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1
Taylor, J. M. C. "The structure and properties of some mixed transition metal oxides." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382735.
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Plassmeyer, Paul. "Metal-Oxide Thin Films Deposited from Aqueous Solutions: The Role of Cation/Water Interactions." Thesis, University of Oregon, 2017. http://hdl.handle.net/1794/22295.
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Metal-oxide thin films are used in a wide variety of electronic devices. Although many techniques have been developed to deposit thin films of metal oxides, there is still a need for alternative cost- and energy-effective deposition methods. Deposition of metal oxide thin films from aqueous solutions of all-inorganic metal salts is a viable method that meets these needs. Although many aqueous-deposited metal-oxide thin films have been successfully incorporated into functioning devices, many of the mechanisms that occur as precursors transition to metal oxides are not well understood.
The work presented in this dissertation is primarily concerned with examining the processes that occur as metal oxide thin films form from spin-deposited aqueous precursor solutions with a particular focus on the role of H2O in these processes. Chapter I summarizes methods for thin film deposition, and describes the use of aqueous metal salt solutions as viable precursors for the deposition of metal oxide thin films. Chapter II investigates the precursor chemistry, film-formation processes and properties of LaAlO3 thin films deposited from aqueous precursors. This chapter also serves as general guide to the processes that occur as metal-oxide thin films form from spin-deposited aqueous precursors. Chapters III and IV focus on the effects of H2O(g) during spin-deposition of precursor thin films and during the annealing process in which precursors are converted to metal oxides, respectively. The presence of H2O(g) during spin-deposition has a striking effect on the thickness of the resulting thin films and also affects the elemental gradient and density profiles. During annealing, H2O(g) reduces the temperatures at which counterions are expelled and influences the metal-hydroxide framework formation and its condensation to a metal oxide. The data also indicate that H2O(g) enhances diffusion of gaseous byproducts from within the films. Chapter V focuses on precursor concentration and its impact on the thermal evolution of thin films. The processes involved in the conversion of precursors to metal oxide thin films occur at lower temperatures as precursor concentration decreases. Although this is likely in part due to thickness effects, concentration-dependent precursor speciation may also be involved in lowering the temperatures at which films densify.2019-02-17
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Imagawa, Haruo. "Study on Metal Oxide Nanomaterials for Automotive Catalysts." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/158079.
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Geere, R. G. "X-ray absorption spectroscopy and its application to the study of calcium sites in silicate glasses." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.480514.
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Pérez, Mirabet Leonardo. "Synthesis, characterization and functionalization of metal and metal oxide nanoparticles. TEM Microscopy study." Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/129498.
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Aquesta tesis doctoral està centrada en desenvolupar noves rutes sintètiques per tal d’obtenir i funcionalitzar els següents tipus de nanoestructures:
- Nanopartícules d’or i plata dispersables en aigua, funcionalitzades amb àcid 3-mercaptopropiònic i coordinades amb carbonils de reni.
- Magnetita i ferrites del tipus MFe2O4 (M= Co, Mn, Cu, Zn) recobertes amb oleilamina, la qual les fa dispersables en medis orgànics tals com hexà, toluè i diclorometà.
- Nanovaretes de goethita (i de maghemita) recobertes amb etilendiamina, sintetiztades en un reactor d’autoclau.
- Nanoestructures “core-shell” del tipus Fe3O4@Au, sintetitzades mitjançant diferents mètodes.
