bluuebunny/crossref_metadata_2025 huggingface dataset:
Realism, Reception, 1968, and West Africa
Authors: Andrade Susan Z.
Published: September 2012

This essay traces the critical history of African novels; it aligns “postcolonial reading” with the rise of poststructuralism in the United States and the United Kingdom. It correctively reads for realism three novels, all published in 1968 and not usually considered mimetic: Le devoir de violence (Mali), Les soleils des indépendances (Côte d’Ivoire), and The Beautyful Ones Are Not Yet Born (Ghana). Only Devoir has been particularly important to the conversation about postcolonial literature and form, thanks to Kwame Anthony Appiah. Andrade’s first claim is that the relation of African novels to realism is not simply naive. What happens when readers shift their attention away from the question of resistance that has so defined the field and ask instead: How does the novel produce its effects? Where does realism lie in this constellation of aesthetics and politics? Andrade’s second claim involves periodization and uneven development. The events that produced the 1968 social explosions in the global North are bound up with the earlier liberation movements of the global South. Thus the global South’s 1968, partially reflected in these novels, offers a perspective on the neoliberalism of the global North’s 1980s.
Peripheral Realism, Millennial Capitalism, and Roberto Bolaño’s 2666
Authors: Deckard Sharae
Published: September 2012

In Roberto Bolaño’s posthumous magnum opus, 2666, a type of peripheral realism in which realist aesthetics are impurely intermingled with the irreal is crucial to the novel’s registration of the uneven structural relations of capitalist modernity. This essay explores three layers of the novel’s conception of reality in the Mexican borderlands: first, the Ciudad Juárez femicides as objects of representation; second, the economic conditions underlying the systemic violence perpetrated against female maquiladora workers and the rift between labor and capital; and third, the relation of art to ideology and reality and the artist’s problematic role in representing either the murders or their structural causes. Deckard argues that 2666 is a “world-system novel” that reformulates realist aesthetics to interrogate the ideological nature of art and the limits of realism while encoding the conditions of millennial capitalism in the semiperiphery.
V. S. Naipaul and Historical Derangement
Authors: Krishnan Sanjay
Published: September 2012

The consensus that the postcolonial writer must be on the side of the oppressed prevents critics from grasping the original ways in which V. S. Naipaul’s untypical writings are attuned to the historical predicament of the periphery. Naipaul’s premise is that subjects in the periphery are shaped by complex pasts that they are not well placed to comprehend. For historical reasons, peripheral societies lack the institutions and practices required for an adequate grasp of modernity’s profoundly disruptive effects. The globalizing forms of colonialism and capitalism diverted the social trajectories of the peasant formations of the precapitalist world. According to Naipaul, these deranging effects are precisely what the peripheral artist excavates. Writers born of this historical milieu must, in his view, also note how their work partakes of the order it describes. Those who explore their formation in this way may discover new ways of seeing the affiliations between subjected parts of the world. In this light, derangement also assumes a productive force: it makes available new perspectives derived from shared but diverse expressions of peripheral historicity. The fundamental significance of Naipaul’s writing lies in its inauguration of a style of peripheral reflection.
On Failing to Make the Past Present
Authors: Best Stephen
Published: September 2012

A good deal of recent scholarship into the slave past proclaims that the past’s political significance resides in its continuity with our present, finding both ethical moment and critical motivation in a recovery imperative that seeks to continue, reanimate, or complete the political projects of those who were defeated by history. This ethic of recovery has at times gone by the name “melancholy historicism,” and its paragon text has been Toni Morrison’s Beloved. This essay questions whether recovery predicated on such assumptions is the only way to either have or do slave history, and it ponders the possibility that the unforthcomingness of the past may be the fount of its deepest political (if not human) significance. The essay seeks to make the case for the writing of a history of discontinuity, the model for which is again provided by Morrison, in A Mercy, which by way of its ungenial textual effects expresses the author’s apparent turn away from the affective history project she earlier so capably inspired.
Joint interpretation of AER/FGF and ZPA/SHH over time and space underlies hairy2 expression in the chick limb
Authors: Sheeba Caroline J. , Andrade Raquel P. , Palmeirim Isabel
Published: September 2012

Embryo development requires precise orchestration of cell proliferation and differentiation in both time and space. A molecular clock operating through gene expression oscillations was first described in the presomitic mesoderm (PSM) underlying periodic somite formation. Cycles of HES gene expression have been further identified in other progenitor cells, including the chick distal limb mesenchyme, embryonic neural progenitors and both mesenchymal and embryonic stem cells. In the limb, hairy2 is expressed in the distal mesenchyme, adjacent to the FGF source (AER) and along the ZPA-derived SHH gradient, the two major regulators of limb development. Here we report that hairy2 expression depends on joint AER/FGF and ZPA/SHH signaling. FGF plays an instructive role on hairy2, mediated by Erk and Akt pathway activation, while SHH acts by creating a permissive state defined by Gli3-A/Gli3-R>1. Moreover, we show that AER/FGF and ZPA/SHH present distinct temporal and spatial signaling properties in the distal limb mesenchyme: SHH acts at a long-term, long-range on hairy2, while FGF has a short-term, short-range action. Our work establishes limb hairy2 expression as an output of integrated FGF and SHH signaling in time and space, providing novel clues for understanding the regulatory mechanisms underlying HES oscillations in multiple systems, including embryonic stem cell pluripotency.
The doublecortin-related genezyg-8is a microtubule organizer inCaenorhabditis elegansneurons
Authors: Bellanger Jean-Michel , Cueva Juan G. , Baran Renee , Tang Garland , Goodman Miriam B. , Debant Anne
Published: September 2012

