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1
Yang, Rusen. "Oxide nanomaterials synthesis, structure, properties and novel devices /." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-06212007-161309/.
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Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2008.Peter J. Hesketh, Committee Member ; Zhong Lin Wang, Committee Chair ; C.P. Wong, Committee Member ; Robert L. Snyder, Committee Member ; Christopher Summers, Committee Member.
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Jokela, Slade Joseph. "Stability and structure of hydrogen defects in zinc oxide." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Dissertations/Fall2006/s_jokela_122106.pdf.
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Yan, Xiaodong. "Controllable fabrication of zinc oxide functional nano-/micro-structure in aqueous solution." Thesis, University of Auckland, 2010. http://hdl.handle.net/2292/5930.
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Nanostructures of ZnO show intriguing chemical, electrical, and physical properties and are promising for a broad range of applications in catalysis, electronics and photonics. Cost-effective techniques that can be used to prepare structures with controllable compositional, structural, and functional properties are fundamental to the utilization of ZnO in small scale devices with enhanced performance. Although many methods have been developed to fabricate ZnO nanostructures, systematic research on functional materials development based on ZnO is still needed as this fascinating material probably has the richest family of low-dimensional nanostructures. The research reported in this thesis aims to develop ZnO-based nanostructural materials using a facile and low-temperature aqueous solution growth approach, to analyze their compositional, mechanical, structural, and functional properties using advanced characterization techniques, to get a better understanding of the mechanisms behind nanostructure growth, and to explore their potentials in catalytic, optical, and electronic applications. In the first part of this thesis, low-dimensional ZnO nano-/micro-rods with tailored structural property (growth direction, aspect ratio, and surface distribution density) were grown on glass substrates in aqueous solutions containing zinc salt and hexamethylenetetramine at temperatures generally lower than 95oC. The substrates were pre-deposited with a thin layer of ZnO seeds using a magnetron sputter. The potential influences of growth conditions, typically including concentration, pH, type of zinc salt, solution temperature, reaction duration, and inorganic or organic additive, have been subjected to systematic investigation. This led to an improved understanding of the chemical reactions and nucleation/growth processes involved in the morphological evolution of ZnO-based hierarchical nanostructures. The second part of the thesis, ZnO nano-/micro-rod arrays with controllable distribution density have been successfully synthesized by adjusting the initial pH of the weak acidic growth solution. ZnO arrays with a large inter-rod space provide a good opportunity for characterizing the property of an individual rod. In this research, mechanical property tests have been successfully peformed directly on a single rod without the need of any complicated sample preparation. The electronic properties of these aligned ZnO nanorod arrays have also been explored by studying the I-V characteristics of both heterojuction and homojuction p-n devices. In next two chapters, complex ZnO structures, including nanotubes and three-dimensional ball-shaped clusters have been presented and disscussed, respectively. The morphology and microstructure of these structures were characterized by scanning electron microscopy, transmission electron microscopy, and in-situ cathodoluminescence. The corresponding growth mechanisms were proposed based on the analysis of the characterization results. Chapter 7 describes that aligned ZnO nano-rod arrays were further used as templates to prepare a novel composite nanostructure. By coating these ZnO nanorods with TiO2 nanowires using magnetron sputtering technique, a ZnO/TiO2 core-brush structure has been successfully achieved. Their morphology and microstructure have been investigated using scanning electron microscopy, transmission electron microscopy, powder X-ray diffractometer, energy-dispersive X-ray spectroscopy and X-ray Photoelectron Spectroscopy. This composite nanostructure shows a significantly enhanced photocatalytic activity in decomposition of a typical organic dye under UV and sunlight irradiation. This new structure has many other interesting properties and may have great potential in other optoelectronic applications. In the last part of this thesis, conclutions and future works are addressed according to the synthesis, characterization and application results.
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Yoshihara, Jun. "Model copper/zinc oxide catalysts for methanol synthesis : the role of surface structure /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/8539.
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Kuo, Fang-Ling. "Electrical and Structure Properties of High-κ Barium Tantalite and Aluminum Oxide Interface with Zinc Oxide for Applications in Transparent Thin Film Transistors." Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc84233/.
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ZnO has generated interest for flexible electronics/optoelectronic applications including transparent thin film transistors (TFTs). For this application, low temperature processes that simultaneously yield good electrical conductivity and optical transparency and that are compatible with flexible substrates such as plastic, are of paramount significance. Further, gate oxides are a critical component of TFTs, and must exhibit low leakage currents and self-healing breakdown in order to ensure optimal TFTs switching performance and reliability. Thus, the objective of this work was twofold: (1) develop an understanding of the processing-structure-property relationships of ZnO and high-κ BaTa2O6 and Al2O3 (2) understand the electronic defect structure of BaTa2O6 /ZnO and Al2O3/ZnO interfaces and develop insight to how such interfaces may impact the switching characteristics (speed and switching power) of TFTs featuring these materials. Of the ZnO films grown by atomic layer deposition (ALD), pulsed laser deposition (PLD) and magnetron sputtering at 100-200 °C, the latter method exhibited the best combination of n-type electrical conductivity and optical transparency. These determinations were made using a combination of photoluminescence, photoluminescence excitation, absorption edge and Hall measurements. Metal-insulator-semiconductor devices were then fabricated with sputtered ZnO and high-κ BaTa2O6 and Al2O3 and the interfaces of high-κ BaTa2O6 and Al2O3 with ZnO were analyzed using frequency dependent C-V and G-V measurements. The insulator films were deposited at room temperature by magnetron sputtering using optimized processing conditions. Although the Al2O3 films exhibited a lower breakdown strength and catastrophic breakdown behavior compared to BaTa2O6/ZnO interface, the Al2O3/ZnO interface was characterized by more than an order of magnitude smaller density of interface traps and interface trapped charge. The BaTa2O6 films in addition were characterized by a significantly higher concentration of fixed oxide charge. The transition from accumulation to inversion in the Al2O3 MIS structure was considerably sharper, and occurred at less than one tenth of the voltage required for the same transition in the BaTa2O6 case. The frequency dispersion effects were also noticeably more severe in the BaTa2O6 structures. XPS results suggest that acceptor-like structural defects associated with oxygen vacancies in the non-stoichiometric BaTa2O6 films are responsible for the extensive electrical trapping and poor high frequency response. The Al2O3 films were essentially stoichiometric. The results indicate that amorphous Al2O3 is better suited than BaTa2O6 as a gate oxide for transparent thin film transistor applications where low temperature processing is a prerequisite, assuming of course that the operation voltage of such devices is lower than the breakdown voltage. Also, the operation power for the devices with amorphous Al2O3 is lower than the case for devices with BaTa2O6 due to the smaller fixed oxide charges and interface trap density.
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Masuda, Yoshitake, Mitsuru Ohta, Won-Seon Seo, Wolfram Pitschke, Kunihito Koumoto, 佳丈 増田, and 邦仁 河本. "Structure and thermoelectric transport properties of isoelectronically substituted (ZnO)5In2O3." Elsevier, 2000. http://hdl.handle.net/2237/6208.
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Tu, Wei-Lun Scharf Thomas W. "Processing, structure, and tribological property interrelationships in sputtered nanocrystalline ZnO coatings." [Denton, Tex.] : University of North Texas, 2009. http://digital.library.unt.edu/ark:/67531/metadc12207.
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Yang, Yang, and 楊暘. "Atomic structure studies of zinc oxide (0001) polar surface by low energy electron diffraction at multiple incident angles." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48199515.
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Zinc oxide surfaces have been of considerable interest because of their favorable properties, such as high electron mobility, good transparency, large electronic breakdown field and wide bandgap. Knowing the surface structure of ZnO is the key to better understand the above phenomena and to further develop its applications.
In this thesis, the Patterson Function was evaluated by inversion of LEED I-V spectra at multiple incident angles to determine the surface structure of the ZnO(0001) polar surface. The sample was prepared by degassing and then 15 cycles of argon sputtering and annealing. The experimental LEED I-V spectra from multiple incident angles were taken from the sample. After processing the data by a macro program in OPTIMAS and a Matlab program, a clean Patterson Function map showing the inter-atomic pair distances was obtained. It was then compared with the simulated Patterson Function map of the proposed 1×1 bare surface model. As a result, the spots positions in the simulated Patterson Function map matched well with that of the experimental Patterson Function map.
On the other hand, the LEED I-V curve fitting work was done by the surface science group of City University of Hong Kong. Six models were proposed by them and normal incidence theoretical LEED I-V spectra were calculated to fit with the experimental LEED I-V curves provided by us. Among the six models 2×2 Zn point defect model was fitted to be the best model with the R-factor 0.244. We also compared the multiple scattering simulated Patterson Function map of 2×2 Zn point defect model with the experimental one to verify the validity of the model. As a result, the model fit the experimental data. So we conclude that in general 1×1 model support the order part, and 2×2 top layer Zn defect model best fits the random missing part.published_or_final_version
Physics
Master
Master of Philosophy
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Günter, Marco Maria. "Structure and activity of copper-zinc oxide catalysts studied using X-ray diffraction and absorption spectroscopy." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=962998508.
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Önsten, Anneli. "Surface Reactivity and Electronic Structure of Metal Oxides." Doctoral thesis, KTH, Materialfysik, MF, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-33667.
