Dissertations / Theses on the topic 'Low-temperature Techniques'
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Hopkins, S. C. "Optimisation, characterisation and synthesis of low temperature superconductors by current-voltage techniques." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604224.
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The reaction-diffusion behaviour of bronze process Nb3Sn wires has been modelled, and good agreement has been obtained between predicted and measured compositions and Nb3Sn layer thicknesses for a wide range of isothermal heat treatments. Isothermal and two-stage heat treatments have been assessed for uniformity of Nb3Sn layer thicknesses and predicted critical current behaviour, and suggestions for optimising heat treatments and wire designs have been made. The electrical resistivity of bronze as a function of temperature and composition has been measured, and its annealing behaviour investigated. These results have been used with the diffusion model to calculate the electrical resistivity during isothermal heat treatment. Most features are in good agreement with experiment results, suggesting that this technique has potential for the monitoring and control of bronze process wire heat treatments. Discrepancies and areas for improving in the calculations have been identified, and these will form the subject of future work. A critical current characterisation system using pulsed currents and pulsed magnetic fields, Cryo-BI-Pulse, has been developed with Metis Instruments and Equipment. Excellent agreement with DC measurements has been obtained for a copper-matrix NbTi wire and a nickel-matrix MgB2 tape, but discrepancies have been found for materials with resistive matrix materials. These discrepancies are mostly caused by current transfer effects when testing very short samples, and can be addressed by testing longer samples and improving the analysis of the measured sample voltages.
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Georgiacodis, D. N. "Low temperature ion-irradiation effects in silicon studied by ion-channelling techniques." Thesis, University of Sussex, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304345.
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Lopez-Calvo, Alfredo Manzanares Carlos E. "Vibrational spectroscopy in cryogenic solutions application of thermal lensing and Fourier transform techniques to the study of molecular C-H overtone transitions /." Waco, Tex. : Baylor University, 2006. http://hdl.handle.net/2104/4873.
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Abdullah, J. B. "The assessment of high temperature damage in 2.25 Cr - IMo low alloy steel using ultrasonic techniques." Thesis, Swansea University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635833.
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In petrochemical plants and power generating utilities, creep behaviour will affect the service life of components operating at elevated temperatures and stresses. Non-destructive techniques which detect creep damage are therefore important for assessing the remaining service life of the affected components. Whilst various non-destructive techniques have been reported, further studies are necessary to refine and assess the potential of these techniques for quantitative measures to be used for residual life-time prediction. In this thesis, the use of ultrasonic techniques to quantify creep cavitation in 2.25Cr-1Mo low alloy steel was explored. In contrast to conventional methods which only examine surface effects, these approaches should be capable of monitoring both surface and volumetric changes. A computer-based ultrasonic system was developed and testing procedures to characterise the metallurgical variables and creep damage in both ferritic and bainitic 2.25Cr-1Mo steel materials have been established. To evaluate the effects of high temperature exposure to assess microstructural changes and the development of creep damage, a systematic approach with a three-stages experimental work has been undertaken. Firstly, the effects of grain size and phase transformation product on ultrasonic behaviour were evaluated. Samples have been prepared with ferritic and bainitic microstructures. Austenitisation procedures were selected so that samples were produced with average grainsizes in the range 21 to 96 μm. Secondly, ultrasonic techniques were used to characterise microstructural changes due to thermal ageing effects. Materials in ferritic and bainitic microstructures were aged at 700°C for times from 2 to 2000 hours. Thirdly, the assessment of creep damage using ultrasonic techniques was undertaken. This was performed on specimens which had been subjected to creep at various stresses, in a temperature range of 575 to 625°C. In all cases, ultrasonic measurements were supported by optical microscopy, tensile testing and surface hardness measurements to document metallurgical condition.
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Spalholz, Hans. "Development of Short Term Storage Techniques for Grafted Vegetable Seedlings." Thesis, The University of Arizona, 2013. http://hdl.handle.net/10150/293734.
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Vegetable grafting confers soil-borne disease resistance through the use of selected rootstocks. Additional costs associated with grafted vegetable seedling propagation limit grower access to this technology. The use of low temperature storage in grafted seedling production reduces labor costs and allows propagators to meet the seasonal and narrow-window demand of growers. For the first part of the experiment 22 genotypes of Solanaceae or Cucurbitaceae seedlings were evaluated in low temperature storage conditions (5 or 12°C). Seedling performance was better in 12°C storage than in 5°C storage. For the second part of the experiment watermelon, the most low-temperature sensitive species found in our first study, was grafted onto two different commercial rootstocks or on to other watermelon seedlings and stored at 12°C for two and four weeks. Both 'Strong Tosa' and 'Emphasis' rootstocks conferred chilling tolerance during storage to watermelon scions, allowing storage of grafted plants for two weeks.
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Beale, Andrew Michael. "Novel low temperature preparation methods for mixed complex oxide catalysts and their characterisation via in situ SR techniques." Thesis, University College London (University of London), 2003. http://discovery.ucl.ac.uk/1453143/.
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Thankaraj, Salammal Shabi [Verfasser]. "Structural and morphological investigations of Poly(3-alkylthiophene) thin films prepared by low and room temperature casting and spin coating techniques / Shabi Thankaraj Salammal." Siegen : Universitätsbibliothek der Universität Siegen, 2012. http://d-nb.info/1024804259/34.
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Kadri, Mohammed. "Formation à basse température et nouvelles techniques de caractérisations [sic] du disiliciure de tungstène WSi2." Grenoble 1, 1987. http://www.theses.fr/1987GRE10053.
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Le disiliciure wsi::(2) pour la metallisation d'un circuit vlsi (contacts et lignes d'interconnexion) est forme a une temperature aussi basse que possible en utilisant la structure "sandwich" a-si: h(150 a)/w(110 a)/a-si: h(540 a)/c-si implantee par des ions a faible courant et a temperature ambiante. La concentration residuelle d'oxygene dans les couches de w et de a-si:h et a leur interface a une influence decisive sur la formation et la resistivite de wsi::(2). Les plus faibles temperatures de formation de wsi::(2) atteintes sont les plus basses, 550**(o)c apres recuit, 350**(o)c apres implantation de w puis recuit. Les resistivites sont aussi plus faible. Interet et sensibilite de la spectroscopie ir dans la caracterisation des impuretes
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Kermarrec, Edwin. "Nouveaux états quantiques de spin induits par frustration magnétique sur le réseau kagome." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00783605.
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La déstabilisation de l'ordre antiferromagnétique de Néel au profit de nouvelles phases quantiques à température nulle à deux dimensions est envisageable grâce au phénomène de frustration magnétique. Le modèle théorique de spins Heisenberg S=1/2 répartis sur le réseau bidimensionnel frustré kagome, constitué de triangles joints uniquement par leurs sommets, est susceptible de stabiliser des phases quantiques originales de liquides de spin, qui ne présentent aucune brisure de symétrie à T = 0. Cette thèse a été consacrée à l'étude expérimentale de deux types de composés de spins S=1/2 (Cu2+) à géométrie kagome à l'aide de techniques spectroscopiques locales, la RMN et la μSR, ainsi que de mesures thermodynamiques (susceptibilité magnétique, chaleur spécifique). Dans Mg-herbertsmithite, la frustration est générée par une interaction d'échange premiers voisins antiferromagnétique J et est responsable d'un comportement liquide de spin jusqu'à des températures de l'ordre de J/10000. Par rapport au composé isostructural antérieur, Zn-herbertsmithite, nous avons montré qu'il possédait des propriétés physiques similaires tout en permettant une caractérisation fine du taux de défauts de substitutions Cu/Mg. Nos expériences réalisées à partir d'échantillons contrôlés permettent d'étudier finement l'origine des plateaux de relaxation observés en μSR à basse température en lien avec l'existence des défauts de spins interplans. La kapellasite et l'haydéite possèdent des interactions ferromagnétiques (J1) et antiferromagnétiques (Jd), offrant la possibilité d'explorer le diagramme de phases générées par la compétition de ces interactions sur le réseau kagome. Pour la kapellasite, nos mesures de μSR démontrent le caractère liquide de spin jusqu'à T ≈ J1/1000. La dépendance en température de la susceptibilité magnétique sondée par RMN du 35Cl ainsi que de la chaleur spécifique permettent d'évaluer le rapport Jd/J1 = 0.85, qui localise classiquement son fondamental au sein d'une phase originale de spins non coplanaires à 12 sous-réseaux appelée cuboc2. Les interactions présentes dans l'haydéite localisent son fondamental au sein de la phase ferromagnétique, en bon accord avec nos mesures qui indiquent une transition partielle à caractère ferromagnétique à T = 4 K. Cette étude confirme la pertinence du réseau kagome frustré pour la stabilisation de phases quantiques originales et démontre l'existence d'une nouvelle phase liquide de spin sur ce réseau, distincte de celle attendue pour des spins couplés antiferromagnétiquement.
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Grobler, Thelma. "Two-dimensional gas chromatography : a novel technique for iron low temperature Fischer-Tropsch selectivity studies." Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/5327.
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Includes abstract.Includes bibliographical references (leaves 158-178).
Fischer-Tropsch synthesis is a process that catalytically converts hydrogen and carbon monoxide into a large variety of hydrocarbons and oxygenated products. Over the years many researchers have attempted to describe the full product spectrum (ranging from C1 to C100+) but due to the complexity of the product and shortcomings of certain analytical techniques (or equipment) most researchers were only able to construct product distributions from extrapolations of data recorded from analysis of the C1 to C5 fraction of the Fischer-Tropsch product. With recent advances in analytical technology and the development of comprehensive two-dimensional gas chromatography (GCxGC) it may now be possible to analyze the complex Fischer-Tropsch products in a relatively short time while delivering good separation of even minor compounds such as oxygenates and branched compounds. The aim of this study was to investigate if two-dimensional gas chromatography (GCxGC) really results in improved separation and identification of compounds in the complex Fischer-Tropsch product spectrum and will lead to a more complete product distribution especially of the minor compounds such as branched hydrocarbons, ketones, aldehydes and acids. For this study GCxGC equipment, supplied by Zoex Corporation, was connected to a micro slurry phase reactor system to provide for both on-line gas analysis as well as off-line product analysis. GCxGC methods were developed to analyze the hot tail gas and oil products from Fischer-Tropsch synthesis. Thereafter a test sample (C6 to C30 oil product from Fischer- Tropsch synthesis process) was injected several times into both the GCxGC and 1D GC systems. The purpose of this was to compare the detection ability and accuracy of the two instruments.
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Miura, Masashi, Masakazu Itoh, Yusuke Ichino, Yutaka Yoshida, Yoshiaki Takai, Kaname Matsumoto, Ataru Ichinose, Shigeru Horii, and Masashi Mukaida. "Effect of Sm/Ba substitution on the J/sub c/ in magnetic field of SmBCO thin films by low temperature growth technique." IEEE, 2005. http://hdl.handle.net/2237/6778.
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Zheng, Hanguang. "Processing and Properties of Die-attachment on Copper Surface by Low-temperature Sintering of Nanosilver Paste." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/42658.