Doublecortin-domain containing (DCDC) genes play key roles in the normal and pathological development of the human brain cortex. The origin of the cellular specialization and the functional redundancy of these microtubule (MT)-associated proteins (MAPs), especially those of Doublecortin (DCX) and Doublecortin-like kinase (DCLKs) genes, is still unclear. The DCX domain displays the ability to control MT architecture and bundling. However, the physiological significance of such properties is not fully understood. To address these issues, we sought post-mitotic roles of zyg-8, the sole representative of the DCX-DCLK subfamily of genes in C. elegans. Previously, zyg-8 has been shown to control anaphase-spindle positioning in one-cell stage embryos, but functions of the gene later in development have not been investigated.

Here we show that wild-type zyg-8 is required beyond early embryonic divisions for proper development, spontaneous locomotion and touch sensitivity of adult worms. Consistently, we find zyg-8 expression in the six touch receptor neurons (TRNs), as well as in a subset of other neuronal and non neuronal cells. In TRNs and motoneurons, zyg-8 controls cell body shape/polarity and process outgrowth and morphology. Ultrastructural analysis of mutant animals reveals that zyg-8 promotes structural integrity, length and number of individual MTs, as well as their bundled organization in TRNs, with no impact on MT architecture.
On the Effects of Changing Gaussian Program Version and SCRF Defining Parameters: Isopropylamine as a Case Study
Authors: Amado Ana M , Fiuza Sónia M , Batista de Carvalho Luis A E , Ribeiro-Claro Paulo J A
Published: September 2012

The present study reports a performance evaluation of the new Gaussian program version G09 relatively to the previous one in what concerns the SCRF formalism. The potential improvements achieved by changing program version and other SCRF defining parameters (like radii and SCRF models) were evaluated, by comparing the predicted values of several molecular properties with the corresponding experimental values reported in the literature. The relevance of the dispersion effects in the prediction of those molecular properties was inferred by considering the G09 newly implemented B97D DFT. On the whole, the results showed that the precision achieved in the molecular properties prediction is strongly dependent on the choice of the computation defining parameters. Moreover, direct comparisons between results obtained using either G03 or G09 require precaution.
Stereoselective Synthesis of the C1–C16 Fragment of Goniodomin A
Authors: Nakajima Motohiro , Fuwa Haruhiko , Sasaki Makoto
Published: September 2012

Stereoselective synthesis of the C1–C16 fragment of the antifungal marine polyether macrolide goniodomin A is described. A Stille-type coupling of organostannanes and thioesters was exploited as the key carbon–carbon bond-forming process, namely for the formation of the C7–C8 and C11–C12 bonds. Construction of the spiroacetal domain via acid-catalyzed acetalization of a triol-enone 30 unexpectedly provided a mixture of natural 11S spiroacetal 2, unnatural 11R spiroacetal 32, and constitutional isomer 33. Fortunately, it was eventually found that protection of the C5 hydroxy group as its acetate facilitated the isolation of natural 11S isomer 47 via acid-catalyzed equilibration of unnatural 11R isomer 48 and avoided the formation of a constitutional isomer, thereby increasing the efficacy of the spiroacetalization process.
Food restriction alters villi morphology in obese rats: gut mechanism for weight regain?
Authors: Zhang Jian Gang , Sun Xiao Wei , Gao Peng , Xie Lan , Liu Wen Qian , Xiao Hai Tao , Ai Hua
Published: September 2012

Weight regain after a long-term weight-loss program is a greater problem in obesity treatment than is weight reduction. Hence, the gut may elevate the absorption rate and nutrient transportation remarkably during chronic food restriction. The extension of gut absorption may be one possible reason for weight regain. But there is little information about the mechanisms that regulate intestinal absorption during food restriction. In this study, we show that the surface absorptive areas of gut villi may be enlarged in the jejunum of rats maintained on a food restriction regimen compared with animals submitted to swimming or sedentary behavior. Our findings show that simply reducing the amount of food intake results in an increased appetite accompanied with obvious weight regain, and suggest that the resulting enlargement of villi surface areas plays a key role in the regain of weight reduction. These results bolster accumulating evidence that gut absorption may be a substantial mechanism for resistance of weight loss and enhancing the weight regain process.
Genetic background determines inflammatory angiogenesis response to dipyridamole in mice
Authors: Sampaio Fernanda Portella , Castro Pollyana Ribeiro , Marques Suzane Mota , Campos Paula Peixoto , Ferreira Mônica Alves Neves Diniz , Andrade Silvia Passos
Published: September 2012

