Somsak , DeLong Bancherd 
Published: April 2011

ABSTRACTAn effort has been made to improve the brightness of the a-SiC:H Thin Film LED (TFLED) by using highly-thermal conductive Metal (SUS) sheet substrates instead of glass substrates. The structure of the TFLED is metal substrate/n a-SiC:H/i a-SiC:H/p a-SiC:H/ITO. The results from the preliminary examination show that at room temperature; 1) the threshold current necessary for the observation of the emission for the TFLED deposited on a SUS substrate is half of that for a glass substrate, 2) the highest brightness is about 5 cd/m2 for a SUS substrate while about 1 cd/m2 for a glass substrate.
High Performance Metallization Issues for Ulsi
Authors: Rosenberg Robert 
Published: April 2011

ABSTRACTThe microelectronics industry is accelerating towards increasingly sophisticated circuit technology to interface with and drive a wide spectrum of products from low power to supercomputation systems. The base Si CMOS technology will span the applications such that optimization must be achieved by personalized wiring for each industry sector. As the feature size decreases to 0.25/µm or less, the interconnect metallization becomes a dominant technological challenge as circuit speeds, reliability and manufacturing costs are directly affected. The label "high performance" must now be defined in the context of the application. For example, as scaling proceeds for increased density and circuit speed, current density increase will impact lifetime by electromigration. Methods of simulation of fundamental degradation modes and design software tools must be developed and used in concert with performance simulation to optimize interconnect metallization ground rules early in the development cycle. Availability of such tools for interconnects is practically nonexistent, spurring significant focus on this direction by the materials community.
Interfacial Reactions of Co and Si/Co Films on GaAs
Authors: Kwak J. S. , Baik H. K. , Lee J. I. , Noh S. K. , Shin D. W. , Park C. G. 
Published: April 2011

ABSTRACTInterfacial reactions of Co and Si/Co films on GaAs have been investigated using X-ray diffraction(XRD), Auger electron spectroscopy(AES), cross-sectional transmission electron microscopy(XTEM), microdiffraction, and energy dispersive spectroscopy(EDS). Cobalt starts to react with GaAs at 380°C by formation of ternary phase, most probably Co2GaAs. At 420°C, CoGa nucleates at the Co and Co2GaAs interface and grows with Co2GaAs. At higher temperature, Co2GaAs disappears and CoGa/GaAs layer structures are formed. Annealing of the layer-deposited Si/Co films at 380°C results in the formation of Co2GaAs. At 420°C, the entire layer of Co is consumed, while Co2Si transforms to CoSi, and binary phases, CoGa and CoAs, are formed on top of the ternary phase beneath the CoSi layer. In the subsequent reaction, CoSi grows at the expense of the decompositions of CoGa and CoAs at 460°C. At 600°C, ternary phase is decomposed, and CoSi forms interface with GaAs. This finding can be understood from the calculated Si-Co-Ga-As quaternary phase diagram.