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The foci of this thesis are the metal oxides Cu2O, ZnO and Fe3O4 and their interaction with water and sulfur dioxide (SO2). The intention is to study SO2-induced atmospheric corrosion on a molecular level. All studies are based on photoelectron spectroscopy (PES) and scanning tunneling microscopy (STM) measurements. The band structure of Cu2O in the Γ-M direction has been probed by angle-resolved PES (ARPES). It reveals a more detailed picture of the bulk band structure than earlier data and gives the first experimental evidence of a dispersive hybridized Cu 3d-Cu 4s state. The experimental data is compared to band structure calculations. The structure of clean metal oxide surfaces and impact of sample preparation have been studied. Oxygen vacancies can form a (√3x√3)R30° reconstruction on Cu2O(111). Oxygen atoms adjacent to copper vacancies, steps or kinks are shown to be adsorption sites for both water and SO2. Annealing temperature influences the defect density and hydrogen content in ZnO, which can have large impact on the surface properties of ZnO(0001). Water is shown to adsorb dissociatively on ZnO(0001) and partly dissociatively on Cu2O(111). The dissociation occurs at undercoordinated oxygen sites on both surfaces. Water stays adsorbed on ZnO(0001) at room temperature but on Cu2O(111), all water has desorbed at 210 K. SO2 interacts with one or two undercoordinated O-sites on all studied oxide surfaces forming SO3 or SO4 species respectively. SO4 on Fe3O4(100) follows the (√2x√2)R45° reconstruction. On Cu2O(111) and ZnO(0001), SO2 adsorbs on defect sites. An SO3 to SO4 transition is observed on Cu2O(111) when heating an SO3 adsorbate layer from 150 K to 280K. Coadsorption of water and SO2 on ZnO(0001) and Fe3O4(100) has been studied briefly. Water blocks SO2 adsorption sites on ZnO(0001). On Fe3O4(100) and on one type of reduced ZnO(0001) sample, SO2 dissociation to atomic sulfur or sulfide occurs to a higher extent on water exposed surfaces than on clean surfaces. Water thus appears to increase the charge density on some surfaces. Further studies are needed to reveal the cause of this unexpected effect.QC 20110516
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Liu, Bo-Hong [Verfasser]. "Preparation and Structure of Ultra-Thin Zinc Oxide Films on Pt(111), Ag(111) and Cu(111) / Bo-Hong Liu." Berlin : Freie Universität Berlin, 2015. http://d-nb.info/1080522115/34.
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Tisseraud, Céline. "Origine et impact de la synergie Cu-ZnO sur l'hydrogénation catalytique du CO2 en méthanol." Thesis, Poitiers, 2016. http://www.theses.fr/2016POIT2295/document.
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L’hydrogénation catalytique du CO2 est considérée comme l’une des voies de valorisation les plus prometteuses pour la production du méthanol. Cette synthèse, souvent accompagné par une formation de CO, a fait l’objet de nombreuses études dans la littérature. Cependant, les résultats obtenus sur des catalyseurs à base de Cu et de ZnO ont démontré que cette réaction n’est pas aussi simple qu’elle y paraissait. Il y a encore beaucoup de controverses et d’interrogations sur la nature des sites actifs et sur les différentes étapes réactionnelles mises en jeu lors de la réaction. L’objectif de ce travail est d’apporter des éléments de compréhension sur la nature des sites actifs et leur rôle sur l’activation du CO2 et de H2. L’étude sur des catalyseurs modèles (mélanges mécaniques et matériaux préparés par coprécipitation) a permis de mettre en évidence un effet de synergie entre Cu et ZnO lié à des phénomènes de migration. Ce travail a montré que la production de méthanol est étroitement liée à la création d’une phase oxyde de type CuxZn(1-x)Oy (lacunaire en oxygène) induit par un effet de Kirkendall à l’interface Cu-ZnO, favorisant l’épandage de l’hydrogène. Différents modèles mathématiques ont été développés afin de déterminer la concentration des contacts entre Cu et ZnO. Les résultats obtenus ont démontré qu’il est possible de corréler directement l’activité du catalyseur avec la concentration de contacts et que cela peut permettre ainsi de prédire la composition chimique idéale du catalyseur pour un design de matériau donné. L’expertise complète de la relation design-activité a permis le développement de matériaux Cu-ZnO de type cœur-coquille 100% sélectif en méthanolThe catalytic CO2 hydrogenation is considered to be one of the most promising methods for methanol production. This synthesis, often accompanied by a CO formation, had been the subject of many studies in the literature. However, the results obtained on Cu and ZnO based catalysts demonstrated that the reaction is not as simple as it appear to be. There is still a lot of controversies and interrogations concerning the nature of the active sites and the different reactional steps involved during the reaction. The objective of this work is a better understanding of the nature of the active sites and their role on CO2 an H2 activation. A study on model catalysts (mechanical mixtures and materials prepared by coprecipitation) allowed to demonstrate that the synergetic effect between Cu and ZnO linked to a migration phenomenon. This work showed that the methanol production was closely linked to the CuxZn(1-x)Oy oxide phase creation (with oxygen vacancies) induced by a Kirkendall effect on Cu-ZnO interface, thereby promoting the hydrogen spillover. Different mathematical models were developed to determine the concentration of contacts between Cu and ZnO. The results obtained demonstrated that it is possible to directly correlate the catalyst’s activity with the concentration of contacts between Cu and ZnO, which in turn allowed predicting optimal catalyst chemical composition for a particular design of a material. The full expertise of the design-activity relationship allowed the development of Cu-ZnO core-shell type materials with a 100% selective to methanol
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Chung, Wing-lun, and 鍾詠麟. "Determination of surface atomic structures of Bi₂Se₃(111)-(2X2) film and ZnO nano-rods by low energy electron diffraction." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/202356.
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Tu, Wei-Lun. "Processing, Structure, and Tribological Property Interrelationships in Sputtered Nanocrystalline ZnO Coatings." Thesis, University of North Texas, 2009. https://digital.library.unt.edu/ark:/67531/metadc12207/.
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Solid lubricant coatings with controlled microstructures are good candidates in providing lubricity in moving mechanical assembly applications, such as orthopedics and bearing steels. Nanocrystalline ZnO coatings with a layered wurtzite crystal structure have the potential to function as a lubricious material by its defective structure which is controlled by sputter deposition. The interrelationships between sputtered ZnO, its nanocrystalline structure and its lubricity will be discussed in this thesis. The nanocrystalline ZnO coatings were deposited on silicon substrates and Ti alloys by RF magnetron sputtering with different substrate adhesion layers, direct current biases, and temperatures. X-ray diffraction identified that the ZnO (0002) preferred orientation was necessary to achieve low sliding friction and wear along with substrate biasing. In addition, other analyses such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) were utilized to study the solid lubrication mechanisms responsible for low friction and wear.
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Lee, William (Chun-To). "Harvesting Philosopher's Wool: A Study in the Growth, Structure and Optoelectrical Behaviour of Epitaxial ZnO." Thesis, University of Canterbury. Electrical and Computer Engineering, 2008. http://hdl.handle.net/10092/2507.
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This thesis is about the growth of ZnO thin films for optoelectronic applications. ZnO thin films were grown using plasma assisted molecular beam epitaxy and were studied using various conventional and novel characterisation techniques. The significance of different growth variables on growth efficiency was investigated. The growth rate of ZnO films was found to be linearly dependent on the Zn flux under O-rich growth conditions. Under Zn-rich conditions, the growth rate was dependent on both atomic and molecular oxygen flux. By characterising the oxygen plasma generated using different RF power and aperture plate designs and correlating the results with the growth rates observed, it was found that atomic oxygen was the dominant growth species under all conditions. Molecular oxygen also participated in the growth process, with its importance dependent on the aperture plate design. In addition, an increase in growth temperature was found to monotonically decrease the growth rate. A growth rate of 1.4 Å/s was achieved at a growth temperature of 650 ℃ by using an oxygen flow rate of 1.6 standard cubic centimetres utilising a plasma source with a 276 hole plate operating at 400 W, and a Zn flux 1.4✕10¹⁵ atoms/cm²⋅s. Characterisation of the MBE grown thin films revealed that the qualities of ZnO thin films were dependent on the growth conditions. Experimental evidence suggested that a maximum adatom diffusion rate can be achieved under Zn-rich conditions, giving samples with the best structural quality. O-rich conditions in general led to statistical roughening which resulted in rough and irregular film surfaces. Experimental results also suggested that by increasing the atomic oxygen content and decreasing the ion content of the plasma, the excitonic emission of the ZnO thin films can possibly be improved. It was also found that the conductivity of the films can possibly be reduced by increasing the plasma ion content. By investigating the evolution of the buffer layer surface during the early stages of growth, dislocation nucleation and surface roughening were found to be important strain relief mechanisms in MBE grown ZnO thin films that affected the crystal quality. The usage of LT-buffer layers was found to improve substrate wetting, and was shown to significantly reduce dislocation propagation. Further strain reduction was achieved via the application of a 1 nm MgO buffer layer, and a significant reduction of carrier concentration and improvement in optical quality was subsequently observed. A carrier concentration of <1✕10¹⁶ cm⁻³ and a near band emission full width half maximum of 2 meV was observed for the best sample. The study of electrical characteristics using the variable magnetic field Hall effect confirmed the existence of a degenerate carrier and a bulk carrier in most MBE grown ZnO thin films. The bulk carrier mobility was measured to be ~120 - 150 cm²/Vs for most as-grown samples, comparable to the best reported value. A typical bulk carrier concentration of ~1✕10¹⁶ - 1✕10¹⁸ cm⁻³ was observed for as-grown samples. Annealing was found to increase the mobility of the bulk carrier to ~120 - 225 cm²/Vs and decrease the bulk carrier concentration by two orders of magnitude. Using time resolved photoluminescence, it was found that the radiative recombination in MBE grown ZnO thin films was dominated by excitonic processes, and followed a T³⁄² trend with temperature. A maximum radiative lifetime of 10 ns was observed for as-grown samples. The non-radiative lifetime in ZnO thin films was dominated by the Shockley-Read-Hall recombination processes. The modelling of the temperature dependence of the non-radiative lifetime suggested that an electron trap at ~0.065 eV and a hole trap at ~0.1 eV may be present in these samples. The application of time resolved photoluminescence also allowed the direct observation of carrier freeze-out in these ZnO films at low temperature.
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Tarkin, Eylem. "Characterization And Study Of Solution Properties Of Poly(propylene Oxide) Synthesized By Metal Xanthate Catalysts." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1086099/index.pdf.
