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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Nano-sized group III oxides prepared by implantation-assisted growth techniques. / CUHK electronic theses & dissertations collection

January 2008 (has links)
In this project, nano-sized gallium oxide and indium oxide produced by ion implantation of nitrogen/carbon and subsequent rapid thermal annealing (RTA) have been investigated. The material synthesis technique is based on using implantation of different species, which include nitrogen, carbon, oxygen and argon, with variable implant dosage to form an amorphous surface layer on GaAs or InP substrates. RTA then provides the required thermal energy for the amorphous material to re-crystallize. We found that the type of implanted species play an important role in controlling the material for nation during the RTA stage. Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were conducted to provide detailed characterization on the samples. For the nitrogen/carbon implanted samples, RTA at 950°C resulted in the formation of single crystalline Ga2O3 nano-ribbons on the sample surface. These Ga2O3 ribbons possess strong visible photoluminescence and cathodoluminescence. For the carbon implanted InP samples, In2O3 nanowires were found on the InP sample surface when RTA was performed at 750°C. However, In2O 3 nanowires only occurred when gold was present. On the other hand, when the nitrogen implanted samples were annealed in pure nitrogen ambient, a Raman peak at 577cm-1 associated with GaN was observed. Cross-sectional TEM showed that the thickness of the region containing GaN was about 40nm. We also used the synthesized GaN as a buffer layer to grow ZnO film by using MOCVD. The possible formation mechanisms of these nanomaterials and the role of the implanted species are discussed. For the nanowires with gold nano-particles at the free end, we believe that they are synthesized by vapour-liquid-solid (VLS) mechanism. On the other hand, the growth of nano-wires in the cases where no gold nano-particles on the free end may be explained on the basis of a vapour-solid (VS) mechanism. For the case of carbon or nitrogen implantation, carbon works as a reduction agent and nitrogen favours the formation of group III nitride template, which may lead of the growth of nano-wires. / Lo, Kwong Chun. / "March 2008." / Adviser: Aaron H. P. Ho. / Source: Dissertation Abstracts International, Volume: 70-03, Section: B, page: 1887. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (p. 112-119). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.
162

Synthesis and characterization of 1D CuInX2 and Cu2ZnSnX4 (X=Se, S) nanostructures. / 銅銦硒/硫和銅鋅錫硒/硫一維納米結構的合成與表徵 / Synthesis and characterization of 1D CuInX2 and Cu2ZnSnX4 (X=Se, S) nanostructures. / Tong yin xi/liu he tong xin xi xi/liu yi wei na mi jie gou de he cheng yu biao zheng

