bluuebunny/crossref_metadata_2025 huggingface dataset:
Intelligent Electromechanical Actuators to Modernize Ship Operations
Authors: TESAR DELBERT , KRISHNAMOORTHY GANESH
Published: February 2009

The Navy is determining the viability of replacing hydraulic actuation for Navy platforms by using advanced torque‐dense electromechanical actuators (EMAs). The goal is to create a Standardized Actuator Building Block (SABB) to open up the ship architecture, enhancing performance while reducing the threat of obsolescence, enable rapid reconfiguration (fight through) after attack, expand performance, and dramatically shorten the associated logistics trail. This can make refreshment even at sea feasible with significant improvements in ship availability and reduced dock time. Cost is also of increasing interest to the Navy in order to produce more combatant platforms for a given budget. SABBs can be downgraded (to reduce cost) or upgraded (to meet more demanding performance requirements) all within the same set of standards (quick‐change interfaces, sizes, geometry, etc.). These modules can be rapidly replaced even by a nominally trained technician (reducing training costs) and therefore reducing the number of ship personnel. This paper outlines the merits of the crucial component to achieve the abovementioned objectives: the EMA. The EMA is the exact equivalent of the computer chip to computers—to drive anything that moves on the ship. In conjunction with the intelligent actuator control framework, developed based on extensive research in robotics and intelligent machines at The University of Texas Robotics Research Group, this technology can now be leveraged to make a significant contribution to the modernization of future ships and submarines.
Melatonin reduces microvascular damage and insulin resistance in hamsters due to chronic intermittent hypoxia
Authors: Bertuglia Silvia , Reiter Russel J.
Published: February 2009

Abstract: Obstructive sleep apnea (OSA) causes intermittent hypoxia (IH) associated with hypertension, insulin resistance and a systemic inflammatory response. We evaluated the effects of melatonin on vasodilation, capillary perfusion in hamster cheek pouch and insulin resistance, hypertension, and reactive oxygen species (ROS) and nitrate/nitrite levels after IH for 4 wk. Syrian hamsters were divided into four groups: control group (CON), IH group, and melatonin (10 mg/kg) intraperitoneally administered daily for 4 wk/30 min before intermittent air (MEL) or IH (IH + MEL) exposure. IH alone caused elevated blood pressure, increased hematocrit, fasting hyperglycemia, elevated ROS and nitrite/nitrate levels, and vasoconstriction and reduced microvascular perfusion. Melatonin treatment of IH‐exposed animals decreased blood pressure, blood glucose, and ROS and nitrite/nitrate levels, and increased vasodilation and capillary perfusion. An oral glucose tolerance test was performed after 4 wk of IH. During the last 30 min of the hyperinsulinemic euglycemic clamp, blood glucose, and insulin levels were identically matched between groups, but the glucose infusion rate was significantly reduced in IH (29.9 ± 1.9 mg/kg/min) versus IH + MEL group (45.4 ± 1.5 mg/kg/min,P < 0.05) demonstrating a decrease in insulin sensitivity. These results suggest that ROS and nitrite/nitrate levels play important roles in the microvascular dysfunction in IH and that this process is attenuated by melatonin. In conclusion, protection induced by melatonin against functional and metabolic impairment in IH is related to the regulation of ROS and nitrite/nitrate levels in the microcirculation. These observations may have importance to OSA pathological changes.
Consequences of Test Score Use as Validity Evidence: Roles and Responsibilities
Authors: Nichols Paul D. , Williams Natasha
Published: February 2009

This article has three goals. The first goal is to clarify the role that the consequences of test score use play in validity judgments by reviewing the role that modern writers on validity have ascribed for consequences in supporting validity judgments. The second goal is to summarize current views on who is responsible for collecting evidence of test score use consequences by attempting to separate the responsibilities of the test developer and the test user. The last goal is to offer a framework that attempts to prescribe the conditions under which the responsibility for collecting evidence of consequences falls to the test developer or to the test user.
An NCME Instructional Module on Using Differential Step Functioning to Refine the Analysis of DIF in Polytomous Items
Authors: Penfield Randall D. , Gattamorta Karina , Childs Ruth A.
Published: February 2009

Traditional methods for examining differential item functioning (DIF) in polytomously scored test items yield a single item‐level index of DIF and thus provide no information concerning which score levels are implicated in the DIF effect. To address this limitation of DIF methodology, the framework of differential step functioning (DSF) has recently been proposed, whereby measurement invariance is examined within each step underlying the polytomous response variable. The examination of DSF can provide valuable information concerning the nature of the DIF effect (i.e., is the DIF an item‐level effect or an effect isolated to specific score levels), the location of the DIF effect (i.e., precisely which score levels are manifesting the DIF effect), and the potential causes of a DIF effect (i.e., what properties of the item stem or task are potentially biasing). This article presents a didactic overview of the DSF framework and provides specific guidance and recommendations on how DSF can be used to enhance the examination of DIF in polytomous items. An example with real testing data is presented to illustrate the comprehensive information provided by a DSF analysis.
Use of rapid tests and antiviral medications for influenza among primary care providers in the United States
Authors: Katz Mark A. , Lamias Mark J. , Shay David K. , Uyeki Timothy M.
Published: February 2009