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Zinc xanthates polymerize propylene oxide into high polymer (PPO) with coordination mechanism. In order to identify structure and stereoisomerisms of this polymer, PPO was subjected to thermal and column fractionation. Obtained fractions were characterized by end-group analysis, cryoscopy, viscometry, IR and 13C-NMR spectroscopy, melting temperature. PPO is composed of a high molecular weight, stereoregular, crystallizable polymer (K-polymer) with low molecular weight (=500 g/mol) D-polymer. Presence of double bonds and hydroxyl terminals was interpreted as the product of an anionic mechanism.
K-Polymers can be thermally fractionated on the basis of their melting temperature (Tm) rather than molecular weight (Mwt). It’
s found that higher Tm fractions have lower Mwt, but they precipitate at higher temperatures than higher Mwt but lower Tm fractions. In column fractionation, K-polymers were deposited on glass beads from isooctane solution in a narrow temperature interval. Then the precipitated samples were split into a number of fractions by using again isooctane but at a higher temperature than the precipitation temperature by increasing residence time from 5 minutes to several hours. It&
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s found that rate of solubility is not controlled by molecular weight, but controlled by percentage crystallinity and Tm. Highest Tm polymers, with relatively higher Mwt showed faster rate of solution than that of lower Tm, lower Mwt but higher percent crystalline fractions. This discrepancy was accounted by suggesting a stereo-block structure where tactic blocks are bound each other with non-crystallizable atactic blocks. The mechanism of polymerization was also discussed in some detail.
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Gutmann, Sebastian. "Electronic Structure Characterization of Nanocrystalline Surfaces and Interfaces with Photoemission Spectroscopy." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3137.
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In this study, photoemission spectroscopy (PES) was used to investigate the electronic properties of nanocrystalline titanium dioxide (TiO2), zinc oxide (ZnO), and cadmium selenide (CdSe). Electrospray deposition technique enabled the preparation of thin films in vacuum from a dispersion prepared outside the vacuum chamber. This method also allowed the step-wise formation of interfaces and the monitoring of the evolution of the electronic structure with intermittent PES characterization. The work function of nanocrystalline TiO2 and ZnO was measured with ultraviolet photoemission spectroscopy (UPS) and low-intensity x-ray photoemission spectroscopy (LIXPS). Measurements on environmentally contaminated surfaces revealed an instantaneous and permanent work function decrease of 0.3-0.5 eV upon exposure to ultraviolet radiation during a UPS measurement. The work function reduction is likely to be related to the formation of a surface dipole caused by the photo-chemical hydroxylation of surface defects. This phenomenon was further investigated with regard to its influence on the electronic structure of the indium tin oxide (ITO)/TiO2 interface found in dye-sensitized solar cells. The experiments suggest that UV radiation can cause a small but significant change of the charge injection barriers at the interface. The determined band line-ups revealed electron injection barriers of ~0.3-0.5 eV, while UV radiation caused an increase of about 0.15 eV. This might have the potential to further impede electron transfer to the ITO electrode and affect the performance of solar cell device. Another type of photovoltaic cell using nanocrystalline material is a heterojunction bulk solar cell. Conversion efficiencies of such devices are currently only about 3% due to the inefficient charge separation at interfaces formed by blending organic and inorganic material. An approach to improve efficiencies in such devices is the use of covalently bonded conductive polymer/inorganic hybrid nanocrystals. In this study a prototypical model system was investigated with PES with the aim to develop a measurement protocol that allows the determination of electronic properties for such hybrid materials. The comparison of the relative core-level binding energies of the organics-functionalized CdSe nanocrystal compared to the ligand-free CdSe nanocrystal and the arylselenophosphate ligand material enabled the determination of the electronic structure at the interface. Core-level measurements support the hypothesis that the Se functionality of the organic ligand coordinates to the Cd sites on the nanopthesis surface.
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Deinert, Jan-Christoph [Verfasser], Julia [Akademischer Betreuer] Stähler, Martin [Akademischer Betreuer] Wolf, Martin [Gutachter] Wolf, Mario [Gutachter] Dähne, and Julia [Gutachter] Stähler. "Zinc oxide surfaces and interfaces: electronic structure and dynamics of excited states / Jan-Christoph Deinert ; Gutachter: Martin Wolf, Mario Dähne, Julia Stähler ; Julia Stähler, Martin Wolf." Berlin : Technische Universität Berlin, 2016. http://d-nb.info/1156016134/34.
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Köhl, Dominik [Verfasser]. "The influence of energetic bombardment on the structure formation of sputtered zinc oxide films : development of an atomistic growth model and its application to tailor thin film properties / Dominik Köhl." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2011. http://d-nb.info/1018218637/34.
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Dumergue, Mathieu. "Luminescence ultraviolette et dynamiques excitoniques dans l’oxyde de zinc massif et nano-structuré." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0032/document.
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Cette thèse présente les travaux effectués au CELIA sur la luminescence ultraviolette et les dynamiques excitoniques dans l’oxyde de zinc (ZnO) sous forme massive et nano-structurée. Les mesures ont été effectuées en conditions expérimentales contrôlées (température, fluence d’excitation), pour différentes énergies de photon excitateur. Nous avons mesuré les spectres d’émission sous excitation à un photon UV (4,66 eV), ainsi que à 3 photons IR (1,55 eV), et proposé un schéma séquentiel de formation des excitons (avec simulations), en particulier pour les excitons DX. Nous avons obtenu une durée de vie nanoseconde de DX dans les deux cas, en désaccord avec la majorité des études publiées dans la littératureThis thesis presents the work carried out at CELIA about ultraviolet luminescence and exciton dynamics in massive and nano-structured zinc oxide (ZnO). Measurements were carried out under controlled experimental conditions (temperature, excitation fluence), according to different excitation photon energies.We measured emission spectra under UV photon excitation (4.66 eV), and 3 IR photons (1.55 eV), and suggested a sequential exciton formation mechanism (with simulations), especially for DX excitons. We found a nanosecond lifetime for DX in both cases, in disagreement with most of the studies published in the literature. Relaxation dynamics of free and bound excitons are linked by the FX trapping process on donor defect and the DX thermal detrapping.Under VUV excitation (20-50 eV), surface effects and strong local excitation density greatly accelerate the relaxation of excitons. Under X excitation (1 keV), good conditions for the formation of DX seems to be close under excitation at 1.55 and 950 eV.The presence of core 2p band of zinc modifies the relaxation dynamics of excitons by the multiplication of local high density excitations zones and the change of the elementary excitations distribution. We have also conducted measurements on nano-particles. The significant surface effects induced by the small size of these system lead to a sharp acceleration of kinetics, masking the intrinsic exciton relaxation process
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Ding, Lu. "Optical and magneto-optical studies of crystalline and nano-structured zinc oxide /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202007%20LU.
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Lord, Alexander M. "Electronic and structural properties of Au contacts on ZnO nanowires." Thesis, Swansea University, 2013. https://cronfa.swan.ac.uk/Record/cronfa42804.
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Zinc Oxide has emerged from an unspectacular past in the field of electronics to become one of the most widely researched materials for future devices. Here we investigate the growth and electrical properties of semiconducting ZnO nanowires for future application in the field of Nano-Devices and present a solution to control the behaviour of the electrical contacts. ZnO nanowires (NWs) from initial growth experimentation and optimisation have been thoroughly characterised both structurally and electrically. Structural characterisation revealed the high quality of nanowires from vapour phase and hydrothermal growth that translated to similar measurements of nanowire resistivity. We have confirmed the results of atomic resolution dark field imaging with simulations that no Au catalyst contaminates ZnO nanowires, which makes the material more desirable than Silicon or GaAs. Within the limits of the dark field imaging the interface of the catalyst particle and the nanowire is abrupt, clean and intimate, with no Au diffusion, interfacial layers or roughness. Electron microscopy reveals the Au has an epitaxial relationship with the ZnO and is solid during growth. Using fabrication and contamination free nanoprobe measurements (four-probe scanning tunnelling microscope) in vacuum a transition from rectifying to Ohmic is dependent on contact size and not the materials or structural variations. We have shown this with the application of the nanoprobe on free standing as-grown catalysed ZnO nanowires. Using the most common nanowire growth methods the structure has been thoroughly characterised to allow the interpretation of electrical measurements of resistivity and Au end contacts. A regime of size dependent contacts to ZnO nanowires provides the necessary knowledge and requirements to fabricate ZnO nanowire devices with controlled properties and function. This is a major hurdle for nanodevices overcome without complicated or difficult processing steps. A nanodevice can be fabricated from a substrate, with contacts, in one- step and with tailored interface properties by controlling the catalyst particle size.
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Skopin, Evgenii. "Etude des premiers instants du dépôt chimique par flux alternés (ALD) de films ZnO ultra minces sur In0,53Ga0,47As, dans le but d'optimiser la résistance de contact d'une structure MIS." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAY016/document.
