1,720,957 research outputs found
The effect of structural characteristics of ZnO and NiO thin films on the performance of NiO/ZnO photodetectors
No full textMaterial properties play an important role in the fabrication of optoelectronic devices such as photodetectors because it is ultimately reflected in their efficiency and performance. To fabricate a NiO/ZnO heterojunction with better structural properties using a low-cost and uncomplicated deposition process, we studied the influence of NiO and ZnO thickness by taking different volumes of spray solution (5, 10, and 15 ml) on the structural and morphological properties that were investigated using the spray pyrolysis technique. When the films' thickness increased, the crystalline structure of both films improved. The deposited ZnO layers have a hexagonal Wurtzite structure with preferable growth orientations along (002). The NiO X-ray diffraction patterns showed that the films were in cubic phase with orientation (111) and the peak density increased with the film thickness. According to our experimental conditions and XRD results, we suggest that thicker NiO and ZnO are the optimal films to fabricate a NiO/ZnO heterostructure. It is found that Raman and XRD results confirm the formation of NiO/ZnO heterostructure. The morphology of NiO/ZnO is smooth and completely covers the substrate without any pinholes. The further investigation related to the effect of NiO and ZnO thin films' structural properties on NiO/ZnO heterostructure photodetector performance is presented using the simulations. It is worth mentioning that based on the suggested transport models, the results confirm that the origin of the dark current has been attributed to the tunneling and thermionic emission at the interface while bulk defects, leading to the increase Shockley-Read-Hall recombination and generation, control the carrier transport. Furthermore, we studied the effect of Gaussian and tail acceptor/donor defects on the current-voltage (J-V) characteristics and responsivity. The obtained results showed that increasing NiO tail states cause an increase in tunneling current. In contrast, the deep defects density in both ZnO and NiO affects the photodetection characteristics, resulting in a decrease in responsivity and photocurrent when these defects increase
Recent Advancements in TiO2 Nanostructures: Sustainable Synthesis and Gas Sensing
Full text linkThe search for sustainable technology-driven advancements in material synthesis is a new norm, which ensures a low impact on the environment, production cost, and workers' health. In this context, non-toxic, non-hazardous, and low-cost materials and their synthesis methods are integrated to compete with existing physical and chemical methods. From this perspective, titanium oxide (TiO2) is one of the fascinating materials because of its non-toxicity, biocompatibility, and potential of growing by sustainable methods. Accordingly, TiO2 is extensively used in gas-sensing devices. Yet, many TiO2 nanostructures are still synthesized with a lack of mindfulness of environmental impact and sustainable methods, which results in a serious burden on practical commercialization. This review provides a general outline of the advantages and disadvantages of conventional and sustainable methods of TiO2 preparation. Additionally, a detailed discussion on sustainable growth methods for green synthesis is included. Furthermore, gas-sensing applications and approaches to improve the key functionality of sensors, including response time, recovery time, repeatability, and stability, are discussed in detail in the latter parts of the review. At the end, a concluding discussion is included to provide guidelines for the selection of sustainable synthesis methods and techniques to improve the gas-sensing properties of TiO2
Effect of the source solution quantity on optical characteristics of ZnO and NiO thin films grown by spray pyrolysis for the design NiO/ZnO photodetectors
No full textZinc Oxide (ZnO) and Nickel Oxide (NiO) thin films were prepared using the spray pyrolysis technique using three different quantities of solution 5, 10, and 15 ml, to modify their optical properties. Optical characterization of the obtained thin films showed that the bandgap and the transparency of NiO and ZnO decrease with increasing solution quantity. The films are highly transparent making them suitable for optoelectronic applications. It is worth noting that NiO has a low growth rate compared to ZnO due to its larger bandgap. The different parameters obtained for both films are then used to simulate the electrical characteristics and the responsivity of a NiO/ZnO heterojunction based PN photodiode. Both the electrical characteristics and the responsivity improve with increasing quantities of solution. These findings may help to find an optimal design for photodiode fabrication
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
Synthesis and Characterization of NiO-GDC Nanowires for High-Performance Solid Oxide Fuel Cell Anodes
No full textSolid Oxide Fuel Cells (SOFC) have attracted increased attention due to their potential to
lower operating temperatures, which is crucial for advancing the widespread application of
SOFCs. Since the power output of a SOFC is closely related to the electrochemical
performance of the electrodes, nanostructuration of the anode increases the surface-to-
volume ratio of the three boundary conditions where the reactions take place. In this work,
the preparation and characterization of nanostructured anodes based on NiO-GDC
nanowires (NWs) are proposed. Synthesized by Vapor-Liquid-Solid growth technique, the
NWs have been systematically investigated by scanning electron microscope (SEM), X-ray
diffraction (XRD), and Raman spectroscopy. Functional characterization of the power
output fuel cell performance together with Electrochemical Impedance Spectroscopy
analysis were carried out at different temperatures and for different oxygen and hydrogen
fuel flows
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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