Limited data are available about how physicians diagnose and treat influenza. We conducted an internet‐based survey of primary care and emergency physicians to evaluate the use of influenza testing and antiviral medications for diagnosis and treatment of influenza. In April 2005, an electronic link to a 33‐question, web‐based survey was emailed to members of the American College of Physicians, American Academy of Pediatrics, American Academy of Family Physicians, and American College of Emergency Physicians. Of the 157 674 physician members of the four medical societies, 2649 surveys were completed (1·7%). The majority of participants were internists (59%). Sixty percent of respondents reported using rapid tests to diagnose influenza. Factors associated with using rapid influenza tests included physician specialty, type of patient insurance, and practice setting. After controlling for insurance and community setting, emergency physicians and pediatricians were more likely to use rapid influenza tests than internists [odds ratio (OR) 3·7, confidence interval (CI): 2·3–6·1; and OR 1·7, CI: 1·4–2·1, respectively]. Eighty‐six percent of respondents reported prescribing influenza antiviral medications. Reasons for not prescribing antivirals included: patients do not usually present for clinical care within 48 hours of symptom onset (53·0%), cost of antivirals (42·6%) and skepticism about antiviral drug effectiveness (21·7%). The use of rapid tests and antiviral medications for influenza varied by medical specialty. Educating physicians about the utility and limitations of rapid influenza tests and antivirals, and educating patients about seeking prompt medical care for influenza‐like illness during influenza season could lead to more rapid diagnosis and improved management of influenza.
Characterisation of a highly pathogenic influenza A virus of subtype H5N2 isolated from ostriches in South Africa in 2004
Authors: Abolnik Celia , Londt Brandon Z. , Manvell Ruth J. , Shell Wendy , Banks Jill , Gerdes Gertruida H. , Akol George , Brown Ian H.
Published: February 2009

Objectives  The HPAI H5N2 strain that caused an outbreak in ostriches of the Eastern Cape Province, South Africa in 2004 was characterized.

Design  Haemagglutination inhibition (HI) and agar gel immunodiffusion (AGID) were performed on sera from ostrich farms in the outbreak region, and intravenous pathogenicity (IVPI) tests, reverse‐transcriptase‐polymerase‐chain reaction (RT‐PCR), nucleic acid sequencing and phylogenetic comparisons were performed on the HPAI H5N2 virus isolated during the outbreak.

Results  The deduced amino acid sequence at the HA0 cleavage site determined by RT‐PCR and nucleotide sequencing was PQREKRRKKRGLF and thus the virus fell within the definition of a highly pathogenic virus, but in an IVPI test in chickens on the virus isolated from the index case and a value of 0·63 was recorded, which is below the criterion for highly pathogenic viruses in this in vivo test. After a further passage in embryonated eggs a second IVPI was carried out and an elevated value of 1·19 was obtained. Cloacal swabs were taken from the initial IVPI birds, inoculated into embryonated chickens eggs and a third IVPI was then performed on the resulting haemagglutinating, infective allantoic fluid. An index of 2·73 was recorded.

Conclusions  HI tests appeared to be the more sensitive test compared to AGID when testing for antibodies to avian influenza in sera. An ostrich‐derived virus with a virulent HA0 cleavage site was not initially virulent in chickens but after passage in the latter the virulence increased. Phylogenetic analyses demonstrated the link between AI viruses carried by wild ducks and those infecting ostriches.
Seasonal and pandemic influenza surveillance considerations for constructing multicomponent systems
Authors: Brammer Lynnette , Budd Alicia , Cox Nancy
Published: February 2009

Abstract  Surveillance for influenza is essential for the selection of influenza vaccine components and detection of human infections with novel influenza A viruses that may signal the start of a pandemic. Virologic surveillance provides the foundation from which this information can be obtained. However, morbidity and mortality data are needed to better understand the burden of disease, which, in turn, can provide useful information for policy makers relevant to the allocation of resources for prevention and control efforts. Data on the impact of influenza can be used to identify groups at increased risk for severe influenza‐related complications, develop prevention and control policies, and monitor the effect of these policies. Influenza surveillance systems frequently monitor outpatient illness, hospitalizations, and deaths, but selection of influenza surveillance components should be based on the surveillance goals and objectives of the jurisdiction.
Media, Politics and Climate Change: Towards a New Research Agenda
Authors: Anderson Alison
Published: February 2009

Climate change is one of the most pressing issues of our time, and the media have been demonstrated to play a key role in shaping public perceptions and policy agendas. Journalists are faced with multiple challenges in covering this complex field. This article provides an overview of existing research on the media framing of climate change, highlighting major research themes and assessing future potential research developments. It argues that analysis of the reporting of climate science must be placed in the wider context of the growing concentration and globalization of news media ownership, and an increasingly ‘promotional culture’, highlighted by the rapid rise of the public relations industry in recent years and claims‐makers who employ increasingly sophisticated media strategies. Future research will need to examine in‐depth the targeting of media by a range of actors, as well as unravel complex information flows across countries as media increasingly converge.
Beetle abundance–environment relationships at the Subantarctic–Patagonian transition zone
Authors: RUGGIERO ADRIANA , SACKMANN PAULA , FARJI‐BRENER ALEJANDRO G. , KUN MARCELO
Published: February 2009

Abstract.

The spatial variation in the abundance of individuals may be associated with the variation in environmental variables. The productivity hypothesis proposes that climate affects plant productivity, which may limit the abundance of beetles. The thermal‐limitation hypothesis proposes the direct effect of ambient temperature may limit beetle abundance. We analysed the abundance of epigaeic beetles at the Subantarctic–Patagonian transition to test for these abundance–environment relationships.