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Ce travail porte sur l'étude des étapes initiales du dépôt de couches atomiques de ZnO (ALD) sur une surface (100) de In0,57Ga0,43As, par l'utilisation de techniques de caractérisation in situ (rayonnement synchrotron). En raison de la grande mobilité des électrons, le semi-conducteur III-V InGaAs est un matériau potentiel pour remplacer le canal de Silicium dans les transistors à effet de champ (MOSFET). Afin de diminuer la hauteur de la barrière Schottky et la résistance de contact, une couche ultra-mince (tunnel) de ZnO peut être insérée entre le métal et le semiconducteur InGaAs. Au cours de ces dernières années, la technique ALD, compatible avec les spécifications de l'industrie et basée sur des réactions chimiques de surface auto-limitantes, est utilisée pour la fabrication de films minces conformes et homogènes avec un contrôle sub-nanométrique de l’épaisseur. Cependant, le comportement au cours de la croissance diffère fortement en fonction de la surface du substrat. Ainsi, l'étude des premières étapes ALD est particulièrement intéressante afin d’améliorer la compréhension des mécanismes de croissance en vue de la création de films ultra-minces.Pour ce faire, nous avons développé et mis à niveau un réacteur thermique ALD (MOON) dédié. Il peut être installé sur des lignes de lumière synchrotron afin d’étudier la croissance des matériaux in situ avec des techniques telles que la fluorescence X, l’absorption X, la spectroscopie des rayons X ainsi que la diffraction X en incidence rasante. De plus, des techniques optiques de caractérisation in situ peuvent être utilisées en laboratoire ou couplées en milieu synchrotron. Les expériences au synchrotron ont été réalisées sur les lignes de lumière SIRIUS (SOLEIL, Saint-Aubin (France)) et ID3 (ESRF, Grenoble (France)).Nous montrons que dans sa phase initiale, la croissance ALD de ZnO est inhibée par le substrat (100) InGaAs, ce qui conduit à un régime transitoire avant le régime de croissance ALD stable. La première phase du régime transitoire conduit à la formation d’une couche d’oxyde de Zinc, ultra-mince (~1 nm d'épaisseur), fabriquée avec un taux de croissance très faible. L'absorption X et la diffusion X en incidence rasante montrent qu’à ce stade le matériau ZnO est désordonné (non cristallisé) et présente un ordre à courte distance caractérisé par une structure wurtzite embryonnaire. Ensuite, le régime transitoire entre dans une deuxième phase (croissance 3D), le taux de croissance par cycle (GPC) augmente, atteint un maximum puis diminue jusqu'à une valeur constante (croissance ALD stable). Afin de mieux comprendre le mode de croissance 3D nous avons développé un modèle géométrique qui schématise la croissance d’îlots hémisphériques par ALD. Ce modèle permet d'obtenir des paramètres quantitatifs de croissance.En modifiant le débit d’eau (H2O) utilisée comme réactif pendant le processus ALD, il est possible de contrôler le délai (ou le nombre de cycles) avant le début de la croissance 3D. Cet effet est très probablement lié à la variation de la densité des groupes hydroxyle à la surface de l'InGaAs. Par ailleurs, nous avons caractérisé la croissance ALD de ZnO pour différentes températures du substrat InGaAs (dans et hors fenêtre ALD). Les cartes de diffusion des RX réalisées en cours de dépôt, montrent l’apparition d’une phase cristallisée à longue distance en lien avec le démarrage de la croissance 3D. À température élevée, hors de la fenêtre ALD, nous observons une texturation de la couche ZnO lorsque son épaisseur augmente. Aucune relation d’épitaxie n’est observée.Enfin, nous rendons compte de l'utilisation de couches ZnO ultraminces sur InGaAs pour les contacts électriques. La résistance de contact des échantillons de métal/ZnO/InGaAs a été mesurée à l'aide de la méthode Transfert Length Method (TLM). Nous montrons que la résistivité de contact spécifique des tampons Al/p-InGaAs est réduite par l’insertion d’une couche tunnel ZnO entre l'Al et l'InGaAs dopé pThis work focuses on the study of the initial stages of ZnO atomic layer deposition (ALD) on atomically flat (100) In0.57Ga0.43As surface, notably by using in situ synchrotron techniques. Due to high electron mobility, III-V InGaAs semiconductor has been recognized as a promising material to replace Silicon channel in the metal-oxide-semiconductor-field-effect transistors (MOSFET). Ultrathin ZnO layer on InGaAs can be used as a passivation layer at the interface with the gate transistor dielectric, as well as tunneling layer inserted in between metal/InGaAs contact to decrease the Schottky barrier height and the contact resistance. In the recent years, ALD technique based on self-limiting surface chemical reactions has received world-wide attention for manufacturing highly conformal and homogeneous thin films with sub-nanometer thickness control at low temperatures compatible with industry specifications. However, the growth behavior strongly differs depending on the substrate surfaces. Thus for the creation of few monolayers thick films, the study of ALD in the initial stages of growth is of particular interest for improving the understanding of the growth mechanisms.For that purpose, we have developed and upgraded a thermal ALD reactor (MOON:MOCVD/ALD growth of Oxide Nanostructures) dedicated to monitor the growth of materials by in situ characterization techniques. The MOON reactor can be moved to synchrotron centers for monitoring material growth in situ by using X-ray based techniques, notably X-ray fluorescence, X-ray absorption, XRR, and grazing incidence diffraction. Also, optical in situ techniques can be used in the laboratory. In this work, we show the results of experiments obtained at two synchrotron beamlines, i.e. SIRIUS (SOLEIL, Saint-Aubin (France)) and ID3 (ESRF, Grenoble (France)).We show that ZnO growth in the initial stages is inhibited by the (100) InGaAs substrate, leading to a transient regime prior to the steady ALD is achieved. We report a detailed investigation of this transient regime and find that an ultra-thin (~1-nm-thick) 2D layer is indeed fabricated but with a growth rate so low that one may believe that nothing has been deposited on the surface. We identify the structural and chemical properties of that ultra-thin layer. Only afterward does the substrate inhibited of type 2 growth mode begins: as the cycle number increases, the growth per cycle (GPC) increases, then reaches a maximum and level down to a constant value (steady growth). For a better understanding of the 3D growth mode by reproducing the experimental growth per cycle curves we have developed a geometric model that schematizes the growth of hemispheroid islands by ALD. We show that this model allows obtaining quantitative growth parameters.When water is used as a reactant, we showed that by changing the water flow during the ALD process, it is possible to control the time delay (or cycle number) prior to 3D growth begins. It is very likely that the water flow controls the density of hydroxyl groups on the InGaAs surface. We also demonstrated ZnO ALD for different InGaAs substrate temperatures. By combining in situ X-ray absorption and grazing incidence scattering techniques, we identified a short-range-order atomic structure of the ZnO material, with an embryonic ZnO wurtzite, prior to 3D growth, then a long-range-order structure is detected both by X-ray absorption and X-ray diffraction, together with the appearance of a microstructure. At higher growth temperature, outside of the ALD window, we observed the well-known ZnO texturing when the layer thickness increases.At last, we report on the use of ultrathin ZnO layers on InGaAs in the electrical contact structure. The contact resistance of metal/ZnO/InGaAs samples was measured using Transfer Length Method (TLM). We show that specific contact resistivity of Al/p-InGaAs pads is reduced by inserting a ZnO tunnel layer in between Al and p-doped InGaAs
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Offenberger, Sean Alan. "Investigation of Zinc Oxide Nanowires for Impedance Based Structural Health Monitoring." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/82502.
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The goal of this work is to investigate the piezoelectricity of composite laminates embedded with layers of zinc oxide (ZnO) nanowires. ZnO nanowire embedded composites have the potential to sense and actuate giving the potential for these smart composites to serve the function of being load bearing structures and monitoring the integrity of the structure. This work examines the piezoelectric characteristics of composite beams by investigating their electromechanical coupling in the form of vibration under the presence of electrical excitation. With the help of a mathematical model, piezoelectric constants are estimated for these samples. A layer of ZnO nanowires were grown on plane woven fiberglass fabric that was incorporated into a carbon fiber epoxy composite. The beam deflection velocity was measured as a varying voltage was applied to the composite. Using Hamilton's Principle and Galerkin's method of weighted residuals, a mathematical model was derived to estimate piezoelectric constants for the composites from the experimental data. Piezoelectric properties were determined using vibrational testing and a mathematical model. Piezoelectric constants h31, g31, and d31 were estimated to be 9.138 E7 V/m, 6.092 E-4 Vm/N, and 2.46 E-14 respectively. To demonstrate the electromechanical coupling, ZnO nanowire composites were bonded to Al beams that were progressively damaged to determine if a change in electrical impedance could be observed to correspond to the change in structural impedance of the host beam. Changes in impedance were detected by a change in root mean squared deviation damage metric M. A significant correlation was shown between increasing damage in the host beam and an increase in damage metric M.Master of Science
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Zou, Lanlan, and 邹兰兰. "Annealing studies on the structural and magnetical properties of Co implanted ZnO single crystal." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49799691.
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As a wide band gap semiconductor, Zinc Oxide (ZnO) has recently attracted considerable attention due to its wide applicability. Transition metal (TM) doped ZnO is one of the most intensive research field in the last decade because of its possible application in spintronics devices. The Co-implanted ZnO has been considered as one of the most promising candidate in the field of diluted magnetic semiconductor (DMS).
In this study, the magnetic and structural properties of Co-implanted ZnO single crystal were investigated. ZnO single crystals were implanted with 100 keV-Co ions at 300K with a fluence of 1014cm-2and subsequently annealed at 750oC and 900oC respectively. The samples were studied by secondary ion mass spectrometry, X-ray diffraction, photoluminescence, X-ray photoemission spectroscopy and vibrating sample magnetometer. The as-implanted sample seemed to be phase pure while the spinel secondary phase ZnCo2O4 was present in 750oC and 900oC samples showed trace ofCo3O4,Zn0.52Co2.48O4 and metallic Co cluster. All the samples exhibited ferromagnetism at room temperature in low field region, and the magnetic moment was found to decrease and increase after the heat treatment. In high field region, typical paramagnetism was the dominating magnetic property. More than one ferromagnetic mechanism is involved to explain the experimental results.published_or_final_version
Physics
Master
Master of Philosophy
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Piot, Lucas. "Influence de l’énergie d’interface sur les transitions de phase sous pression : étude de nanoparticules d’oxydes fonctionnels." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10238/document.