January 2011 (has links)
Pei, Congjian = 銅銦硒/硫和銅鋅錫硒/硫一維納米結構的合成與表徵 / 裴聰健. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 76-78). / Abstracts in English and Chinese. / Pei, Congjian = Tong yin xi/liu he tong xin xi xi/liu yi wei na mi jie gou de he cheng yu biao zheng / Pei Congjian. / Abstract --- p.i / 論文摘要 --- p.ii / Acknowledge: --- p.iii / Contents: --- p.iv / List of Figures: --- p.vii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Background --- p.3 / Chapter 2.1. --- Overview --- p.3 / Chapter 2.2 --- Methodology --- p.3 / Chapter 2.2.1 --- General growth strategies for synthesizing nanowires (NWs) --- p.3 / Chapter 2.2.2 --- Synthesis NWs from vapor phase (VLS mechanism) --- p.4 / Chapter 2.2.3 --- Synthesis NWs from solution phase --- p.7 / Chapter 2.2.4 --- Synthesis NWs assist by template --- p.8 / Chapter 2.3 --- Instrumentation --- p.10 / Chapter 2.3.1 --- XRD (X-Ray Diffraction) --- p.10 / Chapter 2.3.2 --- SEM (Scanning Electron Microscopy) --- p.11 / Chapter 2.3.3 --- TEM (Transmission Electron Microscopy) --- p.13 / Chapter Chapter 3 --- Synthesis and characterization of In2Se3 nanowires --- p.17 / Chapter 3.1 --- Overview: --- p.17 / Chapter 3.2 --- Experimental Section: --- p.17 / Chapter 3.3 --- Results and Discussions: --- p.19 / Chapter 3.3.1 --- Results of high temperature (~800oC) synthesized sample --- p.20 / Chapter 3.3.2 --- Results of the low temperature (~600oC) synthesized sample --- p.26 / Chapter 3.3.3 --- Results of thermal evaporate CuInSe2 source: --- p.30 / Chapter 3.4 --- Conclusion: --- p.31 / Chapter Chapter 4 --- Synthesis and Characterization of ID CuInSe2 and CuInS2 structures via template assist method --- p.33 / Chapter 4.1 --- Overview: --- p.33 / Chapter 4.2 --- Experimental: --- p.33 / Chapter 4.2.1 --- Fabrication of CuInSe2 nanowire arrays --- p.34 / Chapter 4.2.1 --- Fabrication of CuInS2 nanowire arrays --- p.35 / Chapter 4.3 --- CuInSe2 nanowire arrays: --- p.36 / Chapter 4.4 --- CuInS2 nanotube &nanowire array: --- p.42 / Chapter 4.5 --- Discussion of the formation mechanisms: --- p.45 / Chapter 4.6 --- Conclusion: --- p.50 / Chapter Chapter 5 --- Synthesis of ordered single-crystalline nanowires arrays of Cu2ZnSnS4 and Cu2ZnSnSe4 --- p.51 / Chapter 5.1 --- Overview: --- p.51 / Chapter 5.2 --- Experimental: --- p.52 / Chapter 5.3 --- Results and discussion: --- p.54 / Chapter 5.4 --- Discussion of the formation mechanisms: --- p.68 / Chapter 5.5 --- Conclusion: --- p.72 / Chapter Chapter 6 --- Summary --- p.73 / Reference: --- p.76
163

Luminescent properties of zinc-blende ZnCdSe =: 閃鋅礦結構ZnCdSe的螢光性質. / 閃鋅礦結構ZnCdSe的螢光性質 / Luminescent properties of zinc-blende ZnCdSe =: Shan xin kuang jie gou ZnCdSe de ying guang xing zhi. / Shan xin kuang jie gou ZnCdSe de ying guang xing zhi

January 1996 (has links)
by Ng Po Yin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 57-59). / by Ng Po Yin. / Acknowledgments --- p.I / Abstract --- p.II / Table of contents --- p.III / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Interest in ZnxCd1-xSe/InP --- p.1 / Chapter 1.2 --- Our work --- p.2 / Chapter 1.3 --- Usefulness of PL --- p.4 / Chapter 1.4 --- Growth conditions of ZnSe/GaAs and ZnxCd1-x/InP --- p.4 / Chapter 1.5 --- Purposes of studying ZnSe/GaAs --- p.5 / Chapter 1.6 --- Inhomogeneity of ZnxCd1-xSe/InP --- p.5 / Chapter Chapter 2 --- Experimental setup and procedures --- p.7 / Chapter 2.1 --- Experimental setup --- p.7 / Chapter 2.2 --- Measurements performed --- p.10 / Chapter 2.3 --- Experimental procedures --- p.10 / Chapter Chapter 3 --- Results and discussion --- p.12 / Chapter 3.1 --- RT and 9K PL of ZnSe/GaAs --- p.12 / Chapter 3.2 --- "Excitation power density dependent, RT and 9K PL of ZnxCd1-xSe/InP" --- p.20 / Chapter 3.3 --- Temperature dependent PL of ZnSe/GaAs and ZnxCd1-xSe/InP --- p.45 / Chapter Chapter 4 --- Conclusions and future work --- p.55 / References --- p.57
164

Structural, optical and sensing properties of cobalt and indium doped zinc oxide prepared mechano-chemically