We collected beetles using 450 pitfall traps within a ~150 × 150 km area representative of the Subantarctic–Patagonian transition. We used path analysis to evaluate the relationships between beetle abundance and plant cover, litter biomass, averaged minimum and daily temperature range, and mean annual precipitation. We used principal coordinates of neighbour matrices to model the spatial autocorrelation of the data.

The abundance of beetles increased strongly with tree canopy cover and less strongly with herb cover. The increase in shrub cover had a positive effect on beetle abundance in areas to the east of the transition, within the scrubland‐steppe, but it has a negative effect on beetle abundance in areas to the west of the transition, within the forests. The association between beetle abundance and minimum daily temperature was negative or weak throughout. Increased temperature variation had a negative effect on beetle abundance.

We suggest that indirect positive climatic effects mediated through plant cover are important to account for the variation in beetle abundance, which favours the productivity hypothesis. Thermal limitation may operate locally through variation in daily temperature range.
Isolation and characterization of microsatellite markers from the limpet Cellana grata
Authors: NG W. C. , CHAN M. N. , SLINGSBY G. , WILLIAMS GRAY A. , LEUNG F. C. C.
Published: February 2009

This note describes the development of nine polymorphic microsatellite loci in the limpet Cellana grata to investigate population structure and cohort variation in this species. The number of alleles ranged from seven to 22 and observed heterozygosity ranged from 0.62 to 0.95. Deviation from the Hardy–Weinberg equilibrium was detected in two loci, both as a result of heterozygote deficiency. Null alleles were detected in one of these loci. These genetic markers will be used to investigate the genetic structure of C. grata populations, as well as variation among cohorts of this common intertidal species.
Isolation and characterization of polymorphic microsatellite loci for the northern flicker (Colaptes auratus; Aves)
Authors: KUHN SYLVIA , WIEBE KAREN L. , KEMPENAERS BART
Published: February 2009

To investigate the mating system of northern flickers (Colaptes auratus), we developed primers for 14 microsatellite loci and screened them in 68 unrelated adults and their offspring. All markers were highly polymorphic with 9 to +36 alleles per locus. One marker was Z‐chromosome linked; one marker exceeded the size standard range and could not be analysed further. We checked the other 12 markers for Mendelian inheritance in 36 broods for which the social parents were known. Seven markers showed evidence for the presence of null alleles, and three of those showed significant deviation from Hardy–Weinberg equilibrium. Markers were generally unlinked.
Species‐specific primers for predation studies of the pollen beetle, Meligethes aeneus (Coleoptera, Nitidulidae)
Authors: CASSEL‐LUNDHAGEN ANNA , ÖBERG SANDRA , HÖGFELDT CAROL , EKBOM BARBARA
Published: February 2009

Species‐specific primers were developed for the pollen beetle (a pest in oilseed rape) for studies of predation by natural insect predators. Two forward and three reverse primers were designed within the mitochondrial COI gene and used in combination to amplify fragments in the size range of 163–290 bp. Remains of pollen beetle DNA were consistently detected in Pardosa spiders up to 24 h after ingestion but dropped drastically at 48 h. These primers will facilitate studies on biological control of this oilseed rape pest. Detection time was not correlated with fragment length as might be expected as the DNA gradually degrades into progressively shorter fragments over time.
Armeria saviana sp. nov. (Plumbaginaceae) from central Italy
Authors: Selvi Federico
Published: February 2009

The new species Armeria saviana, endemic to an isolated mountain chain of the Tyrrhenian Antiappennine system in south Tuscany, central Italy, is described and illustrated. The plant is diploid with 2n=18. It can be distinguished from the related species A. denticulata (Bertol.) DC and A. canescens (Host) Ebel, mainly by leaf characters, capitula, bracts and flowers. The systematic position of the controversial taxon A. majellensis Boiss. subsp. ausonia F. Bianchini, to which the new species has formerly been assigned by some authors, is discussed. A lectotype for A. denticulata is designated.
Physicochemical and electrical characterizations of atomic layer deposition grown HfO2 on TiN and Pt for metal-insulator-metal application
Authors: Jorel C. , Vallée C. , Gourvest E. , Pelissier B. , Kahn M. , Bonvalot M. , Gonon P.
Published: February 2009

This work reports on the study of two HfO2 metal-insulator-metal structures using two different bottom metal electrodes: Pt and TiN. Different spectroscopic techniques had been used for the physicochemical characterization in order to study the junction interface and determine the oxide thickness and crystallinity: parallel angle resolved x-ray spectroscopy, vacuum ultraviolet ellipsometry, and attenuated total reflectance. Electrical characteristics of the structures with different oxide thicknesses and an evaporated gold counterelectrode are shown. Best results for very thin HfO2 films in terms of voltage linearity are obtained with the platinum electrodes. This is correlated with differences observed between the continuous conductivity when using Pt electrode instead of TiN electrode.
Irradiation effect on dielectric properties of hafnium and gadolinium oxide gate dielectrics
Authors: García H. , Dueñas S. , Castán H. , Gómez A. , Bailón L. , Barquero R. , Kukli K. , Ritala M. , Leskelä M.
Published: February 2009