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As the first level interconnection in electronic packages, chip attachment plays a key role in the total packaging process. Sintered nanosilver paste may be used as a lead-free alternative to solder for die-attachment at sintering temperature below 300 °C without applying any pressure. Typically, the substrate, such as direct bond copper (DBC) substrates, has surface metallization such as silver or gold to protect the copper surface from oxidation during the sintering process. This study focused on developing techniques for die-attachment on pure copper surface by low-temperature sintering of nanosilver paste. One of the difficulties lies in the need for oxygen to burn off the organics in the paste during sintering. However, the copper surface would oxidize, preventing the formation of a strong bond between sintered silver and copper substrate.
Two approaches were investigated to develop a feasible technique for attachment. The first approach was to reduce air pressure as a means of varying the oxygen partial pressure and the second approach was to introduce inert gas to control the sintering atmosphere. For the first method, die-shear tests showed that increasing the oxygen partial pressure (PO2) from 0.04 atm to 0.14 atm caused the bonding strength to increase but eventually decline at higher partial pressure. Scanning electron microscopy (SEM) imaging and energy dispersive spectroscopy (EDS) analysis showed that there was insufficient oxygen for complete organics burnout at low PO2 condition, while the copper surface was heavily oxidized at high PO2 levels, thus preventing strong bonding. A maximum bonding strength of about average 8 MPa was attained at about PO2 = 0.08 atm. With the second method, the die-shear strength showed a significant increase to about 24 MPa by adjusting the oxygen exposure temperature and time during sintering.
The processing conditions necessary for bonding large-area chips (6 mm à 6 mm) directly on pure copper surface by sintering nanosilver paste was also investigated. A double-print process with an applied sintering pressure of less than 5 MPa was developed. Die-shear test of the attached chips showed an average bonding strength of over 40 MPa at applied pressure of 3 MPa and over 77 MPa under 12 MPa sintering pressure. SEM imaging of the failure surface showed a much denser microstructure of sintered silver layer when pressure was applied. X-ray imaging showed a bond layer almost free of voids. Because the samples were sintered in air, the DBC surface showed some oxidation. Wirebondability test of the oxidized surface was performed with 250 μm-diameter aluminum wires wedge-bonded at different locations on the oxidized surface. Pull test results of the bonded wires showed a minimum pull-strength of 400 gram-force, exceeding the minimum of 100-gf required by the IPC-TM-650 test standard.Master of Science
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Amro, Raed. "Power cycling capability of advanced packaging and interconnection technologies at high temperature swings." Doctoral thesis, [S.l. : s.n.], 2006. https://monarch.qucosa.de/id/qucosa%3A18552.
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Xiao, Kewei. "A diffusion-viscous analysis and experimental verification of the drying behavior in nanosilver-enabled low-temperature joining technique." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/25137.
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The low-temperature joining technique (LTJT) by silver sintering is being implemented by major manufacturers of power electronics devices and modules for bonding power semiconductor chips. A common die-attach material used with LTJT is a silver paste consisting of silver powder (micron- or nano-size particles) mixed in organic solvent and binder formulation. It is believed that the drying of the paste during the bonding process plays a critical role in determining the quality of the sintered bond-line. In this study, a model based on the diffusion of solvent molecules and viscous mechanics of the paste was introduced to determine the stress and strain states of the silver bond-line. A numerical simulation algorithm of the model was developed and coded in the C++ programming language. The numerical simulation allows determination of the time-dependent physical properties of the silver bond-line as the paste is being dried with a heating profile. The properties studied were solvent concentration, weight loss, shrinkage, stress, and strain. The stress is the cause of cracks in the bond-line and bond-line delamination. The simulated results were verified by complementary experiments in which the formation of cracks in bond-line and interface delamination was observed during the pressure-free drying of a die-attach nanosilver paste. Furthermore, the important drying parameters, such as drying pressure, low temperature drying time and temperature ramp rate of nanosilver LTJT process, are experimentally studied and analyzed with the numerical simulation. The simulated results were consistent with the experimental findings that the quality of sintered silver bond-line increases with increasing external drying pressure, with increasing low temperature drying time, and with decreasing temperature ramp rate. The insight offered by this modeling study can be used to optimize the process profile that enable pressure-free, low-temperature sintering of the die-attach material to significantly lower the cost of implementing the LTJT in manufacturing.Ph. D.
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Ichino, Yusuke, Yutaka Yoshida, Kouichi Inoue, Toshinori Ozaki, Yoshiaki Takai, Kaname Matsumoto, Masashi Mukaida, Ryusuke Kita, Ataru Ichinose, and Shigeru Horii. "Effect of BaZrO3 Addition and Film Growth on Superconducting Properties of (Nd,Eu,Gd)Ba2Cu3Oy Thin Films." IEEE, 2009. http://hdl.handle.net/2237/13894.
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Poole, Warren J., Matthias Militzer, J. Huang, S. C. Vogel, and C. Jacques. "The study of low-temperature austenite decomposition in a Fe–C–Mn–Si steel using the neutron Bragg edge transmission technique." Elsevier, 2007. http://hdl.handle.net/2429/397.
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A new technique based on the study of the transmitted neutron beam has been developed to study the low-temperature decomposition of austenite in a 0.4 wt.% C–3 wt.% Mn–2 wt.% Si steel. Experiments were conducted in which the neutron beam continuously passed through a specially designed layered sample, the temperature of which could be controlled to allow for a high-temperature austenization treatment followed by accelerated cooling to an isothermal transformation temperature in the range of 275–450 °C. It was possible to measure the volume fraction of the face-centred cubic (fcc) and body-centred cubic (bcc) phases and the carbon concentration of the fcc phase by characterizing the neutron Bragg edges in the transmitted beam. This provides a technique for in situ continuous measurements on the decomposition of austentite. The technique has been validated by comparing the data with other experimental techniques such as dilatometry, quantitative optical metallography and room temperature X-ray diffraction.
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Venclíková, Michaela. "Využití pěnoasfaltu v asfaltových směsích." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-372058.
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In this diploma thesis there are described the issues use of foamed bitumen as binder in asphalt mixtures. The thesis is divided into two parts, theoretical and practical. The aim of theoretical part was to elaborate an overview of technologies, which allow to reduce the temperature during the production and laying of asphalt mixtures. The aim of the practical part was to compare the selected empirical and functional parameters of two types of asphalt mixtures produced in two variants, with hot bitumen and foamed bitumen. Attention was paid mainly to stiffness and low temperature parameters.
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Houbloss, Samir. "Detection thermique de l'absorption optique : developpement de la technique, informatisation, etudes d'elements 3d dans des materiaux iii-v." Clermont-Ferrand 2, 1988. http://www.theses.fr/1988CLF21078.
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Developpement d'une technique nouvelle de detection de l'absorption optique, tres sensible aux basses temperatures. Construction d'un spectrometre equipe de differents cellules et informatise. L'appareillage a permis la detection des bandes et des raies a zero phonon associees a la presence du chrome, du vanadium et du titane dans les materiaux iii-v
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Casado, Mathieu. "Water stable isotopic composition on the East Antarctic Plateau : measurements at low temperature of the vapour composition, utilisation as an atmospheric tracer and implication for paleoclimate studies." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLV058/document.
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Les carottes de glace permettent de reconstruire le climat du passé, à partir entre autre de la composition isotopique de l’eau (δ18O, δ17O et δD). Sur le plateau Est Antarctique, les températures très froides et les faibles accumulations permettent de remonter le plus loin dans le passé (jusqu’à 800 000 ans) mais compliquent l’interprétation du signal isotopique. Premièrement, les reconstructions des variations de température dans les carottes de glace à partir des isotopes de l’eau se basent sur des modèles pour décrire l'évolution de la composition isotopique de la vapeur et de la phase condensée le long du cycle de l’eau. Ces modèles, qui ont été développés au cours des dernières décennies, reposent sur la connaissance de coefficients du fractionnement isotopique associé à chaque transition de phase et sur des hypothèses pour représenter la micro-physique des nuages.Lors de la formation de flocons de neige à basse température, 2 types de fractionnements isotopiques doivent être pris en compte : le fractionnement isotopique à l'équilibre, associé à la transition de phase vapeur-glace et le fractionnement isotopique cinétique lié aux différentes diffusivités des différents isotopes. A basse température, les déterminations des coefficients du fractionnement du fractionnement à l’équilibre présentent d’importantes différences et n’ont jamais pu être mesurées à des températures inférieures à -40°C. Or la température moyenne annuelle à Dome C est de -54°C atteignant jusqu’à -85°C l’hiver. Les diffusivités des différents isotopes quant à elles n’ont jamais été mesurées à des températures inférieures à 10°C. Toutes ces lacunes résultent dans des incertitudes importantes sur le lien entre la composition isotopique et la température dans des conditions comme celles du Plateau Est Antarctique.De plus, dans ces conditions froides et arides, les processus physiques qui affectent la composition isotopique de la neige après la déposition des flocons deviennent importants compte tenu du faible apport annuel de précipitation. Pour estimer l’impact de ces processus de post-déposition sur la composition isotopique, il est nécessaire de bien caractériser le fractionnement isotopique à l’interface neige/atmosphère pour des températures allant jusqu’à -90°C.Afin d’améliorer les reconstructions quantitatives de température l’étude des processus affectant la composition isotopique de la glace à très basse température est donc primordiale. Dans cette optique, ma thèse a été à l’interface entre les études de processus au laboratoire et en Antarctique et le développement instrumental afin de pouvoir réaliser des mesures isotopiques encore inédites, en particulier à très basse humidité. D’un côté, j'ai développé d’un nouveau spectromètre infrarouge aux performances bien au-delà des instruments commerciaux. En effet, la fréquence du laser est stabilisée par rétroaction optique par une cavité ultra-stable jusqu’à un niveau de stabilité de l’ordre du hertz. La lumière est ensuite injectée dans une cavité CRDS hautes performances avec une sensibilité de 10-13 cm-1.Hz-1/2. Ceci permet de mesurer la composition isotopique avec une précision inférieure au ppm.En parallèle, des expériences au laboratoire ont permis de renforcer les connaissances sur les processus affectant les isotopes de l’eau, en particulier le fractionnement lié à la transition de phase vapeur - glace et le fractionnement cinétique lié aux différentes diffusivités des différents isotopes en modélisant le fractionnement lié à la diffusion près d’un point froid. Enfin, durant une campagne en Antarctique, j’ai pu réaliser parmi les premières mesures de la composition isotopique de la vapeur et de la glace en Antarctique et appliquer les modèles physiques des processus à des données de terrain. Ces mesures montrent que le cycle de sublimation/condensation contribue de manière importante à la composition isotopique de la neige sur le plateau Est AntarctiqueIce cores enable reconstruction of past climates, from among others water stable isotopic composition (δ18O, δ17O et δD). On the East Antarctic Plateau, very cold temperature and low accumulation provide the longest ice core records (up to 800 000 years) but embrangle the interpretation of isotopic composition. First, reconstructions of temperature variations from ice core water isotopic composition are based on models used to describe the evolution of the isotopic composition of the vapour and of the condensed phase over the entire water cycle. These models have been developed during the last decades and depend upon precise determinations of isotopic fractionation coefficients associated to each phase transition and upon hypotheses to describe cloud microphysics.During the formation of snowflakes at low temperature, two types of isotopic fractionations need to be taken into account: equilibrium fractionation, associated to the vapour to ice phase transition and kinetic fractionation associated to the difference of diffusivity of the different isotopes. At low temperature, determinations of equilibrium fractionation coefficients present important discrepancies and have never been realised for temperature below -40°C. However, mean annual temperature at Dome C is around -54°C reaching -85°C in winter. For the diffusivities of the different isotopes, they have never been measured at temperature below 10°C. All these gaps result in important uncertainties on the link between isotopic composition and temperature, especially for cold and dry conditions such as encountered on the East Antarctic Plateau.Furthermore, because of the very low amount of precipitation, physical processes affecting the isotopic composition of the snow after the deposition of snowflakes can results in an important contribution to the isotopic budget. In order to estimate the impact of the post-deposition processes on the water vapour isotopic composition, it is necessary to characterise the isotopic fractionation at the snow/atmosphere interface for temperature down to -90°C.In order to improve isotopic paleothermometer performances, it is primordial to study processes affecting snow isotopic composition. Toward this goal, my Ph-D has been at the interface between monitoring of processes affecting isotopes, both in laboratory experiments and field studies, and instrumental development to push the limits of water vapour isotopic composition trace detection. On one hand, new developments in optical feedback frequency stabilisation applied for the first time to water isotopic composition monitoring provide performances beyond any commercial instrument and can be used for thorough processes studies. The laser frequency is stabilised by optical feedback from an ultra-stable cavity to the hertz level. Then, the light is injected in high performances cavity with a sensibility of 10-13 cm-1.Hz-1/2. This enables measuring isotopic composition with a precision below the ppm level.On the other hand, laboratory experiments have supported theories about isotopic fractionation associated to the vapour to ice phase transition and to kinetic fractionation linked to the difference of diffusivities of the different isotopes. Finally, these physical models have been collated to field measurements realised at Dome C in Antarctica, which are among the first water vapour and snow isotopic composition measurements realised inland Antarctica. These measurements show how important is the contribution of the sublimation condensation cycles to the snow isotopic composition budget on the East Antarctic Plateau
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Lin, Yan-Tsang, and 林彥滄. "Process- and Temperature-Compensated Techniques and Solar-Powered Techniques of Low-Noise Amplifiers." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/95157027375063136087.
