1,720,956 research outputs found
Cu katkılı TiO2 ince filmlerin memristiv davranışı ve karakterizasyonu
No full textAmaç: Bu çalışmada Cu katkılı TiO2 ince filmlerin Cu/Pt/TiO2:Cu ve TiO2/SiO2/p++Si/Al yapılarında memristiv davranış ve karakterize edilerek incelemesi yapıldı.Yöntem: Bu çalışma Plazma bazlı sıçratmaya ek bir teknik olarak Yüksek Güçlü Darbeli Manyetik Sıçratma (HiPIMS) tekniği ile ince filmlerin biriktirilmesi veya kaplanmasını ihtiva etmektedir. HiPIMS, yüksek deşarj gücüyle püskürtülen atomların yüksek iyonlaşma oranı ile üretildiği, magnetron hedefine düşük tekrarlama frekansı ile yüksek güçlü ve kısa darbeler gerilim uygulamaya dayanmaktadır. Yüksek gerilim uygulanan hedefin, Ar gibi bir inert gaz iyonları ile bombardıman edilir. Film büyümesi hedeften sökülen atomların iyonları ile oluşan yüksek yoğunluktaki plazma ile kontrol edilir. Bileşik malzemelerin biriktirilmesi için metal hedefler, CH4, N2, O2, vb gibi gazlarlın atmosferi altında R-HiPIMS veya benzeri tekniklerle manyetik sıçratma ile elde edilir ve oksit, nitrit ve karbide gibi bileşiklerin ince filmler büyütülür.Bulgular: Oksijen akış hızı ile ilgili TiO2 büyüme oranının sonuçları, 0.4sccm HiPIMS için değerlendirldi. (Cu/Pt/TiO2: Cu veya TiO2/SiO2/p++Si/Al) yapıları için cam altlık üzerinde 2 fCu ve fCu katkılı DC darbesi ile büyütülrn TiO2 optik soğurma ölçümlerinden bant aralıkları sırasıyla 3.78, 3.6 ve 3.7eV'dir. Katkısız ve 10, 15, 25% Cu katkılı TiO2 olarak memristörün (I-V) karakterleri, TiO2 için simetriktir ve doğrultucu özellik gözlenmezken, Cu katkılı cihazlarda asimetrik. AFM sonuçları, 30nm'lik yüzey morfolojisi üzerinde saf ve (10, 15, 20, 25% 30) Cu katkılı TiO2 için sırasıyla 0.3, 0.41, 0.16 ,0.48, 0.52, 0.77 (Rms) nm pürüzlülük oluştuğu görüldü. Cu oranının 5% az (p++Si/SiO2/Au/Pt/TiO2/Cu/Au) aygıt yapısıdan 250 ̊C'deki ısıl işlemin daha iyi bir performans ile belirgin hesterisiz alanı gözlendi.Sonuç: Cu katkısı tüm yaptığımız cihazların ince filmler üzerinde; (i) ince filmin kristalleşme üzerinde bir ihmal edilecek etkisi var ve XRD sonuçlar bunu teyit etmektedir; (ii) katkı oranı artığında ince filmlerin band aralığını azalması optik ölçümlerinden anaşıldı ve memristörün elektriksel karakterizasyonuna göre memristörün set gerilimi daha yüksek gerilime kaymaktadır. Ayrıca filament olusumu yüksek gerilimde olduğundan, katkı oranı artışı daha çok akım geçişine sebep olmaktadır; (iii) Pt/TiO2:Cu/p++Si/Al aygıtı için üst kontakt degiştirilerek bakır kullanıldı ve asimetrik I-V ilişkisi gözlendi; (iv) 250 ̊ C'da tavlanan numune az Cu katkılı numunelerde (1.5 ile 3%Cu katkısı) memristive özelliğin belirginleştiyi gözlendi.</p
THE BAND ENERGY ENGINEERING ON HIGH EPOXY (OR HYDROXYL) CONTENT GRAPHENE OXIDE
No full text Nowadays, the superior properties of carbon-based materials especially nano structural derivation like graphene and graphene oxide (GO) spot light to the researchers. The GO has been suggested as an alternate material in device miniaturization due to its atomic structure. The memristors and nonvolatile memories are settled in these categories as a solution for the scaling limitation problem in the Moor’s law. Therefore, the GO can influence the memristor performance and characteristics. The current–voltage characteristics as the most significant parameter in the memristor design are considered. On the other hand [Formula: see text]–[Formula: see text] characteristic depends on the active layer (GO) bandgap energy in the metal/oxide/metal structure and therefore, needs to be explored. In the GO-based memristor, the bandgap energy can be changed by the percentage of the oxygen groups in comparison to the carbon on graphene sheets. Thus, the other parameters are overstated by the bandgap energy. In the presented work, the energy bandgap of a high epoxy group content of GO sheets is engineered. The opening of the bandgap in the graphene oxide by high epoxy groups content with the ratio of (O/C [Formula: see text] 50%) is studied. In other words, the oxygen adsorption effect on the Hamiltonian of the system is explored. For the proposed structure, the bandgap energy is modeled and the acceptable value (approximately equal to 2.799[Formula: see text]ev for epoxy groups) is obtained. Moreover, the hydroxyl group adsorption effect on the bandgap of the graphene oxide by high content hydroxyl group is considered (approximately equal to 2.647[Formula: see text]ev for epoxy groups). Consequently, the different absorption energy effects on the bandgap of the GO is participated and the opening bandgap in the range of 2[Formula: see text]ev to 3[Formula: see text]ev is obtained. The excitonic effect on the suggested model by epoxy groups and hydroxyl groups is explored and it is realized that the energy levels in the Dirac points of epoxy groups are closer than those of the hydroxyl groups. </jats:p
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
- …
