1,720,975 research outputs found
ANALYTICAL ELECTRON-MICROSCOPY OF SI1-XGEX/SI HETEROSTRUCTURES AND LOCAL ISOLATION STRUCTURES
No full textThe convergent beam electron diffraction (CBED) technique has been applied to determine the lattice strain in Si1-xGex/Si heterostructures and in local isolation structures. Both plan and cross-sections have been investigated by transmission electron microscopy. In the heterostructures, the strain value obtained by CBED along the growth direction epsilon(CBED) is affected by ii relaxation induced by the thinning process in a direction normal to the cross-section plane, being generally smaller than the bulk tetragonal value epsilon(T). This effect can be overcome using the large angle CBED technique on plan sections. In addition, in the heterostructures the Ge concentration has been determined by energy dispersive X-ray spectrometry: allowing the pseudomorphicity of the samples to be evaluated. All the values of strain and Ge concentration thus obtained ale in good agreement with those deduced from Rutherford backscattering spectrometry. In isolation structures, the CBED technique has been applied to determine the distribution of the components of the strain tensor along a line parallel to the pad oxide/substrate interface. The values obtained are in agreement with the predictions of a previously reported simple model
Influence of experimental parameters on the determination of tetragonal distortion in heterostructures by LACBED
No full textThe LACBED technique has been applied to the determination of the tetragonal distortion in Si1-xGex/Si heterostructures, which are of great interest in the device technology. The strain determination has been performed on plan sections in an analytical electron microscope. The agreement between this strain value and the tetragonal distortion is influenced mainly by the local sample flatness and the acceleration voltage
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
Microstructural features assessment of different waterlogged wood species by NMR diffusion validated with complementary techniques
Full text linkWood is a hygroscopic, multi-scale and anisotropic natural material composed of pores with different size and differently oriented. In particular, archaeologically excavated wood generally is waterlogged wood with very high moisture content (400%–800%) that need to have a rapid investigation at the microstructural level to obtain the best treatment with preservative agents. Time-dependent diffusion coefficient D(t) quantified by Pulse Field Gradient (PFG) Nuclear Magnetic Resonance (NMR) techniques provides useful information about complex porous media, such as the tortuosity (τ) describing pore connectivity and fluid transport through media, the average-pore size, the anisotropic degree (an). However, diffusion NMR is intrinsically limited since it is an indirect measure of medium microstructure and relies on inferences from models and estimation of relevant diffusion parameters. Therefore, it is necessary to validate the information obtained from NMR diffusion parameters through complementary investigations. In this work, the structures of five waterlogged wood species were studied by PFG of absorbed water. D(t) and τ of water diffusing along and perpendicular to vessels/tracheids main axes together with relaxation times and an were quantified. From these parameters, the pore sizes distribution and the wood microstructure characterization were obtained. Results among wood species were compared, validated and integrated by micro-imaging NMR (μ-MRI), environmental-scanning electron-microscope (ESEM) images, wood dry density and imbibition times measurement of all woods. The work suggests that an vs τ rather than the estimated pore size diversifies and characterize the different wood species. As a consequence diffusion-anisotropy vs tortuosity could be an alternative method to characterize and differentiate wood species of waterlogged wood when high resolution images (μ-MRI and ESEM) are not available. Moreover, the combined use of D(t) and micro-MRI expands the scale of dimensions observable by NMR covering all the interesting length scales of wood
Drawbacks to using NIST electromigration test-structures to test bamboo metal lines
No full textIn this work the applicability of NIST electromigration
test patterns when used to test “bamboo” metal lines is discussed. Wafer level tests on passivated and nonpassivated samples employing the AI-1 %Si/TiN/Ti metallization scheme were performed. Straight metal lines 1000 pm long and 0.9 um or 1.4 um wide were tested at two different current densities, j = 3 MA/cm2 and j = 4.5 MA/cm2, keeping the stress temperature at T = 230°C. The failures occurred mainly in the end segment areas and hindered the evaluation of the electromigration resistance of the test lines. In order to avoid this problems, completely different test patterns containing a number of geometrical variations should be defined
DOPANT ACTIVATION, CARRIER MOBILITY, AND TEM STUDIES IN POLYCRYSTALLINE SILICON FILMS
No full textPolycrystalline silicon films, deposited by low-pressure chemical vapor deposition at 570° and 620°C, and doped withphosphorus by ion implantation, have been studied in terms of: dopant activation, carrier Hall mobility, and microstructure,as a function of the annealing temperature. Higher activation and carrier mobility were obtained on samples depositedat lower temperature, which were amorphous [by x-ray diffraction and transmission electron microscopy (TEM)] afterthe deposition step, in contrast with those deposited at higher temperature, which were polycrystalline. Transmissionelectron microscopy observations on a cross section showed a better recrystallization of the amorphous films during ahigh-temperature step, and mean grain size values which agree qualitatively with those calculated from grain boundarymobilities
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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