Ionizing radiation effects on the electrical properties of HfO2, Gd2O3, and HfO2∕SiO2 based metal-oxide-semiconductor (MOS) capacitors have been studied. High-k dielectrics grown by atomic layer deposition and high-pressure Sputtering were exposed to photon radiation (18MeV photons). Capacitance-voltage curves, deep-level transient spectroscopy, conductance and flat-band voltage transients, and current-voltage techniques were used to characterize the samples. An increment in bulk dielectric trap densities has been observed when the samples were exposed to the ionizing radiation. These traps give rise to a flat-band voltage displacement, the extent of which depends on the gate dielectric used. High-k/silicon interface quality becomes worse after irradiation. An increment in the gate leakage current was also observed when irradiating the samples. Disorder-induced gap state density inside the insulator increases in the case of Gd2O3 MOS based samples, which seems to be the most affected by ionizing radiation.
Effective work function engineering by lanthanide ion implantation of metal-oxide semiconductor gate stacks
Authors: Fet A. , Häublein V. , Bauer A. J. , Ryssel H.
Published: February 2009

While the debate about the exact cause of Fermi level pinning in metal-high-k dielectric gate stacks is ongoing, several solutions for engineering the threshold voltage Vt of the gate stacks have been proposed. Engineering the flat-band voltage Vfb translates into an effective control of the threshold voltage. This study uses ion implantation as a tool to adjust Vfb by doping the gate stack. It is shown that lanthanide implantation can modulate the effective work function for n-type gate electrodes. Ion implantation of dysprosium (Dy) and lanthanum (La) into the gate stack achieves significant flat-band voltage shifts of about −1 and −3V, respectively, for a dose of 1×1014cm−2. By increasing the implantation dose and energy, larger shifts in the flat-band voltage are obtainable.
Development of a conductive atomic force microscope with a logarithmic current-to-voltage converter for the study of metal oxide semiconductor gate dielectrics reliability
Authors: Aguilera L. , Lanza M. , Bayerl A. , Porti M. , Nafria M. , Aymerich X.
Published: February 2009

A new configuration of conductive atomic force microscope (CAFM) is presented, which is based in a conventional AFM with a logarithmic current-to-voltage (log I-V) amplifier. While a standard CAFM allows to measure a current dynamic range of typically three orders of magnitude (0.1–100pA), with the new setup it is possible to measure up to nine orders of magnitude. The extended current range allows to evaluate the reliability of gate dielectrics in a single electrical test, overcoming the limitations of standard CAFM configurations. The setup has been tested by analyzing breakdown (BD) spots induced in SiO2 and high-k layers. For current measurements, the results show that I-V characteristics and current images (measured at a constant voltage) can be easily obtained in a wide dynamic range, which can reveal new details of the BD mechanisms. In particular, the setup was used to investigate the area electrically affected by the breakdown event in SiO2 and HfO2∕SiO2 stacks.
Gas sensing materials based on TiO2 thin films
Authors: Iftimie Nicoleta , Luca D. , Lacomi Felicia , Girtan Mihaela , Mardare Diana
Published: February 2009

Ti O 2 thin films were prepared by spray pyrolysis using a solution of titanium tetrachloride and ethyl alcohol. The deposition was performed onto different substrates (silicon, quartz, glass) maintained at the same temperature, 270°C. After annealing, a predominant rutile structure is obtained for films deposited onto silicon and quartz substrates, as revealed by x-ray diffraction patterns. The TiO2 films were exposed to different gases, at different temperatures, in order to evaluate their gas sensitivity. The optimum operating temperatures, showing the highest gas sensitivity, were determined for some gases (acetone, ethanol, methane, and liquefied petroleum gas).
Study on the characteristics of toluene-tetraethoxysilane hybrid plasma-polymer thin films
Authors: Cho S.-J. , Bae I.-S. , Lee S. , Jung D. , Choi W. S. , Boo J.-H.
Published: February 2009

This study investigated the interaction of varied plasma power with ultralow-k toluene-tetraethoxysilane (TEOS) hybrid plasma-polymer thin films, as well as changing electrical and mechanical properties with varied radio frequency (rf 13.56MHz) power of plasma. The hybrid films with low dielectric constants were deposited on silicon(100) substrates by plasma enhanced chemical vapor deposition system. Toluene and tetraethoxysilane were utilized as organic and inorganic precursors. In addition, bubbling ratio of TEOS to toluene is 1:10. The as-grown hybrid plasma-polymer thin films were characterized by Fourier transform infrared spectroscopy, atomic force microscopy (AFM), nanoindentation, I-V curves, and capacitance. To analyze their trends of electrical and mechanical properties, the thin films were grown under conditions of various rf powers. The IR spectra showed them to have completely different chemical functionalities from the liquid toluene and TEOS precursors. The AFM images showed changing of surface roughness that depended on different deposition rf powers. An MTS nanoindenter® was used to measure the hardness and Young’s modulus that increased as-deposition rf power increased, with the highest values being 2.69 and 27.6GPa at 50W of deposition rf power. An impedance analyzer was utilized for measurements of the I-V curves (for leakage current density; 1×10−9A∕cm2 at 1MV∕cm) and capacitance (for dielectric constant; 1.69).
Photoluminescence from high-pressure-annealed silicon dioxide
Authors: Wong C. K. , Misiuk A. , Wong Hei , Panas A.
Published: February 2009