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碩士國立高雄師範大學
電子工程學系
101
This thesis proposes the process- and temperature-compensated techniques and the solar-powered techniques of the low-noise amplifier (LNA). For process and temperature compensation, a body-bias technique is used to compensate the RF parameters of the LNA. This LNA is designed and implemented using the 0.18 μm CMOS standard process. For process compensation, the variation in noise figure (NF) is reduced from 0.8 dB to 0.2 dB and the variation in gain is reduced from 5.33 dB to 0.2 dB. For temperature compensation, the variation in noise figure (NF) is reduced from 1.25 dB to 0.89 dB and the variation in gain is reduced from 1.06 dB to 0.35 dB. For solar self-powering, a 2.4 GHz LNA is designed and implemented using the 0.18 μm CMOS standard process for ZigBee applications. A solar panel with a regulator circuit directly converts solar power to the electrical power of the LNA, as required to provide green energy. Measurements of the solar-powered 2.4 GHz LNA are made, revealing that the NF is 2.91 dB, the gain is 10.89 dB, and the input-referred third-order intercept point (IIP3) is 0 dBm. A voltage of 0.6 V is supplied to the LNA and the power consumption is then 1.08 mW.
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Lee, Shin-De, and 李信德. "Low Temperature Bonding Techniques for Sealing Teflon Based Microfluidic Devices." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/66478814280063664162.
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碩士國立中山大學
機械與機電工程學系研究所
100
Microfluidics emerged during the early 1990s with channel networks in silicon or glass. Microprocessing of these materials is labor-intensive and time-consuming, it requires sophisticated equipment in a clean room, and often involves hazardous chemicals. The subsequent use of polymer greatly simplified the fabrication of microchips and led to the rapid development of the field. Polymer such as poly(dimethylsiloxane) (PDMS), has other attractive properties, such as being elastic (easy to make efficient microvalves), permeable to gases, and compatible with culturing biological cells. Despite these advantages, applications of PDMS chips are severely limited by a few drawbacks that are inherent to this material: (i) strong adsorption of molecules, particularly large biomolecules, onto its surface; (ii) absorption of nonpolar and weakly polar molecules into PDMS bulk; (iii) leaching of small molecules from PDMS bulk into solutions; and (iv) incompatibility with organic solvents. To overcome all these problems, Teflon plastics seem to be the perfect solution. They are well-known for their superior inertness to almost all chemicals and all solvents; they also show excellent resistance to molecular adsorption and molecule leaching from the polymer bulk to solutions. However, Teflon has a high chemical inertness of the surface, which is restricted the bonding temperature (>260°C).It is not conducive to the low-temperature packaging process. This study presents a simple and rapid process for sealing Teflon-based microfluidic chip at a temperature of 140oC which is lower than typical bonding temperature of 260oC. A simple ammonium plasma treatment is used to enhance the surface energy of Teflon substrates such that the bonding temperature can be greatly reduced. Results indicate that the ammonium plasma treated Teflon substrates can be sealed using hot press bonding at a temperature of 140oC for 20 min. The measured iv bonding strength for the Teflon-based microfluidic devices is higher than those bonded at a reported temperature of 260oC for 60 min. It shows the measured contact angle for the Teflon substrates treated with different plasmas. Results indicated that the ammonium hydroxide plasma exhibited the best wettability property and the contact angle reached the minimum value of 45o after 5 min of treatment. The ESCA analysis showed the best Defluorination by ammonium plasma. The fluorine/carbon atomic ratio degraded from 1.96 to 1.10 by 5 minutes. The measured bonding strength for the Teflon substrates bonded with different surface activation protocols. Results showed that the bonding strength was enhanced upto 93% after the plasma treatment. The plasma treatment not only enhanced the bonding strength but also reduced the bonding temperature and time. The measured surface roughness only increased 15±5 nm (Ra) after the plasma treatment, which is acceptable for most applications in microfluidic systems. Finally, the fluorescence optical architecture and cross-chip successfully detected and isolated ΦX-174 fragment of DNA samples confirmed the Teflon substrate for the emerging microfluidic plastic chip. The developed method provides a simple and rapid way to fabricate Teflon-based microfluidic devices.
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Chen, You Shen, and 陳宥伸. "Preparation of Perovskite Solar Cells Using Low-temperature Solution Processing techniques." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/f2tg2d.
Full textAbstract:
碩士長庚大學
光電工程研究所
104
Solar is a renewable energy, Power generation process does not produce greenhouse gases carbon dioxide emissions, for the protection of the environment is very helpful; from 2012 to the rapid progress of perovskite solar cells, compared with silicon solar cells, which have the advantages of low material cost, Preparation of solution method, low cost manufacturing process, and its photoelectric conversion efficiency of silicon solar cells is expected to catch up, many scientists have also invested in this research effort. Perovskite solar cells perovskite layer made way roughly divided into two types, one is to use the one-step production, is to methylamine iodide (MAI) with lead iodide (PbI2) both Moore and other dissolved proportion after DMF was spin-coated on a substrate; and a two-step rule is the first spin-coated on a substrate PbI2, then soaked after film or iodine drops methylamine grow perovskite crystalline; used in this experiment produced a two-step method. We found that the changed PbI2 standing time will affect their different deposition patterns, the extent of the longer standing PbI2 the aggregation of particles leading to greater perovskite crystal patterns will vary from can be observed on the XRD perovskite films of different PbI2 standing time in the (001) peak characteristic changes significantly, standing at the time when the minimum peak 150s, 150s on behalf of the use of standing time making PbI2 film with 30mg/mL of MAI has the best solution crystalline state. Our success to make efficiency of 10.57% perovskite solar cells, JSC of 16.85mA/cm2, VOC is 1.01V, F.F. of 61.9%, also after continuous measurements found in the first four days up to maximum efficiency 12.65 %. Discussion with the addition of lead iodide standing time of lead iodide with methyl iodide amine concentration both outside, in order to improve the stability of the device, we also try to join the mesoporous layer observation element of the performance, first we direct the dense layer on the ZnO production of mesoporous TiO2 layer, then a two-step method to create elements, we change the spin speed to create different mesoporous layer, only the most efficient battery JSC of 8.89mA/cm2, VOC can reach 1.04V, F.F. of 50.4% efficiency of 4.66%, showed that under these conditions we did not have better cell performance. In addition, we also try to use the TTIP and TiO2(P90) to two different solution volume ratio of production to replace the dense layer of dense ZnO layer found in full without adding TTIP conditions, cell efficiency of up to 7.94%, then this condition further change speed control different mesoporous layer film, you can then create the conditions 1500rpm efficiency of 10.39% of the element JSC up 16.82mA/cm2, VOC is 1.008V, F.F. was 61.3%.
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Lu, Wei Xin, and 盧維新. "Application of low-temperature deposition and high-temperature rapid thermal treatment techniques on the fabrication process of silicon gate oxides." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/25388417596047777464.
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Wang, Shen-De, and 王獻德. "Study on Fluorine Passivation Techniques and the Reliability for Low Temperature Polycrystalline Silicon Thin-Film Transistors." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/83465719750608671993.
Full textAbstract:
博士國立交通大學
電子工程系所
94
In this thesis, various fluorine passivation techniques for fabricating high-performance and high-reliability polycrystalline silicon thin-film transistors (poly-Si TFTs) are proposed and discussed. In addition, the On-current (Ion) and Off-current (Ioff) instabilities of poly-Si TFTs under electrical stress are thoroughly investigated. At last, a new scheme by employing high-resolution scanning capacitance microscopy (SCM) is developed to scan the breakdown spots on oxide films. First, a process-compatible CF4 plasma treatment for fabricating high-performance solid-phase-crystallized (SPC) poly-Si TFTs is demonstrated. Using this technique, fluorine atoms can be introduced into poly-Si films to passivate trap states, and hence the performance of SPC poly-Si TFTs can be significantly improved. The fluorinated SPC poly-Si TFTs exhibit good subthreshold slope, low threshold voltage, and better On/Off current ratio. The fluorinated poly-Si TFT also shows approximately 22.8 % enhancement in the maximum field-effect mobility. Moreover, the CF4 plasma treatment also promotes the device’s hot-carrier immunity. Then, CF4 plasma treatment combined with excimer laser annealing (ELA) is proposed to fabricate high-performance ELA poly-Si TFTs. Fluorine can effectively passivate the trap states near the SiO2/poly-Si interface. With fluorine incorporation, the electrical characteristics of ELA poly-Si TFTs are significantly improved. The CF4 plasma treatment also improves the device reliability of ELA poly-Si TFTs with respect to hot-carrier stress, which is due to the formation of strong Si-F bonds. Another fluorine passivation technique is also proposed by adopting fluorinated silicate oxide (FSG) as a buffer layer. Experimental results reveal that the device performance, uniformity and reliability can be remarkably improved with appropriate fluorine content (2% to 4%) in the FSG layer. Then, the On-current (Ion) and Off-current (Ioff) instabilities of poly-Si TFTs are thoroughly investigated under various electrical stress conditions. The stress-induced device degradation is studied by measuring the dependences of Ion and Ioff on the applied drain/gate voltages. From the results, dissimilar variations of Ion and Ioff can be observed, which is attributed to the variances in the amount of trap charges in the gate oxide and the spatial distributions of trap states generated in the poly-Si channel. A comprehensive model for the degradation of Ion and Ioff in poly-Si TFTs under various electrical stress conditions is proposed. Finally, scanning capacitance microscopy (SCM), combined with atomic force microscopy (AFM), is employed to investigate the dielectric breakdown phenomena in SiO2 films. The localized breakdown spots can be clearly imaged by this technique. The breakdown spots exhibit signals with low differential capacitance (dC/dV) due to high conductivity. The diameters of these breakdown spots are from 6 nm to 13.5 nm. Moreover, according to the corresponding AFM images, their surface morphology shows little change after the occurrence of oxide breakdown.
