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PECULARITIES OF PLASMA PROCESSES OVER SEMICONDUCTOR GAS DISCHARGE SYSTEM
No full textBu çalışmada termal olmayan plazma işlemleri neon (Ne) gazı ortamında
düzlemsel bir boşalma hücresindeki gaz boşalması, yarıiletken elektrodun farklı
alan çapları D, farklı elektrotlar arası mesafeleri d ve Ne gazı için atmosfer
basıncına kadar incelendi. GaAs yarıiletken katotlu gaz boşalma sisteminin
akım voltaj karakteristikleri (AVK) ve Işık Şiddeti-Voltaj Karakteristiği geniş
bir gaz basıncı p (15÷760 Torr) aralığında deneysel olarak araştırıldı. Ne
gazından elde edilen deneysel sonuçlar hava ortamındaki sonuçlarla
karşılaştırıldı. p ≥ 220 Torr için Hava ortamında boşalma ışık emisyonu (BIE)
şiddetinin oldukça azaldığı ve atmosfer basıncına doğru yok olduğu, buna
mukabil Ne için özellikle atmosfer basıncına doğru en yüksek BIE şiddetine
ulaşıldığı tespit edildi. Kararlı boşalma bölgeleri ve kontrol edilebilir çalışma
rejimi termal olmayan plazma işlemleri için belirlendi. Elde edilen en önemli
sonuçlardan biri Ne gazı ortamında, atmosfer basıncında Townsend
boşalmasının elde edilmesidir. Yarıiletken gaz boşalma sisteminin (YGBS)
kararsız olduğu şartlar belirlendi. EL2 derin elektronik seviyelerin varlığının,
materyalin N-tipli NDD' sine ve sonuç olarak GaAs fotodetektöre yeterince
yüksek voltaj uygulandığında akım osilasyonlarına yol açtığı tespit edildi.
Ayrıca, YGBS'nde BIE'nin bölgesel olarak artma olanağı araştırıldı.
v
Mikrokanallı yalıtkan ayırıcı kullanılarak gaz boşalma aralığında kırılma
voltajının (Uk) yaklaşık 100 V azaldığı ve akım değerinin iki katı kadar arttığı
tespit edildi. YGBS'nde mikrokanallı yalıtkan ayırıcının kullanılması ile Ne
ortamında ışık şiddetinin 3 katı arttığı tespit edilmiştir. Kızılötesi görüntüleri
görünür bölgeye çevirmek için dizayn edilmiş olan ışığa duyarlı YGBS'nde
optimal çalışma şartları tespit edilmiştir. Ne gazı ortamında ve atmosfer
basıncında çalışabilen, yarıiletken katotlu, geniş bir emisyon alanına sahip, UV
ve görünür bölgede homojen bir ışık kaynağı geliştirildi.In this study, non-thermal plasma process in a planar gas discharge system with
Neon gas environment was studied experimentally at various interelectrode
distances d and different inner diameters D of the electrode areas of the
semiconductor cathode up to atmospheric pressure. The Current-Voltage
Characteristics (CVC) and Light intensity-Voltage Characteristics of the gas
discharge system with GaAs cathode have been studied in a wide range of the
gas pressure p (15÷760 Torr). Experimental results which were obtained from
Ne gas were compared with the results from air. Gas discharge light emission
intensities decrease in air medium for p ≥ 220 Torr and decay towards
atmospheric pressure. On the other hand, the highest gas discharge light
emission intensity values were reached for Ne towards atmospheric pressure.
Stable discharge regions and controllable working mode were identified.
Obtaining Townsend discharge at atmospheric pressure when Ne used is one of
the most important results. Also the conditions were underlined which
semiconductor gas discharge structure (SGDS) is unstable. The presence of deep
electronic levels of defects, called EL2 centers, results the N-type NDR of the
material, caused to oscillations in current when a dc voltage of a high magnitude
is applied to a GaAs photodetector. Possibilities regarding increase of gas
discharge light emission intensity for SGDS were investigated.