Apart de sintetitzar aquests tipus de nanopartícules, aquesta tesis també està centrada en dur a terme una caracterització completa de les nanopartícules obtingudes. Per a aquest propòsit, tècniques analítiques tant microscòpiques com no microscòpiques han estat utilitzades. El procés de caracterització, especialment la part basada en fer servir Microscopis de Transmissió d’electrons (MET) ha tingut lloc no sols a la Universitat Autònoma de Barcelona (UAB) sinó també al “Center for Electron Nanoscopy” (CEN) durant una estada de quatre mesos a Dinamarca.This PhD thesis is focused on developing new synthetic routes to obtain and functionalize the following kinds of nanostructures: - Water-dispersible gold and silver nanoparticles functionalized with 3-mercaptopropionic acid and coordinated to rhenium carbonyl species. - Magnetite and MFe2O4 (M= Co, Mn, Cu, Zn) ferrite nanoparticles capped with oleylamine, which makes them dispersible in organic solvents such as hexane, toluene and dichlorometane. - Water-dispersible goethite (and maghemite) nanorods capped with ethylenediamine, synthesized in an autoclave reactor. - Water-dispersible Fe3O4@Au core-shell nanostructures, synthesized via some different methods. Apart from synthesizing those kinds of nanoparticles, this thesis is also focused on carrying out a complete characterization of the obtained structures. To this purpose, both microscopic and no microscopic characterization techniques have been used. The characterization process, specially the part based on using Transmission Electron Microscopes (TEM), has taken place not only at the “Universitat Autònoma de Barcelona” (UAB) but also at the “Center for Electron Nanoscopy” (CEN) during a four months stay in Denmark.
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Yagoubi, Benabdella. "A study of some thin transition metal oxide films." Thesis, Brunel University, 1989. http://bura.brunel.ac.uk/handle/2438/5348.
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This thesis analyses the effect of varying the compositions of co-evaporated V205/TeO2, W03/CeO2, SiO/TeO2 and W03/TeO2 amorphous thin films on their electrical and optical properties. Some information about the electronic properties of these oxides may be obtained by comparison of the results. In the oxide systems containing transition metal ions the expression for hopping energy at low temperatures contains a term due to the hopping energy of polarons in addition to that due to the disorder. In the dielectric SiO/TeO2 thin films the distortion of 'the molecule is thought to be quite weak and thus the carriers do not form polarons. They would move by hopping at the band edge at low temperatures and by excitation to a mobility edge at high temperatures. The electrical conductivity of V205/TeO2 amorphous thin films is discussed in the light of the Mott(1968) theory. The optical absorption edge was found to obey the direct forbidden transitions equation cc ico=B(fiw-EOP)3'2. The frequency-squared dependence of the conductivity of W03/CeO2 thin films (high content of CeO2) in the frequency region where the capacitance is constant is associated with the lead resistance according to Street et al (1971). The optical energy gap of the films varies with the composition in same way as in doped crystalline semiconductors. The value of the, optical W03/Ce02 was calculated using the Davis and Mott (1970) formula for non-direct optical transitions. The capacitance of SiO/TeO2 thin films is found to be almost independent of frequency as well as of temperature. This is due to a strong ionic bonding which characterises a good insulator. The optical absorption edge of SiO/TeO2 is found to be sharper than that of W03/ CeO2 and very similar to that found in most crystalline solids. The value of the optical energy gap is calculated using the same formula as in W03/CeO2. The systematic change of the optical gap with composition is observed only in a limited range of compositions. The a. c electrical properties of W03/Te02 amorphous thin films are described using the Springett(1974) and Elliott(1977) models. The optical absorption edge of WO3/TeO2 is found to lead to new arguments about the origin of the Urbach edges.The a. c electrical conductivity shows a frequency dependence of the form as ca wS in all samples studied in the present work. The mechanism of conduction at low temperatures with the index varying from 0.5 to I is thought to be due to hopping of electrons between localized states in the gap. At high fields the d. c current shows a non-linear dependence on the applied electric field. This is thought to be due to either space charge or Schottky effects in the oxides containing transition metal ions. In SiO/TeO2 dielectric films, the non-linear dependence of current on the electric field is thought to be due to either the Poole-Frenkel effect or at slightly lower fields it could be due to impurities.
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Bienati, Massimiliano. "Ab initio study of the chemical reactivity of metal clusters and metal oxide clusters." Doctoral thesis, [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=96444237X.
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Manakkadu, Sheheeda Mariam. "SYNTHESIS AND TRIBOLOGICAL STUDY OF SELECTED DOUBLE METAL OXIDE NANOMATERIALS." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/221.