Effect of treatment at high temperature (HT) (up to 1200°C) under high hydrostatic pressure (HP) (up to 1.5GPa) on the photoluminescence (PL) of silicon dioxide films was investigated. The authors found that the PL intensity of the oxide films grown in pure oxygen can be significantly enhanced by the HT-HP treatment. Four PL peaks, at wavelengths of about 570, 620, 720, and 950nm, were found. The 570 and 950nm peaks are attributed to the defect centers and amorphous Si, respectively. The luminescence at 620 and 720nm is attributed to the quantum confinement effect involving the silicon nanocrystallites embedded in the oxide film. The PL intensities are strongly governed by the preparation conditions of the as-grown oxide layer as well as by the annealing conditions. Raman study indicates that both amorphous and crystalline Si phases coexist in the HT-HP processed samples. The formation of Si nanocrystallites is attributed to the phase separation effect involving Si suboxide.
Light emission and photoluminescence from high-k dielectrics containing Ge nanocrystals
Authors: Chang Shu-Tong , Liao Shu-Hui
Published: February 2009

A metal/HfAlO∕Si light emitting diode with Ge nanocrystals embedded in HfAlO has the visible light emission (610nm) and the infrared emission (760nm). The image and Ge content are measured by the transmission electron microscopy and Raman spectroscopy. The photoluminescence of Ge nanocrystals embedded in HfAlO has a peak wavelength at 700nm, while the peak wavelength at 725nm is observed for Ge nanocrystals embedded in HfO2. The difference of it may be due to the larger band gap of HfAlO as compared to HfO2.
Electron paramagnetic resonance characterization of defects in HfO2 and ZrO2 powders and films
Authors: Barklie R. C. , Wright Sandra
Published: February 2009

Electron paramagnetic resonance (EPR) measurements have been made on HfO2 and ZrO2 both as films on silicon and as monoclinic phase powders with the aim of characterizing the defects in these high κ oxides. The measurements on as-received, gamma irradiated, and both vacuum and air annealed powders reveal many types of defect, some of which are involved in charge trapping. Several, possibly all, of these defects may be at or near a surface of the particles. Films were deposited by e-beam evaporation but only those grown during low-energy Ar+ ion irradiation reveal EPR spectra of defects associated with the films.
Progressive degradation of TiN∕SiON and TiN∕HfO2 gate stack triple gate SOI nFinFETs subjected to electrical stress
Authors: Rafí J. M. , Simoen E. , Mercha A. , Collaert N. , Campabadal F. , Claeys C.
Published: February 2009

In this contribution, the authors analyze first results about the impact of electrical stress on triple gate SOI nFinFETs with metal gate (TiN) and SiON or HfO2 gate dielectrics, with particular emphasis on the roles of fin width and back gate polarization. A similar progressive degradation of the characteristics is observed for both types of gate dielectric devices. An increasing degradation with reducing fin width is observed for a certain range of wide fin devices (between about 3μm and 130nm), which could be attributed to a higher contribution of corner effects or lower quality side surfaces. However, the narrowest triple gate FinFETs with geometries around the nominal values of this technology (70nm long and 30nm wide fins) show reduced degradation with electrical stress. Under the studied experimental conditions, no clear impact on device degradation is observed for different back gate bias conditions applied during electrical stress. A typical dielectric breakdown mode characterized by a sudden decrease in drain current, accompanied by a significant increase in front gate current, is observed quite often in devices subjected to strong or long stress conditions. From the analysis of the encountered postbreakdown source/drain asymmetries, it is inferred that most of such catastrophic failures under VFG=VD stress regime may correspond to gate-to-source dielectric breakdown.
Interface states formation in a localized charge trapping nonvolatile memory device
Authors: Shapira Asia , Shur Yael , Shacham-Diamand Yosi , Shappir Assaf , Eitan Boaz
Published: February 2009

Two NROM nonvolatile memory devices that are practically identical but exhibit different postcycling characteristics are investigated. Electrical characterizations combined with two-dimensional drift diffusion simulations were employed to quantify and differentiate the retention loss mechanisms. The comparison demonstrates the coexistence of two retention loss mechanisms, lateral charge transport in the nitride layer, and hot carrier induced interface states formation and anneal. The fabrication conditions in the various studies reported in the literature and the resultant impact on interface states formation are most likely the cause of the formally nonresolved debate regarding the origin of retention loss in NROM technology. The reduction in interface state formation during cycling is a key to achieving high reliability NROM cells and products.
Dependence of etch rates of silicon substrates on the use of C4F8 and C4F6 plasmas in the deposition step of the Bosch process
Authors: Rhee Hyongmoo , Lee Hae Min , Namkoung Yun Mi , Kim Chang-Koo , Chae Heeyeop , Kim Yil Wook
Published: February 2009

The Bosch process was carried out using SF6∕C4F8 or SF6∕C4F6 plasmas during the etching/deposition steps to examine the etch profiles and etch rates of silicon. The fluorocarbon film deposited in a C4F6 plasma was thicker and more strongly bonded than the film deposited in a C4F8 plasma, which led to a shorter deposition time for the C4F6 plasma. The deposition rate of the fluorocarbon films on the different locations of the silicon substrate in both C4F8 and C4F6 plasmas decreased in the following order: top>bottom>sidewall. However, the normalized deposition rate of the bottom surface with respect to the top surface was higher for the C4F8 plasma (0.92) than for the C4F6 plasma (0.65), indicating that a thicker fluorocarbon film was deposited at the bottom of the pattern in C4F8 plasma under the same process conditions. This resulted in a higher etch rate of the silicon substrate using C4F6 plasma during the deposition step of the Bosch process, even though a fluorocarbon film with a similar thickness had been deposited on the top surface for both C4F8 and C4F6 plasmas.
Detailed characterization of hydrogen silsesquioxane for e-beam applications in a dynamic random access memory pilot line environment
Authors: Keil K. , Choi K.-H. , Hohle C. , Kretz J. , Szikszai L. , Bartha J.-W.
Published: February 2009