Inflammation and angiogenesis, key components of fibrovascular tissue growth, exhibit considerable variability among species and strains. We investigated whether the response of inbred and outbred mice strains to dipyridamole (DP) on these processes would present similar variability. The effects of the drug on blood vessel formation, inflammatory cell recruitment, collagen deposition and cytokine production were determined on the fibroproliferative tissue induced by sponge implants in Swiss and Balb/c mice. Angiogenesis as assessed by hemoglobin (Hb) and vascular endothelial growth factor (VEGF) concentrations differed between the strains. Swiss implants had the highest Hb content but the lowest VEGF concentrations. Systemic DP treatment exerted an antiangiogenic effect on Balb/c implants but an proangiogenic effect on Swiss implants. The inflammatory enzyme activities myeloperoxidase (six-fold higher in Balb/c implants) and N-acetyl- β-d-glucosaminidase were reduced by the treatment in Balb/c implants only. Nitrite concentrations were also higher in Balb/c implants by 40% after DP treatment. Tumor necrosis factor-alpha levels were similar in the implants of both strains and were not reduced by DP. Transforming growth factor β-1 levels and collagen deposition also varied between the strains. The inbred strain had similar levels of the cytokine but implants of Swiss mice presented more collagen. DP treatment reduced collagen deposition in Balb/c implants only. Our data showing the influence of the genetic background on marked heterogeneity of inflammatory angiogenesis components and differential sensitivity to DP may provide some answers to clinical evidence for resistance to angiogenic therapy.
Transportation Problems and Simplicial Polytopes That Are Not Weakly Vertex-Decomposable
Authors: De Loera Jesús A. , Klee Steven
Published: September 2012

Provan and Billera defined the notion of weak k-decomposability for pure simplicial complexes in the hopes of bounding the diameter of convex polytopes. They showed the diameter of a weakly k-decomposable simplicial complex Δ is bounded above by a polynomial function of the number of k-faces in Δ and its dimension. For weakly 0-decomposable complexes, this bound is linear in the number of vertices and the dimension. In this paper we exhibit the first examples of non-weakly 0-decomposable simplicial polytopes. Our examples are in fact polar to certain transportation polytopes.
The Next Decade of Optical Lithography
Authors: Totzeck Michael , Lai Kafai , Smith Daniel
Published: September 2012

No abstract available.
Finite groups with four class sizes of elements of order divisible by at most three distinct primes
Authors: Kong Qingjun
Published: September 2012

Let
Verteiltparametrische Modellierung und Regelung einer 60 m-Feuerwehrdrehleiter
Authors: Pertsch Alexander , Sawodny Oliver
Published: September 2012

Der als Fachwerkstruktur ausgestaltete Leitersatz moderner Feuerwehrdrehleitern neigt aufgrund seiner Länge und begrenzten Steifigkeit zu harmonischen Schwingungen in mehreren Moden. Mit Hilfe des Modells eines abschnittsweise homogenen Euler-Bernoulli-Balkens lassen sich diese Schwingungen aus Messungen rekonstruieren und mit dem hydraulischen Antrieb effektiv dämpfen. In diesem Beitrag werden die Parameteridentifikation und Regelung für den Leitersatz am Beispiel einer IVECO Magirus M60 L erläutert und mittels Versuchsergebnissen validiert.
Algebraische Methodenzur Parameteridentifikation für das schwere Seil
Authors: Gehring Nicole , Knüppel Torsten , Rudolph Joachim , Woittennek Frank
Published: September 2012

Vorgestellt wird eine Methode zur Identifikation von Parameter eines linearen, verteiltparametrischen Modells für das schwere Seil unter ausschließlicher Verwendung gemessener Randgrößen. Die Methode basiert auf der Operatordarstellung der Lösung des zugehörigen Randwertproblems. Aus dieser erhält man durch sukzessives Falten der gemessenen Trajektorien ein System algebraischer Gleichungen in den gesuchten Parametern. Simulationsergebnisse illustrieren den Ansatz.
Modellreduktion von Populationssystemen mit Hilfe von Proper Orthogonal Decomposition
Authors: Mangold Michael , Krasnyk Mykhaylo
Published: September 2012

Der Beitrag beschreibt den Einsatz der Proper Orthogonal Decomposition (POD) für die Modellreduktion von Partikelprozessen in fluider Strömung. Diese Prozessklasse ist von großer Bedeutung für die chemische und pharmazeutische Industrie. Physikalische Modelle solcher Prozesse sind häufig sehr komplex und für Regelungsaufgaben wenig geeignet. POD bietet hier eine attraktive Möglichkeit, zu reduzierten Prozessmodellen zu gelangen, da das Verfahren sehr flexibel ist, keine spezielle Struktur des Referenzmodells erfordert und interne und externe Koordinaten in einheitlicher Weise behandelt. Der Beitrag stellt das Reduktionsverfahren vor und illustriert es an Beispielen.
Verbesserte Subspace-Identification für lineare Systeme mit variierenden Parametern durch rekursive Schätzung
Authors: Buchholz Michael , Werner Samuel
Published: September 2012

Dieser Beitrag stellt rekursive Varianten eines Subspace-Identification-Algorithmus für lineare Systeme mit variierenden Parametern vor. Gegenüber dem zugrunde liegenden Algorithmus in Blockverarbeitung bietet der rekursive Ansatz die Möglichkeit, auf eine vereinfachende Annahme zu verzichten, wodurch bessere Ergebnisse als in Blockverarbeitung erzielt werden können. Die Güte der Algorithmen wird an einem der Literatur entnommenen Benchmark-Beispiel bewertet.
Increasing use of radioiodine in young people with thyrotoxicosis in Great Britain
Authors: Turner Neil , Driver Ian , Salotti Jane A , Pearce Mark S , Cheetham Tim
Published: September 2012

Objective

Radioiodine (RI) is an important therapeutic option in young patients with thyrotoxicosis. We wanted to determine whether RI is being used more frequently in this age group.

Design

National survey of Great Britain (England, Wales and Scotland).

Methods

Sixty-one medical physics departments were asked to provide the age and number of patients with thyrotoxicosis <21 years treated with RI (1990–2008). Information on the total number of RI treatments for thyrotoxicosis was also collected.