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La modification des diagrammes de phase sous pression dans les nanomatériaux en comparaison de matériaux massifs est généralement reliée de façon univoque à l'énergie de surface. L'objectif de ce travail a consisté à étudier l'influence de l'énergie d'interface, définie par l'état de surface (défauts cristallins et chimie de surface) et l'énergie de surface, sur le comportement à haute pression de différents nanomatériaux pour lesquels un effet de taille est fréquemment rapporté. Le contrôle et la caractérisation de l'état de surface de nanoparticules d'Y2O3 nous ont permis de montrer que l'amorphisation sous pression rapportée dans la littérature n'est pas uniquement due à la réduction de la taille de grain mais nécessite une densité de défauts initiale, généralement non contrôlée. Une forte dépendance en taille de la pression de transition dans ZnO est avancée dans la littérature. L'étude sous pression de différents échantillons nanométriques de ZnO (issus de diverses voies de synthèse) a été effectuée par spectroscopie Raman et diffraction de rayons X. La qualité cristalline de ces derniers a été estimée par Photoluminescence, XPS, Raman et IR. Tandis que les échantillons présentant une forte densité de défauts conduisent à une augmentation de la pression de transition, le comportement d'un échantillon "sans défauts" ne diffère que peu de celui de ZnO massif. Différentes approches et extensions de modèles thermodynamiques sont proposées: modèles de Gibbs, Landau et Ginzburg-Landau. Ces derniers ouvrent la voie à la définition d'un protocole expérimental permettant d'obtenir des données fiables pour étudier les transitions de phase de nanomatériaux sous pressionThe modification of phase diagrams under pressure into nanosized materials in comparison with bulk ones is usually attributed to surface energy. The goal of this work has consisted into studying the influence of interface energy, which includes both the surface state (crystalline defects and surface chemistry) and surface energy, on the high-pressure behavior of several nanomaterials for which size effects has been reported. The control and characterization of the surface state for Y2O3 nanoparticles has enabled us to show that the pressure induced amorphization reported into literature is not only linked to size reduction but require an initial density of defects A strong size dependence of ZnO transition pressure is claimed into literature. The high-pressure study of different ZnO nanometric samples (obtained through several ways of synthesis) has been performed by Raman spectroscopy and X-ray diffraction. The crystalline quality of our samples has been investigated by photoluminescence, XPS, Raman and IR. Whereas samples exhibiting a high density of defects lead to an increase of pressure transition, the behaviour of “defect free” nanoparticles is rather equivalent to bulk one. Several approaches and extensions of thermodynamic models are submitted: model of Gibbs, Landau and Ginzburg-Landau. Those models open the way to the definition of an experimental protocol which allow to obtain reliable data in order to study phase transitions of nanomaterials under pressure
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Ross, Ian Mark. "Structural development and physical characterisation of undoped and doped zinc oxide powders." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366428.
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Tola, Pascal. "Détection visible de l'EXAFS : une nouvelle méthode de détection de la structure fine des spectres d'absorption X." Nancy 1, 1992. http://www.theses.fr/1992NAN10002.
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La détection visible de l'EXAFS (extended x-ray absorption fine structure) est une méthode spectroscopique récente qui permet dans certains cas de l'enregistrement du spectre de photoabsorption X et de ses oscillations fines. Le principal avantage escompté est la sélectivité de sites cristallochimiques, qui n'est pas obtenue par les méthodes classiques. Comme l'EXAFS, elle requiert l'emploi du rayonnement synchrotron monochromatisé, et le montage expérimental s'apparente aux techniques XEOL (x-ray emission optical luminescence). Après un rappel de la théorie mise en jeu dans les techniques d'absorption et de fluorescence X. Une analyse XEOL de quelques composés (semiconducteurs, terres rares, porphyrines) est proposée dans une partie expérimentale dont le critère principal est la recherche d'une grande intensité dans les pannes d'émission. Les premiers résultats montrent que l'on a bien également accès, par transformée de Fourier du spectre d'excitation de luminescence, aux distances entre proches voisins dans les systèmes étudies. La sélectivité de site recherchée est atteinte dans l'exemple caractéristique du mélange hétérogène zno/zn tpp. Un transfert d'énergie cohérent est détecté dans certains cas (ex. Zns: tm). Les conditions expérimentales de mesure ont été trouvées déterminantes (échantillons minces, mode réflexion). De plus, la corrélation responsable de la forme exacte du spectre obtenu en détection visible avec les spectres d'absorption ne semble pas élémentaire. Il pourrait donc subsister d'autres limitations a cette méthode.
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Karaliūnas, Mindaugas. "Investigation of Zinc Oxide Heterostructures for Optoelectronic Devices by Means of Spectroscopy Methods." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2013~D_20130925_093437-48058.
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In doctoral dissertation, results of investigation on zinc oxide based semiconductor layers and heterostructures for application in optoelectronics by spectroscopy methods are presented. High quality zinc oxide layers and heterostructures were characterized optically. That is ZnO, ZnO:Ga and MgZnO epitaxial layers grown by molecular beam epitaxy technique, ZnO:N layers grown by magnetron sputtering method, CdZnO/ZnO quantum wells structures for light-emitting diodes grown on GaN layers by combined molecular beam epitaxy and metalorganic chemical vapor deposition techniques. In this work, new data on dynamics and interaction of photoexcited carriers in zinc oxide based structures were acquired. It was shown, that the contribution of impurities bound excitons in the inelastic interaction of free excitons influences the position of luminescence band of the interaction in spectrum. In MgZnO epitaxial layers, the localization of carriers in the field of two different localization centers is described. Due to the localization the radiative recombination efficiency increases significantly and it has importance for application in optoelectronic devices. Investigation of the CdZnO/ZnO quantum wells structures for green spectral range light-emitting diodes showed that low radiative recombination efficiency at room temperature is mainly due to weak carrier localization effect, which is responsible for high efficiency of conventional InGaN/GaN quantum wells structures.Daktaro disertacijoje pristatomi cinko oksido pagrindu užaugintų puslaidininkinių sluoksnių ir jų įvairialyčių darinių, skirtų taikymams optoelektronikoje, tyrimų rezultatai spektroskopijos metodais. Optiškai charakterizuoti aukštos kokybės cinko oksido sluoksniai ir jų įvairialyčiai dariniai: ZnO, ZnO:Ga ir MgZnO epitaksiniai sluoksniai, auginti molekulinės epitaksijos būdu, ZnO:N sluoksniai, auginti magnetroninio dulkinimo būdu, šviesos diodams paruošti CdZnO/ZnO kvantinių duobių dariniai ant GaN sluoksnių, auginti apjungiant molekulinės epitaksijos ir cheminio metaloorganinio junginio nusodinimo iš dujinės fazės auginimo metodus. Šiame darbe surinkta naujų duomenų apie fotosužadintų krūvininkų dinamiką ir sąveiką cinko oksido dariniuose. Nustatyta, kad netamprioje laisvų eksitonų sąveikoje dalyvaujantys prie priemaišų pririšti eksitonai įtakoja sąveikos liuminescencijos juostos padėtį spektre. Aprašyta krūvininkų lokalizacija MgZnO epitaksiniuose sluoksniuose dviejų skirtungų lokalizacijos centrų lauke. Dėl to žymiai padidėja spindulinės rekombinacijos efektyvumas, kas turi didelės svarbos taikymams optoelektronikos prietaisams. CdZnO/ZnO kvantinių duobių darinių, skirtų žalios spektro srities šviesos diodams, tyrimai parodė, kad mažas spindulinės rekombinacijos efektyvumas kambario temperatūroje yra dėl ženkliai silpnesnio krūvninkų lokalizacijos efekto, kuris užtikrina didelį efektyvumą įprastuose InGaN/GaN kvantinių duobių dariniuose.
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Ghifari, Najla. "Microfluidic-based colloidal ZnO microcapsules : synthesis, structure,organization and first applications." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST066.
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Ce travail se concentre sur le développement d’une approche microfluidique originale à base degouttelettes pour générer des sphères de ZnO de taille micrométrique très monodispersées avec une taille et une morphologie bien contrôlées. Cette approche est simple et prometteuse non seulement pour la fabrication de microcapsules de ZnO de taille uniforme, avec une taille ajustable et un contrôle précis à l’échelle micrométrique, mais aussi pour acquérir de nouvelles connaissances sur la compréhension des processus de croissance colloïdale et l’auto-organisation des nanoparticules de ZnO par la voie microfluidique. En outre, ces microparticules peuvent trouver des applications intéressantes dans de nombreux domaines tels que la photonique, le photovoltaïque ou la biomédecine. Ce travail porte sur l’effet des paramètres de fabrication sur la formation de gouttelettes, la taille et la stabilité des microsphères résultantes, ainsi que sur l’étude de leurs propriétés optiques et électriques, encouplant les travaux expérimentaux et théoriques. Nous avons montré la synthèse, dans une gamme micrométrique allant de 10 µm à 30 µm, de microcapsules de ZnO mésoporeuses à enveloppe fine et flexible. Nous étudions la caractéristique polaire des nanoparticules de ZnO et leur auto-organisation interfaciale. En outre, nous révélons que les charges électriques portées par lesunités primaires de ZnO jouent un rôle crucial dans la stabilité des gouttelettes en présence et en absence de molécules chargées. Elle joue également un rôle clé tout au long du processus d’assemblage, de la création des nanoparticules colloïdales de ZnO aux microgouttelettes, et enfin aux microsphères. Nous rapportons, pour la première fois, l’auto-organisation de microgouttelettes de ZnO liquide dopé en réseaux carrés. Nous démontrons qu’un tel résultat révèle l’aspect polaire des microgouttelettes de ZnO et corrobore un changement d’équilibre entre les forces motrices contrôlant l’organisation des nanoparticules de ZnO à l’échelle nanométrique. Nous avons développé différents modèles, en très bon accord avec le champdipolaire et les mécanismes de forces interfaciales, pour étayer les résultatsexpérimentaux mis en avant, et pour expliquer l’organisation interfaciale des nanoparticules de ZnO/RhB sur la base des propriétés d’organisation des gouttelettes de ZnO. À partir de nos résultats et de la dépendance constatée de la taille des microcapsules, de l’épaisseur de la coquille et de la densité de surface des nanoparticules par rapport à la taille des gouttelettes, nous fournissons un modèle original de la contribution des facteurs impliqués dans le mécanisme de formation de la coquilleThis work focuses on the development of an original droplet-based microfluidics approach to generate highly monodisperse micrometer-sized ZnO spheres with well-controlled size and morphology. This approach is straightforward, and promising not only for the fabrication of uniform-sized ZnO microcapsules, with adjustable size and precise control at the microscale, but also for gaining new insights into the understanding of colloidal growth processes and self-organization of ZnO nanoparticles by the microfluidic route. In addition, such microparticles may find interesting applications in many areas such as photonics, photovoltaics, or biomedecine. This work deals with the effect of handling parameters on droplet formation, size, and stability of the resulting microspheres, as well as the study of their optical and electrical properties coupling experimental and theoretical works. We have shown the synthesis, in a micrometric range from 10 mm to 30 mm, of mesoporous ZnO microcapsules with a thin and flexible shell. We investigate the polar feature of ZnO nanoparticles and their interfacial self-organization. Besides, we reveal that the electric charges carried by ZnO primary units play a crucial role in the stability of the droplets in the presence and in the absence of charged molecules. It also plays a key role throughout the assembly process from the creation of the colloidal ZnO nanoparticles to the microdroplets, and finally the microspheres. We report, for the first time, the selforganization of doped-ZnO liquid microdroplets in square arrays. We demonstrate that such a result discloses the polar aspect of ZnO microdroplets and corroborate a shift in the balance between the driving forces controlling the ZnO nanoparticles organization at the nanoscale. We have developed different models, in very good agreement with the dipole-field and interfacial forces mechanisms, to support the experimental results put forward, and to explain the ZnO/RhB nanoparticles interfacial organization based on ZnO droplets organization properties. Based on our findings, and on the stated dependence of the microcapsules size, shell thickness, and nanoparticles surface density versus the droplets size, we provide an original model for the contribution of the involved factors in the shell formation mechanism
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PEREIRA, LUCIANO F. D. "Estudo do gradiente de campo elétrico e da estrutura eletrônica do ZnO dopado com Co e Cd e do HfOsub(2) dopado com Ta por cálculos de primeiros princípios." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10031.