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Double metal oxides such as silver vanadate, as well as silver, copper, and zinc tungstates were synthesized at room temperature by a simple wet chemical route, and their tribological behavior was investigated at high temperature using a pin on disk tribotester against silicon nitride balls. In this chemical method, the resultant precipitates obtained during the sudden mixing of the various reactants were washed with deionized water and absolute alcohol to remove the impurities. The structural and microstructural characterization of the products; using X-ray diffraction (XRD) and scanning electron microscopy (SEM); revealed different structures such as nanorods and nanoparticles of vanadates and tungstates. Silver vanadate nanorods had a length of 0.5-4 µm, width of 100-300 nm and thickness of 50-100 nm, while silver tungstate nanorods had a length of 0.25-3 µm, width of 300-500 nm and thickness of 75-100 nm. The SEM characterization of zinc tungstate revealed the formation of nanoparticles of diameter 30-75 nm. This synthesis process required no surfactants, high temperatures, or long reaction times. All of the synthesized nanomaterials were further tested for their tribological behavior at 250C and 7000C. Silver vanadate (1:2 molar ratio) and zinc tungstate showed good lubrication behavior at 7000C with a coefficient of friction (CoF) in the range of 0.11-0.27. Silver tungstate was found to be lubricious over a broad range of temperatures. The CoF for silver tungstate at 250C was ~0.18, and at HT was in the range of 0.01- 0.15. Therefore silver tungstate may prove to be an excellent lubricant material for a wide range of temperature applications. The low CoFs at high temperatures may be due to their layered atomic structure with weak interplanar bonds.
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Bowen, Andrew. "Anodisation and study of oxide films formed on zirconium." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328407.
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Fleischer, Stephen. "A study of gate-oxide leakage in MOS devices." Thesis, [Hong Kong : University of Hong Kong], 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1364600X.
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Dickinson, Calum. "Metal oxide porous single crystals and other nanomaterials : an HRTEM study." Thesis, University of St Andrews, 2007. http://hdl.handle.net/10023/217.
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Three-dimensional porous single crystals (PSCs) are a recent development in the growing world of mesoporous material. The mesoporosity allows for the material to retain their nanoproperties whilst being bulk in size. The current work concentrates on chromium oxide and cobalt oxide PSCs formed in the templates SBA-15 and KIT-6. HRTEM is the main technique used in this investigation, looking at the morphology and single crystallinity of these materials. A growth mechanism for the PSC material is proposed based on HRTEM observations. XRD studies revealed that the confinement effect, caused by the mesopores, reduces the temperature for both cobalt and chromium oxide crystallisation, as well as a different intermediate route from the metal nitrates. The properties of chromium oxide PSC are also investigated magnetically and catalytically. Some metal oxides in different templates are also presented, despite no PSC forming. HRTEM work on other nanomaterials, based on collaboration, is also presented.
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De, Los Santos Valladares Luis. "Study of thin metal films and oxide materials for nanoelectronics applications." Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/244598.
