bluuebunny/crossref_metadata_2025 huggingface dataset:
CD4+T-Cell Responses Are Required for Clearance of West Nile Virus from the Central Nervous System
Authors: Sitati Elizabeth M. , Diamond Michael S.
Published: November 2006

Although studies have established that innate and adaptive immune responses are important in controlling West Nile virus (WNV) infection, the function of CD4+T lymphocytes in modulating viral pathogenesis is less well characterized. Using a mouse model, we examined the role of CD4+T cells in coordinating protection against WNV infection. A genetic or acquired deficiency of CD4+T cells resulted in a protracted WNV infection in the central nervous system (CNS) that culminated in uniform lethality by 50 days after infection. Mice surviving past day 10 had high-level persistent WNV infection in the CNS compared to wild-type mice, even 45 days following infection. The absence of CD4+T-cell help did not affect the kinetics of WNV infection in the spleen and serum, suggesting a role for CD4-independent clearance mechanisms in peripheral tissues. WNV-specific immunoglobulin M (IgM) levels were similar to those of wild-type mice in CD4-deficient mice early during infection but dropped ∼20-fold at day 15 postinfection, whereas IgG levels in CD4-deficient mice were ∼100- to 1,000-fold lower than in wild-type mice throughout the course of infection. WNV-specific CD8+T-cell activation and trafficking to the CNS were unaffected by the absence of CD4+T cells at day 9 postinfection but were markedly compromised at day 15. Our experiments suggest that the dominant protective role of CD4+T cells during primary WNV infection is to provide help for antibody responses and sustain WNV-specific CD8+T-cell responses in the CNS that enable viral clearance.
Visualization of α-Helices in a 6-Ångstrom Resolution Cryoelectron Microscopy Structure of Adenovirus Allows Refinement of Capsid Protein Assignments
Authors: Saban Susan D. , Silvestry Mariena , Nemerow Glen R. , Stewart Phoebe L.
Published: November 2006

The structure of adenovirus was determined to a resolution of 6 Å by cryoelectron microscopy (cryoEM) single-particle image reconstruction. Docking of the hexon and penton base crystal structures into the cryoEM density established that α-helices of 10 or more residues are resolved as rods. A difference map was calculated by subtracting a pseudoatomic capsid from the cryoEM reconstruction. The resulting density was analyzed in terms of observed α-helices and secondary structure predictions for the additional capsid proteins that currently lack atomic resolution structures (proteins IIIa, VI, VIII, and IX). Protein IIIa, which is predicted to be highly α-helical, is assigned to a cluster of helices observed below the penton base on the inner capsid surface. Protein VI is present in ∼1.5 copies per hexon trimer and is predicted to have two long α-helices, one of which appears to lie inside the hexon cavity. Protein VIII is cleaved by the adenovirus protease into two fragments of 7.6 and 12.1 kDa, and the larger fragment is predicted to have one long α-helix, in agreement with the observed density for protein VIII on the inner capsid surface. Protein IX is predicted to have one long α-helix, which also has a strongly indicated propensity for coiled-coil formation. A region of density near the facet edge is now resolved as a four-helix bundle and is assigned to four copies of the C-terminal α-helix from protein IX.
Screening Random Peptide Libraries with Subacute Sclerosing PanencephalitisBrain-Derived Recombinant Antibodies Identifies Multiple Epitopes in the C-Terminal Region of the Measles Virus Nucleocapsid Protein
Authors: Owens Gregory P. , Shearer Andrew J. , Yu Xiaoli , Ritchie Alanna M. , Keays Kathryne M. , Bennett Jeffrey L. , Gilden Donald H. , Burgoon Mark P.
Published: November 2006

Infectious and inflammatory diseases of the CNS are often characterized by a robust B-cell response that manifests as increased intrathecal immunoglobulin G (IgG) synthesis and the presence of oligoclonal bands. We previously used laser capture microdissection and single-cell PCR to analyze the IgG variable regions of plasma cells from the brain of a patient with subacute sclerosing panencephalitis (SSPE). Five of eight human IgG1 recombinant antibodies (rAbs) derived from SSPE brain plasma cell clones recognized the measles virus (MV) nucleocapsid protein, confirming that the antibody response in SSPE targets primarily the agent causing disease. In this study, as part of our work on antigen identification, we used four rAbs to probe a random phage-displayed peptide library to determine if epitopes within the MV nucleocapsid protein could be identified with SSPE brain rAbs. All four of the SSPE rAbs enriched phage-displayed peptide sequences that reacted specifically to their panning rAb by enzyme-linked immunosorbent assay. BLASTP searches of the NCBI protein database revealed clear homologies in three peptides and different amino acid stretches within the 65 C-terminal amino acids of the MV nucleocapsid protein. The specificities of SSPE rAbs to these regions of the MV nucleocapsid protein were confirmed by binding to synthetic peptides or to short cDNA expression products. These results indicate the feasibility of using peptide screening for antigen discovery in central nervous system inflammatory diseases of unknown etiology, such as multiple sclerosis, neurosarcoidosis, or Behcet's syndrome.
Evidence for CDK-Dependent and CDK-Independent Functions of the Murine Gammaherpesvirus 68 v-Cyclin
Authors: Upton Jason W. , Speck Samuel H.
Published: November 2006