Hydrogen silsesquioxane (HSQ) has interesting applications as an electron-beam resist and hardmask. In this work, HSQ was investigated with regard to the postcoat delay, isofocal dose for an optimum process window, e -beam proximity effect correction, and the molecular structure in order to better understand the processing. Several independent methods were set up and applied to characterize the structuring of HSQ with e-beam including contrast measurements, basedose-over-critical-dimension tests, the isofocal dose method, the doughnut test, and Fourier transform infrared analysis. HSQ was coated on 300mm bare silicon wafers and exposed with a 50kV variable shaped e-beam writer in the dynamic random access memory pilot line environment of Qimonda Dresden and Fraunhofer CNT. The postcoat delay showed no significant influence on the exposure results. A dose difference between the basedose and the isofocal dose was observed, which indicates a working point in a suboptimal process window related to the poor contrast. The FTIR analysis showed a molecular structure change up to 600μC∕cm2. Finally, a point-spread-function for HSQ has been generated for the first time. In summary, the results from this detailed characterization show promise for a manageable process.
Latest results from the SEMATECH Berkeley extreme ultraviolet microfield exposure tool
Authors: Naulleau Patrick P. , Anderson Christopher N. , Chiu Jerrin , Dean Kim , Denham Paul , George Simi , Goldberg Kenneth A. , Hoef Brian , Jones Gideon , Koh Chawon , La Fontaine Bruno , Ma Andy , Montgomery Warren , Niakoula Dimitra , Park Joo-on , Wallow Tom , Wurm Stefan
Published: February 2009

Microfield exposure tools (METs) continue to play a dominant role in the development of extreme ultraviolet resists. One of these tools is the 0.3 numerical aperture SEMATECH Berkeley MET operating as a resist and mask test center. Here the authors present an update on this tool, summarizing the latest test and characterization results. They provide an update on the long-term aberration stability of the tool and present line-space imaging in chemically amplified photoresist down to the 20nm half-pitch level. Although resist development has shown substantial progress in the area of resolution, line edge roughness (LER) remains a significant concern. In this manuscript the authors further present a summary of recent LER performance results and consider the effect of mask contributors to the LER observed from the SEMATECH Berkeley MET.
Electrical investigations on metal/ferroelectric/insulator/semiconductor structures using poly[vinylidene fluoride trifluoroethylene] as ferroelectric layer for organic nonvolatile memory applications
Authors: Henkel K. , Lazareva I. , Mandal D. , Paloumpa I. , Müller K. , Koval Y. , Müller P. , Schmeißer D.
Published: February 2009

Poly[vinylidene fluoride trifluoroethylene] (P[VDF/TrFE]) is a ferroelectric polymer and a candidate for the application in a ferroelectric field effect transistor, which is considered as a nonvolatile and nondestructive readout memory cell. In this contribution the authors focus on metal/ferroelectric/insulator/semiconductor capacitor structures with P[VDF/TrFE] as ferroelectric layer. Measuring the capacitance of Al/P[VDF/TrFE]/SiO2/Si stacks in dependence of the applied bias and analyzing the oxide capacitance in dependence of the thickness of the ferroelectric layer, they observe a formation of an interfacial nonferroelectric layer. This layer is responsible for reduced values of polarization profound for thinner P[VDF/TrFE] layers in this system. Capacitance-time measurements at such stacks show the possibility to distinguish between a higher and a lower capacitance state for more than 5 days. Long-time measurements revealed imprint and fatigue-like behavior.
Analytical modeling of tunneling current through SiO2–HfO2 stacks in metal oxide semiconductor structures
Authors: Coignus J. , Clerc R. , Leroux C. , Reimbold G. , Ghibaudo G. , Boulanger F.
Published: February 2009

This work presents an original approach to model direct tunneling current through high-κ dielectrics including SiO2 interfacial oxide from electron inversion layers. Quantum confinement is taken into account by means of an improved triangular well approximation including physically-based analytical corrections of subband energy levels. An efficient way to compute tunnel transmission probability is also proposed, taking into account the reflections on discontinuous dielectrics interfaces. Finally, this model has been successfully validated by comparison to both numerical simulations and experimental results.
Different mechanism to explain the 1∕f noise in n- and p-SOI-MOS transistors fabricated on (110) and (100) silicon-oriented wafers
Authors: Gaubert Philippe , Teramoto Akinobu , Cheng Weitao , Hamada Tatsufumi , Ohmi Tadahiro
Published: February 2009