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Made available in DSpace on 2014-10-09T12:34:00Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:01:05Z (GMT). No. of bitstreams: 0
Tese (Doutoramento)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Pandey, Bimal. "Synthesis, Characterization, Structural, and Optical Properties of Zinc Oxide Nanostructures Embedded in Silicon Based Substrates." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc500222/.
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Structural and optical properties of ZnO nanostructures synthesized by low energy ion implantation technique were examined. ZnO molecular ions were implanted into Si/SiO2 substrates at room temperature and then furnace annealed under different temperatures and environments. In all as-implanted samples only Zn nanostructures with varying diameters distributed into the Si/SiO2 matrices were observed. No trace of ZnO was found. The distributions of Zn nanostructures in Si/SiO2 closely matched results from Stopping and Range of Ions in Matter (SRIM) simulations. During annealing at 750 oC, Zn diffused both toward and away from the surface of the substrate and combine with oxygen to form ZnO nanostructures. At higher annealing temperatures ZnO bonding started to break down and transfer to zinc silicate (Zn2SiO4), and at 900 oC the ZnO was completely converted into Zn2SiO4. The average sizes of Zn/ZnO nanostructures depended on the ion fluence. If the fluence increased the average sizes of nanostructures also increased and vice versa. For room temperature photoluminescence (RT-PL), band-edge emission in the ultraviolet (UV) region was observed from all samples annealed at 700 oC/750 oC and were slightly blue shifted as compare to bulk ZnO. Donor-bound exciton (D,X) and acceptor-bound exciton (A,X) transitions were observed in low temperature photoluminescence (PL). The lifetime of both donor-bound excitonic emission (D, X) and acceptor-bound excitonic emission (A, X) were found to be in the picosecond (ps) range.
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Liu, Zhaoting. "Synthesis, characterization and properties of wood-templated oxides with hierarchical porous structures." Troyes, 2009. http://www.theses.fr/2009TROY0004.
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Les nouveaux morph-génétiques poreux matériaux ont des potentielles applications dans les domaines de séparation et purification des matières, de l’adsorption sélective, de la fonction optique et de la conception de capteurs. Mais il est difficile de fabriquer ce genre de matériau par les techniques traditionnelles. Du fait de la diversité de ces matériaux, les structures bois morph-génétiques poreuses sont complexes et sont formées par les organismes eux-mêmes (morph-transformation génétique). Inspiré par cette transformation macro-biologique, la technologie morph-transformation génétique peut être utilisée dans la fabrication de ses nouveaux matériaux morph-génétiques poreux. Le but de notre recherche est la mise au point des nouvelles méthodes de fabrication des matériaux morph-génétique à partir de biomodèles oxydes de structure poreuse du bois, d’étudier leurs propriétés optiques et de détection de gaz de bois-modèle spécifiques. Dans le présent travail, le biomodèle oxyde de fer, l'oxyde de nickel et l'oxyde de zinc avec les structures morph-génétique du bois sont fabriqués en utilisant la technologie de morph-transformation génétique. Les processus physiques et chimiques de transformation sont analysés et les paramètres de fabrication sont optimisés. Le règlement d'oxydes de microstructures par divers processus de paramètres sont établi. La valeur numérique dans multi échelles de structures poreuses d'oxydes est analysée et les propriétés optiques et de détection de gaz des matériaux morph-génétique poreux sont exploitées dans ce travailHierarchical porous materials have displayed important researching and application values at the fields of separation and purification, selective adsorption, optical function, and sensor design etc. Some preparation methods have been designed to fabricate porous materials. But these traditional methods have to use specific equipments and complicated techniques, and obtained porous materials have single pore size distributions with single functions. The morph-genetic transformation technology is a simple processing technology to fabricate re-fined hierarchical porous materials using organ-isms as template. The organisms in nature are the perfect unities of highly delicate structures and effectively complex functions through mil-lions of years of evolution and natural survival law, which prepare plentiful structural tem-plates for hierarchical porous materials. In the present work, wood-templated Fe2O3, ZnO and NiO with hierarchical porous structures were fabricated through replication wood’s morphology and structure. The synthetic mechanism was studied to optimize the parameters of morph-genetic technology, and wood-templated oxides with wood’s structures were fabricated successfully. The porous structures in multi-scales, the optical properties and the gas sensing properties of wood-templated oxides were researched in detail
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Yang, Liu. "Caractérisation de couches minces de ZnO élaborées par la pulvérisation cathodique en continu." Phd thesis, Université du Littoral Côte d'Opale, 2012. http://tel.archives-ouvertes.fr/tel-00919764.
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Ce mémoire concerne un ensemble d'élaboration et de caractérisation de couches minces à base de ZnO par la pulvérisation cathodique en continu. L'étude structurale montre que le traitement thermique lors du dépôt et post-dépôt à l'air ont une influence similaire sur l'augmentation de la taille de cristallites jusqu'à une température de 250°C. À partir de cette température critique, la taille des cristallites continue à augmenter en fonction de la température de recuit, alors qu'elle diminue légèrement avec la température de dépôt. L'étude morphologique montre que le traitement thermique lors du dépôt a une influence plus marquée sur la rugosité que celui à l'air de l'ambiante à 470°C. En fonction de la température de dépôt la résistivité électrique en continu diminue lorsque celle-ci augmente. Ce phénomène est directement lié à la qualité de la structure cristalline des films. À l'inverse, le recuit post-dépôt à l'air rend le film plus résistif. La deuxième partie de ce travail porte sur des mesures de bruit en 1/f. Nous montrons que le bruit est très sensible à la température de dépôt et à l'orientation des cristallites dans le matériau. Le bruit obtenu dans le sens transversal est plus élevé que celui obtenu dans le sens longitudinal. De plus, le bruit mesuré en présence de lumière peut être beaucoup plus élevé. Par un modèle simple, nous avons montré que ce phénomène est relié à la photoconductivité et à la présence de défauts en surface du matériau. Enfin, une technique photothermique par radiométrie unfrarouge a été utlilisée pour effectuer une caractérisaiton thermophysique du matériau. Cette technique permet de déterminer les paramètres optiques et thermiques de l'échantillon. Une étude théorique de l'évolution du signal photothermique en fonction de la fréquence de modulation a permis de mettre en évidence les conditions dans lesquelles on peut mesurer ces paramètres avec précision.
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CORDEIRO, MOACIR R. "Investigação de interações hiperfinas em Zn(1-x)MT(x)O, onde MT=(V, Cr, Mn, Fe, Co, Ni, Cu) pela técnica de correlação angular gama-gama perturbada." reponame:Repositório Institucional do IPEN, 2012. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10073.
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Made available in DSpace on 2014-10-09T12:34:26Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:09:48Z (GMT). No. of bitstreams: 0
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Deacon, Liam Matthew. "Structural, electronic and magnetic studies of polar zinc oxide surfaces and their interfaces with ultra-thin cobalt films." Thesis, University of Reading, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.625440.
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Zinc oxide (ZnO) has a desirable combination of opto-electronic properties that, when combined with magnetic transition metal dopants such as cobalt, place it at the forefront of next generation materials to harness both electron charge and spin in the field now known as spintronics. In this thesis the polar (0001) surfaces of ZnO single crystals are revisited and used as a basis for the growth of ultrathin cobalt films before subsequent processing in an effort to produce a CoZnO dilute magnetic semiconductor. A method using Zn sublimation partial pressures is given that provides reliable preparation of clean ZnO(0001) surfaces and comparisons between these two surface terminations are made on the basis of LEED, STM, UPS and XPS arguments.
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Egal, Magali. "Structure and properties of cellulose/NaOH aqueous solutions, gels and generated objects." Ecole nationale supérieure des mines de Paris, 2006. http://www.theses.fr/2006ENMP1419.