Results

Forty-three departments (70%), with representation from 21 of the 25 most populous areas of Great Britain, provided data on 69 258 treatments. The number of treatments recorded on patients <21 years during this period was 560 (0.9%). The frequency of treatments in young people as a percentage of the total increased from 0.2% in 1990 to 1.5% in 2008 (P<0.001). When the 18 centres submitting at least 17 years of data were analysed, a similar pattern was observed. The maximum number of young people treated was greatest in 2008 (62) with a fall in the youngest age at which RI was administered from 18 years (1990) to 11 years (2008).

Conclusions

A rising proportion of patients with thyrotoxicosis receiving RI are in those <21 years. This is largely due to an increase in the number of young people treated with a reduction in the minimum age at RI administration. We suspect that European clinicians are becoming more comfortable with RI treatment in young people with thyrotoxicosis, although a changing incidence is a potential contributing factor.
Effects of oxygen concentration on in vitro maturation of canine oocytes in a chemically defined serum-free medium
Authors: Salavati Mazdak , Ghafari Fataneh , Zhang Tiantian , Fouladi-Nashta Ali A
Published: September 2012

Canine oocytes require an extended period of culture (72 h)in vitrofor nuclear maturation to the metaphase II stage, which also results in high degeneration. Canine cumulus oocyte complexes were isolated by slicing from ovaries collected after ovariohysterectomy and cultured in serum-free synthetic oviductal fluid incubated at low (5%) or high (20%) oxygen levels. Changes in oocyte nuclear maturation rates, H2O2levels within the oocytes and mRNAs of reactive oxygen species inhibitory genes superoxide dismutase 1 and 2 (SOD1and2), glutathione reductase (GSR), glutathione peroxidase (GPX1), and catalase (CAT) were quantified. Higher meiotic resumption from germinal vesicle breakdown up to MII was observed in low O2(41.8±13.1%) compared to high O2(15.8±8.2%) (P=0.014) after 52 h of culture (n=112). Extension of the culture period up to 84 h at low O2(n=457 oocytes) produced the highest meiotic resumption at 72 h (64.1±6.0%;P=0.008), compared with 52 h. Oocytes (n=110) cultured in high O2contained higher levels of peroxidase measured using the 2′,7′-dichlorodihydrofluorescein diacetate fluorescence assay after 72 h of culture compared with low O2(P=0.004). High O2-cultured oocytes also showed higher amounts ofSOD1,SOD2,GSR,GPX1, andCATmRNA. Vitamin E in high oxygen level was able to decrease degeneration (P=0.008) but had no improving effect on percentage of oocytes in MII. These results for the first time showed that low oxygen gas composition improves nuclear maturation rates and alleviates the oxidative stress for canine oocytes duringin vitromaturation.
Electron-Spin Polarization in Tunnel Junctions with Ferromagnetic EuS Barriers
Authors: Hao Xin , Moodera J. S. , Meservey R.
Published: September 2012

Spin-resolved tunneling in the structure metal-EuS-metal has been obtained. The metal electrodes used in our experiments being non-magnetic, polarization of the tunnel current is attributed to the conduction band splitting in EuS below its ferromagnetic Curie temperature. Enhanced Zeeman splitting in the superconducting aluminum film is also observed.
Magnetic Anisotropy Constants of Epitaxial (110) Fe/GaAs Films from 77k To 293k Studied by Magneto-Resistance
Authors: Lottis Daniel K. , Prinz G. A. , Dahlberg E. Dan
Published: September 2012

A first-order phase transition in the magnetization of Fe films, driven by an applied magnetic field, was first reported by Hathaway and Prinz [1]. Further studies were performed on this phase transition using anisotropic magnetoresistance measurements by Riggs and Dahlberg [2]. Here we report the extension of these studies to include temperatures between 77K and 293K. Emphasis is on a determination of the fourth-order and uniaxial anisotropy constants (K1 and Ku). It is shown that the temperature dependence of the anisotropy energies in these films varies with thickness, which may be useful in sorting out the origin and magnitude of different contributions to the total effective anisotropy. The present study suggests that similar studies of (110) iron on other substrates might contribute to achieving a better understanding of in-plane anisotropies in epitaxial films.
Magnetic Resonance Studies of Fe/Ag Superlattices with Fe Layers < 6 Monolayers Thick
Authors: Krebs J. J. , Jonker B. T. , Prinz G. A.
Published: September 2012

X-band magnetic resonance has been used to study a set of Fe/ Ag(001) superlattice (SL) samples with Fe layers only 0.9–5.5 monolayers (ML) thick. The samples (grown by MBE and previously examined by Mossbauer and magnetization techniques) were studied thoughout the 5–300 K range. The SL's with t(Fe) < 3 ML exhibit a marked downturn in their resonance fields below a temperature which decreases with t(Fe) and, simultaneously, the linewidths increase. We suggest that this behavior is due to magnetic relaxation processes in these samples.
Magnetic Microstructure of Thin Films and Surfaces: Exploiting Spin-Polarized Electrons in the SEM and STM
Authors: Pierce D. T. , Scheinfein M. R. , Unguris J. , Celotta R. J.
Published: September 2012

Magnetic microstructure, that is the configuration of domains and domain walls in a magnetic material, is of both fundamental interest and of crucial importance for device applications. For example, the ultimate density of magnetic information storage is limited by the sharpness of a domain boundary. The magnetic microstructure of a thin film or surface depends sensitively on its physical structure which is strongly affected by sample preparation or growth. High resolution magnetization imaging is necessary to determine the domain configuration that occurs for a particular sample preparation and the changes that take place under external perturbations such as applied magnetic field, stress or temperature.
Spin Polarized Inelastic Electron Scattering From Ni (110)
Authors: Hopster H. , Abraham D. L. , Pappas D. P.
Published: September 2012