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Different types of thin metal films and oxide materials are studied for their potential application in nanoelectronics: gold and copper films, nickel nanoelectrodes, oxide nanograin superconductors, carboxyl ferromagnetic microspheres and graphene oxide flakes. The crystallization and surface morphology of gold and copper films on SiO2/Si substrates is investigated as a function of annealing temperature. Annealing arranges the Au crystallites in the [111] direction and changes the morphology of the surface. Relaxation of the Au layer at high temperatures is responsible for the initial stages of cluster formation. These may form at disordered points on the surface and become islands when the temperature is increased. In the case of Cu/SiO2/Si films, oxides are formed after thermal oxidation at different temperatures up to 1000 °C. The phase evolution Cu -> Cu + Cu2O -> Cu2O -> Cu2O + CuO -> CuO is detected. Pure Cu2O films are obtained at 200 °C, whereas uniform CuO films without structural surface defects are obtained in the temperature range 300 - 550 °C. A resistivity phase diagram, which is obtained from the current-voltage response of the copper oxides, is presented. In the case of thin nickel films, the necessary reagents, conditions and processes required to obtain nano and atomic gaps between soft and clean nickel electrodes are described by using a conventional electrochemical cell. Current-voltage characteristics are also presented to evaluate possible applications of the nanogap electrodes in electronic nanodevices. In addition to the metal surfaces, oxides materials such as the superconductor LaCaBaCu3O7 (La1113), carboxyl ferromagnetic microparticles and graphene oxide flakes are studied. La1113 is a high critical temperature superconductor with TC(onset) = 80 K and its structure is similar to the tetragonal YBCO. This thesis explores the attachment of La1113 nanograins on Au(111) surfaces through selfassembled monolayers of HS-C8H16-HS [octane (di)thiol] for their potential application in nanotransistors. It is found that La1113 particles (100 nm mean diameter) can be functionalized by octane (di)thiol without affecting their superconducting critical temperature (TC = 80 K). A design for a superconducting transistor fabricated by immobilized La1113 nanograins in between two gold electrodes which could be controlled by an external magnetic field gate is suggested. Furthermore, the mechanical reorientation of thiolated ferromagnetic microspheres bridging a pair of gold electrodes under an external magnetic field is studied. Finally, a flexible film made of graphene oxide flakes is prepared and characterized by X ray diffraction. It is achieved by the chemical oxidation of commercial graphite and the subsequent reaction with NaOH. It is found that the interlayer distance between graphene increases upon oxidation due to the formation of chemical groups and results in the delamination and flexibility of the flakes.
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Denison, Kieth Royston. "A study of photo-induced wettability changes at metal oxide semiconductor surfaces." Thesis, Lancaster University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.651293.
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Colloidal semiconductor photocatalytic materials such as Ti02• α-Fe203 and Sn02 have been used in laboratory-scale pollution abatement systems, reducing I oxidising both organic and inorganic impurities / toxins to chemically useful and / or biologically harmless compounds. For Ti02 there are potentially two distinct photoinduced phenomena: the first is the photocatalytic redox phenomena described above. The second involves photolytically induced high wettability or superhydrophilicity. The longer the surface is illuminated with IN light, the smaller the contact angle formed between the air - water - TiO2 interfaces until, in some cases the angle approaches zero. We have studied Photo-induced SuperHydrophilicity (PISH) on mesoporous TiO2(M-Ti02) films produced from reverse micellar solutions of titanium isopropoxide. M-Ti02 films have been deposited on quartz by spin coating and shown to clearly exhibit phot(}-induced wettability when irradiated with ultra-band gap light. Using a new continuous contact angle measurement technique. the time dependence of the photo-induced wettability changes on the film have been evaluated through the spreading of a sessile water drop. Results obtained at 100% RH, 293 K showed that drops on M-Ti02 exhibited a photo-induced "stick-slip" behaviour. The thermodynamic driving force for this photo-induced stick-slip has been attributed to the departure of the system from capillary equilibrium as the equilibrium contact angle of the drop, θo, decreased with illumination time. Based on this model, a simple theoretical description of photo-induced stick-slip has been derived and used to calculate a value of the potential energy barrier opposing the onset of movement of the triple line, U = 6.26 X 10-6 J m-1. This is the first time that U has been quantified for a surface with photo-induced wenability. Micro gravimetric studies of M-Ti02 layers in humid atmospheres show that, especially at RH > 95%, illumination of the M-Ti02 surface leads to a photo-induced watcr adsorption I condensation at the semiconductor / gas interface. Studies of this photo-induced water condensation on M-Ti02 coated crystals as a function of crystal age / experiment run number indicates that there are two possible modes of condensation - in-pore / in-layer condensation and condensation over the outer surface of the layer.
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Díez, García María Isabel. "Preparation and study of ternary metal oxide photocathodes for solar energy conversion." Doctoral thesis, Universidad de Alicante, 2018. http://hdl.handle.net/10045/74451.