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Il est connu que la cellulose peut être dissoute dans des solutions aqueuses d’hydroxyde de sodium dans un petit domaine de concentration (6-10% NaOH) et de températures (-10°C/-4°C). Les solutions de cellulose ainsi obtenues ne sont pas stables et gélifient en fonction du temps et de la température. Il a également été montré que la présence d’additifs –tels qu’oxyde de zinc et urée – améliore la dissolution des fibres de cellulose et la stabilité des solutions.It has been reported that cellulose can be dissolved in aqueous sodium hydroxyde solutions in a narrow range of NaOH concentrations (6-10%) and temperatures (-10°C/-4°C). Cellulose solutions obtained are not stable and gelation occurs with time and temperatures increase. It has been also showed that the presence of additives, such as urea or zinc oxide, in solvent system improves the dossolution of cellulose fibres and the solution stability.
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Lippert, Marc. "Elaboration et caractérisation de couches minces piezoélectriques d'oxyde de zinc obtenues par pulvérisation cathodique." Valenciennes, 1999. https://ged.uphf.fr/nuxeo/site/esupversions/6a235e1a-0eaf-4bd6-a862-aafdf1dd7913.
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L'étude porte sur l'élaboration et la caractérisation de couches minces d'oxyde de zinc (ZnO) obtenues par une technique de pulvérisation cathodique radiofréquence magnétron. Ces couches sont analysées par des techniques classiques de caractérisation des matériaux : la diffraction des rayons x et le microscope électronique a balayage. Ces films minces présentent deux orientations préférentielles suivant la position face à la cible et sous certaines conditions de dépôt : une couche bien texturée ou l'axe c est perpendiculaire à la surface du substrat et une couche qui possède un axe c parallèle au plan du substrat et d'orientation (110). Ces films sont ensuite analysés pour déterminer leurs propriétés piézoélectriques. Pour ce faire deux autres méthodes ont été mises au point : une méthode de mesure du temps de vol des ondes ultrasonores générées dans le transducteur qui permet de dire si la couche est piézoélectrique ou pas ainsi que son mode de vibration. L'autre méthode est consacrée a la détermination directe du coefficient de couplage électromécanique par la mesure de l'impédance électrique de ce même transducteur. Cette dernière méthode a été testée sur des transducteurs utilisant un cristal de niobate de lithium (LiNbO#3) collé par diffusion métallique d'indium et nous a permis de retrouver un coefficient de couplage supérieur a 95% de la valeur théorique. Les couches minces de ZnO réalisées, présentaient la particularité de générer des ondes transversales, avec un coefficient de couplage approchant les 45% de la valeur théorique du matériau massifThe study focuses on the elaboration and the characterization of thin layers of zinc oxide (ZnO) obtained by a cathodic radiofrequency magnetron sputtering. These layers are analyzed by classic characterization techniques of materials : the diffraction of rays X and the scanning electronic microscope. These thin films present two preferential orientations following the osition in the face of the target and under some conditions of deposit : a layer well textured where the c-axis is perpendicular to the surface of the substrate and a layer that possesses a -axis parallel to the plan of the substrate and this orientation is (110). These films are then analyzed to determine their piezoelectric properties. Two other methods have been developed :a method of measure of the transit time of ultrasound waves generated in the transducer if the layer is piezoelectric. This method permits to determine also its vibration mode. The other ethod is devoted to the direct determination of the electromechanical coupling coefficient by the measure of the electrical impedance of this same transducer. This last method have been ested on transducers using a crystal of lithium niobate (LiNbO3) bonded by indium metallic diffusion and we have permitted to find a coupling coefficient superior to 95% of the theoretical value. Thin layers of ZnO realized, presented the particularity to generate transverse waves , with a coupling coefficient approaching 45% of the theoretical value of the massive material
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Badre, Chantal. "Etude de la réactivité de surface par mesure d'angle de contact : influence de la fonctionnalisation et de la structure : applications aux films d'oxyde de zinc électrodéposés." Paris 6, 2007. https://pastel.archives-ouvertes.fr/pastel-00004902.
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Le travail présenté dans ce manuscrit concerne l’étude de la réactivité de surface par mesures d’angles de contact. Nous nous sommes plus particulièrement intéressés à l’élaboration de surfaces texturées rugueuses. Dans la première partie, nous avons préparé des polymères formés d’un mélange de PVC et d’acide laurique. Puis, ces films sont rendus rugueux en y incorporant des billes d’aérosil. Mais, l’inconvénient de ce type de surface réside dans le fait qu’il n’est pas aisé d’en modifier la morphologie ni de la contrôler. Dans la deuxième partie, nous nous sommes intéressés à des matériaux dont la rugosité peut être facilement contrôlée comme le ZnO. Différentes morphologies sont obtenues par électrodépôt. La mouillabilité de ces films est facilement modifiable en fixant des molécules organiques telles que l’octadécylsilane ou des acides gras. Nous avons ainsi réussi à préparer des surfaces superhydrophobes. L’étude a été étendue sur d’autres molécules à caractère redoxIn this work, we studied the surface reactivity by contact angle measurements. In our case, we were particularly interested in preparing textured surfaces with different roughness scales. Firstly, we have prepared smooth polyvinylchloride polymers acidified with lauric acid. Then, aerosil balls are added to create some roughness on the polymer. Controlling the roughness and the morphology of these polymers remain a main disadvantage that leaded us to use other materials with easier roughness control like Zinc Oxide (ZnO). Different morphologies were prepared by electrodeposition such like nanorods and nanowires. It is well known that the wettability of ZnO can be modified by applying the bottom-up process. We used self assembled layers (SAMs) of organic molecules like octadecylsilane and fatty acids. We succeeded to prepare superhydrophobic surfaces with the highest contact angle 176° ever obtained on ZnO. The study was extended and ferrocene probe molecules were used
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Molepo, Mahlaga Phineas. "Computational study of the structural phase transitions and pressure dependent electronic structure of ZnO." Thesis, 2012. http://hdl.handle.net/10539/11941.
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We use rst-principles calculations based on density functional theory to study the
structural properties and pressure-induced solid-solid phase transitions of ZnO. Both
the local-density approximation (LDA) and the PBE96 form of the generalized gradi-
ent approximation (GGA) are employed together with the projector augmented wave
(PAW) method to mimic the electron-ion interaction. The electronic structure is
investigated by the HSE hybrid functional and a partially self-consistent GWapprox-
imation. We consider the wurtzite (B4), rocksalt (B1), zinc blende (B3), CsCl (B2),
PbO (B10), NaTl (B32), WC (Bh), BN (Bk), NiAs (B81) and AsTi (Bi) modi cations
of ZnO. The calculated structural properties in the B4, B3, B1 and B2 phases compare
acceptably well with those found in previous theoretical studies, as is the transition
pressure between them. We nd that the B4 phase is the most preferred low-pressure
candidate in ZnO while the B2 phase is favorable at high pressures. Apart from the
previously reported B4!B1!B2 phase transition, our study reveals other possible
paths for a transition from B4 to B2 phase with the Bk, Bh, B10, and B81 structures
as intermediate phases. It is found that the HSE and the GW approach o¤er a signif-
icant improvement to the prediction of band-gaps in ZnO. The band-gaps are found
to increase with increasing pressure leading to the structural phase transitions.
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VanLeeuwen, Dawn. "Completeness and sufficiency under normality in mixed model designs." Thesis, 1993. http://hdl.handle.net/1957/35705.
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Chia-HuiLu and 呂嘉輝. "Zinc Oxide Thin Film MEMS Gas Sensor with Different Structure." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/na42xn.
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Thorbahn, Jeremy G. "Local Structure and the Photoelastic Response in Zinc-modified Oxide Glass." Thesis, 2013. http://hdl.handle.net/10222/35368.
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Understanding the relationship between the structure of materials and their properties
allows for the development of new applications and technologies. Here the relationship
between local structure and optical properties in several binary oxide glass systems
containing zinc oxide was examined, in particular the relationship between structure,
applied stress and induced birefringence in a glass. The empirical model introduced by
Zwanziger and co-workers posits a negative correlation between the ratio of the bond
length to coordination number in a glass and the induced birefringence; zinc oxide in this
model is predicted to be exactly at the threshold between positive and negative
birefringence and is thus of particular interest to investigate. XAFS and Raman
spectroscopy were used to determine local structure while the Sénarmont compensator
method, Abbe refractometry and spectroscopic ellipsometry were used to measure optical properties.
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Hsaio, Chia-Pin, and 蕭家斌. "Study of Zinc Oxide with Nanodendrite Structure for Ethanol Sensing Applications." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/ecer87.
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碩士國立中山大學
電機工程學系研究所
103
In this thesis, the PNPN heterojunctions with three-dimensional nanodendrite structure were developed for ethanol sensing applications. Firstly, the p-type silicon substrates were etched into nanorods structure by immersing in a mixture of chemical solution. The solution is composed of silver nitrate (AgNO3) and hydrofluoric acid (HF). Next, a zinc oxide (ZnO) film was deposited on the Si nanorods as a seed layer by RF sputtering system. Hydrothermal method was used immediately for growing ZnO nanowires. Copper oxide (CuO) and ZnO thin film were deposited sequentially also by sputtering on the surface of the ZnO nanowires. Once again, a second hydrothermal method was utilized to produce more branches of ZnO nanowires. Finally, the aluminum (Al) electrodes were deposited on the top and the bottom of the Si-NR/ZnO-NW/CuO/ZnO-NW (PNPN) heterojunctions to complete the sensing devices. Nanodendrite structure has a larger response area, which can enhance the sensing ability. These structures were examined by X-ray diffraction (XRD) and scanning electron microscope (SEM) for the crystallinity, morphology and thickness. The characteristics of the materials were analyzed and discussed for the optimal device parameters. Different etching times and different seed layer sputtering times were investigated for comparing their sensing performances. According to the experimental results, the all planar device Si/ZnO/CuO/ZnO has only 25% of sensitivity. On the other hand, the device with nanodendrite structure is effectively raised to 90%. The response and recovery times are shortened to 16 s and 40 s, respectively. The large surface to volume ratio of the nanostructure enhances the sensing ability of the device to ethanol gas. It has a great potential for applying into industrial security and prevention of drunk driving.