Gamma-2 herpesviruses encode homologues of mammalian D-type cyclins
(v-cyclins), which likely function to manipulate the cell cycle,
thereby providing a cellular environment conducive to virus replication
and/or reactivation from latency. We have previously shown that the
v-cyclin of murine gammaherpesvirus 68 is an oncogene that binds and
activates cellular cyclin-dependent kinases (CDKs) and is required for
efficient reactivation from latency. To determine the contribution of
v-cyclin-mediated cell cycle regulation to the viral life cycle,
recombinant viruses in which specific point mutations (E133V or K104E)
were introduced into the v-cyclin open reading frame were generated,
resulting in the disruption of CDK binding and activation. While in
vitro growth of these mutant viruses was unaffected, lytic replication
in the lungs following low-dose intranasal inoculation was attenuated
for both mutants deficient in CDK binding as well as virus in which the
entire v-cyclin open reading frame was disrupted by the insertion of a
translation termination codon. This replication defect was not apparent
in spleens of mice following intraperitoneal inoculation, suggesting a
cell type- and/or route-specific dependence on v-cyclin-CDK
interactions during the acute phase of virus infection. Notably,
although a v-cyclin-null virus was highly attenuated for reactivation
from latency, the E133V v-cyclin CDK-binding mutant exhibited only a
modest defect in virus reactivation from splenocytes, and neither the
E133V nor K104E v-cyclin mutants were compromised in reactivation from
peritoneal exudate cells. Taken together, these data suggest that lytic
replication and reactivation in vivo are differentially regulated by
CDK-dependent and CDK-independent functions of v-cyclin,
respectively.
Mutation of YMYL in the Nipah Virus Matrix Protein Abrogates Budding and Alters Subcellular Localization
Authors: Ciancanelli Michael J. , Basler Christopher F.
Published: November 2006

Matrix (M) proteins reportedly direct the budding of paramyxoviruses from infected cells. In order to begin to characterize the assembly process for the highly lethal, emerging paramyxovirus Nipah virus (NiV), we have examined the budding of NiV M. We demonstrated that expression of the NiV M protein is sufficient to produce budding virus-like particles (VLPs) that are physically and morphologically similar to NiV. We identified in NiV M a sequence, YMYL, with similarity to the YPDL late domain found in the equine infectious anemia virus Gag protein. When the YMYL within NiV M was mutated, VLP release was abolished and M was relocalized to the nucleus, but the mutant M proteins retained oligomerization activity. When YMYL was fused to a late-domain mutant of the Ebola virus VP40 matrix protein, VP40 budding was restored. These results suggest that the YMYL sequence may act as a trafficking signal and a late domain for NiV M.
A NUMERICAL METHOD FOR PRICING AMERICAN-STYLE ASIAN OPTIONS UNDER GARCH MODEL
Authors: SHAO DAN
Published: November 2006

This article develops a numerical method to price American-style Asian option in the context of the generalized autoregressive conditional heteroscedasticity (GARCH) asset return process. The development is based on dynamic programming coupled with the replacement of the normally distributed variable with a binomial one and the whole procedure is under the locally risk-neutral valuation relationship (LRNVR). We investigate the computational and implementation issues of this method and compare them with those of a candidate procedure which involves piecewise-polynomial approximation of the value function. Complexity analysis and computational results suggest that our method is superior to the candidate one and the generated GARCH option prices are capable of reflecting the changes in the conditional volatility of underlying asset.
PRICING FLOW COMMODITY DERIVATIVES USING FIXED INCOME MARKET TECHNIQUES
Authors: HINZ JURI , WILHELM MARTINA
Published: November 2006

In this work, the valuation of energy-related financial contracts written on prices of flow commodities (such as natural gas, oil and electrical power) will be elaborated. Due to restrictions on storability of the underlying, the pricing of flow commodity derivatives is not trivial and thus correct valuation is still under discussion. In this paper, an axiomatic setting is followed, which provides a connection to interest rate theory, whose toolkit we utilize to consistently price frequently quoted flow commodity options such as caps, floors, collars and cross commodity spreads.
INSIDER TRADING RULES AND PRICE FORMATION IN SECURITIES MARKETS: AN ENTROPY ANALYSIS OF STRATEGIC TRADING
Authors: KEIBER KARL LUDWIG
Published: November 2006

This paper addresses the issue of how insider trading rules affect price formation in securities markets and suggests the application of information theory to market microstructure theory. We analyze a variant of the setting in [20] by simply introducing a more general criterion for informational efficiency borrowed from information theory — namely maximum information transmission. The analysis shows that both the insider's optimal trading strategy and the market price of the risky security depend on the insider trading restriction. Insider trading restrictions are reported to be detrimental to the liquidity of the securities market. We find that a unique insider trading rule exists which implements semi-strong form informational efficiency of the securities market. Alternative restrictions on insider trading give rise to either underreaction or overreaction in securities prices. Too strict insider trading rules are shown to account for excess volatility in securities prices. Contrary to common notion, the uninformed investors are shown to be hurt by too restrictive insider trading rules. We conclude that loose insider trading rules are preferred by the group of investors as a whole.
Immunobiology of Allogeneic Hematopoietic Stem Cell Transplantation
Authors: Welniak Lisbeth A. , Blazar Bruce R. , Murphy William J.
Published: November 2006