The spin dependent energy loss mechanisms in low-energy electron scattering from a ferromagnetic Ni(110) surface are studied. It is shown that exchange scattering can be the dominant loss mechanism for small energy losses. The energy-, angle and temperature dependence of spin asymmetries are studied in detail.
Point Defect Detector Studies of Ge+ Implanted Silicon upon Oxidation
Authors: Meng H. L. , Prusstn S. , Jones K. S.
Published: September 2012

Previous results [1] have shown that type II (end-of-range) dislocation loops can be used as point defect detectors and are efficient in measuring oxidation induced point defects. This study investigates the interaction between oxidation-induced point defects and dislocation loops when Ge+ implantation was used to form the type II dislocation loops. The type II dislocation loops were introduced via Ge+ implants into <100> Si wafers at 100 keV to at doses ranging from 2×1015 to l×1016/cm2. The subsequent furnace annealing at 900 °C was done for times between 30 min and 4 hr in either a dry oxygen or nitrogen ambient. The change in atom concentration bound by dislocation loops as a result of oxidation was measured by plan-view transmission electron microscopy (PTEM). The results show that the oxidation rate for Ge implanted Si is similar to Si+ implanted Si. Upon oxidation a decrease in the interstitial injection was observed for the Ge implanted samples relative to the Si implanted samples. With increasing Ge+ dose the trapped atom concentration bound by the loops actually decreases upon oxidation relative to the inert ambient implying oxidation of Ge+ implanted silicon can result in either vacancy injection or the formation of an interstitial sink.
The Sensitivity of Renninger Scan Intensities with Al Content in Ga1-xA1xAs/GaAs Samples
Authors: Sasaki J.M. , Campos C. , Cardoso L. P.
Published: September 2012

The influence of the Al concentration in the X-Ray Renninger scans (RS) for the GaAlAs/GaAs system is investigated. The RS simulation program MULTX [Defect Control in Semiconductors, K. Sumino (ed.) Elsevier Sci. Pub. (North Holland), 1990, 1535] allows for the better choice of peak/background ratio which shows enough sensitivity to detect Al content changes. The three (000, 002, 111) and four beam (000, 002, 113, 111) peak/background ratios decrease with the increment of the Al content according to the structure factor calculation.
Evaluation using A Noncontact Laser Beam Induced Conductivity/Current Method for the Silicon-on-Insulator made by Wafer Bonding
Authors: Usami A. , Nakai T. , Fujiwara H. , Ishigami S. , Wada T. , Matsuki K. , Takeuchi T.
Published: September 2012

In this study, we evaluate the electrical characteristics of the silicon on insulator (SOI) layer made by the wafer bonding method using a photoconductivity modulation method, in other words, noncontact laser beam induced conductivity/current (LBIC) method. The He-Ne laser pulse (λ= 633nm, pulse width=2ms) is used as the carrier-injection light source.

The detected signal intensity decreases at the void area as compared with at the center area of the SOI layer where there are no voids. The positions of the voids revealed by the proposed method are in good agreement with those by X-ray topography. We also measure the lifetime using the photoconductivity decay method using the laser diode. The lifetime at the void area is much shorter than that at the center area. It is considered that the decrease in the detected signal intensity at the void area is due to reduction in the minority carrier lifetime.
The Lack of Trapping Centers for Positrons at the Interface of W/Si System and the Investigation of the Depletion Layer in the Schottky Barrier by Positrons as Test Charge Simulating Holes
Authors: Tanigawa S. , Tabuki Y. , Wei L. , Hinode K. , Kobayashi N. , Onai T. , Owada N.
Published: September 2012

Interfacial phenomena in the W-Si systems were studied by a monoenergetic positron beam. Doppler broadening profiles of the positron annihilation were measured as a function of incident positron energy. Tungsten thin films of 100 nm in thickness were deposited on p-type, 10 »cm Cz-grown Si wafers with (100) orientation by the DC magnetron sputtering method. Specimens were annealed at various temperatures in order to form suicides. It was found that the position of the interface of both W/Si and W silicide/Si is very different from the position expected from a simple situation neglecting the effect of electric field on the diffusion of positrons. This fact arouse the utility of positrons as a test charge to probe directly the electric field gradient in the Schottky barrier.
An Investigation of Vacancy Concentrations in Bulk Silicon
Authors: Zimmermann Horst , Ryssel H.
Published: September 2012

A method will be presented, which allows the quantitative determination of distributions of single vacancies in bulk silicon. The method uses deep level transient spectroscopy (DLTS) measurements of the platinum or gold concentration after diffusion at a low temperature. An analytical expression allows the calculation of the vacancy concentration from the measured platinum or gold concentration. Vacancy concentrations vary at least from 2.0×1012 to 2.2×1014 cm3 in float zone silicon. The vacancy concentrations in Czrochalski (CZ) silicon are in the range of 4×1012 to 2×1013 cm3. Microwave photoconductive decay instead of DLTS allows much faster measurements of vacancy distributions on whole wafers. Furthermore, both methods allow the investigation of oxygen precipitation in CZ silicon.
Study of Electrical Properties of Defects in Soi Films by Wafer Bonding
Authors: Usami Akira , Natori Taichi , Ito Akira , Ishigami Shun-ichiro , Tokuda Yutaka , Wada Takao
Published: September 2012

