Made available in DSpace on 2015-03-03T11:52:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-07-16Bitstream added on 2015-03-03T12:07:24Z : No. of bitstreams: 1 000806683.pdf: 1193891 bytes, checksum: 1226deee936f356b44515bf10a7e5739 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Filme finos de AZO foram sintetizados sobre substratos de vidro utilizando um alvo de Zn-Al (5% at Al) com 99,999% de pureza através da técnica RF magnetron sputtering reativo a temperatura ambiente. As propriedades estruturais, elétricas, ópticas e morfológicas foram investigadas em função da variação da pressão de argônio no intervalo de 10 a 50 mTorr. As análises de DXR revelaram que os filmes obtidos são policristalinos come estrutura hexagonal wurtzita e orientação preferencial no plano (002). Além disso, mostrou que o aumento da pressão, reduziu os valores tensão e ocasionou o aumento da presença de vazios entre os grãos. Para todos os filmes finos obtidos as medidas de transmitância óptica apresentaram valores acima de 80% na região visível do espectro entre 500-700 nm. Já os valores de gap óptico decresceram de 3,68 para 3,55 eV com o aumento da pressão. O filme sintetizado a 10 mTorr apresentou os melhores resultados em termos de densidade de portadores e mobilidade elétrica, sendo os valores 2,68 x 10 cm-3/Vs, respectivamente / Aluminum zinc oxide (AZO) thin films were synthesized on glass substrates by radiofrequency (RF) magnetron sputtering of a Zn-Al (5at% Al) target of 99.999% purity at ambient temperature. The structural, electrical, optical and morphological properties of the films were investigated as a function of the argon pressure, which was varied from 10 to 50 mTorr. X-ray diffraction (XRD) analyses revealed that the films obtained are polycrystalline with a hexagonal wurtzite structure with a preferential orientation in the (002) plane. In addition, it was show than an increase in pressure reduced the tension and produced an increase in the inter-grain spaces. For all of the films produced optical transmission was above 80% in the visible region (wavelength between 500 nm and 700 nm). As the system pressure was increased the optical gap fell from 3.68 to 3.55 eV. The film synthesized at 10 mTorr presented the best results in terms of the carrier density and electrical mobility, which were 2.68 x 10 cm-3 and 3.0 cm2/Vs, respectively

No description available.

Orientador: José Roberto Ribeiro Bortoleto / Banca: Tersio Guilherme de Souza Cruz / Banca: Rogério Pinto Mota / O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Resumo: Neste trabalho, foram realizadas duas séries de deposição de filmes finos de ZnO crescidos sobre substrato de vidro pela técnica de RF magnetron sputtering reativo. Na primeira, investigou-se a influência da temperatura nas propriedades dos filmes crescidos no intervalo de temperatura de 50 a 250ºC. Posteriormente, na segunda série, investigou-se a evolução da dinâmica de crescimento destes filmes com o tempo através dos expoentes de escala com a finalidade de identificar os mecanismos superficiais presentes. Para isso, foram depositados filmes finos de ZnO crescidos na temperatura do substrato de 100ºC, variando o tempo de deposição de 0 a 120 min. As propriedades estruturais e ópticas dos filmes foram analisadas por difratometria de raios-X e espectroscopia no ultravioleta-viável, respectivamente. A partir disso, foi possível determinar a orientação cristalográfica, a tensão residual, o tamanho de grão, a espessura e os parâmetros ópticos dos filmes como transmitância média, energia de gap óptico e índice de refração n. As propriedades morfológicas foram investigadas pela microscopia de força atômica e eletrônica de varredura. Assim, as imagens de AFM foram usadas para determinar a rugosidade superficial, para calcular o comprimento lateral, consequentemente, encontrar o expoente de crescimento B e o expoente que define a evolução do comprimento de onda característico da superfície p. A composição química e a densidade superficial dos filmes de ZnO crescidos em diferentes temperaturas do substrato foram determinadas pela espectroscopia de retro espalhamento Rutherford / Abstract: In this workm two series of grown ZnO thin films deposition on glass substrate by reactive RF magnetron sputtering technique were performed. At first, the influence of temperature on the properties of the grown films in the temperature range from 50 to 250ºC was investigated. In the second series, the evolution of the growth dynamics of these films with the time was analyzed using scaling concepts in order to identify the superficial mechanisms. For this purpose, the grown films in the substrate temperature of 100ºC were deposited by varying the deposition time of 0 to 120 min. X-ray diffraction an ultraviolet-visible spectroscopy were employed to characterize the characterize the structural and optical properties of the films, respectively. From this crystallographic orientation, residual stress, grain size, thickness and the optical parameters of the films as average transmittance, optical band gap and refractive index n were determined. The morphological properties were investigated by atomic force and scanning electron microscopy. Thus, AFM images were used to determine the surface roughness, to calculate the lateral length and, consequently, find the growth exponent b and expoent defining the evolution characteristic wavelength of the surface p. Rutherford backccattering spectroscopy was employed to determine the chemical composition of the grown ZnO films on different substrate temperatures and its surface densisties / Mestre