The investigation of the low frequency noise in p- and n-channel semiconductor-on-insulator–metal oxide semiconductor transistors fabricated on (100) and (110) silicon-oriented wafers using high advanced processes has been carried out. While for both orientations the 1∕f noise in the n-channel transistors can be explained through the ΔN formalism, the p-channel ones seem to follow the Hooge model. In addition, the new orientation presents a noise level higher than the conventional one. Furthermore, the authors showed that when there is a gap of one decade between the Si(100) and Si(110) p-channel transistors, this one has been reduced to a factor of 2 in the case of the n-channel ones. Finally, by combining the highly advanced microwave-excited high-density plasma oxidation process with the alkali-free five-step cleaning process, it has been possible to fabricate on both surfaces a very high quality oxide with a very low density of traps.
Application of plasma enhanced chemical vapor deposition silicon oxynitride layers in nonvolatile semiconductor memory devices
Authors: Mroczyński Robert , Beck Romuald B.
Published: February 2009

In this paper, the authors present the new double gate dielectric structure for the nonvolatile semiconductor memory (NVSM) devices which is based of hafnium dioxide (HfO2). The novelty of this structure relays on the introduction of ultrathin silicon oxynitride (SiOxNy) formed by plasma enhanced chemical vapor deposition (PECVD). Fabricated test structures with the PECVD layers show repetitious behavior of the hysteresis characteristics in comparison to structure with silicon dioxide as the tunnel (bottom) dielectric, which the stability of hysteresis loop is observed after completing first stressing loop. Moreover, the memory window expressed as the flat-band voltage shift versus stress voltage is very wide (1.68V) and the maximum charge which can be stored by the double gate dielectric stack is of the order of 6×1012(cm−2). Comparison of current density versus gate voltage characteristics of investigated metal-insulator-semiconductor systems demonstrated significantly a decrease of the leakage current for double gate dielectric layers with PECVD oxynitride. In addition, the dielectric constant of SiOxNy (annealed)/HfO2 system is about 11.7 which results in the greatest decrease of equivalent-oxide thickness value among the investigated dielectric stacks. The results presented in this paper show a potential to apply PECVD silicon oxynitride layers in NVSM devices.
Review on the reliability characterization of plasma-induced damage
Authors: Martin Andreas
Published: February 2009

In this review, essential topics on reliability characterization of plasma-induced damage are discussed. First, the basic degradation of a metal-oxide-semiconductor (MOS) gate oxide from plasma processing steps is described. Second, the reliability characterization techniques and basics are discussed and problem areas are highlighted. Discussion points include the antenna ratio definition, test structure layout employing MOS transitors with and without antennas, stress and measurement sequence including a revealing stress, use of protection elements against plasma-charging, plasma-charging effects on metal-insulator-metal capacitors, and plasma-charging effects on high-k dielectrics of field-effect transistors.
Correlation of microscopic and macroscopic electrical characteristics of high-k ZrSixO2−x thin films using tunneling atomic force microscopy
Authors: Weinreich W. , Wilde L. , Kücher P. , Lemberger M. , Yanev V. , Rommel M. , Bauer A. J. , Erben E. , Heitmann J. , Schröder U. , Oberbeck L.
Published: February 2009

Tunneling atomic force microscopy (TUNA) is used to identify leakage current characteristics in SiO2 doped ZrO2 thin films within the nanometer scale. TUNA current maps and local TUNA I-V curves provide similar tendencies such as conventional macroscopic I-V curves concerning the dependence of leakage current on thickness and doping level. However, microscopic data additionally visualize the influence of minimal deviations in composition or morphology on the electrical film homogeneity not observable by macroscopic techniques. Therefore, optimization of the SiO2 dopant concentration in ZrO2 is possible. Additionally, information regarding the nonuniformity of charge trapping can be obtained out of local TUNA I-V curves implying the broad potential of TUNA.
Electrical characteristics of metal-ferroelectric (BiFeO3)-insulator (Y2O3)-semiconductor capacitors and field-effect transistors
Authors: Lin Chih-Ming , Shih Wen-chieh , Lee Joseph Ya-min
Published: February 2009

Metal-ferroelectric-insulator-semiconductor (MFIS) capacitors and field effect transistors (FETs) with Al∕BiFeO3∕Y2O3∕Si structure were fabricated. The capacitance-voltage (C-V) characteristics exhibit clockwise hysteresis loop due to the ferroelectric polarization of BiFeO3. The maximum C-V memory window was 0.88V at a sweep voltage range of 5V. Low leakage current density of 7×10−9A∕cm2 was measured at an applied voltage of 5V using MFIS capacitors. The IDS-VDS and IDS-VGS characteristics of MFISFETs were measured. The subthreshold slope was 170mV∕dec and the maximum electron mobility was 155cm2∕Vs.
Impact of nitridation on recoverable and permanent negative bias temperature instability degradation in high-k/metal-gate p-type metal oxide semiconductor field effect transistors
Authors: Aoulaiche M. , Kaczer B. , Roussel Ph. J. , O’Connor R. , Houssa M. , De Gendt S. , Maes H. E. , Groeseneken G.
Published: February 2009

Negative bias temperature instability is investigated on TaN metal-gated HfSiO(N) p-type metal oxide semiconductor field effect transistors. A previously developed measurement technique that allows to distinguish between the recoverable and the permanent components of the Vth shift is employed. When applied to nitrided and nonnitrided stacks, it is found that the permanent component is at most weakly influenced by the nitridation, while the recoverable component is strongly enhanced in the nitrided stacks. The nitrogen-related defect, which is responsible of the recoverable component increase, is clearly observed in the stress induced leakage current spectrum.
Impact of progressive oxide soft breakdown on metal oxide semiconductor parameters: Experiment and modeling
Authors: Gerrer L. , Ribes G. , Ghibaudo G. , Jomaah J.
Published: February 2009