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Hu, Shen-Chih, and 胡慎知. "The Study of Resource Recycling of Sludge by Low-Temperature Co-melting and Surface Modified Techniques." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/33371822772130335997.
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博士國立東華大學
材料科學與工程學系
101
Sewage sludge is produced by urban waste water treatment. Because of the perishable organic substances, sludge disposal without advanced treatment can produce public health problem. Lightweight aggregate synthesized with sewage sludge is a feasible method for sludge recycling and natural constructive materials saving, but the sintering temperature is always over 1000 oC to form melting glassy phase and large energy is consumed. This study focused on adding some low melting point compounds (H3BO3 and Na2CO3) as flux in order to lower the sintering temperature of artificial aggregates. Water adsorption, apparent porosity, bulk density, compressive strength, and soundness test were applied to evaluate the effect of experiment condition on the characteristics of synthetic aggregates. In addition, there were three other wastes which were used as raw materials for aggregates synthesis in this study, including sludge ash derived from sewage sludge, paper sludge and stone manufacturing sludge. As a result, all these industrial waste could be transformed to lightweight aggregates by thermal treatment and the characteristics of these aggregates were different in a reasonable range. According to the experimental design, sewage sludge was adjusted by adding SiO2 to make the SiO2/Al2O3 ratio of the conditioned sludge up to 4. When the flux of H3BO3 was used, 3 wt% of conditioned sludge of CaO was added to prevent the occurrence of black core phenomenon. Conditioned sewage sludge mixed with 13 wt% H3BO3 and 3 wt% CaO were heated at 400 oC for 0.5 hr and 850 oC for 1hr was followed to get highest compressive strength aggregate. The values of four primary parameters of aggregate (including water adsorption, apparent porosity, bulk density and compressive strength) were 3.88 %, 3.93 %, 1.05 g/cm3, 29.7 MPa. The flux was Na2CO3, the highest value of compressive strength of aggregates were got when sludge mixed with 16 wt% Na2CO3 and sintered at 400 oC for 0.5 hr; 900 oC for 1 hr. The values of the four primary parameters of aggregates are 1.36 %, 1.7 %, 1.26 g/cm3, and 27.7 MPa. Sewage sludge ash was also adjusted by adding SiO2 and the ratio of SiO2/Al2O3 was 4. The identical dosages of both H3BO3 and Na2CO3 were 22 wt% of conditioned ash. When the flux was H3BO3, the synthetic aggregates with high compressive strength were sintered at 900 oC for 15 min. When the flux was Na2CO3, the aggregates with higher compressive strength were sintered at 900 oC for 0.5 hr. The values of the four primary parameters of aggregates mentioned above were 5.43 %、5.15 %、0.97 g/cm3、29.2 MPa and 1.42 %、1.64 %、1.17 g/cm3、88.4 MPa respectively. Because the content of Si of paper sludge was too low, SiO2 was added to make the SiO2 content up to 12 wt% of the wet paper sludge. The dosage of H3BO3 was 18 wt% of the conditioned paper sludge and the sintering program was 890 oC for 30 min. The aggregates synthesized with this procedure have the lower water adsorption and the values of the four primary parameters of aggregates are 4.64 %, 2.77 %, 0.6 g/cm3, and 13.2 MPa. Lightweight aggregates can be produced from stone manufacturing sludge with 15 wt% of H3BO3. The sintering program was set for 850 oC 15 min. The water adsorption, apparent porosity, bulk density and compressive strength of the aggregates were 0.21 %, 0.35 %, and 1.67 g/cm3 and 66.9 MPa. Sewage sludge, sewage sludge ash and paper sludge were investigated to be adsorbent for Methylene Blue (MB, cationic dye) and Procion Red MX-5B (PR, ionic dye). Sewage sludge contained organic compounds with oxygen-rich functional group (such as humic substances) which can adsorb pollutants in the water. In order to improve the adsorption ability and filtration efficiency of sewage sludge, Fe3O4 was synthesized on the sewage sludge by hydrothermal method. Fe3O4 can not only act as an adsorptive site for ionic dye, but also decrease the specific resistance of sewage sludge by crystallization. The experimental results showed that ideal pH for modified magnetic sewage sludge to adsorb MB and PR were 6 and 3, and the isotherm adsorption was fitted well to Langmuir equation. The maximum adsorption capacity for MB and PR were 25.06 and 18.83 mg/g. Pseudo-first-order and pseudo-second-order models were utilized to realize the kinetic adsorption of MB and PR. The adsorption data of both dyes were fitted pseudo-second-order model well and the activation energy of MB and PR adsorption were 42.78 kJ/mol and 32.69 kJ/mol, respectively. The crystalline of Fe3O4 synthesized on sewage sludge improved the filtration efficiency of modified magnetic adsorbent and the filtration resistance was decreased from 1.34×107 s2/g to less than 0.08×107 s2/g. Different from sewage sludge, sludge ash was under thermal treatment and the organic compounds were oxidized to CO2 so that sludge ash particle possessed no organic functional group on the surface. In this study, ferrite process was also conducted on sludge ash and Fe3O4 can act as adsorptive site for ionic dyes because Fe3O4 can provide electrostatic attraction to ionic dyes. The zeta potential of Fe3O4 was positive in acid and anionic dye can be adsorbed. Similarly, that was negative in alkali solution and cationic dye can be adsorbed. As the result of adsorption, MB was well adsorbed in pH 9 and that for PR was 2.7 which corresponded to the zeta potential of modified magnetic sludge ash. The isotherm adsorption and kinetic adsorption of MB and PR were also investigated. For isotherm adsorption, the results were fitted Langmuir equation well and the maximum adsorption capacities of MB and PR were 22.27 mg/g and 28.8 mg/g. For kinetic adsorption, pseudo-first-order and pseudo-second-order models were utilized to examine the adsorption behavior and the results were fitted pseudo-second-order models well. The activation energy calculated from Arrhenius equation was 61.7 kJ/mol for MB and 9.07 kJ/mol for PR. Owing to paper sludge contained large amount of organic compounds such as fibers and lignin, it could be pyrolyzed to form activated carbon for dye adsorption. In this study, paper sludge was pyrolyzed under nitrogen atmosphere at 600 oC 1 hr. Then, sample was washed with 1 M HCl and DI water, and dried in an oven. The zeta potential measurement of adsorbent showed that the isoelectric point of paper sludge derived activated carbon was around 3 which meant PR should be adsorbed well below pH 3 and that of MB was in neutral or alkali solution. The effect of pH on adsorption, isotherm adsorption and kinetic adsorption were examined to realize the adsorption behavior of paper sludge derived activated carbon. The results of adsorption in different pH condition were conformed to the results of zeta potential. The data of isotherm adsorption experiment revealed that the adsorption behavior can be described by Langmuir equation well and the maximum adsorption capacities of MB and PR were 119.1 mg/L and 65.8 mg/L. Kinetic adsorption revealed that the adsorption of two dyes were fitted pseudo-second-order model well, and the activation energy of MB and PR adsorption were 8.66 and 2.47 kJ/mol.
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Shye, Der-Chi, and 史德智. "Low-Temperature Processing Techniques Applied on Barium Strontium Titanate Films for the Applications of DRAM Storage Capacitors." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/85373278879314570415.
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博士國立交通大學
電子工程系所
93
The characteristics of (Ba, Sr)TiO3 thin films, prepared by novel techniques of low temperature treatments, were systematically studied in this thesis. Pt/TiN/Ti/Si substrates were applied on each sample to simulate the real capacitor over bit-line (COB) structure of dynamic random access memory (DRAM). (Ba, Sr)TiO3 (BST) films were sputtered by radio frequency (RF) magnetron system with dual targets at low substrate temperature, lower than 450oC (340oC at sample surface), and the effects of the process parameters were also investigated. The work pressure, the sputtering gun power and the gas-mixing ratio are the important parameters in the BST film deposition. Material analyses and electrical testing show that the low temperature BST films are significantly affected by those process parameters. The O2/(Ar+O2) mixing ratio (OMR) is a most critical parameter during BST film sputtering. Plasma emission spectra indicate that the deposition rate declines at a higher OMR due to oxide formation on the target surface. The dielectric constant of the BST films can reach a maximum of 364 at 5% OMR. The ten-year lifetime of the time-dependent dielectric breakdown (TDDB) implies that the reliability of the capacitor can be enhanced at a higher OMR due to the compensation of oxygen vacancies and smaller grain sizes. Current-voltage analysis indicates that the leakage current of the Pt/BST/Pt capacitor is limited by Schottky emission (SE)/Poole-Frenkel emission (PF) at a lower/higher applied field, accordingly. The applied field boundary between SE and PF shifts toward higher field as OMR increases. Moreover, an energy-band model was proposed and this leakage mechanism was also discussed. Post low-temperature treatments were applied on the BST films to further improve their crystallinities and electrical properties. A novel process, KrF excimer laser annealing (ELA) at the wavelength of 248 nm, had been undertaken to implement BST films at a process temperature of 300o C to avoid the steep thermal gradient in thin films. The dielectric constant of the amorphous (α) BST film was remarkably enhanced from 80 to over 250 after ELA treatment. The optical testing and the heat conduction analyses indicate that the underlayer films and devices cannot be damaged during ELA treatment due to a very shallow light absorption depth (20 nm) of the BST film at the wavelength of 248-nm. Besides, the laser energy fluence and film thickness greatly influence the thermal conduction and the temperature distribution within the BST films. In the meanwhile, the as-deposited films revealed (mm0) preferred orientation, and, intriguingly, the preferred orientations changed into (m00) and (mmm) after ELA treatments. The optical and the high frequency properties may be affected by this preferred-orientation change. However, although the ELA can perform “shallow-depth annealing” for BST thin film, the degradation of upper surface is strongly influenced by the laser energy fluence. Hence, the leakage current will be significantly affected by the energy fluence of the laser. The leakage current of the ferroelectric film increases after sputtering process and post ELA treatment, but post oxygen plasma treatment can effectively improve the BST film surface to suppress the leakage at low processing temperature of 250oC. According to the analysis results in this thesis, the oxygen plasma treatment can effectively passivate the oxygen vacancies of BST films, decreasing the leakage currents. The leakage current can be reduced as many as two orders of magnitude under proper control of plasma conditions. The characteristics of the dielectric reliability, TDDB, can be also improved by this treatment due to the compensation of the surface oxygen vacancies. In addition, a nano-scaled chromium (Cr) layer is applied onto (Ba, Sr)TiO3 (BST) thin film capacitor as an inter-layer to enhance thermal stability of capacitance and suppress leakage current. Temperature coefficient of capacitance (TCC) using this BST/Cr/BST (200nm/2nm/200nm) multifilm can achieve 30% lower than that using BST mono-layer (400nm) film. Besides, the leakage current can be also greatly suppressed by applying this nano-scaled Cr layer onto BST thin film capacitor. TCC and leakage current behave as functions of Cr thickness, so the optimal properties can be obtained with the Cr thickness of 2nm. Microstructure analysis suggests that the interfacial continuity strongly influences the TCC and leakage property due to scattering centers and series capacitance formed at imperfect interface. The correlated mechanisms between electric and material properties are systematically investigated in this work. BST thin film can be the most promising candidate for Giga-bit generation cell capacitor, because the low temperature processes can be compatible to the IC’s integration. In this thesis, the optimal properties of the BST films can be obtained by adjusting process parameter, applying post treatments and using thermal stabilization structures to achieve thorough low-temperature processes.