Made available in DSpace on 2014-06-11T19:30:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-01-21Bitstream added on 2014-06-13T19:00:08Z : No. of bitstreams: 1 rosa_am_me_bauru.pdf: 2854287 bytes, checksum: f1ee4fc5222e24b424620844f6d140c2 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Neste trabalho, foram realizadas duas séries de deposição de filmes finos de ZnO crescidos sobre substrato de vidro pela técnica de RF magnetron sputtering reativo. Na primeira, investigou-se a influência da temperatura nas propriedades dos filmes crescidos no intervalo de temperatura de 50 a 250ºC. Posteriormente, na segunda série, investigou-se a evolução da dinâmica de crescimento destes filmes com o tempo através dos expoentes de escala com a finalidade de identificar os mecanismos superficiais presentes. Para isso, foram depositados filmes finos de ZnO crescidos na temperatura do substrato de 100ºC, variando o tempo de deposição de 0 a 120 min. As propriedades estruturais e ópticas dos filmes foram analisadas por difratometria de raios-X e espectroscopia no ultravioleta-viável, respectivamente. A partir disso, foi possível determinar a orientação cristalográfica, a tensão residual, o tamanho de grão, a espessura e os parâmetros ópticos dos filmes como transmitância média, energia de gap óptico e índice de refração n. As propriedades morfológicas foram investigadas pela microscopia de força atômica e eletrônica de varredura. Assim, as imagens de AFM foram usadas para determinar a rugosidade superficial, para calcular o comprimento lateral, consequentemente, encontrar o expoente de crescimento B e o expoente que define a evolução do comprimento de onda característico da superfície p. A composição química e a densidade superficial dos filmes de ZnO crescidos em diferentes temperaturas do substrato foram determinadas pela espectroscopia de retro espalhamento Rutherford / In this workm two series of grown ZnO thin films deposition on glass substrate by reactive RF magnetron sputtering technique were performed. At first, the influence of temperature on the properties of the grown films in the temperature range from 50 to 250ºC was investigated. In the second series, the evolution of the growth dynamics of these films with the time was analyzed using scaling concepts in order to identify the superficial mechanisms. For this purpose, the grown films in the substrate temperature of 100ºC were deposited by varying the deposition time of 0 to 120 min. X-ray diffraction an ultraviolet-visible spectroscopy were employed to characterize the characterize the structural and optical properties of the films, respectively. From this crystallographic orientation, residual stress, grain size, thickness and the optical parameters of the films as average transmittance, optical band gap and refractive index n were determined. The morphological properties were investigated by atomic force and scanning electron microscopy. Thus, AFM images were used to determine the surface roughness, to calculate the lateral length and, consequently, find the growth exponent b and expoent defining the evolution characteristic wavelength of the surface p. Rutherford backccattering spectroscopy was employed to determine the chemical composition of the grown ZnO films on different substrate temperatures and its surface densisties

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.

