1,720,962 research outputs found
The influence of surface treatments on the electrical characteristics of polysilicon emitter bipolar transistors
No full textBehaviour and effects of fluorine in annealed n+ polycrystalline silicon layers on silicon wafers
No full textA comprehensive study is made of the behaviour and effects of fluorine in n+ polysilicon layers. Sheet resistance, TEM and SIMS are used to obtain quantitative data for the breakup of the interfacial oxide, the epitaxial regrowth of the polysilicon and the fluorine and arsenic distributions. The fluorine significantly increases both the initial oxide breakup and the initial polysilicon regrowth. It also produces inclusions in the layer which can affect the subsequent polysilicon regrowth and the arsenic distributions. Three regrowth stages and two regrowth mechanisms are distinguished and interpreted and a value of approximately 6x1011cm2s-1 is deduced for the effective diffusivity of fluorine in polysilicon at 950°C
Epitaxial regrowth of n+ polycrystalline silicon at 850 ºC induced by fluorine implantation
No full textA study is made of fluorine implantation into n+ polycrystalline silicon (polysilicon), with the aim of producing completely epitaxially regrown polysilicon emitters at lower temperatures. Polysilicon-on-silicon sheet resistance measurements are made to obtain an indication of the amount of polysilicon regrowth, and cross-section transmission electron microscope examinations to directly observe the regrowth. Samples given a fluorine implant, followed by a 1000 °C/10 min preanneal, show 50% epitaxial regrowth of the polysilicon after an emitter drive-in of only 850 °C/ 30 min. In contrast, in the absence of fluorine, negligible regrowth occurs even after an emitter drive-in of 850 °C/480 min
Activation energy for fluorine transport in amorphous silicon
Get PDFThe transport of ion implanted F in amorphous Si is studied using secondary ion mass spectroscopy and transmission electron microscopy. Significant redistribution of F is observed at temperatures in the range 600°C to 700°C. The measured F depth-profiles are modelled using a simple Gaussian solution to the diffusion equation, and the diffusion coefficient is deduced at each temperature. An activation energy of 2.2eV±0.4eV for F transport is extracted from an Arrhenius plot of the diffusion coefficients. It is shown that the F transport is influenced by implantation induced defects
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
Microstructural characterization of heteroepitaxial layers of III-V compound semiconductors
Get PDFThis work describes results obtained from TEM, TED and HREM studies of MBE and MOCVD InASySb1-y, MOCVD InxGa1-xAs, MOCVD InPySb1-y and MOCVD GaPySb1-y layers which were grown over a wide range of conditions. These semiconductor layers are of considerable importance for a variety of applications in optoelectronic and high-speed devices. TEM/TED investigations showed that phase separation occurs in MBE InAsSb layers, resulting in two phases with platelet structures ~5 to ~200nm thick approximately parallel to the layer surface. Phase separation was dependent on growth temperature and layer composition. Anisotropic geometry of the platelets was observed when viewed in the [110] and [110] directions. The compositions of the two phases were derived by TED and EDX analyses. A model for the phase-separated layers was proposed based on the presence of a miscibility gap and using the lateral and island growth mechanisms. TEM results of InGaAs, InPSb and GaPSb layers showed a fine scale modulated contrast (8-20nm in scale) which is a characteristic of alloy clustering occurring by spinodal decomposition, and a fine scale speckle contrast (4-5nm in scale). TEM/TED studies showed that [110] diffuse intensity lines in [001] TED patterns of InGaAs are not related to the fine scale modulated contrast but to the fine scale speckle contrast. It was concluded that a fine scale modulated contrast due to alloy clustering coexists with a fine scale speckle contrast associated with static atomic displacements from the average lattice in InGaAs. For InPSb and GaPSb, a fine needle-like contrast was also observed, which corresponds to diffuse streaks in the [110] patterns. This fine needle-like contrast was attributed to segregation of atoms at missing rows of atoms in the reconstructed growing surface. TED investigations revealed CuPt-type ordering in some of the InGaAs, InAsSb and InPSb layers. Regardless of alloy systems and growth conditions, the ordering occurred on only two of the four possible {111} variants. The degree of ordering was strongly dependent on growth conditions. Two variants of the ordered regions in InGaAs nucleated separately. TED/HREM studies of the ordered structure in InGaAs revealed a direct relationship between the inclination and elongation of superlattice spots and the morphology of anti-phase boundaries present within the domains. Two competing processes of surface-induced ordering, and bulk-induced disordering within a transition region, were considered to interpret the growth condition dependence of the ordering in InGaAs. A model for the ordering observed was proposed based on the surface reconstruction mechanism. MBE InAsSb strained layer superlattices (SLSs) were examined by TEM and HREM techniques. Defect configuration and the atomic structure of tetragonal distortion of the SLSs were directly imaged. Defect behaviour was dependent on the geometry of the SLSs. Possible relaxation mechanisms for the SLSs were proposed
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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