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Wang, jui-hao, and 王瑞豪. "Fabrication of Low-Temperature Poly-Si Thin-Films Using Hot-Wire CVD and Al-induced Crystallization Techniques." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/99574835223515040275.
Full textAbstract:
碩士國立中興大學
材料工程學研究所
93
The study utilized hot-wire chemical vapor deposition (HWCVD) which mixed different ratio of SiH4 and H2 to deposit Si-film rapidly and also used aluminum-induced crystallization (AIC) to fabricate high-quality polycrystalline silicon (poly-Si) films which served as a seed layer and accumulated large grain poly-Si films quickly above the seed layer. The purpose of the study was to investigate the change of AIC thin films due to different annealing time and temperature, and to further analyze characteristics by X-ray diffraction (XRD), Raman spectroscopy diffraction techniques, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Hall measurement of the seed layer that was produced by the AIC technique and poly-Si films on seed layer that were deposited by HWCVD. For analysis of each layer, the poly-Si film have been used to detect the crystallization and preferred (111), (220) and (311) orientation by XRD and Raman spectroscopy diffraction techniques which be stronger than AIC-film. The microstructures of each film were observed by SEM and TEM. It was found that the AIC of grain was approximately 1 µm and the Si layers formed on seed layer of grain (1 µm in size) can be obtained. However, the lateral grain size of poly-Si (deposited on seed layer) was larger than the poly-Si films deposited directly on a glass substrate by HWCVD. Since the Si-atoms deposit in the orientation of seed layer, the poly-Si would be obtained. As a result, high crystalline fractions (91 and 95%) and high electron mobility (22 and 18 cm2/V-s) of poly-Si films were obtained by using a combination of HWCVD and AIC techniques.
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Krywko-Cendrowska, Agata. "Low temperature, electrochemical deposition of silicon based films and their characterization by electrochemical, spectroscopic and microscopic techniques." Doctoral thesis, 2014. https://depotuw.ceon.pl/handle/item/952.
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The goal of the PhD thesis was electrochemical deposition and characterization of the photoactive in aqueous solutions SiOx films for potential applications as a photoanode material.
The experimental work of the thesis included electrodeposition of SiOx layers and their spectroscopic and microscopic analysis, photoelectrochemical characterization and optimization of the deposition conditions (potential and time of the deposition, type of the substrate, concentration of the SiHCl3 precursor) in order to obtain the highest photocurrent density in the studied systems.
The SiOx layers were deposited on the surface of Au, Pt and Cu electrodes from propylene carbonate (PC) solutions with SiHCl3 as silicon source. Because of the low conductivity of SiHCl3/PC solutions 0.1 M tert-butyl ammonium bromide (TBAB) was used as the supporting electrolyte. It was shown that the chemical composition, thickness and photoactivity of the films depended on the type of the substrate, SiHCl3 concentration and the deposition potential value. In order to determine the electrochemical window (stability) of the electrolyte and the potential range of the SiHCl3 reduction cyclic voltammetry (CV) was used. The potential range of SiHCl3 reduction varied depending on the type of the substrate used. In case of each substrate the deposition potential was chosen in order to fit into the beginning, center and the end of the reduction wave. The thickness of the deposits varied from 1 to 24 μm and the highest thickness was observed for the deposits obtained on Cu electrode.
The application of electrochemical, spectroscopic and microscopic techniques allowed the determination and optimization of the deposition conditions in order to obtain SiOx layers of the highest photoactivity and stability against the aqueous solutions.
The SiOx layers obtained on Au and Pt showed an n-type photoactivity (photooxidation reaction) in PC solution whereas films produced on Cu showed a p-type behavior (arising from a photoreduction reaction). The photoactivity of the films in 0.1 M perchloric acid (HClO4) aqueous solution was of an n-type independently on the type of the electrode used for the electrodeposition and the photocurrent was stable in time. By application of FTIR and XPS, it was shown that in each case after photogalvanic measurements the films still contained SiOx and in some cases also Si:H.
The highest value of the photocurrent (ca. 100 μm×cm-2) was registered for the deposit obtained on Au at -2.7 V vs. Ag. The photocurrent observed in water solution could result either from the reaction of oxygen (O2) photoevolution, or from the process of the films‘ photodecomposition, i.e. oxidation of a silicon based film (SiOx) to silica (SiO2). In order to distinguish between these two processes the charges required for film photodecomposition and the charge flowing during the photocurrent measurement were compared. It was shown that the photooxidation reaction observed during the illumination of the deposits in an aqueous solution corresponded to continuous O2 photoevolution. The possible negative influence of the mechanical degradation of the films (i. e. while drying) or eventually a non ideal ohmic deposit/electrode contact on the registered photocurrent density magnitude was mentioned as well.
In this thesis, it was demonstrated for the first time that SiOx based films directly electrodeposited in an organic solution could be photoactive in an aqueous solution. The observed electrical energy saving resulting from the exploitation of light energy corresponded to ca. 1.3 V. The presented results can open possibilities of cheap and efficient silicon based photoelectrodes preparation for construction of photogalvanic cells (i.e. wet photocells) for the water splitting process.Celem pracy było elektrochemiczne otrzymywanie i charakterystyka fotoaktywnych w roztworach wodnych filmów SiOx w celu potencjalnego zastosowania ich jako fotoanod. Praca eksperymentalna obejmowała elektroosadzenie warstw SiOx i ich spektroskopową i mikroskopową analizę, fotoelektrochemiczną charakterystykę oraz optymalizację warunków nanoszenia (potencjał i czas nanoszenia, rodzaj substratu, stężenie prekursora SiHCl3) w celu zarejestrowania możliwie najwyższych gęstości fotoprądów w badanych układach. Filmy SiOx osadzane były na powierzchniach elektrod Au, Pt i Cu z roztworu węglanu propylenu (PC) z użyciem trichlorosilanu (SiHCl3) jako źródła krzemu. W związku z niskim przewodnictwem roztworu SiHCl3/PC, zastosowano 0.1 M bromek tert-butylo amoniowy (TBAB) jako elektrolit pomocniczy. Wykazano, że chemiczny skład osadów, ich grubość oraz fotoaktywność zależała od rodzaju substratu, stężenia SiHCl3 i wartości potencjału osadzania. Woltamperometria cykliczna (CV) używana była w celu określenia szerokości okna elektrochemicznego (trwałości) elektrolitu oraz określenia zakresu potencjału redukcji SiHCl3 w zależności od używanego substratu. Zakres redukcji SiHCl3 był różny w zależności od zastosowanej elektrody, jednak w każdym przypadku starano się tak dobrać wartość potencjału osadzania aby znajdowały się na początku, w centrum i na końcu zakresu sygnału. Grubość osadów wynosiła od 1 do 24 μm, przy czym największe wartości zaobserwowano dla osadów otrzymanych na elektrodzie Cu. Użycie technik elektrochemicznych, spektroskopowych i mikroskopowych pozwoliło na określenie i optymalizację warunków osadzania filmów tak, aby otrzymać warstwy SiOx możliwie jak najbardziej fotoaktywne i stabilne w roztworach wodnych. Warstwy SiOx otrzymane na Au i Pt charakteryzowały się fotoaktywnością n-typu (reakcja fotoutlenienia) podczas pomiarów fotowoltaicznych w roztworze organicznym, natomiast filmy utworzone na Cu wykazały zachowanie typu p (pochodzące od reakcji fotoredukcji) w roztworach PC. Fotoaktywność osadów w wodnym roztworze kwasu nadcholowego (HClO4) była typu n, niezależnie od tego, na jakiej elektrodzie lub przy jakiej wartości potencjału były one osadzone. Za pomocą technik FTIR i XPS wykazano, że w każdym przypadku po pomiarze fotogalwanicznym filmy nadal zawierały SiOx, a niekiedy także Si:H. Ze wszystkich osadzonych filmów najwyższą wartość gęstości fotoprądu (100 μAcm-2) zarejestrowano dla filmu otrzymanego na Au przy -2.7 V vs. Ag. Fotoprąd zaobserwowany w wodnym roztworze HClO4 mógł pochodzić zarówno z fotowydzielania tlenu (O2), jak i z procesu fotokorozjii filmu, na przykład utlenienia SiOx do krzemionki (SiO2). W celu rozróżnienia tych dwóch procesów porównane zostały wartości ładunków potrzebne do ich realizacji z ładunkiem fotoprocesu zachodzącego w układzie. Wykazano, że reakcja fotoutlenienia zaobserwowana w toku pomiaru fotoelektrochemicznego w wodnym roztworze pochodziła od ciągłego fotowydzielania O2. W rozprawie poruszone były również kwestie mogące negatywnie wpływać na wartości uzyskiwanych gęstości fotoprądów takie jak degradacja mechaniczna (na przykład na etapie suszenia osadu) lub też ewentualna niedoskonałość kontaktu omowego pomiędzy elektrodą a półprzewodzącym osadem SiOx. W toku niniejszej pracy po raz pierwszy zademonstrowano, że warstwy SiOx elektrochemicznie osadzone w roztworze organicznym były fotoaktywne w roztworze wodnym. Zaobserwowany zysk energetyczny uzyskany przy użyciu oświetlenia wynosił około 1.3 V. Zaprezentowane wyniki otwierają możliwość konstrukcji tanich i wydajnych fotoelektrod opartych na Si i zastosowania ich w ogniwach fotogalwanicznych (tzw. ogniwach mokrych).
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"Analyzing Techniques for Increasing Power Transfer in the Electric Grid." Master's thesis, 2012. http://hdl.handle.net/2286/R.I.15926.