A thesis submitted to the Faculty of Engineering and the Built Environment in fulfilment of the requirement for the Degree of Masters of Science, University of the Witwatersrand, Johannesburg, 2019 / Drilling Mud holds an important role in the drilling process in such a way that it is a determinant key to the success of the operation as well as the money spent throughout the process. Indeed the success and the cost of the operation can be severely impacted by some challenges experienced while drilling such as temperature and pressure conditions which leads to fluid loss, fluid deterioration...As a result there is a need to formulate a fluid with desirable rheological properties to withstand such undesirable parameters. Therefore this work was aimed to improve emulsion drilling fluids (EDFs) based nanoparticles with enhanced properties. Many investigations were performed to find a proper emulsion stability as well as a good drilling fluid performance. The stability of the prepared emulsion drilling fluids was done using surfactant with different concentrations for several days. After several days of preparation, the EDFs containing DTAB as surfactant have showed a better emulsion stabilizer compared to the Triton X-100 ones. In addition an investigation combining both NPs and surfactants confirmed the used of NPs to improve DF and revealed the effective use of ZnO NPs for drilling fluids application and preferentially with DTAB as surfactant. Following that result, the 2nd part of the work was based on the synthesis and characterization of CNCs as NPs to formulate EDF with DTAB as surfactant. The CNCs NPS were successfully obtained via the method of oxidation of microfibrillated cellulose through TEMPO-mediate and after characterization using TEM, spherical NPs with small size varying from 10-50nm were observed. The FANN® Model 35 viscometer served to display the behavior of the shear stress and viscosity of the prepared fluids against variable shear rate at variable NPs and temperature concentration. The rheological and filtration properties were increase with increase in CNCs content from 0.8 to 1.2% of fluid in room temperature and with an increase in temperature. / PH2021

No description available.

We are surrounded by enormous amounts of ambient mechanical energy that goes to waste such as rain drops, human footfalls, air flow, ocean waves, just to name a few. If such otherwise wasted mechanical energy can be effective converted into electricity, self-powered electronics are very likely to be realized, which can address the limitations of traditional power supplies in many cases, such as wireless sensor networks. Here in this work, two types of energy-harvesting nanogenerators (NGs) based were studied. For piezoelectric nanogenerators, zinc oxide (ZnO) nanowires (NWs) were used as building blocks to develop integrated NGs based on a number of ZnO NWs instead of a single NW. Two types of integrated NGs were developed, which consist of lateral NW arrays and vertical NW arrays. The electric output power was substantially enhanced compared to the design with a single NW. For triboelectric nanogenerators, triboelectric effect was innovatively used as an effective means of harvesting mechanical energy. The operating principle can be explained by the coupling between triboelectric and electrostatic effect. Two types of operating modes were invented, i.e. contact mode and sliding mode. Triggered by commonly available ambient mechanical energy such as footfalls, the maximum output power reached up to 1.2 W. More importantly, self-powered systems were built by using the NG as a power source. It can provide real time power for up to 600 commercial LED bulbs. This research not only provides the fundamentals for NGs but also demonstrates the practicability of using the self-powered technology in our daily life.

