1,720,982 research outputs found
EFFECTIVE CHARGE OF ENERGETIC HEAVY IONS IN GASES, SOLIDS AND PLASMAS
No full textLa charge effective qeff d'ions partiellement épluchés est déterminée par l'équilibre entre la capture électronique et le stripping du milieu ralentisseur. Les conséquences des variations des sections efficaces correspondantes sur qeff, sont étudiées pour des ions quasi-complètement épluchés, et d'autres, de charge arbitraire. Les deux paramètres signifiants sont les effets de densité dans la cible, et les effets dus à la température du plasma. Ici, on se limite à la densité. On discute les observations expérimentales en cible solide et gazeuse, respectivement. On présente un nouveau modèle des effets de densité sur des ions quasi-complètement strippés. On discute les dE/dx correspondants en milieu dense, qui peuvent varier sur 20 %. Le taux de stripping d'un ion lourd de faible charge est beaucoup plus élevé dans un solide que dans un gaz.The effective stopping-power charge qeff for partially stripped ions is determined by a balance of the electron capture and loss cross sections within the stopping medium. The consequences for qeff of relative changes in these cross sections are considered for nearly fully stripped ions and for partially stripped ions. Two physical factors leading to such changes are density effects in the stopping medium, and plasma temperature effects. This paper concentrates on the role of density effects. Experimental observations of a genuine gas-solid density effect are discussed, and a new rigorous model of this effect for nearly fully stripped ions is presented. Implications for dE/dx in dense media are discussed, and are shown to be significant at the 20% level. Furthermore the stripping rate for a heavy ion of low charge state entering a medium will be considerably higher in a solid than in gas
Investigations of ultra shallow junction ion implanted biaxial tensile strained silicon by means of X-Ray, Raman and photoacoustic techniques
Get PDFThe application of strain to the active channel region of the metal-oxide-semiconductor-field-effect-transistor (MOSFET) has become a necessary practice in integrated circuit (IC) fabrication. The introduction of strain allows increased carrier mobilities, and concomitant device performance enhancements, which are independent of MOSFET scaling. Biaxial tensile strained silicon ("-Si), resulting from epitaxial growth of silicon on a Si1!xGex virtual substrate gives rise to enhanced electron mobilities and, for certain dopants, increased electrical activation. For these reasons it is the material of interest in this thesis.
The prospects for industrial implementations of "-Si are heavily dependent on the effects of device processing steps, and the controllability of defect and dopant profiles. Of special interest to the current work is the suitability of "-Si subjected to low energy antimony implants and low thermal budget rapid thermal anneal (RTA), for the production of ultrashallow, abrupt junctions, appropriate for future generation source-drain extensions (SDE).
Examined in the wider project are the effects of strain on dopant activation and diffusion through Differential Hall and SIMS measurements carried out by project partners. These
measurements provide context for the work herein and demonstrate the desirability of "-Si as a n-MOSFET channel material.
For our part, the effects of implant and anneal processes are investigated through both high resolution x-ray diffraction and micro-Raman (µ-Raman) spectroscopy. Synchrotron x-ray topography is used to identify the strain relaxation processes in both the "-Si epilayer and
the Si1!xGex virtual substrate. Data obtained during the project called into question the validity of traditional µ-Raman interpretations in the context of degenerately doped silicon, under these conditions additional theoretical considerations are necessary. The µ-Raman data presented herein demonstrates sensitivities to both implant damage and to dopant activation and these dependencies are
theoretically accouncted for.
Finally, Photoacoustic Spectroscopy is shown to be a technique capable of non-destructive detection of ion implant damage within the top ⇠10 nm of the silicon. These uniquely sensitive measurements araise due to the particular experimental set up used which invoke
a strong dependence on the thermal interface resistance within the sample
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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