1,721,645 research outputs found
Ion implantation into GaN: Opportunities and problems
No full textWe summarize here our recent results on structural and optical characteristics of wurtzite GaN films bombarded under a wide range of implant conditions, as studied by Rutherford backscattering/channeling (RBS/C) spectrometry, transmission electron microscopy (TEM), atomic force microscopy (AFM), and cathodoluminescence (CL). Our results highlight current problems, associated with implantation-produced disorder, which may hinder a successful application of Ion implantation in the fabrication of GaN-based devices
Polymer nanocomposites based on P3OT, TPU and SWNT: Preparation and characterization
No full textSingle walled carbon nanotubes (SWNTs) were incorporated in polymer nanocomposites based on poly(3-octylthiophene) (P3OT), thermoplastic polyurethane (TPU) or a blend of them. Thermogravimetry demonstrated the success of the purification procedure employed in the chemical treatment of SWNTs prior to composite preparation. Stable dispersions of SWNTs in chloroform were obtained by non-covalent interactions with the dissolved polymers. Composites exhibited glass transitions, melting temperatures and heat of fusion which changed in relation to pure polymers. This behavior is discussed as associated to interactions between nanotubes and polymers. The conductivity at room temperature of the blend (TPU-P3OT) with SWNT is higher than the P3OT/SWNT composite
Ion-implanted GaAs for ultrafast saturable absorber applications
No full textThe status of our work on Arsenic and Oxygen implanted GaAs for ultrafast saturable absorber applications is reviewed. We show that the response time and absorption modulation are both reduced by implantation whilst the nonbleachable losses increase. Similar combinations of response time and modulation can be achieved using either ion species and various combinations of dose and annealing temperatures. Furthermore, it is shown that, in order to exploit the full capacity of this material, amorphisation during implantation should be avoided, and the samples should be annealed afterwards, leading to the predominance of point defects. We give several guidelines to the creation of a high performance GaAs saturable absorber through implantation. Response times < 400fs are achievable while still maintaining 80% of the absorption modulation of unimplanted GaAs
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
Towards nanomemories: Ge growth on naturally and artificially nanostructured Si surfaces
Full text linkV-grooved GaAs/AlGaAs quantum wires with side wall quantum wells intermixed by pulsed anodization and rapid thermal annealing
No full textNovel impurity-free interdiffusion (IFID) technique, namely, pulsed anodization and subsequent rapid thermal annealing, is applied8 to study GaAs/AlGaAs multiple quantum wires grown by metalorganic chemical vapour deposition on V-grooved GaAs substrate, Photoluminescence (PL) and cathodoluminescence (CL) emissions are observed from GaAs quantum wires. IFID increases both carrier confinement in quantum wires and the efficiency of excess carrier transferring from sidewall quantum wells to quantum wires, where the excess carriers are generated either by optical pumping (PL) or electron pumping (CL)
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
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