Allogeneic hematopoietic stem cell transplantation (HSCT) has evolved into an effective adoptive cellular immunotherapy for the treatment of a number of cancers. The immunobiology of allogeneic HSCT is unique in transplantation in that it involves potential immune recognition and attack between both donor and host. Much of the immunobiology of allogeneic HSCT has been gleaned from preclinical models and correlation with clinical observations. We review our current understanding of some of the issues that affect the success of this therapy, including host-versus-graft (HVG) reactions, graft-versus-host disease (GVHD), graft-versus-tumor (GVT) activity, and restoration of functional immunity to prevent transplant-related opportunistic infections. We also review new strategies to optimize the GVT and improve overall immune function while reducing GVHD and graft rejection.
Intermolecular Interactions in Biomolecular Systems Examined by Mass Spectrometry
Authors: Wyttenbach Thomas , Bowers Michael T.
Published: November 2006

With the development of electrospray and matrix-assisted laser desorption ionization, mass spectrometry (MS) evolved into a powerful tool in the field of biochemistry. Whereas MS is primarily analytical in nature, an increasing number of MS research groups employ the method to address fundamental biochemical questions. Probing the interaction of noncovalently bound molecules in the mass spectrometer is one of the most interesting MS-based experiments possible today, with the potential of making a significant contribution to the basic understanding of the structure and function of biochemical complexes. Here we review a number of current research efforts employing primarily MS techniques to investigate intermolecular interactions in biochemical systems. Examples chosen include the interaction of biomolecules with solvent molecules; interactions between nucleic-acid molecules, in particular, interactions in duplex and quadruplex structures; and interactions between proteins involved in neurodegenerative diseases. Finally we conclude by presenting a few examples of very large biomolecular assemblies in the mega-Dalton range analyzed by MS.
Integration of HfxTayN Metal Gate Electrode with High-k Gate Dielectric in MOS Devices
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

In this work, the composition effects of hafnium (Hf) and tantalum (Ta) in HfxTayN metal gate on the thermal stability of metal-oxide-semiconductor (MOS) devices were investigated. The work function of the HfxTayN metal gate can reach a value of ~4.6 eV (midgap of silicon) by suitably adjusting the Hf and Ta compositions. In addition, with a small amount of Hf incorporated into a TaN metal gate, excellent thermal stability of electrical properties, including the work function, the equivalent oxide thickness (EOT), interface trap density and defect generation rate characteristics, can be achieved after a post-metal anneal up to 950 oC for 45 s. Experimental results indicate that Ta-rich HfxTayN is a promising metal gate for advanced MOS devices.
Lanthanum Oxides for Gate Insulator Applications
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

Feasibility study on La2O3 for gate insulator application is conducted. Thin film of La2O3 showed densification and interfacial layer formation depending on the annealing temperature. Among various heat treatments, low temperature annealing showed high electron mobility peak of 261 cm2/Vs. Annealing after gate formation improved the mobility up to 319 cm2/Vs, however, the EOT increases from 1.29 to 2.33 nm. By inserting Y2O3 layer under La2O3, interfacial layer formation can be suppressed at high temperature annealing. Low frequency noise measurement shows one or two order higher noise level compared to that of SiO2 MOSFET.
Nanocrystalline Silicon Quantum Dot Devices
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

Electron transport and photonic properties of silicon nanocrystals prepared by plasma processes are described with particular emphasis on silicon nanocrystals memory, microscopic charge measurement by KFM, NEMS devices, silicon photonic devices, and high-density assembly of silicon quantum dots.
Characterization of Electronic Charged States of Si-Based Quantum Dots and Their Application to Floating Gate Memories
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

Si quantum dots (Si-QDs) with and without Ge core were prepared on thermally-grown SiO2 in a self-assembling manner by controlling the early stages of LPCVD. The surface potential changes in individual dots caused by charging or discharging of one electron or a few as were evaluated by using a AFM/Kelvin probe technique. The influence of phosphorous doping to Si-QDs on their electron charging and discharging characteristics was also been studied. Electrical characteristics of MOS capacitors and nMOSFETs with Si-QDs floating gates confirm multiple-step charging to and discharging from the Si-QDs floating gate at room temperature.  From the temporal changes in the drain current with gate voltage switching, it is suggested that the change in the electron distribution in the Si-QDs floating gate play an important role to trigger the transition from a metastable charged state to the next charged state.
Anodically Produced Alumina Dielectric for Organic Electronic Devices
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

The properties of the dielectric strongly influence the performance of organic thin-film transistors.We see the influence of the roughness of the dielectric on the mobility of pentacene transistors. Organic thin film field-effect transistors (OTFTs) are particularly interesting as their fabrication processes are much less complex compared with conventional Si technology, which involves high-temperature and high-vacuum deposition processes and sophisticated photolithographic patterning methods. In general, low-temperature deposition and solution processing can replace the more complicated processes involved in conventional Si technology. The achieved hole mobilities went up to 5 cm2 /V s in the case of pentacene. Major influences on the mobility have been the purification, deposition conditions of the organic semiconductor and the properties of the dielectric surface. Variations in the surface chemistry cause large changes in the mobility of the OTFT. In addition, several publications mention a reduction in mobility due to increased surface roughness. In this letter, we show experimental results that quantify the influence of the roughness of the dielectric on the mobility.
New Non-Volatile Memory with Magnetic Nano-Dots
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