Full textAbstract:
abstract: The worldwide demand for electric energy is slated to increase by 80% between the years 1990 and 2040. In order to satisfy this increase in load, many new generators and transmission lines are planned. Implementations of various plans that can augment existing infrastructure have been hindered due to environmental constraints, public opposition and difficulties in obtaining right-of-way. As a result, stress on the present electrical infrastructure has increased, resulting in congestion within the system. The aim of this research is to analyze three techniques that could improve the power transfer capability of the present electric grid. These include line compaction, use of high temperature low sag conductors and high phase order systems. The above methods were selected as they could be readily employed without the need for additional right-of-way. Results from the line compaction tests indicate that line compaction up to 30% is possible and this increases the power transfer capability up to 53%. Additional advantages of employing line compaction are the reduction in electric and magnetic fields, increase in system stability and better voltage regulation. High temperature low sag conductors that were applied on thermally limited lines were seen to increase the power transfer capability. However, a disadvantage of this technique was that the second most congested line, limits the power transfer capability of the system. High phase (six phase) order system was noted to have several advantages over three phase system such as lower voltage requirement to transfer equal amount of power and lower electric and magnetic field across the right of way. An IEEE 9 and 118 bus test system were used to evaluate the above mentioned techniques.Dissertation/Thesis
M.S. Electrical Engineering 2012
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Hayes, Briana. "Elimination of parasites using non-thermal and low temperature techniques and effect on chemical and sensory quality of raw oysters." 2006. http://purl.galileo.usg.edu/uga%5Fetd/hayes%5Fbriana%5Fk%5F200608%5Fms.
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Serrazina, Ricardo Nazaré. "Flash sintering of lead free perovskite oxides towards sustainable processing of materials for energy and related applications." Doctoral thesis, 2021. http://hdl.handle.net/10773/32637.
Full textAbstract:
Piezoelectrics as K0.5Na0.5NbO3 (KNN) have currently an emerging importance
due to their lead-free nature and high transition temperature, which permits a
wide range of high-tech applications as sensors, actuators, energy harvesters,
biosensors, etc. However, monophasic dense KNN products are yet difficult to
obtain, due to the high temperature and long time of conventional sintering
processes.
This PhD proposes a new method to densify materials abruptly above a threshold
condition using FLASH sintering, where the densification occurs by a
combination of furnace environment (temperature and/or atmosphere) and
electrical field directly applied to the specimen. There are several proposed
mechanisms for FLASH. Joule heating is the most reported one, but also defectrelated
theories have been proposed. The phenomena are not yet completely
understood, but most probably, FLASH sintering is a combination of both effects,
with particle surfaces energy and conductivity performing a significant role.
The present work aims to exploit FLASH for sintering of KNN ceramics but also
to depict the fundamental phenomena behind FLASH sintering, and specifically,
FLASH sintering of KNN. The ultimate goal is to develop sintering of ceramics
towards room temperature, contributing to the energy economy low thermal
budget of ceramic industry.
The use of Finite Element Modelling (FEM) tools allowed to study the particle
orientation effect on the Joule heating during FLASH, while the simulated
temperature gradients were used to explain the presence of FLASH sinteringinduced
stresses in dense ceramics. The production of different size and purity
KNN powders permitted to establish the link between FLASH temperature (TF)
and particle size/purity. Following, the establishment of an engineered thermal
cycle before the application of the electric field for the FLASH was responsible
for increasing the final densification of KNN ceramics to 95%. The link between
FLASH parameters, as current density and holding time, was determined and
the relationship with final density and grain size of ceramics studied. TEM and
FEM studies allowed to propose a FLASH sintering mechanism for KNN,
in which the current flow through particles’ surfaces promotes the partial melting of
contacts and the particle sliding towards pore removal and compact
densification.
To allow a significant decrease on the TF of KNN, atmosphere-assisted FLASH
sintering (AAFS) was presented, and the temperatures were decreased to TF ≈ 265 ºC, however, the final densification was limited to 79%.
The ferroelectric and dielectric performance of FLASH sintered KNN was studied
and compared with that of conventionally sintered ceramics. Similar performance
was attained after a heat treatment for electrode cure; however, a detailed
analysis revealed FLASH sintering-fingerprints in both as-sintered and heattreated
ceramics.
This work presents a clear contribution for the development of FLASH sintering
in ceramics, namely in piezoelectric KNN.Piezoelétricos como o K0.5Na0.5NbO3 (KNN) têm uma importância emergente devido à sua natureza livre de chumbo e variada aplicabilidade em componentes como sensores, atuadores, dispositivos de recolha de energia, biossensores, etc. No entanto, o KNN monofásico continua a ser difícil de produzir devido à elevada temperatura e tempo associados ao processo de sinterização convencional. Este doutoramento propõe a utilização de um método alternativo de densificação, a sinterização FLASH, que acima de uma condição limite promove a densificação repentina de cerâmicos por uma combinação de ambiente do forno (atmosfera e/ou temperatura) com a aplicação de campo elétrico diretamente no material. Existem vários mecanismos reportados para explicar a sinterização FLASH. O aquecimento por efeito de Joule é um dos mais reportados e aceites, mas também têm sido sugeridos mecanismos envolvendo a criação e movimento de defeitos por efeito do campo elétrico. Uma compreensão clara do fenómeno continua por ser apresentada, mas muito provavelmente a sinterização por FLASH resulta duma combinação destes dois efeitos, sendo que a energia e condutividade das superfícies das partículas desempenham um papel fundamental. Este trabalho pretende explorar a sinterização por FLASH de cerâmicos, mas também estudar os seus fenómenos fundamentais, mais especificamente, na sinterização FLASH de KNN. O objetivo último deste trabalho é o desenvolvimento de processos de sinterização de cerâmicos que operem à temperatura ambiente, contribuindo para a economia energética e sustentabilidade da indústria cerâmica. A utilização de ferramentas de Modelação por Elementos Finitos (MEF, ou FEM) permitiu estudar o efeito da orientação das partículas na geração de calor por efeito de Joule durante o FLASH, enquanto a modelação da distribuição temperatura local e respetivos gradientes térmicos foram usados para explicar tensões induzidas em cerâmicos densos. A produção de pós de KNN com diferentes tamanhos e pureza permitiu estabelecer a sua relação com a temperatura de FLASH (TF). Em consequência, o estabelecimento de um ciclo térmico apropriado, antes da aplicação do campo elétrico, permitiu obter cerâmicos de KNN com densidade relativa de 95%. A ligação entre os parâmetros de FLASH, como densidade de corrente e tempo, foi determinada, e a relação com a densidade final e tamanho de grão dos cerâmicos foi estudada. Estudos em TEM e FEM permitiram propor um mecanismo para a sinterização por FLASH de KNN, em que o fluxo de corrente pelas superfícies das partículas promove uma fusão parcial nos seus contactos e o rearranjo para a remoção de poros e densificação do compacto. De forma a permitir um decréscimo acentuado na TF do KNN, a sinterização FLASH assistida por atmosfera foi apresentada, e a temperatura foi diminuída para TF ≈ 265 ºC. No entanto, a densificação final foi limitada aos 79%. As propriedades ferroelétricas e dielétricas do KNN sinterizado por FLASH foram estudadas e comparadas com as de cerâmicos sinterizados convencionalmente. Um desempenho semelhante entre ambos foi obtido após um tratamento térmico para cura de elétrodos. No entanto, uma análise detalhada mostrou que as propriedades são afetadas pelo processo de FLASH em cerâmicos tratados ou não termicamente. Este trabalho apresenta uma contribuição clara no desenvolvimento da sinterização FLASH de cerâmicos, especificamente, no piezoelétrico KNN.
Programa Doutoral em Materiais e Processamento Avançados
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Fernandes, Bruno João Baptista. "pMOSFET fabrication using a low temperature pre-deposition technique." Master's thesis, 2016. http://hdl.handle.net/10362/20677.
Full textAbstract:
The objective of this work was to develop a fully functional pMOSFET using a new method for dopant pre-deposition done at low temperature (90ºC) using PECVD. This technique has many advantages when compared to the traditional manufacturing method, namely it is more cost effective, simpler and faster. Because it does not require an oxide layer to create the patterns, it can be conjugated with other low temperature techniques.
To obtain a functional pMOSFET, this work was divided in four different studies. The objective of the first study was to achieve metal-semiconductor ohmic contacts. To obtain a perfect ohmic contact of aluminum in a n-type silicon wafer, it is necessary to create a narrow space-charge region in order to allow carrier tunneling. That was reached by using a highly doped n-type hydrogenated amorphous silicon thin film made with a phosphine gas phase concentration of 1.5%, followed by a one-hour diffusion process at 1000ºC. A sheet resistance of 22.9 Ω/□ and a phosphorus surface concentration of 5.2 × 1019 aṫ cm-3 were obtained.
The second study consisted of producing p+n junctions varying the surface concentration and the diffusion time and temperature. The best diodes produced have significantly different profiles. The first was produced with a deep junction and a 0.165% diborane in the gas phase and presents the following parameters: rectification ratio of 6.01 × 103, threshold voltage of 0.53 V and an ideality factor of 1.74. The second diode was produced with a shallow junction and using a 1.5% diborane in the gas phase with the parameters: rectification ration of 3.94 × 103, a threshold voltage of 0.46 V and an ideality factor of 2.58.
Regarding the oxide characteristics for application as gate dielectric (third study), it was determined that the best oxides were produced by wet oxidation with a thickness of about 1300 Å.
After finishing the previous studies, it was possible to produce a fully functional p-type field effect transistor (fourth study). The MOSFETs worked in enhancement mode with the best parameters being: a threshold voltage of -4 V and a field effect mobility of 106.56 cm2/Vs.
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Sheu, Jong-Long, and 許忠龍. "Deep Level Characterization of Low-Temperature GaAs by Photoreflectance Technique." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/08582353000214100877.
Full textAbstract:
碩士國立交通大學
電子物理系
87
Photoreflectance (PR) spectroscopy is an optical and non-destructive technique and is widely used to characterize electronic properties of semiconductor materials and structures. We applied PR method to measure the deep levels of low-temperature grown GaAs samples. By analyzing the transient response of PR spectrum amplitude to the modulation frequence, we can acquire the time constants of deep levels at various sample temperatures. The Arrhenius plot relating the measured time constants and sample temperatures provides the information of the ionization energies and carrier-capture cross-section areas of deep levels. In this study, we characterize the deep levels of GaAs grown at 250 by molecular beam epitaxy (MBE) technique. By using this optical deep level transient spectroscopy (DLTS) technique, we found three deep levels along with the sample. The ionization energies of these deep levels are 0.657, 0.591, and 0.0587eV, respectively. The deep levels with 0.591 and 0.657eV ionization energies are attributed to the As precipitation and As antisite in the low-temperature GaAs sample, respectively. The 0.0587eV-related deep level has not yet been reported in the literature. Although the factor causing this deep level was not analyzed , we are confident on the validity of our measurement data which are partially consistent with possible known data. In summary, we demonstrated the versatile power of PR technique to characterize the electronic properties of semiconductors. By using the PR technique to perform the optical DLTS, we found some special deep level which was not be identified by other conventional DLTS system.
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Lin, Pu-Chou, and 林莆洲. "Low-temperature Technique for High-efficiency Perovskite Hybrid Photovoltaic Devices." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/84984263513403614102.