Silicon-on-insulator films fabricated by the wafer bonding technique were studied with capacitance-voltage (c-V) and deep-level transient spectroscopy (DLTS) measurements. For our experiments, two kinds of SOI wafers were prepared. Many voids were present in one sample (void sample), but few voids were in the other sample (no void sample). Before annealing, two DLTS peaks (E-0.48 eV and Ec-0.38 eV) were observed in the SOI layer of the void sample. For the no void sample, different two DLTS peaks (Ec-0.16 eV and Ec-0.12 eV) were observed. The trap with an activation energy of 0.48 eV was annealed out after 450 °C annealing for 24 h. On the other hand, other traps were annealed out after 450 °C annealing for several hours. During annealing at 450 °C, thermal donors (TDs) were formed simultaneously. In usual CZ sil icon, a DLTS peak of TD was observed around 60 K. In the no void sample, however, a TD peak was observed at a temperature lower than 30 K. This TD was annihilated by rapid thermal annealing. This suggests that the TD with a shallower level was formed in the no void sample after annealing at 450 °C.
Hydrogen Passivation and Reactivation of Bistable Thermal Donors in Silicon
Authors: Bohne D. I. , Deak P. , Weber J.
Published: September 2012

The dissociation of Thermal Donor-hydrogen complexes is studied by infra-red absorption, CV and DLTS profiling. Silicon samples are prepared to contain only TD1 and TD2 and in particular only TD1 is exhibiting bistable properties. After hydrogen passivation, annealing in the dark under reverse bias leads to a first order reactivation of TD1 and TD2. A marked difference in the dissociation energies is found (ED(TD1 - H) = 1.67eV, ED (TD2 - H)≈ 1.9eV). Our results suggest that TD1 and TD2 have a different microscopic structure.
Donor Reactivation Kinetics and Hydrogen Redistribution in the Space Charge Layer of N-Type Silicon
Authors: Wu Y. -A. , Roos G. , Johnson N. M. , Herring C.
Published: September 2012

The passivation and reactivation of As donor dopants in n-type Si was studied with both monatomic hydrogen and deuterium. Hydrogenated Schottky diodes were characterized with C-V and DLTS measurements. The reactivation kinetics of the As-H and As-D complexes were studied in the space-charge layer of reverse biased diodes in the temperature range from 60°C to 120°C. These bias-anneals yield dissociation time constants for As-H, from which an averaged activation energy of 1.17±0.1 eV was determined. Although the dissociation of the As-H complex is appreciably slower than that previously measured for P-H, the activation energy is within about 0.05 eV of that determined previously for the P-H complex (1.2 eV). The depth redistribution of the As-H complexes after bias-annealing agrees with the previous conclusion that hydrogen can assume a negative charge state in n-type Si.
The Effect of D-Defect in Silicon Single Crystal on Oxygen Precipitation
Authors: Fusegawa I. , Fujimaki N. , Yamagishi H.
Published: September 2012

We investigated the effect of D-defect in CZ silicon single crystals on the oxygen precipitation by two-step thermal treatments consisting of the first annealing in nitrogen ambient at 1073K and the second annealing in dry oxygen ambient at 1273K. The density of D-defect was measured by counting ‘flow patterns’ using an optical microscope after preferential etching in Secco's solution for 30 minutes. It was found that the amount of oxygen precipitation along the growth axis was not affected by D-defect. The predominant factor of the oxygen precipitation after the two-step thermal process is the nuclei of oxygen precipitation generated around 723K during CZ crystal growth.
Effect of Fluorine on the Dopant Diffusion of Through-Oxtoe Implanted Boron in Si - a Correlation with Microstructural Defects
Authors: Huang J. G. , Lam A. , Jaccodine R. J.
Published: September 2012

In case of boron through-oxide implant, it has been shown that the knocked-in oxygen atoms segregate at initially nucleated dislocation sites during the incubation and no significant junction movement is detected. The trapping of oxygen proceeds up to a certain time at which oxygen-precipitation occurs and this leads to an ejection of excess Si interstitials and further enhancing boron diffusion. However, with fluorine addition we believe that fluorine incorporation in SiO2 and/or SiO2/Si interface not only releases the strain gradient but also suppresses the silicon interstitials ejection and by this means suppresses the oxidation-enhanced boron diffusion. Correlated results of TEM microdefect structures and spreading resistance profiles are used to further support our postulation.
Interaction of Solute in Atoms with Dislocations in Lec GaAs
Authors: Burle-Durbec N. , Rakotobe A. , Pichaud B. , Minari F.
Published: September 2012

We summarize here experimental results about moving dislocations and dislocations sources, in In-doped GaAs; several selective behaviours between α (As core in the glide set) and β dislocations are noticed. We try to correlate these observations with material structure and composition, and we propose a model of atomic interaction between In and α partial dislocations which could explain most of experimental observations. Some ideas about In diffusion are also developed.
Oxygen Precipitation Nonuniformity for Thermal History Around 723K During Cz Crystal Growth
Authors: Fusegawa I. , Yamagishi H.
Published: September 2012