We proposed a new non-volatile memory with magnetic nano-dots (MND) dispersed in an insulating film as charge retention layer. We evaluated fundamental characteristics of FePt magnetic nano-dot film which is employed in such new magnetic nano-dot memory. We successfully formed a highly ordered L10 phase face-centered tetragonal structured FePt nano-dot (< 4.2nm) films on Si3N4 (5nm)/SiO2 (10nm)/silicon substrates and SiO2(10nm)/ silicon substrate by using SAND method. The uniformity of FePt particle size is dramatically improved by introducing a Si3N4 buffer layer on SiO2/Si substrate. In addition, it is found that FePt nano-dot film formed on Si3N4 (5nm)/SiO2(10nm)/Si substrate has a large coerce-ivity of ~22 kOe at room temperature.
Forty Years of Moore's Law: Ever Smaller Transistors and Ever Larger Wafers
Authors: Hutcheson G. Dan
Published: November 2006

It has been forty years since Gordon Moore first posited what would one day come to be known as Moore's Law. Gordon's ideas were more than a forecast of an industry's ability to improve; they were a statement of the ability for semiconductor technology to contribute to economic growth and even the improvement of mankind in general. More importantly, Moore's Law set forth a vision of the future that harnessed the imaginations of scientists and engineers to make it all possible.
Introductory Remarks: 300 mm
Authors: Gilles D. , Huber W.
Published: November 2006

Abstract not Available.
Parameters of Intrinsic Point Defects in Silicon Based on Crystal Growth, Wafer Processing, Self- and Metal- Diffusion
Authors: Voronkov Vladimir V. , Falster Robert
Published: November 2006

The vacancies and self-interstitials in silicon are involved, in a straightforward way, in various phenomena such as formation of grown-in microdefects, diffusion of metals (Au, Zn), self-diffusion and installation of vacancy depth profiles into wafers by Rapid Thermal Annealing. The available data is sufficient to deduce the diffusivities and equilibrium concentrations of the intrinsic point defects leaving only one parameter (the migration energy of self-interstitials) not specified. The diffusivities are high while the equilibrium concentrations are remarkably low.
Growth Technologies for 300 mm Arsenic Heavily Doped Silicon Single Crystals
Authors: Tu Hailing , Zhou Qigang , Zhang Guohu , Dai Xiaolin , Wu Zhiqiang , Jia Taotao
Published: November 2006

Arsenic heavily doped silicon substrates are vital to the power devices and power integrated circuits. The present work focuses on the series growth technologies for 300 mm silicon crystals heavily doped with arsenic. The 22 hot zone has been employed and growth parameters have been optimized to improve the yield of the as-grown ingots. The systemic processes have been applied for the human safety and environmental concerns, which guarantee the exhaust gas and water have met the requirement for the national laws of the environmental protection.
Defect Formation Behaviors in Heavily Doped Czochralski Silicon
Authors: Sugimura Wataru , Ono Toshiaki , Umeno Shigeru , Hourai Masataka , Sueoka Koji
Published: November 2006

To reveal a difference of defect formation behaviors,i.e. grown-in void formation during crystal growth and oxide precipitation in n- and p-type silicon, we have investigated by using heavily boron- and arsenic-doped silicon crystals. The density of void defects in heavily boron doped silicon was decreased with a shrinking OSF-ring, but in arsenic doped silicon were increased with resistivities below 3.3mΩcm. On the other hand, for oxygen precipitation, the nucleation rate in boron doped silicon was enhanced with increasing resistivities, while decreased by one tenth in reference to lightly doped silicon for resistivities up to 4.4mΩcm in arsenic doped silicon. These contrastive phenomena between n- and p-type cannot be explained with a growth model of precipitates by an accelerated diffusion of oxygen in silicon. We believed that the nucleation rate of oxide precipitates related to a dependence of point defects on fermi level closely.
Warp of Silicon Wafers Produced from Wire Saw Slicing: Modeling, Simulation, and Experiments
Authors: Gupta Puneet , Kulkarni Milind S.
Published: November 2006

The slicing of wafers from a silicon ingot by the wiresaw process involves the cutting action of the fine slurry particles trapped between the wire and the ingot surface being cut. The heat generated from the cutting action of the slurry is partly convected away by the fast moving slurry at the point of cut. The remainder of the heat leads to differential thermal expansion of the ingot depending on the local conditions at the instant and location of cut. It is conjectured that the non-uniform heat generation and partition is responsible for the warp observed in wafers as cut by the wiresaw process. In this study, a coupled thermal and structural finite element based approach is utilized to model and simulate warp of sliced wafers. Within the constraints and assumptions of the coupled FE model, excellent comparison of simulation results with experimental warp data is observed.
Defect Dynamics in the Presence of Nitrogen and Oxygen in Growing Czochralski Silicon Crystals
Authors: Kulkarni Milind S.
Published: November 2006

Many structural imperfections form in silicon crystals during their Czochralski growth. The distribution of these microdefects can be strongly influenced and controlled by the addition of impurities such as nitrogen to the crystal. A model describing the Czochralski defect dynamics in the presence of nitrogen and oxygen is proposed and solved. The reactions between vacancies and self-interstitials, nitrogen monomers and dimers, nitrogen and vacancies, and the reactions involving vacancies, oxygen, and complexes of vacancies and oxygen are incorporated, along with the formation of various microdefects-the agglomerates of vacancies, self- interstitials, and of oxygen (silicon dioxide). All microdefects are approximated as spherical clusters. The formation of all clusters is described by the classical nucleation theory. The clusters, once formed, grow by a diffusion-limited kinetics. The microdefect distributions in Czochralski crystals growing under steady state as well as unsteady state are discussed.
Analytical Modeling of the Interaction of Vacancies and Oxygen for Oxide Precipitation in RTA Treated Wafers
Authors: Kissinger Gudrun , Dabrowski Jaroslaw , Sattler Andreas , Seuring Christoph , Mueller Timo , Richter H. , von Ammon Wilfried
Published: November 2006