vii
Breakdown potential (Ub) is decreased around 100 V by using dielectric
microchannel dielectric spacer in gas discharger gap. Light intensity is
multiplied three times in SGDS with Ne environment by using dielectric
microchannel spacer. Optimal working conditions are determined for SGDS
designed to convert infrared images to visible region. By using the infrared
light to excite the semiconductor cathode of the system, we have shown that the
uniform discharge light emission of the device with Ne in the gap can serve as a
source of UV and visible light at atmospheric pressure
EXAMINATION OF AlxGa1-xAs/GaAs NANOSTRUCTURES WITH CHEMICAL ETCHING METHOD
No full textBu tez çalışmasında tek kristaller ve MBE tekniği ile büyütülen AlxGa1-
xAs/GaAs nanoyapılarının ıslak kimyasal aşındırma yöntemi kullanılarak
ortaya çıkan yüzey morfolojisi ve numunenin kalitesi incelendi. Numune
kalınlığındaki değişimi profilometre ile yüzeyindeki pürüzlülüğü Spektroskopik
Elipsometre ile ve yüzeydeki kusurların görüntülerini optik miroskop ile analiz
edildi. Bizim burada ıslak kimyasal aşındırma yönteminde kullandığımız
aşındırıcı solüsyon sitrik asit/hidrojen peroksit (C6H8O7/H2O2)'dir. Literatürde
hem sitrik asit/hidrojen peroksit hemde farklı solüsyonlarla yapılan
aşındırmalar, bizim yaptığımız çalışmalarla karşılaştırıldı. Bir materyali
diğerinden daha hızlı ortadan kaldıran, seçici aşınım yapan aşındırıcı solüsyon
değeri belirlendi.
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In this study, the surface morphology and sample quality of wet chemical etched
AlxGa1-xAs/GaAs nanostructures which were growth by MBE techniques and
single crystals has been examined. The change in thickness of sample with
profilometry, the roughness on the surface with spectroscopic elipsometry and
the displays of defect on surface with optic microscop are analyzed. The etching
solution used in this study was citric acid/hydrogen peroxide (C6H8O7/H2O2).
Herewith, we present the comparison between our studies and previously
carried studies for citric acid/hydrogen peroxide etching in the literature. The
etching solution value, which removes a material faster than other one and
makes selective etching, is determined
InGaAsP/InP ÇOKLU KUANTUM KUYULU ÇATI DALGA KILAVUZLU LAZER DİYOTLARIN FABRİKASYONU VE LAZER DİYOT PARAMETRE ANALİZİ
No full textBu çalışmada kullanılan 1,3 ve 1,55 μm ışıma dalgaboylu InxGa1-xAsyP1-y/InP
çoklu kuantum kuyulu lazer diyot yapıları metal organik kimyasal buhar
biriktirme (MOCVD) tekniğiyle büyütüldü. Büyütülen yapıların çatı dalga
kılavuzlu Fabry-Perot lazer diyot fabrikasyonu farklı tipteki pasivasyon
tabakaları (SiO2 ve SiNx) kullanılarak fotolitografi sistemi yardımıyla yapıldı.
Lazer diyot parametre analizleri sonucunda, SiO2 pasivasyon tabakalı lazerin
daha düşük eşik akımına, diferansiyel dirence ve daha yüksek çıkış gücüne
sahip olduğu görüldü. p-InGaAs kontak tabakalı lazer diyotlar için omik
kontakların geliştirilmesi amacıyla Transmisyon Çizgi Modeli (TLM)
numunelerinin fabrikasyonu yapıldı. Bilgimiz dahilinde, p-InGaAs tabakası için
altın içeren ve içermeyen nadir bulunur metal silikat omik kontaklar ilk defa
oluşturularak, kontakların analizi TLM kullanılarak gerçekleştirildi. Yapılan
analizler sonucunda, elde edilen karakteristik kontak direncinin günümüz
optoelektronik aygıtlarının sahip olduğu karakteristik kontak direnci ile aynı
mertebede olduğu görüldü.The 1,3 and 1,5 μm emission wavelength InxGa1-xAsyP1-y/InP multi quantum
well (MQW) laser diode structures used in this work were grown using metal
organic chemical vapor deposition (MOCVD) technique. The fabrication of
ridge waveguide Fabry-Perot laser diodes with different passivation layers (SiO2
and SiNx) were made using photolithography system. The laser parameter
analysing results shows that the laser diode with SiO2 passivation layer has
lower threshold current, differential resistance and higher output power. To
improve the ohmic contact properties the Transmission Line Model (TLM)
samples were fabricated. According to our knowledge, the Au and non-Au
based rare earth metal silicate ohmic contacts were formed for the first time
and the analyzing of ohmic contacts were performed using TLM. As a result,
the obtained specific contact resistivities were found in the same order of
nowadays optoelectronic device's contact resistivities
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
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
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