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Huai-ShanChin and 秦懷山. "Effect of Zinc-Oxygen Ration in Crystal Structure and Luminescence Properties of Zinc Oxide Thin Films." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/26873x.
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博士國立成功大學
工程科學系
105
In this study, a reactive radio frequency magnetron sputtering method was used to deposit zinc oxide (ZnO) thin films on indium tin oxide substrates at room temperature. By changing the oxygen concentrations and thermal annealing parameters, the effects of ZnO ratio on the crystal structure and luminous properties of the ZnO thin films were explored. The experiment results showed that an increase in oxygen concentration gradually decreased excess Zn content in the thin films and made the thin film crystallization situation more noticeable. Next, the as-deposited ZnO thin films were subjected to different temperatures and dwelling times in a heat treatment furnace, which effectively enhanced the internal crystallinity and luminous properties of the thin films. According to the post-annealing scanning electron microscopy image, ZnO thin films deposited under a sputtering pressure and oxygen concentration of 5 mtorr and 40%, respectively, showed progressive increases in ZnO grain size when thermal annealing temperature or dwelling time was increased; however, the effect of thermal annealing temperature increase on ZnO grain size increase was considerably stronger than that of dwelling time increase on ZnO grain size increase. The X-ray diffractometer analysis showed that the crystallization directions of ZnO (002), (101), (102), and (103) gradually improved as thermal annealing temperature increased. The photoluminescence (PL) spectrum showed that ultraviolet (UV) light intensity increased with thermal annealing temperature and dwelling time. Nevertheless, at a thermal annealing temperature of 600 °C or a dwelling time of 60 min, UV light radiation intensity began to weaken and even showed a long wavelength and a weak green light emission peak. Related analysis of experiment results confirmed that the thermal annealing process not only improved the internal crystallinity of the thin films, but also promoted the growth of internal defects and other crystal phases of the thin films.
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Chou, Tsung-Wei, and 周宗蔚. "Influence of Zinc Sulfide Shell Structure on Hydrogen Sensing Properties of Zinc Oxide Nanorod-based Gas Sensor." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/3d2q4e.
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碩士國立暨南國際大學
應用材料及光電工程學系
106
In this thesis, we first grew the seed layer on the silica sensor by spin coating methods. Then, we used hydrothermal methods to deposit the zinc oxide nanorods on top of the seed layer to make the zinc oxide nanorod sensors. After the growth of ZnO nanorods was completed, a similar hydrothermal method was used to grow a zinc sulfide shell on the surface of zinc oxide nanorods with different parameters. Thus, the zinc oxide nanorod sensor with core/shell structure was fabricated. Based on the sensing results, it can be seen that the electric resistance was increased after the zinc sulfide coating was formed, thereby increasing the sensing capability of the sensor. In addition, we also performed various material characterizations on these nanostructures including field-emission scanning electron microscope (FESEM), photoluminescence (PL), X-ray diffraction (XRD), transmission electron microscopy (TEM),electron spectroscopy for chemical analysis (ESCA) and other tests. The results show that after the two-step hydrothermal methods, the surface of ZnO nanorods was sulfurized to become ZnS shell and had good crystallinity in the structure. Owing to the simple, environmentally-friendly and low-cost features of this experimental process, it is expected to develop into a sensor that can be used to monitor the hydrogen gas in working environments in the future. These zinc sulfide / zinc oxide core shell structures can also be developed for applications such as solar cells, lighting and other purposes.
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Yang, Jan-Liang, and 楊展亮. "The Effect of One-Dimensional Zinc Oxide Structure and Growth by Aluminum." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/40326267436506103491.
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碩士逢甲大學
電子工程所
97
In this study, the ZnO nanowires were deposited on ITO/glass substrate using chemical vapor deposition system. The microstructure of ZnO nanowires is discussed with various deposition conditions, such as concentration ratio of Al/Zn and deposition temperature. The ITO/glass substrate was cleared using acetone and DI water. The temperature of reactive source is 550, 675, 864, and 896 ℃. The chamber pressure was 4 and 8 Torr. The gas flows of Ar and O2 with deposition times for 2 hours were 65 and 100 sccm, respectively. The structures of nanowires were observed by field emission scanning electron microscopy (FE-SEM). Chemical composition of the as-prepared ZnO2 nanowire arrays were analyzed by energy dispersive spectrometer (EDS). The crystal properties of the nanowires were evaluated by X-ray diffraction (XRD).
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Chen, Chih-jung, and 陳志榮. "Synthesis and Characterization of One-Dimensional Indium Zinc Oxide and Tin Oxide Structure by Chemical Vapor Deposition." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/86152193625492345715.
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博士逢甲大學
電機與通訊工程所
98
In this study, one-dimensional Indium Zinc Oxide (IZO) and tin oxide (SnO2) nanostructures have been successfully synthesis on ITO glass substrate via chemical vapor deposition in low temperature with vapor-liquid-solid (VLS) mechanism. Morphology of IZO and SnO2 nanowires arrays were observed with field emission scanning electron microscopy (FE-SEM). The IZO nanowires optimal experimental parameters are growth pressure is 1 Torr, argon gas flow of 50 sccm and oxygen flow 10 sccm. In this environment, the idea temperatures are 700 ℃ for indium (In) particles and 550 ℃ for zinc (Zn) particles. Nanowires have uniform diameters of approximately 100 nm to 150 nm, and their lengths are up to tens of 5 μm The SnO2 best growth temperatures are 450 ℃ and growth pressures were 8 × 10-1 Torr, respectively. In the catalyst, the nickel (Ni) catalyst compared to platinum (Pt) catalyst is a more effective reduction of one-dimensional SnO2 nanostructure on the ITO glass, the length of nanowires is about 1 μm ~ 2 μm, under the catalytic reaction conditions and low-temperature growth processes of one-dimensional SnO2 nanostructure on the ITO glass with an average diameter of about 20 nm ~ 50 nm. The X-ray diffraction (XRD) results show that the as-synthesized nanowires are crystalline with highly preferential orientation. Energy dispersive spectrometer (EDS) analysis shows that the composition ratio and confirmed in this material are indeed IZO and SnO2 nanowires.
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Hu, Shen-Hsien, and 胡慎顯. "Design and Fabrication of Zinc Oxide Piezoelectric Devices with Periodic Graphene-like Structure." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/9k7cvu.
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碩士國立虎尾科技大學
機械設計工程研究所
102
Today in SAW devices in the field, the film acoustic resonator generally a simple multi-layer structure of production of the resonator, the process time is extremely time consuming and labor intensive to limit breakthrough process on while operating the missing man on more challenges to the process yield on sex. In this paper, the use of MEMS process technology enables micron film etched graphics designed four different piezoelectric structures (flat, supercell, one-defect and two-defects), the use of aerosol deposition technology to produce different sizes of piezoelectric structures micron thickness, and then use high-temperature furnace annealing films modified by lift from the electrode pattern completion method, when the image forming electrode can be the final element lithography acoustic components with the completion of the etching experiments to explore the effects of micron and nano-sized structures with different thickness dimension of the frequency response. The simulation and experimental study was divided into two parts, the use of finite element analysis software COMSOL Multiphysics 3.5a by the size and thickness of the piezoelectric parameters of the model to explore the structure of the piezoelectric elements of different scale thickness of the dispersion relation, and capacitance analysis ratio characteristics. Using a network analyzer measurements RF, signal frequency response of Phase change. Simulation results show that the link R0.0875 mm diameter rod width 0.0025 mm and link structure of 15N×9M frequently in the low range (0~100 MHz) the most significant trends in the form of dual-component two-defects, such graphene pressure electrical component band position between about 20 ~ 30 MHz.
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Fishburn, James R. "Local structure determination in the amorphous polymer electrolyte: Poly(propylene oxide)-zinc bromide." 1996. https://scholarworks.umass.edu/dissertations/AAI9619386.
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Polymer electrolytes are neutral polymers that are complexed with salts. They may show promise for use in energy storage devices. However, the conductivity in polymer electrolytes is several orders of magnitude low for use in this application. A major hindrance to improving the conductivity is a lack of understanding of the conduction mechanism. The local structure in the amorphous polymer electrolyte, poly(propylene oxide)-zinc bromide ( (PPO) $\sb{\rm x}$ZnBr$\sb2$), was investigated to obtain a microscopic snapshot of the ionic structure in the conducting amorphous phase. This would provide insight into the conduction mechanism through elucidation of polymer-ion and ion-ion interactions. A combination of differential anomalous x-ray scattering (DAS) and extended x-ray absorption fine structure (EXAFS) were used to determine the structure around the Zn and Br ions in (PPO) $\sb{\rm x}$ZnSr$\sb2$, where x = 6,16. On average, two bromines and two oxygens were coordinated with each Zn. This represented a mixture of species described by the formula ZnBr$\sb{\rm 4-Y}$(O)$\sb{\rm Y}\sp{\rm Y-2}$, of which the majority were the tetrahedral species Zn(O)$\sb4\sp{2+}$ and ZnBr$\sb4\sp{2-}.$ The nature of the ionic groups implied that the conductivity in (PPO) $\sb{\rm x}$ZnBr$\sb2$ would not be high enough to be useful for many applications. This work was also important for the novel application of DAS for investigating polymer electrolytes. The accuracy of DAS in calculating coordination numbers was increased. Two approximations were tested for a weighting factor used when calculating coordination numbers from the peak areas in the differential Radial Distribution Functions (dRDF). A k-peak approximation was more accurate than a k-averaged approximation. Finally, Quasi-Elastic Neutron Scattering (QENS) was used to study the local motions of the polymer chains and to correlate them to the structure determined by DAS and EXAFS. Only preliminary results were obtained and a more complete analysis is needed before any conclusions about the chain motions can be made.