We have investigated the impact of RTA induced vacancy supersaturation on oxide precipitation based on as much as possible experimental and theoretical values. Oxygen precipitation after RTA processing was found to be controlled by the initial concentration of interstitial oxygen in a sixth power dependency and frozen vacancies just in a cubic dependency. The formation of tensile strained nVO2 clusters seems to be the favored process for coherent nucleation of oxide precipitates. The reduction of interstitial oxygen can be accurately modeled for the temperature range from 1150 {degree sign}C to 1250 {degree sign}C using Ham's theory for precipitate growth and an empirical relation based on nucleation of oxide precipitates by agglomeration of VO2 complexes. During RTA treatments at temperatures {greater than or equal to} 1300 {degree sign}C vacancies seem to be consumed by other processes. Below RTA temperatures of 1150 {degree sign}C, oxide precipitation is dominated by shrunken as-grown precipitate nuclei because as-grown nuclei can be dissolved only at RTA temperatures {greater than or equal to} 1150 {degree sign}C.
Introductory Remarks: Materials and Process Integration
Authors: Ikeda S. , Rodder M.
Published: November 2006

Abstract not Available.
Multiple Gate MOSFETs
Authors: Maszara Witold P. , Krivokapic Zoran , Xiang Qi , Lin Ming-Ren
Published: November 2006

Planar single-gate transistors have been recently demonstrated with reasonable performance at sub-20 nm of physical gate length. However, a need for high performance transistors with channels shorter than that, as expressed by 2005 ITRS goals, requires devices with more than one gate, which facilitates better control of electrostatic charge in the channel. Double- and triple-gate transistors with their process integration complexity will likely become a device of choice for the high performance logic circuits in second decade of the 21st century. This paper will discuss various approaches to realization of those multi-gate fully depleted channel devices and their performance and process integration issues and layout design challenges for sub-20 nm gates. We also discuss issues related to designing circuits with multi-gate fin-based devices.
Defect Engineering Considerations for Strained Silicon Substrates
Authors: Claeys C. , Eneman Geert , Scholz Mirko , Loo Roger , Verheyen Peter , De Meyer Kristin , Simoen Eddy R.
Published: November 2006

Defect-engineering parameters influence the electrical performance of p-n junctions in strained silicon (SSi) substrates. The thin SSi layers were deposited on thin Strain Relaxed SiGe Buffers (SRBs), whereby strain relaxation is achieved by implementing a thin C-doped SiGe layer. Processing variables studied are the depth dC of this layer and the carbon concentration, determining the threading dislocations (TDs) density. As references, step-graded SRB material and standard Czochralski silicon was used. Combined current-voltage and capacitance-voltage measurements indicate that within the range studied (2-3x105 to 1-2x107 cm-2), the TDD has the strongest impact on the reverse current density and generation lifetime. Additional leakage current is created by defects associated with the carbon-rich layer, when present in the junction depletion region. The electrical activity of the TDs also depends on the well doping type (n- or p). The largest activity is observed in n+/p junctions, which are technologically the more relevant ones.
Low-resistance Ti/n-type Si(100) Contacts by Monolayer Se Passivation
Authors: Zhu J. , Yang X. , Tao M.
Published: November 2006

Low-resistance contacts fabricated by selenium passivation between Ti and n-type Si(100) substrates have been characterized by low-temperature I-V, four-point probe and circular transmission line methods. The Ti-Si contacts on Se- passivated samples demonstrate a significant reduction in Schottky barrier height over control samples in low- temperature I-V. Sheet resistance of the contacts on Se- passivated 1019 cm-3 doped n-type Si(100) substrates shows a 30% reduction as compared with control samples. Accordingly, the extracted contact resistance decreases by about one order of magnitude for samples with different Ti thicknesses and different annealing temperatures. A 125%-2900% reduction in contact resistivity is achieved by Se passivation on highly- doped n-type SOI substrates with 500 Aå un-doped Si buffer layer. The reduction in contact resistance is attributed to the minimization of interface states between Ti and Si(100) surface.
Introductory Remarks: Integrated Metrology and Diagnostics
Authors: Fabry L. , Hattori Takeo
Published: November 2006

Abstract not Available.
Scenario for a Yield Model Based on Reliable Defect Density Data and Linked to Advanced Process Control
Authors: Nutsch Andreas , Oechsner R.
Published: November 2006