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The future energy demand will require a change in the current energy supply. In this regard, the production of hydrogen by photoelectrochemical solar cells is a promising alternative because the fuel is obtained from water and, importantly, its combustion is free of carbon. Many metal oxides, including those having a complex stoichiometry (i.e. ternary oxides) behave as semiconductors and present good stability in aqueous environments, making them attractive candidates for water splitting devices. This thesis focuses on the preparation and study of ternary metal oxide materials as photoelectrodes for water splitting, with emphasis on photocathodes. These materials must meet the requirements for a practical device: low cost, non-toxicity, made of Earth abundant elements, environmentally friendly, etc. The thesis also aims at the study of strategies to improve their photoelectrochemical response. lt comprises the investigation of the kinetics of hydrogen generation reaction and the characteristics of the electrode solution interface by photoelectrochemical impedance spectroscopy. The main points can be summarized as: (i) the effect of an electrochemical oxidative pretreatment in CuFe2Ü4 photocathodes (ii) the investigation of water splitting mechanisms in CaFe2Ü4 photocathodes, (iii) the effect of metal doping in LaFeO3 photocathodes (iv) the study of the photoelectrochemistry of compact and nanoparticulate YFeO3 photocathodes and (v) the effect of a reductive electrochemical treatment in NiTiO3 photoanodes, and comparison with the effect of the treatment in anatase electrodes.
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Poudel, Tilak. "Study of Novel Metal Oxide Semiconductor Photoanodes for Photoelectrochemical Water Splitting Applications." University of Toledo / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1574613964790043.
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Wei, Daming. "Study of high dielectric constant oxides on GaN for metal oxide semiconductor devices." Diss., Kansas State University, 2014. http://hdl.handle.net/2097/17393.
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Doctor of PhilosophyDepartment of Chemical Engineering
James H. Edgar
Gallium nitride is a promising semiconductor for fabricating field effect transistors for power electronics because of its unique physical properties of wide energy band gap, high electron saturation velocity, high breakdown field and high thermal conductivity. However, these devices are extremely sensitive to the gate leakage current which reduces the breakdown voltage and the power-added efficiency and increases the noise figures. To solve this problem, employing a gate dielectric is crucial to the fabrication of metal insulator semiconductor high electron mobility transistors (MISHEMTs), to reduce the leakage current and increase the magnitude of voltage swings possible. For this device to be successful, imperfections at the oxide-semiconductor interface must be suppressed to maintain the high electron mobility of the device. This research explored multiple high dielectric constant gate oxides (Al[subscript]2O[subscript]3, TiO[subscript]2, and Ga[subscript]2O[subscript]3), deposited on different crystalline orientations and polarities of GaN by atomic layer deposition (ALD) to form metal oxide semiconductor capacitors, including effects of pretreatment on N-polar GaN, ALD TiO[subscript]2/Al[subscript]2O[subscript]3 nano-laminate on thermal oxidized Ga-polar GaN and ALD Al[subscript]2O[subscript]3 on [Italic]c- and [Italic]m-plane GaN Surface pretreatments were shown to greatly alter the morphology of reactive N-polar GaN which is detrimental to the electrical properties. 14 nm thick ALD Al[subscript]2O[subscript]3 films were directly deposited on N-polar GaN without thermal or chemical pretreatments which yield a smooth surface (RMS=0.23 nm), low leakage current (2.09 x 10[superscript]-[superscript]8 A/cm[superscript]2) and good Al[subscript]2O[subscript]3/GaN interface quality, as indicated by the low electron trap density (2.47 x 10[superscript]10 cm[superscript]-[superscript]2eV[superscript]-[superscript]1). In the nano-laminate study, a high dielectric constant of 12.5 was achieved by integrating a TiO[subscript]2/Al[subscript]2O[subscript]3/Ga[subscript]2O[subscript]3 oxide stack layer, while maintaining a low interface trap density and low leakage current. There was a strong correlation between the surface morphology and electrical properties of the device discovered from comparing the ALD Al[subscript]2O[subscript]3 on [Italic]c- and [Italic]m-plane GaN, namely smooth surface lead to small hysteresis. These results indicate the promising potential of incorporation gate dielectric for future GaN devices.