Manamela, Mahlatse Fortunate January 2018 (has links)
Thesis ((MSc. (Physics)) -- University of Limpopo, 2018 / The mechano-chemical technique was employed to synthesise the undoped, cobalt and indium single and double doped ZnO nanoparticles powder samples. The x-ray diffraction (XRD), scanning electron microscopy (SEM), raman spectroscopy (RS), ultraviolet-visible spectroscopy (UV-vis), and photoluminescence (PL) spectroscopy were employed to characterise the prepared samples. The XRD and energy dispersive spectroscopy (EDS) results confirmed that the prepared samples were of hexagonal wurzite form. In addition, it was found that the diffraction pattern for In-ZnO nanoparticles display an additional peak which was associated with In3+ dopant. The peak suggest that In3+ ions prefer the interstitial site in the hexagonal ZnO structure. Doping the ZnO nanoparticles with Co and In did not significantly affect the lattice parameters but the average grain sizes of the nanoparticles were found to be reduced. The morphology of the samples revealed by the SEM images appear to be more spherical. The Raman modes obtained from the excitations wavelength of 514.532 nm further indicated that the prepared samples were of hexagonal ZnO structures. The energy band gap of the prepared samples were calculated from the UV-vis data which showed that the doped ZnO nanoparticles had smaller energy band gap compared to the undoped ZnO nanoparticles. The excitation wavelength of 350 nm were used in the PL study where various defects related emissions were observed for the doped and undoped ZnO nanoparticles. The kenosistec station equipment was used to investigate the prepared samples for gas sensing application. Ammonia (NH3), methane (CH4) and hydrogen sulphide (H2S) gases were probed. In all the response curves observed, the undoped and double doped ZnO nanoparticles are being favoured at a temperature range 200 – 350oC. In addition, the double doped ZnO nanoparticles was found to be more sensitive to CH4 at low temperatures and low v concentrations. / National Research Foundation (NRF) and Council for Scientific and Industrial Research (CSIR)
165

Design of a FEEP Thruster for Micro-/Nano-Satellites

Badami, Muhammad Ali January 2019 (has links)
CubeSat development has seen a rise since the first launch in 2003 due to faster design process and low launch costs. It has played a vital role in providing access to space to small start-ups and academic organizations with low budgets. It has also enabled the testing of different upcoming technologies in space and has helped in providing hands-on experience to students taking part in design of such platforms. University of Pisa, in collaboration with SITAEL, has also taken an initiative to design and develop a CubeSat to test the FEEP thruster, design of which is presented in the thesis. A FEEP system was designed to fit within 1U dimensions and with a dry mass of approximately 820 grams. The system is based on slit emitter which provides an advantage over already available technologies in the market which uses needle emitters. Slit emitter scan achieve multiple Taylor cones without the need of clustering as used in needle emitters and also have a higher Thrust to Power Ratio. A propellant comparison was done considering all the properties required for an ideal propellant for a FEEP system. This comparison led to the selection of indium as working propellant which has an atomic mass of 114.8 u and a melting point of 156.6 °C. The FEEP system was designed keeping in mind easy assembling and modularity of thruster for ease in changing parts. The design consists of three different modules that are assembled separately and then joined together to complete the assembling of the system. The propellant tank, which also houses the emitter, has an internal volume of 32.75 cm3 and can hold approximately 240 grams of indium, which has a density of 7.31 g/cm3. During mission analysis, a 600km altitude orbit was proposed by analyzing the amount of propellant required for drag compensation and de-orbit maneuver at different altitudes with worst case values for ballistic coefficient and Thrust to Weight Ratio. At this altitude, the propellant requirement is 254.4 grams, 14.4 grams more than that of what can fit in the propellant tank of the designed thruster. However, both design of the system and mission analysis are ongoing processes and changes would be made in the future to either one or both to meet the requirements.
166

Copper Gallium Diselenide Solar Cells: Processing, Characterization and Simulation Studies