Currently, yield enhancement and APC (advanced process control) systems operate independently within the manufacturing process. Yield enhancement has several requirements such as the root cause analysis of yield loss, the reliability of defect density data, and the demand for a link between yield models and APC. For root cause studies chemical analysis uses different preparation techniques to describe the nature and location of contamination or defect densities, e.g. copper bulk contamination or wafer edge effects. The reliability of defect density data and the matching of defect inspection tools improve by the reduction of noise. In combination with a process model this is the prerequisite to set up a random defect-based yield scenario which describes single processes. The combination of this scenario with methods for data acquisition and tracking from APC enhances the prediction of yield.
Standardization of Characterization of Bulk Microdefects and Denuded Zones in Annealed CZ Si
Authors: Takeda Ryuji , Inoue Naohisa , Moriya Kazuo , Kashima Kazuhiko , Nakashima Kenji , Kato Masahiro , Kitagawa Satoru , Ono Toshiaki , Urushido Hiroki , Nango Nobuhito , Akhmetov Vladimir
Published: November 2006

The requirement to standardize measurement methods for BMD (Bulk Micro Defect) density and DZ (Denuded Zone) CZ silicon has lead to the establishment of a SEMI standard for annealed CZ silicon wafers. Therefore, it was decided that we should aim at standardizing the preferential-etching and 90-degrees laser- scattering tomography techniques as a collaborative work between JEITA (Japan Electronics and Information Technology Industries Association) and JSPS (Japan Society of Promotion of Science) 145th Committee. In this work, we carried out a set of round robin tests and examined whether we could jointly standardize both the preferential-etching and the 90 degrees laser-scattering methods. This resulted in a standardized measurement protocol for BMD density and DZ width, which has become known as the JEITA standard EM 3508 [1].
1/f Noise as a Tool to Assess Fermi Level Pinning (EF) at the HfO2/poly-Si Interface in High-k n-MOSFETs
Authors: Srinivasan Purushothaman , Simoen Eddy , Pantisano Luigi , Claeys C. , Misra D.
Published: November 2006

Evidence is provided that 1/f noise may be useful in the analysis of traps responsible for Fermi level pinning at the HfO2/poly-Si or HfO2/FUSI interface in high-k n-MOSFETs. As reference devices, transistors with 1.5 nm SiON gate dielectric have been used. It is shown that adding a few monolayers of HfO2 enhances the normalized noise magnitude in both poly-Si and FUSI devices. The 1/f noise characteristic behaves according to number fluctuations theory and the results are interpreted in terms of trapping and de-trapping of channel carriers by defects in the gate dielectric layer. Differences in trap densities, derived from low-frequency noise spectra are noticed at the gate/dielectric interface, which can explain the Fermi-level pinning in these devices. It is shown that the correlated mobility fluctuations derived from 1/f noise correlate well with the low-field mobility of the n-MOSFETs, demonstrating that the same traps are partly responsible for the mobility degradation.
Influence of Gas Velocity and Humidity on Diethyl Phthalate Adsorption and Desorption on Silicon Surface
Authors: Habuka Hitoshi , Tawada Masaki , Suzuki Kisho , Takeuchi Takashi , Aihara Masahiko
Published: November 2006

The real-time adsorption and desorption of water and diethyl phthalate on silicon surface were studied using a quartz crystal microbalance in ambient nitrogen, having various values of humidity, gas velocity and diethyl phthalate concentration. In a steady state, the adsorbed amount of water and diethyl phthalate is considered to depend only on each concentration in the ambient nitrogen. However, in a non-steady state state, the gas velocity at the quartz crystal microbalance enhances both the adsorption rate and the desorption rate. Therefore, the gas velocity at the measurement point is concluded to be one of the key parameters that influence the organic contamination measurement.
Introductory Remarks: Strained Silicon
Authors: Weber Eicke , Wise Rick
Published: November 2006

Abstract not Available.
Threading vs Misfit Dislocations in Strained Si/SiGe Heterostructures: Preferential Etching and Minority Carrier Transient Spectroscopy
Authors: Lu Jinggang , Zhang Renhua , Rozgonyi George , Yakimov Eugene , Yarykin Nikolai , Seacrist Mike
Published: November 2006

Dislocations in sSi/SiGe heterostructures have been studied structurally by preferential defect etching and electrically by minority carrier transient spectroscopy (MCTS). It is shown that a two-step etching procedure will selectively delineate threading dislocations without interference from misfit dislocations at the buried sSi/SiGe interface. The effect of etching solution temperature is also evaluated, and found to dramatically improve the contrast of threading dislocation etch pits by employing an ice bath etching solution. Complementary electrical characterization of the sSi/SiGe heterostructures has been performed using optically excited MCTS to reveal minority carrier peaks associated with extended defects. The characteristics of corresponding deep levels and their dependence on excitation pulse duration allows us to assign MCTS peaks to dislocations in the strained Si and/or uniform composition SiGe layers.
Improving the Flotation Behavior of a Sulfide Ore by Controlling Electrochemical Interactions during Grinding
Authors: Grano Stephen , Huang Guozhi
Published: November 2006

The effect of grinding media and purging gas during grinding, on the flotation behaviour of a complex copper-lead-zinc sulphide ore was investigated. The optimum recoveries and grades of chalcopyrite were obtained with 21 % chromium medium combined with nitrogen purging. Mild steel medium may depress chalcopyrite flotation due to a high amount of oxidized iron species in the mill discharge. Grinding media displayed an influence on the Eh and galvanic current between media and mineral electrodes. The more electrochemically active the grinding media and the more oxidizing the environment, the greater the amount of oxidised iron in the slurry. Mild steel and high chromium media are more electrochemically active than the examined sulphide minerals. A generic approach to optimizing grinding conditions to improve the flotation separation of sulphide minerals is suggested by the study.
Specific Characteristics of Noble Metal Nanoparticles on Sulfide Minerals Observed by XPS and STS
Authors: Mikhlin Yuri L. , Romanchenko Alexander , Makhova Liudmilla
Published: November 2006

