1,720,958 research outputs found
Investigation of oxygen diffusion barrier properties of reactively sputtered IrO2 thin films
No full textHigh quality IrO2 films are of great interest as electrodes and oxygen barrier layers for PZT and SBT based integrated non-volatile ferroelectric memories. The investigated IrO2 films were reactively DC-sputtered in an Ar/O-2 atmosphere. Generic curves were used for the optimization of the film preparation. The microstructure of the sputtered films was characterized by XRD and it was found that the texture can be adjusted from (110) to (200) by slightly varying the oxygen partial pressure at higher substrate temperatures. This change in microstructure is accompanied by a compositional change from oxygen substoichiometric to oxygen overstoichiometric films. Moreover, the influence of the microstructure on thermal stability and oxygen barrier effectiveness was investigated by SIMS depth profiling using an O-18(2) tracer diffusion method. Oxygen diffusion for process-relevant temperatures (550degrees-765degreesC) was systematically investigated and for the first time oxygen diffusion coefficients in IrO2 were determined by fitting a mathematical model to the measured profiles
Decomposition and nanocrystallization in reactively sputtered amorphous Ta-Si-N thin films
Get PDFThe nanocrystallization process of reactively sputtered thin amorphous Ta-Si-N films is investigated by anomalous small angle x-ray scattering (ASAXS) and x-ray diffraction (XRD). Changes in the microstructure in Ta40Si14N46 films, density variations in the amorphous matrix, decomposition, formation, and growth of nanocrystals after vacuum anneals at different temperatures in the range between 800 and 1000 degreesC are observed and the results of the different techniques are compared. From a Fourier analysis of ASAXS intensities the nanostructure of the investigated ternary system is derived using a model of hard spheres according to Guinier and Fournet. ASAXS investigations indicate that the noncrystalline samples can be described by a monophase fit and the crystallized samples by a bimodal-phase fit, the latter results being consistent with XRD which identifies TaN and Ta5Si3 phases. Detailed analysis shows that TaN nanograins of approximately 2 nm size develop after a decomposition process. Larger grains of Ta5Si3 are observed in addition to the TaN grains if annealing is performed at temperatures higher than 950 degreesC. The aim of these investigations is to give a generally applicable explanation of the barrier failure mechanism for Ta-Si-N diffusion barriers, which is actually observed at temperatures below the crystallization temperature if the films are used in contact with Cu or Al. (C) 2001 American Institute of Physics
Nanocrystallization of amorphous-Ta40Si14N46 diffusion barrier thin films
No full textThe nanocrystallization process in thin amorphous-Ta40Si14N46 films, annealed in the range between 800 and 1000 degreesC for 1 h, is investigated by high-resolution transmission electron microscopy and high-angle annular dark-field and energy-dispersive x-ray analyses. At 800 degreesC clusters of about 2 nm in size indicate that compositional inhomogeneities have developed while the film has still remained structurally amorphous. The sample annealed at 900 degreesC contains a high density of nanograins of TaN measuring about 2 nm as well as amorphous structures measuring 75-100 nm having a high tantalum content. After annealing at 1000 degreesC, an almost entirely crystalline structure is observed with 4-nm-sized particles of cubic TaN and 15-nm-sized grains of Ta5Si3. Possible mechanisms driving these structural changes are discussed. (C) 2001 American Institute of Physics
Preparation and properties of dc-sputtered IrO2 and Ir thin films for oxygen barrier applications in advanced memory technology
No full textIrO2 and Ir thin films have been deposited by do sputtering in Ar/O-2- and pure Ar atmospheres, respectively. The microstructural characterization of the films was done by x-ray diffraction and transmission electron microscopy and showed that (nano-)crystalline Ir and IrO2 films with different textures could be deposited. Stress analyses showed that the stress of the Ir films can be varied from about -3.5 GPa for a deposition temperature of 100 degreesC to nearly zero stress if deposited at 500 degreesC. However, IrO2 films generally exhibited a large compressive stress of about -1.5 GPa, which is nearly independent of substrate temperature, but changed with texture and stoichiometry of the films. Surface and roughness analyses of the cumulatively annealed samples were performed by various analysis methods, and stoichiometry was examined by Rutherford backscattering spectrometry. In situ stress measurements were used to investigate the stress relaxation behavior of the films up to 900 degreesC. We demonstrate that it is generally possible to optimize reactive IrO2 sputter deposition by a detailed study of plasma and deposition conditions via recording generic curves for the sputtering system used. At optimized conditions these fine grained IrO2 films exhibit very high thermal phase stability to at least 800 degreesC for several hours and a very low roughness. The aim of these investigations is to optimize stability of IrO2 films under high temperature conditions for oxygen barrier application in dynamic random access memory and nonvolatile Fe random access memory cells. (C) 2001 American Vacuum Society
Oxygen tracer diffusion in IrO2 barrier films
No full textThe O-18 tracer diffusion method was used to investigate oxygen diffusion in reactively dc-sputtered IrO2 films. The profile measurements were done by secondary ion mass spectrometry. For the investigation of the oxygen diffusivity in the samples a temperature range from 600 to 765 degreesC was chosen. The oxygen tracer diffusion in IrO2 films was found to be described by an Arrhenius law with D-0=(2.8+/-2.5)10(-6) m(2) s(-1) and an activation energy of E-a=(2.73+/-0.07) eV. It was also shown that the extrinsic oxygen diffusion is strongly influenced by the film preparation conditions, which is especially important for the application of IrO2 films as an oxygen barrier in future memory device applications. (C) 2002 American Institute of Physics
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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