We investigated phenomena of oxygen precipitation nonuni-formity along crystal growth axis due to different thermal histories during CZ crystal growth. The oxygen precipitation process employed in this paper was two-step thermal treatments consisting of the first annealing in nitrogen ambient at 1073K for 4 hrs and the second annealing in dry oxygen ambient at 1273K for 16 hrs. The amount of the oxygen precipitation at the shoulder of a silicon single crystal was higher than the one at the tail end. We found this nonuniform distribution profile was due to the thermal history around 723K during crystal growth. Such an nonuniformity could be improved remarkably by adding a preannealing in dry oxygen ambient at 723K for 2 hrs before the two-step thermal treatment.
Characteristics of Oxygen Precipitation in Silicon Wafers Preannealed at 723K
Authors: Fusegawa I. , Iino E. , Hirohata T. , Yamagishi H.
Published: September 2012

We investigated phenomena of oxygen precipitation in silicon single crystals by two kinds of thermal treatment, supposing a CMOS fabrication process. The one consisted of the first annealing at 1123K for 4 hrs and the second annealing at 1423K for 16 hrs. The other one consisted of the annealing at 1273K for 4 hrs and the second annealing at 1423K for 13 hrs. In the results, a single-step preannealing at 723K for 2 hrs was effective for the oxygen precipitation by the former process and nonuniform distribution profiles along crystal growth axis were well improved, however, insufficiently improved against the latter process. We considered a two-step preannealing process consisting of the first annealing at 723K for 2 hrs and the second annealing at 923K for 2 hrs. This new process was effective for the oxygen precipitation by the latter process. Especially, we could obtain uniform distribution profiles of oxygen precipitation along a crystal growth axis.
Stress-Related Defects in Implanted Locos + Trench - Isolated Structures
Authors: Vasquez Barbara , David Theodore N.
Published: September 2012

Poly-buffered local-oxidation of silicon + trench-isolation (PBLT) is a technique being explored for device isolation. In an earlier study, we had reported the presence of dislocations associated with a combination of high-dose (∼5E14 cm2) phosphorous implants and PBLT isolation. In the present study, the behavior of extended defects present in the structures is analyzed in greater detail. The origin and behavior of the defects is modelled to explore potential mechanisms to explain the observations. Implantation induced dislocation-loops interact with stress fields associated with PBLT isolation-trenches. Some of the implant loops (in the presence of a stress field) transform to dislocation sources which then create glide dislocations in the structures. Strategies for defect engineering are discussed, including reducing implant-induced damage (lowering the implant dose) or reducing stress fields (by moving the edge of the implanted region away from the trench). Defect densities can be reduced or eliminated.
Low Frequency Noise in Small MOS Devices
Authors: Uren Michael J.
Published: September 2012

Random telegraph signals can be seen in the conductivity of submicron MOSFETs due to capture and emission from individual SiO2 defects. They show activated capture times, temperature dependent energy levels as well as a complex scattering behaviour. It is shown how 1/f noise in large MOSFETs arises naturally from the properties of these defects and how models based on this understanding can be constructed. 1/f noise is shown to be a poor tool for the study of the traps due to the loss of information associated with averaging over many active signals.
Mechanisms for N-Type Impurity-Induced Disordering of AlGaAs/GaAs Superlattices
Authors: Olmsted B. L. , Houde-Walter S. N. , Enrique Viturro R.
Published: September 2012

We report on a study of disordering by the in-diffusion of a variety of Group IV and Group VI n-type impurities. Secondary ion mass spectroscopy, electrochemical C-V profiling, photoluminescence spectroscopy, and cathodoluminescence spectroscopy were used to determine the extent of interdiffusion, and the spatial distribution of impurities and native defects for impurity-induced disordering. In all cases, the n-type dopants enhance the Al-Ga interdiffusion coefficient over that due to an As overpressure of 2 atm alone. The Si-induced enhancement has been previously attributed to the change in Fermi level with doping and therefore should account for disordering using other n-type impurities. However, we observe important differences in the interdiffusion characteristics (diffusion rate, dopant profiles, energy and intensity of the deep-level emission) induced by Si or Ge, and that by S or Se. Whereas a strong correlation exists between the carrier concentration profile and the disordered regions in the Si-, Ge-, and Se-doped crystals, little direct correspondence is found for crystals doped with S. Instead, the disordering seems to be determined primarily by the presence of Group III vacancies, as is also the case in undoped crystals disordered by an As ambient alone. In addition, the deep level emission at 1.15 and 1.3 eV, which are associated with vacancy defects, correlates well with the extent of the Al-Ga interdiffusion.
Effect of Al Composition on the Deep Level Donors of AlxGa1-xSb/lnAs Single Quantum Wells
Authors: Lo Irai , Mitchel W. C. , Stutz C. E. , Evans K. R. , Manasreh M. O.
Published: September 2012

We have performed Shubnikov-de Haas (SdH) measurements on the AlxGa1-xSb/InAs QW's with x from 0.1 to 1.0 under the negative persistent photoconductivity (NPPC) conditions and confirmed the prediction of Ionized Deep Donor model that the NPPC effect is a universal property for the materials containing ionized deep donors at low temperatures. The time-dependent recombination (electron capture) of the ionized deep donors is similar to that of DX centers. The saturated reduction of carrier concentration in the InAs well increases with increasing x, and rises steeply at about x=0.4. The concentration of deep donors which cause the NPPC in the AlxGa1-xSb/InAs QW's increases with the Al composition.
Gettering of Dissolved and Segregated Impurities in Multicrystalline Silicon Wafers
Authors: Stemmer M. , Perichaud I. , MartiNuzzi S.
Published: September 2012

Phosphorus gettering by diffusion from a POCl3 source was applied to matched wafers cut out of the same region of a cast ingot. Light Beam Induced Current mappings with wavelengths in the range between 840 and 980 nm lead to follow the variation of minority carrier diffusion length after gettering at 900°C for 120 and 240 mn, especially near extended crystallographic defects like dislocations and grain boundaries.