Synchrotron radiation X-ray photoelectron spectroscopy, scanning tunneling microscopy and spectroscopy (STM/STS) have been used to characterize gold and silver species spontaneously deposited from HAuCl4 or AgNO3 solutions onto sulfide minerals at room temperature. The reacted substrates were studied too. It was found that Au 4f7/2 binding energies increase up to 1 eV with decrease in the size of Au0 nanoparticles in the range 3 to 30 nm. This is attributed to a temporal charging of the particles, lessening kinetic energies of the photoelectrons via interaction with final-state photoholes. STS revealed a positive correlation between the current magnitude and the diameter of Au particles, tentatively explained by Coulomb blockade effects. Silver deposited on the minerals exhibited neither shifts of Ag 5d bands, nor Coulomb blockade in STS. Possible mechanisms behind the suppression of electronic tunneling and its potential role for the charge transfer steps in reactions of gold nanoparticles were considered.
Galvanic Interactions Between Gold and Sulfides during Thiosulfate Leaching
Authors: Jeffrey Matthew I. , Thompson Danielle , Chu Chee Keng , Breuer Paul
Published: November 2006

Galvanic interactions which occur between gold and sulfide minerals have a significant impact on the leaching behaviour of gold in copper-ammonia-thiosulfate solutions. At low ammonia concentrations, gold leaches very slowly due to the low Cu(II) concentration. However when electrically connected to unreactive sulfide minerals, the gold leaches much more rapidly as a result of the concurrent reduction of Cu(II) and dissolved oxygen on the mineral surface. At higher ammonia concentrations, the leaching of gold occurs readily due to the high concentration of Cu(II). However, if the gold is electrically connected to chalcocite, there is preferential oxidation of the chalcocite, and hence cathodic protection of the gold. This results in a low gold leach rate and mixed potential.
Electrochemical Study of a Flotation Zinc Concentrate in Sulfuric Acid: Galvanic Interactions Affecting the Rate of Dissolution of Sphalerite
Authors: Nava Jose Luis , González Ignacio , Nava Dora
Published: November 2006

The anodic dissolution of a flotation zinc concentrate (63.4% sphalerite (ZnS), 20.1% pyrite (FeS2), 5% chalcopyrite (CuFeS2), 0.33% galena (PbS), 0.45% tetrahedryte (Cu12Sb4S13) and 0.4% arsenopyrite (FeAsS)) was studied in 1.7 M H2SO4. An electrochemical strategy (based on common electrochemical techniques) was proposed to find the potential range at which each mineral species can be oxidized. Anodic potential pulses were applied to carbon paste electrodes prepared with zinc concentrate (CPE-zinc concentrate). The resulting solutions were analysed by anodic stripping voltammetry (ASV). In addition, the surface of each modified CPE-zinc concentrate was characterized by cyclic voltammetry (CV). The sphalerite is oxidized in the range of 0 < E < 600 mV vs SSE with slow kinetic; similarly, galena dissolution took place in the same range. The dissolution of sphalerite is galvanically protected, while dissolution of chalcopyrite is favored.
The Active-to-passive Transition of Chalcopyrite
Authors: Viramontes-Gamboa Gonzalo , Rivera-Vasquez Berny Fernando , Dixon David G.
Published: November 2006

The active-to-passive transition of chalcopyrite is studied using electrochemical techniques and leaching tests to establish the conditions under which chalcopyrite electrodes display active-passive behavior. Results from potentiostatic anodic polarizations are predictive and agree very well with leaching results while potentiodynamic techniques give only erratic values. The critical current and oxidation rate in the active potential range increases with the concentration of acid, but the passivation potential decreases. The corrosion rate of chalcopyrite was studied at various temperatures and concentrations of acid in electrolytes containing only ferric (no ferrous) using electrochemical impedance spectroscopy; the higher the concentration of acid and the lower the temperature, the lower the corrosion rate.
Electrodeposition of Iron in Aqueous Ferrous Sulfate Solution:Role of Ammonium Ion
Authors: Osseo-asare Kwadwo , Deelo Mike E. , Weil Konrad
Published: November 2006

The role of the ammonium ion during iron deposition in a ferrous sulfate bath was investigated. When cathodic polarizations were performed in a solution of 0.02 M FeSO4 at pH 3, quartz crystal microbalance measurements showed that the presence of ammonium sulfate led to increased mass growth of Fe metal on the cathode surface. The surface pH was measured by placing a flat- bottom electrode behind a stainless steel cathode mesh. Potentiodynamic sweeps generated pH versus potential curves which revealed that in the presence of ammonium sulfate surface pH rose to alkaline levels. These two sets of findings (i.e., mass growth rate of Fe metal and surface pH results) suggest that the ammonium ion enables formation of ferrous ammine species (e.g., Fe(NH3)22+ and Fe (NH3)42+). This inhibits Fe(OH)2 precipitation on the electrode, a process that can lead to surface passivation, and therefore, limited Fe metal deposition.
Gold Electrowinning from Acidic Aqueous Chloride in a Packed Bed Electrode
Authors: Kelsall Geoff , Cheng Chun-Yee , Diaz Miguel , Robson Anna
Published: November 2006