Full textAbstract:
碩士國立中山大學
物理學系研究所
104
Due to the development of technology and gradual depletion of fossil fuels, the energy issue has received wide attention in this century. Solar energy is one of the best choices. Among many types of solar cells, perovskite solar cells suddenly appear on the horizon and the power conversion efficiency has been improved from 3 % to over 20 % in just 6 years. This makes many scholars who originally study in polymer and dye-sensitized solar cells start doing research about perovskite PVs. Halide perovskites have recently emerged as promising materials because of low-cost and high-efficiency. In this study, we develop a new method, Low Pressure Proximity Evaporation Technique (LPPET), combined with Solution Process (SP) to fabricate planar sandwich-like perovskite thin films. We also optimize the methods to improve the power conversion efficiency of the devices. Zinc oxide is widely used in polymer solar cells because of its good electron conductivity and high light transmittance. As a results, we first applied solution processed zinc oxide based on inverted-structure and a simple two-step solution process to fabricate perovskite PV cells. We modified the concentration of CH3NH3I solution to improve the efficiency. We analyzed the effect of interface morphology between perovskite and ZnO and finally, gained a PCE of 13.44 %. Because two-step process is very susceptible to the atmosphere and the formation of perovskite is too quick that causes perovskite grains small and messy, we developed a new method, called Low Pressure Proximity Evaporation Technique (LPPET) to fabricate perovskite layer. At first, we investigate two layered perovskite devices. In order to achieve complete formation of the bottom PbI2 and avoid the excess deposition of MAI on surface, we bring up an idea of using solution process along with LPPET to form a sandwich structure of MAI/PbI2/MAI. However, due to poor thermal stability of the perovskite layer, we found the LPPET process is different to be exercised on ZnO substrate. With appropriate LPPET parameters, we got a PCE of 11.29 % and a very good short-circuit current density of 18.38 mA/cm2. After that, we optimized LPPET process on traditional-structure perovskite PV devices. We found that the annealing step of sandwich-like perovskite layer is the most important factors to get best quality devices. The best crystallization and structure of perovskite could be obtained at 160℃, 35 minutes PbI2 annealing. Consequently, with adequate parameters of LPPET, we achieved efficiency of 15.52 % and large Jsc, 23.91 mA/cm2, also others good electric properties. For a low temperature process under whole atmosphere or under vacuum condition, this is a breakthrough of the perovskite solar cells and mass production.
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Tseng, Huan-Chun, and 曾煥均. "Characterization of Low Temperature Poly Silicon TFTs with Laser Crystallization Technique." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/82450430811591421675.
Full textAbstract:
碩士國立交通大學
電機資訊學院碩士在職專班
93
It was extensively discussed the high-performance low temperature polycrystalline silicon (LTPS) application in monitor. In this thesis, many processes of crystallization means were discussed and the characterization of low temperature polycrystalline silicon (LTPS) thin film transistors (TFTs) were studied, in which the HF with the concentration of 0.1 percent was utilized by pre treatment clean process. Many methods and techniques had been proposed to further improve the performance of LTPS TFTs, which include means of prior clean treatment of amorphous silicon thin films, while most of the effort was focused on crystallization of amorphous silicon (a-Si) thin films. First, the electrical characteristics of LTPS TFTs fabricated by excimer laser annealing (ELA) of a-Si thin films which was used different pre treatment processes. From the results of material analysis and device characterization, the relation between electrical characteristics of LTPS TFTs and pre treatment processes conditions with laser annealing conditions had been identified. It was found that caused the surface oxidation of a-Si thin films by pre treatment process and laser energy density had a deep influence on the resulting poly-Si grain structure and electrical characteristics of LTPS TFTs. It was included the different methods of pre treatment process, the first method is surface cleaning with O3 water which concentration was 20ppm, the second method was surface cleaning with H2O2 water which concentration was 30%, the third method was surface cleaning with UV light exposure which wave length was 254um, and all of these methods can advance the surface oxidation of a-Si thin films, it had the difference at long time or short time treatment. When surface of a-Si thin films was completely oxidized by pre treatment process then treated by ELA, the LTPS thin films will be fabricated with grain size about 0.3um, grain shape like square and uniform distribution on surface. In this situation, the LTPS TFTs fabricated by ELA with optimization laser energy density, the field effect mobility of 130 and 90 cm2/V*s could be achieved for n-channel and p-channel ELA LTPS TFTs, respectively. The thresholds voltage had different shift owing to the difference surface oxidation on a-Si thin films. Changing laser scan frequency and energy couldn’t improve the crystalline quality and uniformity of crystallized poly-Si thin films and electrical characteristics of LTPS TFTs. In different ambiance of ELA crystallization had different efficiency, before mention the process of ELA crystallization had ambiance of N2 gas, now the concentration of low O2 with 2000ppm was utilized in ELA crystallization ambiance. From the results of material analysis, the LTPS thin films fabricated by ELA crystallization in ambiance of low O2 concentration had surface roughness like before mention process, the maximums surface roughness was about 80nm and average surface roughness was about 9nm, but the shape had some difference, the LTPS thin films surface roughness of low O2 concentration status had the shape like the cylinder in which the position was grain boundary and potential barrier was larger than grain area. The cylinder top surface were close to the gate bottom, when gate applied the forward bias, it would enhance the high electric file near the gate then induced the average thresholds voltage degradation. LTPS TFT’s fabricated by ELA crystallization in ambiance of low O2 concentration had lower thresholds voltage than N2 ambient condition, the thresholds voltage of +2 and –2 V could be achieved for n-channel and p-channel ELA LTPS TFTs, respectively. At last part of this thesis, the crystallization of continuing wave laser (CW laser) technology would be discussed. Crystallization of amorphous silicon (a-Si) thin films utilized the wavelength 532nm of CW lasers with different power and scan speed. Many factors of influence for grain size were discussed. It included the speed control in stage with different power during laser scanning; front and backside scan on substrate at different scanning speed. Owing to the laser beam energy distribution was the Gauss shape and laser beam size was affected by focus lens and laser power, we employ the focus lens with focus 600mm and focus the laser beam on substrate where the beam diameter was about 150um, when laser power more high the diameter more long. The LTPS thin films were fabricated by CW laser with grain size about 3um, grain shape like long bulk and large grain was aggregated in center area of laser beam on crystallization surface and the LTPS TFTs fabricated at large grain size area, the field effect mobility of 298 and 210 cm2/V*s could be achieved for n-channel and p-channel LTPS TFTs, respectively. The threshold voltages were shifted to 7V owing to the crystallization ambiance was atmosphere.
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Yang, Meng-Syuan, and 楊孟璇. "Study of Amorphous ZnO:Al Thin Films by Low-Temperature Sputtering Technique." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/5pt426.
Full textAbstract:
碩士國立中山大學
物理學系研究所
97
Aluminum doped zinc oxide AZO has been studied for 20 years. It can improve thin films’ thermal stability and transparency in visible range .However AZO is not as good as ITO in conductivity and transparency, that’s why the application of AZO is only limited in few fields. This is because the nature limit of ZnO. Because part of doped Al forms Al2O3 instead of sits on Zn sites, that enhances light and carriers scattering and suppresses the optical transparency and electric conductivity. This study is plane to take advantage of amorphous properties, that may be achieved try grown films at liquid Nitrogen temperature, in which the distribution of Al and Zn will be very uniform and the solubility of Al will be high. ZnO:Al thin films is grown on glass substrates at low temperature by Radio frequency magnetron sputtering system. Low-temperature deposition is done in order to deposit amorphous thin films (ceramic targets ZnO contained 2wt.% Al2O3). The Al3+ in place of Zn2+ should be uniformly distributed in the thin films because of amorphous structure. It expects to find the best deposition condition under a fixed target-to-substrate distance (10cm) by varying growth, such as the deposition mode, PF plasma power and working pressure. AFM, XRD (grazing incident x-ray diffraction) and N&K analyzer were used to measure the thin surface morphology, structure, thickness and transmittance, respectively. The colors of the thin films are very different dependent on the modes of deposition. The low sputtering rate by lower RF power and high working pressure is the key to successfully grow amorphous ZnO:Al films. The amorphous ZnO:Al thin films (a-5) are deposited under 100W of RF power and 50mTorr of working pressure. The transmittance of the assembly of ZnO:Al thin films/glass substrate is the same as glass substrates which inducates the transmittance of films is far above 90%. However, the amorphous ZnO:Al thin films are poor conductor . We also tried to improve it by the post-annealing of ZnO:Al thin films in 2% hydrogen atmosphere. It is found to be not successful.
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Kumar, Vikash. "Sb2Se3 thin-film solar cells via low-temperature thermal evaporation technique." Doctoral thesis, 2022. http://hdl.handle.net/11562/1069306.
Full textAbstract:
There has been a lot of anomalies in the climate in recent years. The situation is getting worse with every passing day, this alarming situation is the talk of the town amongst the world’s scientific community. There has been a consistent search for cleaner and sustainable source of energy which can replace the conventional fossil fuel. To this date renewable energy such as solar, wind, ocean, hydrothermal are in application. Among these, solar photovoltaic (PV) is the most effective and widely used one due to its abundant availability and zero contribution to pollution. In order to harness this energy conventional wafer based solar cells were used which have high cost of production and a longer by back time. Second generation thin film based solar cells are the talk of the time as they can be produced with less consumption of material and energy and hence are economical. Three materials are currently in the market; they are amorphous silicon (a-Si), cadmium telluride (CdTe) and copper indium gallium selenide (CIGS). Amongst them, CIGS has shown the highest efficiency of above 20% in laboratory scale, while CdTe has the highest market share. A drawback with CIGS and CdTe technologies is the use of scarce and expensive elements indium and tellurium. It is therefore clear that these are issues which are of concern for long-term availability of CdTe and CIGS. It is in this context; investigations have been initiated all over the world for an alternative, abundant and non-toxic absorber material. Antimony chalcogenide (Sb2Se3, Sb2S, Sb2(S,Se)3) are promising absorber materials for thin film photovoltaic cells due to their high absorption coefficient (>104cm-1) and optimum direct band gap (~1.2eV). Sb2Se3 has excellent optoelectronic properties with low processing temperature these are key factors responsible for the growing interest within the PV community. The best performing cells have reached above 10% till date. This thesis entitled “Sb2Se3 thin film solar via low thermal evaporation technique” is a detailed study of the fabrication of Sb2Se3 absorber films by low temperature thermal evaporation technique. Films have been as deposited, vacuum annealed as well selenized and studied in detail in this thesis. The studies included in the thesis are divided into eight chapters.
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Chang, Chih-Pang, and 張志榜. "Investigation of Crystallization Technique for Low-Temperature-Processed Poly-Silicon Thin-Film-Transistor." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/895v2a.
Full textAbstract:
碩士國立虎尾科技大學
光電與材料科技研究所
93
The use of low-temperature processed polycrystalline silicon thin-film transistors (LTP poly-Si TFTs) as pixel active elements and in peripheral driver circuits has been an important issue in the development of active-matrix flat panel displays (AMFPDs). This thesis studies a number of crystallization techniques for the high performance LTP poly-Si TFTs to achieve system on panel. Firstly, we propose solid-state continue-wave laser (CW-laser) to crystallized poly-Si films, the distinction of excimer laser, CW-laser possessed high stability, reliability, durable and low-cost. In this way, we used laser scanning speed and energy to analysis a status of grain lateral growth and crystallizes mechanism for various condition, furthermore, we succeed to crystallize great grain size more than 10 μm. To compare excimer laser crystallization (ELC) and Sequential lateral solidification (SLS), CW-laser don’t needed extra procedure to carrier out large grain size. On the other hand, solid-phase crystallization (SPC) had better uniformity but require to long annealing time to crystallized；Therefore, we suggested NH3 plasma treatment at server times before crystallized to shorten crystallization times, in this experiment, we have accomplished shorten crystallization times for NH3 plasma treatment, the novel crystallization method to compared the conventional process (SPC 15 hours) just require 2 hours for SPC to demonstrate NH3 plasma treatment efficiently shorten SPC annealing times and improvement electrical characteristics.