The mappings show that after the gettering treatments, the local values of L increase due to the reduction of the recombination strength of extended defects and to the improvement of the homogeneous regions of the grains.

As SIMS analyses indicate that Fe, Cu and Ni atoms are gettered, it is reasonable to assume that these impurities were initially dissolved in the grains and also segregated at the extended defects.
Spin Polarized Low Energy Electron Microscopy (Spleem) of Single and Combined Layers of Co, Cu, and Pd on W (110)
Authors: Poppa Helmut , Pinkvos Heiko , Wurm Karsten , Bauer Ernst
Published: September 2012

In-situ recording of ultra-thin film growth by Low Energy Electron Microscopy (LEEM) results in accurate determinations of monolayer metal deposition rates for difficult to calibrate deposition geometries. Deposition rates and growth features were determined for Cu and Co on W (110) allowing for thickness control at the submonolayer level. Also, the transparencies of non-Magnetic overlayers of Pd (111) and Cu (111) to very low energy spin polarized electrons were compared and qualitatively explained by band structure considerations. Cu (111) is much more transparent than Pd (111) so that magnetic domain structures can be observed through at least 4 nmof Cu (111). This suggests the use of Cu (111) and other metals of suitable band structure as protective layers for surface magnetic studies.
Theory of the Negative Magnetoresistance in Magnetic Metallic Multilayers
Authors: Hood Randolph Q. , Falicov L. M.
Published: September 2012

The Boltzmann equation is solved for a system consisting of alternating ferromagnetic -normal metallic layers. The in-plane conductance of the film is calculated for two configurations: successive ferromagnetic layers aligned (i) parallel and (ii) antiparallel to each other. The results explain the giant negative magnetoresistance encountered in these systems when an initial antiparallel arrangement is changed into a parallel configuration by application of an external magnetic field. The calculation depends on (A) geometric parameters (the thicknesses of the layers); (B) intrinsic metal parameters (number of conduction electrons, Magnetization and effective masses in the layers); (C) bulk sample properties (conductivity relaxation times); and (D) interface scattering properties (diffuse scattering versus potential scattering at the interfaces). It is found that a large negative magnetoresistance requires, in general, considerable asymmetry in the interface scattering for the two spin orientations. All qualitative features of the experiments are reproduced. Quantitative agreement can be achieved with sensible values of the parameters. The effect can be conceptually explained based on considerations of phase-space availability for an electron of a given spin orientation as it travels through the multilayer sample in the various configurations and traverses the interfaces.
Crystallographic Structure of Cobalt Films on CU (100)
Authors: Heckmann O. , Magnan H. , Le Fevre P. , Chandesris D.
Published: September 2012

The stable structure of cobalt is hexagonal closed packed (hep), but cobalt can be stabilized in the face centered cubic structure (fee) by epitaxy on Cu (100). These films are ferromagnetic with [110] in plane easy axis. The Magnetic anisotropies of these films strongly depend on their structure, and in particular to the possible deviation from the isotropie fee structure. We have studied these films by surface EXAF.S. By recording the spectra both in normal incidence and in grazing incidence we have shown that the Co/Cu (100) films have a face centered tetragonal structure: the mean nearest neighbour distance parallel to the surface is 2.55 Å (same value as in bulk copper) and the interlayer bonds length is 2.50 Å (same value as in bulk cobalt). We conclude that the films are in perfect epitaxy on copper (100) with a contraction of the lattice parameter perpendicular to the surface of 4%. A constant tetragonalization is observed for films of 2 to 15 Monolayers.
Spin Wave Propagation and Brillouin Light Scattering on Antiferromagnetically Coupled Bilayers
Authors: Stamps R. L. , Camley R.E.
Published: September 2012

The ground state spin configuration of antiferromagnetically coupled ferromagnetic thin films is determined by competition between anisotropies, interlayer exchange and the applied magnetic field. It is shown that many details of a ground state spin configuration can be obtained by studying the behavior of the spin wave frequencies as functions of propagation direction and applied field strength. A sensitive dependence on the relative film thicknesses is found for small applied field strengths.
Theory for the Nonlinear Magneto-Optical Kerr-Effect at Ferromagnetic Transition Metal Surfaces
Authors: Pustogowa U. , Hübner W. , Bennemann K. H.
Published: September 2012

The nonlinear Magneto-optical Kerr-effect (NMOKE) has been proven to be an ultrafast spectroscopie probe of the magnetic and electronic properties of ferromagnetic surfaces. Extending our previous theory we calculate the linear and nonlinear Magneto-optical Kerr-spectra of Fe. The results for the nonlinear Kerr spectra are compared with recent experiments on a Fe (110) surface. We derive and discuss general features of the nonlinear Kerr-effect, especially the details of its dependence on exchange interaction and Fermi-level crossings in the Stoner picture and beyond, frequency, and spin-orbit interaction. Furthermore we demonstrate how various electronic material properties, such as d-band width, s-d hybridization or band narrowing due to electronic correlations or caused by geometry (reduced coordination number in thin films), can be extracted from the spectra. As an example, we compare the linear and nonlinear Kerr-spectra of Fe to those of Ni. The extension of our theory to the Kerr spectra of thin magnetic films films as well as of hidden magnetic interfaces occurring in sandwiches and multilayers is discussed.