1,720,963 research outputs found
Growth study and characterization of In-Sb-Te compounds deposited onto different substrates by metal-organic chemical vapour deposition
No full textA systematic study of the deposition parameters for the metal–organic chemical vapour deposition growth of In–
Sb–Te (IST), of interest for phase change memory applications, was performed. Samples were grown on Si/SiO2
and patterned substrates in the (220÷350)°C temperature range and working pressure from 35 to 100×102 Pa,
which resulted in the formation of thin films (down to 30 nm) or IST crystals. The chemical composition of the
IST films was mainly dependent on the deposition temperature. We have demonstrated the possibility to obtain
a conformal and smooth morphology with improved surface roughness for films grown at 260 °C when the
substrate surface is treated with the TrisDimethylaMinoAntimony ([N(CH3)2]3Sb) precursor. The IST-based
chalcogenide films exhibited different crystalline and partially amorphous phases, which may be favourable
for multilevel data storage. The IST growth mechanism was analysed in terms of the structural, compositional
and electrical properties
Structural and electrical analysis of In–Sb–Te‐based PCM cells
No full textTwo In–Sb–Te compounds with low Te content (12 at.% and 17 at.%), deposited by metalorganic chemical vapour deposition, were implemented into prototype phase-change memory devices of size 50 × 50 nm2 and 93 × 93 nm2. These chalcogenides yielded devices with higher threshold voltage than those based on Ge–Sb–Te alloys. The endurance and programming window were markedly improved (from 103 to 106 cycles and from 1 to 2 orders of magnitude, respectively) when employing the Te-richer alloy. Moreover, in situ structural and electrical analysis on TiN/In–Sb–Te/dielectric stacks provided additional insight on the thermal stability of the two ternary phases In3SbTe2 and InSb0.8Te0.2, which were found to coexist in these compounds
Au-catalyzed synthesis and characterisation of phase change Ge-doped Sb-Te nanowires by MOCVD
No full textThe interest in the Ge doped Sb–Te chalcogenide alloy is mainly related to phase change memory applications. In view of phase change device scaling and reduction of programming energy, Sb–Te nanowires (NWs) become an attractive option. In this work, in order to investigate their potential transferability to industrial implementation, the self-assembly of Sb2Te3 NWs and Ge–Sb–Te NWs with Ge content in the range of 1–13% (Ge doping) was studied by coupling the advantages of MOCVD and the Vapour–Liquid–Solid (VLS) mechanism. The results show the structural and compositional gradual changes occurring from pure Sb2Te3 NWs to the previously reported, stoichiometric Ge1Sb2Te4 NWs [[12] M. Longo et al., Nano Lett., 12 (2012) 1509]. The typical diameter of the obtained NWs resulted to be 50 nm, with lengths up to 3 μm. The typology of Au catalyst nanoislands influenced both the NW morphology and the Ge incorporation during the VLS self-assembly; the Ge metalorganic precursor partial pressure affected the NW morphology and their structure. Finally, TEM observations revealed that defect-free, monocrystalline Sb2Te3 and Ge-doped Sb–Te phase change NWs could be obtained
Thermal properties of In-Sb-Te films and interfaces for phase change memory devices
No full textThe thermal properties of two different compositions (Te 12 and 17 at.%) of In–Sb–Te, obtained by met alorganic chemical vapour deposition, were investigated by the 3 x method. The thermal conductivity of
these chalcogenides, of interest for phase change memory applications, was found to decrease with
increasing tellurium content. Thermal treatment at 480 C of these materials caused an increase of their
crystallinity and improved the thermal conductivity. However, this effect was more marked in the
Te-poor composition than in the Te-rich one. In addition, the thermal boundary resistance between
In–Sb–Te and various capping dielectrics (SiO2, Si3N4 and Al2O3) was measured and it was found to be
closely correlated to the interlayer roughness, as indicated by X-ray reflectivity. In this regard, silicon
oxide and alumina yielded a smoother and less resistive interface with In–Sb–Te than silicon nitrid
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
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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