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吳巧慧. "Characterization of application low-temperature BGe ion implantation technique in fabrication shallow-semiconductor devices." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/73066974397620512877.
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Chen, Yu-shiang, and 陳裕翔. "Simulation Characteristics of Surface Acoustic Wave Device Packaged Using Low Temperature Cofired Ceramic Technique." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/06082929939022140304.
Full textAbstract:
碩士義守大學
電機工程學系碩士班
93
Recently, as fast developing in global telecommunication and personal communication getting matured, wireless communication industry tends to become more and more activating. Everyday various products related to telecommunications come to market. In general, those products, no matter they are system level or component level, must satisfy high frequency, miniaturization, and modulization. Because surface acoustic wave (SAW) device could not to integrate on silicon wafer to this day, only low temperature cofired ceramic (LTCC) technology offers a platform to integrate components into a miniaturized module and happens to be coincident with this trend. Hence, this thesis studies the characteristics of a SAW filter that was packaged using LTCC technique. First, the process of LTCC technology was overviewed. Then, the characteristics of a SAW filter packaged by LTCC technique was simulated using two different methods, one is by commercial 3D EM wave simulator (High Frequency Structure Simulator, HFSS) and the other is by a high frequency circuit simulator Ansoft Harmonic. The matching circuits for the SAW filter were as embedded into the package by LTCC. The simulation results show a good agreement by both methods. The technology used in the thesis provides a convenient way to evaluate the performance of SAW devices after packaged with LTCC process.
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Chen, I.-Hui, and 陳怡蕙. "The Development of Observation Technique Using Transmission Electron Microscopy for Liposome at Low Temperature." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/595e62.
Full textAbstract:
碩士國立臺北科技大學
材料科學與工程研究所
103
In the past 30 years, cryo-transmission electron microscopy (cryo-EM) technology has been developed in many aspects for the applications on observing biological and medical specimens. Cryo-EM has been proven to be able to analyze some protein structures Cryo-EM allows users to quick-freeze the bio-samples in vitrified ice, observe the sample under the near-native condition, thus is a powerful tool to understand the samples in the native liquid phase. However, during cryo-EM operation, the high energy electron beam could quickly damage the ice sample. Therefore low-dosage imaging technique is usually used for cryo-EM. Even so, taking an image for a long exposure time could easily result in damaging on the icy bio-samples. Adding some sugar into bio-sample solution before TEM sample preparation was known to preserve the bio specimen better against the damage caused by the electron beam. This work aims for studying the effect of trehalose addition on preserving bio-samples under cryo-EM operation. Liposome was used as the bio-specimens for this study. In this work, various concentrations of trehalose solution were mixed with liposome solutions and made into cryo-EM specimens, then were taken images under different conditions of electron dosages used. The results show that trehalose addition is in fact effective in slowing the electron beam damaging occurring time on the cryo-EM specimen. This finding could be useful for practical applications of cryo-EM operation.
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Lan, Che-wei, and 連哲緯. "The Low-Temperature Bonding Technique for Plastic-Based Microfluidic Chips and its Applications for Micromixers." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/25260062919662294167.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
92
Abstract A new technique for bonding of polymer micro-fluidic devices has been developed. This method can easily bond biochips with complex flow patterns and metal layer. Above all, using a patterned glass, the micro-channel structures on Poly-Methyl Meth-Acrylate (PMMA) substrates were generated by one-step hot embossing procedure. In contrast with the traditional thermal bonding, this paper presents low-temperature and low-pressure packaging for polymer micro-fluidic platforms. Furthermore, the disposable plastic biochip has successfully been tested by the measurement of tensile strength and surface roughness. This paper also reports details of the passive and active micro-mixers. According to experimental and numerical investigations, the mixing performance of passive micro-mixers is expectably to be found. In addition, to quantify the mixing concentration distribution in the micro-channel, it has been demonstrated by launching the image analysis programs. The bonding efficiency of the solvent is twenty four times as strong as thermal bonding efficiency.
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Chen, Tang-Yuan, and 陳瑭原. "Low-Temperature Bonding Technique for Plastic Microfluidic Chips and its Applications on Plastic Diffuser Micropumps." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/07719197619420033940.
Full textAbstract:
碩士南台科技大學
機械工程系
94
A new technique for bonding of polymer micro-fluidic devices has been developed. This method can easily bond biochips with complex patterns. By using a patterned Ni mold, the micro-channel structures on Poly-Methyl Meth-Acrylate (PMMA) substrates were generated by one-step hot embossing procedure and bonding of low temperature. In contrast with the traditional thermal bonding, the method presents low-temperature and low-pressure packaging for polymer micro-fluidic platforms. Furthermore, the tensile strength of the disposable plastic biochip was 179 kgf., which is 2 to 15 times greater than that of conventional methods. This paper also applied this technique on plastic diffuser micro-pumps, based on piezoelectric actuation. The pump was made of -PMMA, and the diameter and depth of the pump chamber was 6 mm and 200 mm, respectively. The working fluid was non-degassed de-ionized (DI) water. The flow rate of 53.6 ml/min was obtained at a 100 Vpp and 400 Hz square wave drivin g signal.
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Chung, Chien-Chen, and 鐘健禎. "Study the Ultrafast Dynamics of High-Tc Superconductor at Low Temperature by Femtosecond Pump-Probe Technique." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/06779363552955463291.
Full textAbstract:
碩士國立交通大學
電子物理系
86
We have preformed a series of transient reflectivity(△R/R) measurements on oxygen-controlled YBCO thin films at different temperatures. A home-made femtosecond pump-probe system including a passively mode-lock Ti:sapphire laser and a continuous transfer cold finger cryostat were used for these measurement. The △R/R curves versus delay time of the oxygen-rich YBa2Cu3Ox (x=6.95) film for temperature ranging from 120K to 20Kwere different from those reports previously. The difference may due to the fact that they used different photon energy (~2eV) for the measurements and the drastically changes of density of states near Fermi level caused by pump beam could be probed. We also find the relaxation time has an abrupt change and become longer at superconducting state for oxygen-rich film while the relaxation time increases slightly with decreasing temperature for oxygen-deficiency (x=6.0) film. Additionally, we also measured the transient differential reflectivity of PBCO thin film. The sign of △R/R at room temperature is positive but it has a tendency to become negative at 240K and finally becomes negative below 220K. The change in sign if △R/R may due to the width of charge-transfer gap decreases when the temperature decreases.
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Yang, Janne-Min, and 楊建民. "Investigation on the Formation Mechanism of Ultra-fine Zn-ferrite Powders at Low Temperature (＜500℃) by Tartrate Technique." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/67347728940886342337.
Full textAbstract:
博士國立成功大學
資源工程研究所
90
In the nonconventional preparation of spinel ferrite powders, the pyrolytic decomposition of precursors often occurs through multi-stage transformation paths, which involve different metastable intermediate phases. The present investigation deals with the synthesis of nano-sized zinc ferrite powders using the tartrate precursor technique. The focus of this investigation is to study the development of the intermediate phase during the decomposition of precursor, as well as the formation mechanism of zinc ferrite. Accordingly, the nano-sized zinc ferrite powders can be obtained at low-temperature (< 500℃) in this study. Characterizations of the various experimental products have been conducted as: (i) thermal behavior by DTA/TG, (ii) crystalline phase determined by XRD and TEM method, (iii) crystallite and particle sizes measured by Scherrer formula-XRD powder method, BET surface area diameters, and TEM, and (iv) magnetic properties and electronic structure of Zn conducted by SQUID and XPS techniques. The experimental results are given as follows: 1.The thermal reaction sequence during the precursor decomposition to synthesize zinc ferrite powders as performed in this work can be noted as follows: Step 1: Decomposition of the tartrate precursor Zn1Fe2-tartrate precursor 2/3Fe3O4＋ZnO Step 2: Oxidation of Fe3O4 2/3 Fe3O4 +1/6O2 γ-Fe2O3 Step 3: Formation of inverse spinel Zn-ferrite γ-Fe2O3＋ZnO (Fe3+)A[Zn2+Fe3+]BO2-4 Step 4: Inverse-normal spinel transformation (Fe3+)A[Zn2+Fe3+]BO2-4 (Zn)A[Fe2]BO2-4 2.The intermediate phase, Fe3O4, could not effectively react with ZnO to synthesize zinc ferrite at low temperature. The key step of preparation of ultrafine zinc ferrite powders by tartrate technique is the preheating process, in which the precursor is thermally treated between 300°and 400℃ for several hours to ensure complete conversion of the Fe3O4 into γ-Fe2O3. Therefore the ultrafine and mono-phase ZnFe2O4 can be obtained at low temperature by preventing the formation of α-Fe2O3 via preheating process. 3.It has been proven that the octahedral sites are preferentially exposed on the spinel surfaces. The γ-Fe2O3 is a cubic spinel, chemical formula of which is (Fe3+)[Fe3+5/3□1/3]O4, where □ stands for the vacancy of cation and distribution on the octahedral sites. Thus the γ-Fe2O3 can provide the cation vacancies on octahedral sites for Zn2+ ions diffusing into the octahedral-structured clusters, and then forming the inverse spinel zinc ferrite. The model of reaction mechanism between γ-Fe2O3 and ZnO is also built-up from the experimental results.
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Hsieh, Chia-Chen, and 謝佳真. "The Study of The Low Temperature Flip-Chip Package by Applying AlGeSn-Based Transient Liquid Phase Bonding Technique." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/em95pz.
Full textAbstract:
碩士國立虎尾科技大學
電子工程系碩士班
101
In this study, the films are proposed that can be apply for low-temperature flip chip package by transient liquid phase bonding as AlGeSn-base. The AlGe/Sn films are deposited by thermal evaporation. And then the sample is placed in the vacuum environment for thermocompression bonding. In this experiment, use to the different film thickness ratio of AlGe and Sn for 280oC~350oC bonding, TAlGe:TSn=1:1, 2:1, 3:1, respectively. To find the best parameters, graphically produced, LED flip chip package and electrical measurements, after shear stress testing, SEM, EDS, and XRD analysis. The results show, the AlGeSn film will have the dendritic structure on the surface and phase separation after bonding at 350oC. TAlGe:TSn= 2:1 after bond at 300oC and 350oC, TAlGe:TSn=3:1 after bond at 350oC for 60min with the best of the shear strength. The XRD analysis, the main diffraction peak is Sn(200), the relative intensity of Ge(111) is between 0.4 to 0.6,and Al(111) is between 0.1 to 0.2. In LED flip chip package, it have the high forward voltage for 4.49V, and increase the thickness to about 4.5μm, the forward voltage drop of 4.7% under 20mA.