1,721,049 research outputs found
Surface/interface engineering InAs quantum-dot based edge-emitting LED for III-V/SiN photonic integrations
No full textEdge-emitting LEDs (ELEDs) possess a high brightness, a high coupling efficiency/tolerance to optical fibres compared with surface-emitting LEDs; whilst a simple structure for fabrication with a low cost compared with their coherent counterparts (i.e., lasers). Therefore, it is a good candidate for short-reach optical communications, optic gyroscopes, gain material for external-cavity lasers, and photonic integrated platforms. Recent breakthrough in InAs quantum-dot (QD) grown on various substrates with emission wavelength in O-band range enables the development of high-brightness ELEDs, including super-luminescent LEDs. In order to efficiently couple the emitting light out of an ELED, an anti-reflection coating (ARC) layer is required. Ideally, the ARC layer is also expected to be a passivation layer to reduce non-radiative recombination and to enhance the device lifetime, which is especially important for the edge-coupling scheme. In this case, the materials are requested to have both the desired refractive index and correct chemical property
Monolithic III-V/SiN co-integration through a butt-coupling scheme towards O-band applications
No full textOver the last decade, silicon nitride (SiN) has been proven a promising CMOS-compatible material platform instead of the already established silicon-on-insulator (SOI) [1]. That arises mainly from its tuneable physical and optical properties [2], its wider transparency window (low absorption in visible and NIR) along with its mid-index identity (low propagation loss) [3], its low thermo-optic coefficient (WDM applications) [4] and its low two-photon absorption (TPA) (non-linear applications) [5]. Furthermore, the capability of a low-temperature 350 °C PECVD growth method [2] along with SiN’s amorphous identity, renders the back end of line (BEOL) integration with active devices achievable. At the same time, the exploitation of photonic integrated chips (PICs) based on silicon (Si) towards coherent communication applications, is restricted due to the absence of fully integrated optical sources on-chip [6]. Even though progress on the III-V/SiN heterogeneous/hybrid approaches has been reported [7], a large scale monolithic integration of lasers on-chip with compact passive devices, still remains a challenge [8] due to the thick III-V buffer and cladding layers [9].In this paper, we demonstrate a monolithic III-V/SiN transition on a silicon substrate. The integration of our optically tunable silicon nitride platform [2] with high-gain GaAs-QD multi-layer stack hetero-epitaxially grown on silicon [10] is numerically investigated. In detail, a straight III-V waveguide (n=3.29-3.5) is connected to N-rich SiN waveguides (n=1.9) in a butt-coupling scheme. A Si-rich SiN layer of an intermediate refractive index (n=2.51) is placed at the active-passive interface, so as to alleviate the high-low refractive index difference, while it passivates the III-V waveguide. Using a protective tetraethylorthosilicate (TEOS) layer, a double layer anti-reflective coating (DLARC) is composed towards the minimization of the coupling loss (CL) and parasitic back-reflection (BR). Moreover, we report on a <−30 dB BR and <0.7 dB CL transition based on optical simulations (Lumerical). In addition, preliminary stand-alone characterization results of <2 dB/cm propagation loss and 0.1 dB/90° bending regarding a 1700 nm wide and 1600 nm thick N-rich SiN platform are demonstrated, setting the ground for a future realization of a single-mode Vernier-based laser
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
A thermally removable SiO<sub>x</sub> surface protecting layer on Si (100) for molecular beam epitaxy
No full textUltra-thin SiOx (with x ≤ 2) layer plays a key role in Si technology especially for the CMOS foundry processes approaching nm-level. Besides various functions of SiOx by only manipulating x value and thickness, [1-3] it becomes a favourable material as surface protecting layer for Si-molecular beam epitaxy (Si MBE), especially important for the growth on patterned Si substrates after a series of fabrication processes. This is because SiOx can be thermally decomposed to generate an atomically flat surface, without introducing any reducing agent (e.g., H2) to affect the growth.[4] Moreover, recent MBE growth indicates that surface reconstructions with bi-atomic terraces can form by thermally removing an oxide layer, which is critical to supress antiphase boundary defects towards high quality III-V materials monolithic grown on Si.[5] However, there has been insufficient knowledge in preparing a reliable thin SiOx protecting layer for MBE growth so far, and consistent confusions of the concepts have been used in literatures regarding the fabrication methods.In this work, we systematically studied the oxidation and deoxidation mechanisms of ultra-thin SiOx layers fabricated on Si (100) for MBE growth. From several growth approaches, a chemically synthesized SiOx thin layer is developed for reproducible thermal deoxidation in a Si MBE chamber. From transmission electron microscopy (TEM) observations, the SiOx thickness is ~2 nm with a clear Si/SiOx boundary to stop further oxidation in air (Fig.a), working well as a surface protection layer. An atomically flat surface is realized after thermal deoxidation process, examined by atomic force microscopy (AFM). The subsequent epitaxial growth is performed with the same MBE by depositing a thin Ge epitaxial layer, as it is not only broadly applied for all group IV integrations but also a good buffer layer for III-V on Si growth. [6,7] The epitaxial layer exhibits a reduced thread dislocation defect density (down to 3×108/cm-2) compared with its counterpart grown on a thermally removed natural oxide layer. In the meantime, a reduced tensile strain from 0.29% to 0.24% were confirmed by x-ray diffraction (XRD) and Raman spectroscopy measurements, corresponding to a variation of Ge-Γ1 transition energy from 0.772 to 0.783 eV confirmed by absorption spectroscopy measurements (Fig.b). Our work introduces a SiOx surface protecting layer for high quality MBE growth on Si substrates, opening a way for both all-group IV and III-V on Si integrations
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