Concentrations < 0.5 mol m-3 (< 102 g m-3) of AuCl4- and AuCl2- ions in 1 kmol HCl m-3 aqueous electrolyte were reduced to elemental gold in a packed bed cathode of 2-3 mm graphite particles, in an electrochemical reactor incorporating a cation- permeable membrane and operated in batch recycle mode. Depletion to concentrations < 5×10-3 mol m-3 (< 1 g m-3) appeared to be mass transport controlled at an applied potential of 0.53 V (SHE) and occurred with < 4 F (mol Au)-1 and specific electrical energy consumptions of ca. 400 kW h (tonne Au)-1. However, atomic absorption and UV spectrophotometry established that, as the ([AuCl4-] + [AuCl2- ]) concentration decayed, the [AuCl2-] : [AuCl4-] molar ratio changed. A (multi-step) mechanism for reduction of AuCl4- ions is proposed, to explain this behaviour, in terms of changing overpotentials for AuCl4- and AuCl2- reduction as total dissolved gold concentrations decreased.
Formation Processes of Chemically Deposited Copper Sulfide Thin Films
Authors: Munce Carolyn G. , Parker Gretel , Hope Gregory A.
Published: November 2006

Copper sulfide thin films and particles were prepared by chemical bath deposition. Bath compositions were altered as well as mechanical processes such as stirring of solutions during the deposition process to determine the effect on resulting films. The films and particles that were formed homogeneously in the bath solutions were analysed by Raman spectroscopy, electron microscopy, X-ray diffraction and electrochemistry. By changing one of the complexing agents, films and particles with varying copper:sulfur ratios were formed. Films that were deposited while the solution stirred formed a thinner layer than those in which the solution was static during the deposition process. The effect of changing specific parameters included an improvement in adhesion properties, a decreased amount of particulate growth within the bath solution, a decrease in the thickness and roughness of the resulting films, and a change in stoichiometry, although these property changes were not always observed in the same system.
Carbon Nanotube Field Effect Transistors for High Speed Electronics
Authors: Zhang Hong , Pesetski Aaron , Baumgardner James , Murduck James , Adam John , Przybysz John
Published: November 2006

The frequency-independent performance of a carbon nanotube field effect transistor (CNT FET), at frequencies as high as 23 GHz, was demonstrated. The FET was fabricated using a top- gated geometry on a quartz substrate. The high frequency measurement was performed on this FET using a novel measurement approach, and for the first time we demonstrated the CNT FET continues to operate at frequencies up to 23 GHz without loss of gain. This observed maximum operating frequency represents a significant breakthrough in the realization of carbon nanotube-based electronics for low-power, high frequency applications.
Molecular Beam Epitaxy of Lithium Niobate Multifunctional Materials Using a Chloride Refractory Metal Chemistry
Authors: Doolittle William A. , Carver Alexander , Henderson Walter , Calley W. Laws
Published: November 2006

A new chloride based chemistry that bypasses many of the traditional pitfalls of Lithium Niobate (LN) epitaxy including the need for electron beam evaporation of refractory metals, and use of complex metal organic precursors prone to pre-reaction is detailed. Methods of dealing with the normally corrosive chloride based chemistry in a Molecular Beam Epitaxy (MBE) chamber are detailed. These methods include careful opening procedures to minimize moisture uptake and a highly effective Li-getter pump that forms a natural desiccant material, LiCl, enhancing water pumping and minimizing corrosive HCl production. The present state of heteroepitaxy of LN on semiconductors is presented with novel optoelectronic and electronic device concepts presented as motivation for development of this multifunctional material - semiconductor system. Future multifunctional applications offer much promise but also strongly hinge on the limits of film quality that can be achieved.
Novel Pd/Ge/Cu Ohmic Contact to n-Type GaAs
Authors: Chen Ke Shian , Lee Cheng-Shih , Chang Edward Yi , Lin Chia-Ching
Published: November 2006

A low contact resistance Pd/Ge/Cu ohmic contact to n-type GaAs is successfully developed. The Pd/Ge/Cu ohmic contact exhibits a very low contact resistivity of 5.73 x 10-7 Ω-cm2 at a low annealing temperature (250 {degree sign}C). This result is comparable to the reported Pd/Ge and Au/Ge/Ni ohmic contact systems to n- type GaAs with doping concentrations about 1x1018 cm-3. The ohmic contact formation mechanisms and microstructure reactions were investigated using x-ray diffraction (XRD), secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM).
Effect of Electrolyte Concentration on Anodic Nanoporous Layer Growth for n-InP in Aqueous KOH
Authors: Lynch Robert , O'Dwyer Colm , Buckley D. N. , Sutton David , Newcomb Simon
Published: November 2006

The surface morphology and sub-surface porous structure of (100) n-InP following anodization in 1 - 10 mol / l aqueous KOH were studied using linear sweep voltammetry (LSV) in combination with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was observed that the pore width increased and the inter-pore spacing decreased with decreasing concentration and that the porous layer depth also varied reaching a maximum thickness at ~2.2 mol / l. It is proposed that preferential pore propagation occurs along <111> directions, contrary to previous suggestions, and that the resulting nanoporous domains, initially formed, have triangular cross-sections when viewed in one of the {110} cleavage planes, 'dove-tail' cross-sections viewed in the orthogonal {110} cleavage plane and square profiles when viewed in the (100) plane of the electrode surface.