Panse, Pushkaraj 28 March 2003 (has links)
The goal of this research project was to contribute to the understanding of CuGaSe2/CdS photovoltaic devices, and to improve the performance of these devices. The initial part of the research dealt with the optimization of a Sequential Deposition process for CuIn(Ga)Se2 absorber formation. As an extension of this, a recipe (Type I Process) for CuGaSe2 absorber layer fabrication was developed, and the deposition parameters were optimized. Electrical characterization of the thin films and completed devices was carried out using techniques such as Two-Probe and Three-Probe Current-Voltage, Capacitance-Frequency, Capacitance-Voltage, and Spectral Response measurements. Structural/chemical characterization was done using XRD and EDS analysis. Current densities of up to 15.2 mA/cm2, and Fill Factors of up to 58% were obtained using the Type I CuGaSe2 Process. VOC's, however, were limited to less than 700 mV. Several process variations, such as changes in the rate/order/temperature of depositions and changes in the thickness of layers, resulted in little improvement. With the aim of breaking through this VOC performance ceiling, a new absorber recipe (Type II Process) was developed. VOC's of up to 735 mV without annealing, and those of up to 775 mV after annealing, were observed. Fill Factors were comparable to those obtained with Type I Process, whereas the Current Densities were found to be reduced (typically, 10-12 mA/cm2, with the best value of 12.6 mA/cm2). This performance of Type II devices was correlated to a better intermixing of the elements during the absorber formation. To gain an understanding of the performance limitations, two simulation techniques, viz. SCAPS and AMPS, were used to model our devices. Several processing experiments and SCAPS modeling indicate that a defective interface between CuGaSe2 and CdS, and perhaps a defective absorber layer, are the cause of the VOC limitation. AMPS simulation studies, on the other hand, suggest that the back contact is limiting the performance. Attempts to change the physical back contact, by changes in the absorber processing, were unsuccessful. Processing experiments and simulations also suggest that the CuGaSe2/CdS solar cell involves a true heterojunction between these two layers.
167

An alternative structure for next generation regulatory controllers and scale-up of copper(indium gallium)selenide thin film co-evaporative physical vapor deposition process

Mukati, Kapil. January 2007 (has links)
Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Babatunde Ogunnaike, Dept. of Chemical Engineering, and Robert W. Birkmire, Dept. of Materials Science & Engineering. Includes bibliographical references.
168

Microstructural development of porous materials for application in inorganic membranes

Mottern, Matthew L., January 2007 (has links)
Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 116-126).
169

NOUVEAUX RADIOTRACEURS PEPTIDIQUES POUR L'IMAGERIE NUCLEAIRE <br />Radiomarquage, évaluations physico-chimiques et pharmacologiques

Ahmadi, Mitra 11 February 2008 (has links) (PDF)
Au cours de la dernière décennie, les radiotraceurs peptidiques sont devenus importants en Médecine Nucléaire pour le diagnostic et/ou la thérapie. Le développement de ces radiopharmaceutiques nécessite la recherche de nouveaux vecteurs spécifiques mais aussi leur évaluation physico-chimique et pharmacologique après radiomarquage.<br />Ces travaux concernent la mise au point et l'optimisation du radiomarquage au technetium-99m, à l'indium-111 et à l'iode-125 de nouveaux radiotraceurs peptidiques, destinés à l'imagerie in vivo de deux processus pathologiques : la néoangiogenèse tumorale et la plaque d'athérome vulnérable, et au suivi de la thérapie d'une maladie autoimmune : le lupus érythémateux disséminé. Le radiomarquage au technétium a été effectué par l'intermédiaire d'un petit synthon tricarbonyle (Isolink), l'indium a été fixé par une macromolécule DOTA et la radioiodation a été réalisée par substitution électrophile. Les paramètres de chaque réaction ont été définis afin que la réaction de marquage présente un haut rendement et une haute activité spécifique. Les réactions sont rapides et reproductibles et la mise en forme compatible avec une utilisation in vivo. Les propriétés physico-chimiques et pharmacologiques (lipophilie, stabilité de marquage in vitro et in vivo, fixation protéique, métabolisation et biodistribution) ont été mesurées. Ces études ont permis de sélectionner les radioligands présentant les meilleurs critères pour une utilisation in vivo en imagerie.
170

Heteroepitaxial growth of InN and InGaN alloys on GaN(0001) by molecular beam epitaxy

Liu, Ying, January 2005 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

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