The impact of a soft breakdown-induced leaky weak spot occurring in the channel has been analyzed by two dimensional simulations of a metal oxide semiconductor field effect transistor within the charge sheet approximation. The model proves very efficient in reproducing the device characteristics variations after soft breakdown (SBD) and enables to properly interpret the correlation observed between device parameter shift (e.g., threshold voltage) and stress-induced gate leakage current. A partitioning study allows us to extract an expression for the channel debiasing at Vd>0 and to discriminate each impact of SBD on device characteristics.
Comparison of standard macroscopic and conductive atomic force microscopy leakage measurements on gate removed high-k capacitors
Authors: Polspoel W. , Vandervorst W. , Aguilera L. , Porti M. , Nafria M. , Aymerich X.
Published: February 2009

Understanding the origin and mechanism of detrimental local phenomena such as charge trapping, trap assisted tunneling, and breakdown in high-k gate oxides adds to the improvement of refining the layer deposition process. Conductive atomic force microscopy (AFM) is a relatively new technique that is able to visualize these local phenomena. In this work we improve the quality of the comparison between standard macroscopic and conductive AFM (C-AFM) microscopic gate leakage measurements by enabling measurements on the exact same dielectric layers of metal gate high-k capacitors and transistors, using a well tuned gate wet etch process. An agreement in leakage current between both measurement types is obtained. Furthermore, we visualize with C-AFM the location and current magnitude of breakdown spots which were induced by standard macroscopic electrical stress. The ability of investigating the local leakage behavior of real devices as it is shown in this work opens the way to better understand gate leakage measurements of any metal-oxide semiconductor device.
Predeposition plasma nitridation process applied to Ge substrates to passivate interfaces between crystalline-Ge substrates and Hf-based high-K dielectrics
Authors: Lucovsky G. , Long J. P. , Chung K.-B. , Seo H. , Watts B. , Vasic R. , Ulrich M. D.
Published: February 2009

Interfaces between crystalline-Si and high-K Hf-based oxide gate dielectrics have a lower-K interfacial transition region (ITR), generally 0.6–0.8nm SiON, which prevents reactions between Si and Hf precursors used in film deposition. These ITRs contribute ∼0.35nm to the equivalent oxide thickness limiting aggressive scaling. This article addresses Hf-based high-K gate dielectrics for devices on crystalline Ge substrates. The band gaps of GeO2 and Ge3N4 are reduced with respect to their Si counterparts, and as such may contribute to increased levels of interfacial defect states. A novel processing sequence is presented for (i) depositing HfO2 and Hf Si oxynitrides (HFSiON) onto N-passivated Ge(111) and Ge(100), and subsequently (ii) removing Ge–N interfacial bonding during 800°C thermal annealing in Ar. Near edge x-ray absorption spectroscopy and medium energy ion scattering measurements have confirmed that the interfacial nitrogen is indeed removed. However, there are reactions between the Ge substrate and deposited high-K dielectrics, as deposited and after annealing to 600–800°C, Ge–O bonding into the high-K gate stacks which result in increased levels of conduction band edge defect states that incorporate these Ge atoms.
Hot carrier degradation in HfSiON∕TiN fin shaped field effect transistor with different substrate orientations
Authors: Young Chadwin D. , Yang Ji-Woon , Matthews Kenneth , Suthram Sagar , Hussain Muhammad Mustafa , Bersuker Gennadi , Smith Casey , Harris Rusty , Choi Rino , Lee Byoung Hun , Tseng Hsing-Huang
Published: February 2009

Hot carrier injection (HCI) degradation is evaluated for n-metal oxide semiconductor (MOS) and pMOS high-κ-fin shaped field effect transistor with (100) and (110) sidewall surface orientations. It was found that impact ionization at the source, in addition to the traditional drain side enhances HCI degradation for the Vg=Vd condition. The degradation increases with decreasing fin length, with negligible dependence on substrate orientation.
Low-k dielectrics for trench isolation in nanoscaled complementary metal oxide semiconductor imagers
Authors: Irrera F. , Puzzilli G. , Ricci L. , Russo F. , Stirpe F.
Published: February 2009

In this article the authors propose a novel T-shaped shallow-trench isolation (STI) technology including an unfilled floating void STI. The structure aims to reduce the dark current in complementary metal oxide semiconductor active-pixel sensor technology and is optimized with respect to the size of the depletion region surrounding the STI, also accounting for the fringe electric field and the leakage current. Simulations indicate that a large air void positioned far from the bottom and top of the T-shaped trench improves performance.
Network Analysis in the Social Sciences
Authors: Borgatti Stephen P. , Mehra Ajay , Brass Daniel J. , Labianca Giuseppe
Published: February 2009

Over the past decade, there has been an explosion of interest in network research across the physical and social sciences. For social scientists, the theory of networks has been a gold mine, yielding explanations for social phenomena in a wide variety of disciplines from psychology to economics. Here, we review the kinds of things that social scientists have tried to explain using social network analysis and provide a nutshell description of the basic assumptions, goals, and explanatory mechanisms prevalent in the field. We hope to contribute to a dialogue among researchers from across the physical and social sciences who share a common interest in understanding the antecedents and consequences of network phenomena.