1,720,956 research outputs found
Study of fluorine behaviour in silicon by selective point defect injection
No full textThis letter reports a point defect injection study of 185 keV 2.3x1015cm?2 fluorine implanted silicon. After an inert anneal at 1000°C, fluorine peaks are seen at depths of 0.3Rp and Rp and a shoulder between 0.5–0.7Rp. The shallow peak (at 0.3Rp) is significantly smaller under interstitial injection than under both inert and vacancy injection conditions. For a longer anneal under interstitial injection, both the shallow peak and the shoulder are eliminated. These results support earlier work suggesting that the shallow fluorine peak is due to vacancy-fluorine clusters which are responsible for suppression of boron thermal diffusion in silicon. The elimination of the shallow fluorine peak and the shoulder is explained by the annihilation of vacancies in the clusters with injected interstitials
Reduced boron diffusion under interstitial injection in fluorine implanted silicon
Full text linkPoint defect injection studies are performed to investigate how fluorine implantation influences the diffusion of boron marker layers in both the vacancy-rich and interstitial-rich regions of the fluorine damage profile. A 185 keV, 2.3?1015 cm?2 F+ implant is made into silicon samples containing multiple boron marker layers and rapid thermal annealing is performed at 1000 °C for times of 15–120 s. The boron and fluorine profiles are characterized by secondary ion mass spectroscopy and the defect structures by transmission electron microscopy ?TEM?. Fluorine implanted samples surprisingly show less boron diffusion under interstitial injection than those under inert anneal. This effect is particularly noticeable for boron marker layers located in the interstitial-rich region of the fluorine damage profile and for short anneal times (15 s). TEM images show a band of dislocation loops around the range of the fluorine implant and the density of dislocation loops is lower under interstitial injection than under inert anneal. It is proposed that interstitial injection accelerates the evolution of interstitial defects into dislocation loops, thereby giving transient enhanced boron diffusion over a shorter period of time. The effect of the fluorine implant on boron diffusion is found to be the opposite for boron marker layers in the interstitial-rich and vacancy-rich regions of the fluorine damage profile. For marker layers in the interstitial-rich region of the fluorine damage profile, the boron diffusion coefficient decreases with anneal time, as is typically seen for transient enhanced diffusion. The boron diffusion under interstitial injection is enhanced by the fluorine implant at short anneal times but suppressed at longer anneal times. It is proposed that this behavior is due to trapping of interstitials at the dislocation loops introduced by the fluorine implant. For boron marker layers in the vacancy-rich region of the fluorine damage profile, suppression of boron diffusion is seen for short anneals and then increased diffusion after a critical time, which is longer for inert anneal than interstitial injection. This behavior is explained by the annealing of vacancy-fluorine clusters, which anneal quicker under interstitial injection because the injected interstitials annihilate vacancies in the clusters
Effect of fluorine on boron diffusion under interstitial injection from the surface
No full textIn this paper, a point defect injection study is performed to investigate the effect of fluorine on boron diffusion when interstitials are injected from the surface. 185keV, 2.3x1015 cm-2 fluorine is implanted into silicon with a boron marker layer located at about Rp/2 of the fluorine implant. This is followed by rapid thermal annealing at 1000oC for times 15 ~120s in an oxygen ambient. The wafers are covered with different layers prior to anneal to introduce different point defect injection effects. When interstitials are injected from the surface, fluorine strongly suppresses boron diffusion for anneal times of 15 and 30s. For longer anneal times, fluorine becomes progressively less effective and the boron diffusion coefficient approaches the value obtained in samples without fluorine. This effect of fluorine on boron diffusion suppression correlates with the presence of a shallow SIMS fluorine peak at ~Rp/2. These results support earlier work showing that vacancy-fluorine clusters at ~Rp/2 are responsible for the suppression of boron diffusion and that these clusters anneal out during long anneal times. Under inert anneal, fluorine has little effect on boron diffusion. An issue of boron cross contamination during the fluorine implant is also identified
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
110GHz fT Silicon Bipolar Transistors Implemented using Fluorine Implantation for Boron Diffusion Suppression
No full textThis paper investigates how fluorine implantation can be used to suppress boron diffusion in the base of a double polysilicon silicon bipolar transistor and hence deliver a record fT of 110 GHz. Secondary Ion Mass Spectroscopy (SIMS) and transmission electron microscopy are used to characterize the effect of the fluorine implantation energy and dose, the anneal temperature and ambient and the germanium pre-amorphisation implant on the fluorine profiles. These results show that retention of fluorine in the silicon is maximised when a high-energy fluorine implant is combined with a low thermal budget inert anneal. TEM images show that a high-energy fluorine implant into germanium pre-amorphised silicon eliminates the end of range defects from the germanium implant and produces a band of dislocation loops deeper in the silicon at the range of the fluorine implant. Boron SIMS profiles show a suppression of boron diffusion for fluorine doses at and above 5?1014cm-2, but no suppression at lower fluorine doses. This suppression of boron diffusion correlates with the appearance on the SIMS profiles of a fluorine peak at a depth of approximately Rp/2, which is attributed to fluorine trapped in vacancy-fluorine clusters. The introduction of a fluorine implant at this critical fluorine dose into a bipolar transistor process flow leads to an increase in cut-off frequency from 46 to 60GHz. Further optimisation of the base-width and the collector profile leads to a further increase in cut-off frequency to 110GHz. Two factors are postulated to contribute to the suppression of boron diffusion by the fluorine implant. First, the elimination of the germanium end of range defects, and the associated interstitial population, by the fluorine implant, removes a source of transient enhanced diffusion. Second, any interstitials released by the dislocation loops at the range of the fluorine implant would be expected to recombine at the vacancy-fluorine clusters before reaching the boron profile
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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