Law, Pak Tsun = 研究氧化鋅納米粒子應用在生物醫學的可能性 / 羅百浚. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (p. 62-63). / Abstracts in English and Chinese. / Law, Pak Tsun = Yan jiu yang hua xin na mi li zi ying yong zai sheng wu yi xue de ke neng xing / Luo Baijun. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Background --- p.2 / Chapter 2.1 --- Introduction of Zinc Oxide Nanostructures --- p.2 / Chapter 2.1.1 --- Biomedical Application of ZnO nanostructure --- p.3 / Chapter 2.2 --- Current problems of Zinc Oxide Nanostructures on Biological Application --- p.5 / Chapter 2.2.1 --- Behaviours of ZnO Nanostructure in Cell Culture --- p.6 / Chapter 2.2.2 --- Cytotoxicity of ZnO Nanostructures --- p.8 / Chapter 2.2.3 --- Other Synthetic Problems --- p.9 / Chapter 2.3 --- Summary --- p.9 / Chapter 3 --- Instrumentation and Experimental Methodology --- p.11 / Chapter 3.1 --- Electron Microscopy --- p.11 / Chapter 3.1.1 --- SEM --- p.12 / Chapter 3.1.2 --- TEM --- p.13 / Chapter 3.1.3 --- Elemental Analysis --- p.14 / Chapter 3.2 --- X-ray Photoelectron Spectroscopy --- p.16 / Chapter 3.3 --- X-ray Diffraction --- p.17 / Chapter 3.4 --- Dynamic Light Scattering --- p.18 / Chapter 3.5 --- Photoluminescence Spectroscopy --- p.19 / Chapter 3.6 --- MTT Assay --- p.20 / Chapter 3.7 --- Cells Incubation --- p.22 / Chapter 4 --- Synthesis and Characterization of Zinc Oxide Nanostructure --- p.23 / Chapter 4.1 --- Hydrophobic Zinc Oxide Nanoparticle --- p.23 / Chapter 4.1.1 --- Synthetic Method --- p.23 / Chapter 4.1.2 --- Characterizations and Property measurements of the ZnO nanoparticles --- p.24 / Chapter 4.2 --- Hydrophilic Zinc Oxide Nanoparticle --- p.29 / Chapter 4.2.1 --- Synthetic Method --- p.29 / Chapter 4.2.2 --- Characterizations and property measurements of the ZnO nanoparticles --- p.30 / Chapter 5 --- Interaction of Zinc Oxide with Human Cells --- p.35 / Chapter 5.1 --- Can Zinc Oxide Nanoparticles Enter the cells? --- p.35 / Chapter 5.1.1 --- Exp erimental --- p.36 / Chapter 5.1.2 --- General Description --- p.36 / Chapter 5.2 --- What Affect the Cellular Uptake of ZnO Nanoparticles? --- p.37 / Chapter 5.2.1 --- Concentration of ZnO Nanoparticles --- p.37 / Chapter 5.2.2 --- Agglomeration of ZnO nanoparticles --- p.40 / Chapter 5.2.3 --- Reaction with Buffer Solution and Culture Medium --- p.41 / Chapter 5.2.4 --- Summary --- p.45 / Chapter 5.3 --- Cell Viability after Introducing ZnO Nanoparticle to the Cells ´Ø --- p.56 / Chapter 5.3.1 --- Experimental --- p.56 / Chapter 5.3.2 --- Results and Discussion --- p.57 / Chapter 6 --- Conclusion --- p.59 / Bibliography --- p.62 / Chapter A --- TEM sample preparation procedure for animal cell --- p.64

One-dimensional and hierarchical nanostructures have acquired tremendous attention in the past decades due to their possible application. In spite of the rapid emergence of new morphologies, the underlying growth mechanism is still not well understood. The lack of effective p-type or n-type doping is another obstacle for many semiconducting nanomaterials. A deeper investigation into these structures and new methods to fabricate devices are of significant impact for nanoscience and nanotechnology. Motivated by a desire to understand the growth mechanism of nanostructures and investigate novel device fabrication method, the research described in this thesis carried out on the synthesis, characterization, and device fabrication of semiconducting nanostructures. The main focus of the research was on ZnO, SnO2, and Zn3P2 for their great capability for fundamental phenomena studying, promising applications in sensors and optoelectronics, and the potential generalization of results to other materials. Within this study the following goals have been achieved: 1) Improved understanding of polar-surface-induced growth mechanism in wurtzite-structured ZnO and generalization of this growth mechanism with the discovery and analysis of rutile ¨Cstructured SnO2, 2) observation of the significance of the transversal growth, which is usually ignored, in interpenetrative ZnO nanowires, 3) rational design and growth control over versatile nanostructures of ZnO and Zn3P2, and 4) conjunction of p-type Zn3P2 and n-type ZnO semiconducting nanostructures for device fabrications. The framework for the research is reviewed first in chapter 1. Chapter 2 gives the detailed experimental setup, synthesis procedure, and common growth mechanism for nanostructure growth. A detailed discussion on the growth of ZnO nanostructures in chapter 3 provides more insight into the polar-surface-induced growth, transversal growth, vapor-solid growth, and vapor-liquid-solid growth during the formation of nanostructures. Polar-surface-induced growth is also confirmed in the growth of SnO2 nanostructures, which is also included in chapter 2. Chapter 3 presents Zn3P2 nanostructures from the newly designed experiment setup and the device fabrication from ZnO and Zn3P2 crossed nanowires.