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Martí, Calatayud Manuel César. "STUDY OF THE TRANSPORT OF HEAVY METAL IONS THROUGH CATION-EXCHANGE MEMBRANES APPLIED TO THE TREATMENT OF INDUSTRIAL EFFLUENTS." Doctoral thesis, Universitat Politècnica de València, 2015. http://hdl.handle.net/10251/46004.
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La presente Tesis Doctoral consiste en la determinación de las propiedades de transporte de diferentes especies catiónicas a través de membranas de intercambio catiónico. Las membranas de intercambio iónico son un componente clave de los reactores electroquímicos y de los sistemas de electrodiálisis, puesto que determinan el consumo energético y la eficiencia del proceso. La utilización de este tipo de membranas para el tratamiento de efluentes industriales no es muy extendida debido a los requisitos de elevada resistencia química y durabilidad que deben cumplir las membranas. Otro asunto importante radica en la eficiencia en el transporte de los iones que se quieren eliminar a través de la membrana. Normalmente, existe una competencia por el paso a través de las membranas entre diferentes especies debido al carácter multicomponente de los efluentes a tratar. Sin embargo, una mejora en las propiedades de las membranas de intercambio iónico permitiría la implantación del tratamiento mediante reactores electroquímicos de efluentes industriales con un contenido importante en compuestos metálicos, tales como los baños agotados de las industrias de cromado. La utilización de una tecnología limpia como la electrodiálisis conllevaría diferentes ventajas, entre las cuales destacan la recuperación de los efluentes para su reutilización en el proceso industrial, el ahorro en el consumo de agua y la disminución de la descarga de contaminantes al medio ambiente.
La determinación de las condiciones de operación óptimas así como la mejora de las propiedades de transporte de las membranas constituye el principal tema de la presente investigación. Para ello, se emplearán diferentes tipos de membrana. En primer lugar, se estudiará el comportamiento de las membranas poliméricas comerciales que poseen unas propiedades de resistencia química elevadas, las cuales se tomarán como referencia. De forma paralela, se producirán membranas conductoras de iones a partir de materiales cerámicos económicos, ya que la resistencia de los materiales cerámicos a sustancias oxidantes y muy ácidas es mayor que la de los materiales poliméricos. Este punto constituye la parte más innovadora de la investigación, puesto que la mayoría de las membranas de intercambio iónico comerciales están basadas en materiales poliméricos que no pueden resistir las condiciones específicas de los efluentes industriales. Una vez determinadas las condiciones de operación óptimas, se realizarán ensayos en plantas piloto con el fin de confirmar los resultados obtenidos mediante las técnicas de caracterización y determinar el grado de recuperación y coste energético asociado a los procesos electrodialíticos de tratamiento de efluentes industriales.Martí Calatayud, MC. (2014). STUDY OF THE TRANSPORT OF HEAVY METAL IONS THROUGH CATION-EXCHANGE MEMBRANES APPLIED TO THE TREATMENT OF INDUSTRIAL EFFLUENTS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/46004
TESIS
Premiado
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Liu, Zhihong. "A study of thermally nitrided silicon dioxide thin films for metal-oxide-silicon VLSI techology /." [Hong Kong : University of Hong Kong], 1990. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12718488.
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Hong, Sampyo. "First-principles study of chemisorbed light gases on transition metal and transition metal oxide surfaces : structure, dynamics and reaction /." Search for this dissertation online, 2005. http://wwwlib.umi.com/cr/ksu/main.
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Hu, Bing. "FABRICATION AND STUDY OF MOLECULAR DEVICES AND PHOTOVOLTAIC DEVICES BY METAL/DIELECTRIC/METAL STRUCTURES." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_diss/222.
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A new class of electrodes with nanometer-scale contact spacing can be produced at the edge of patterned metal/insulator/metal this film structures. A key challenge is to produce insulator layers with low leakage current and have pristine metal contacts for controlled molecular contacts. Atomic layer deposition of high quality Al2O3 thin films onto Au electrodes was enabled by surface modification with a self-assembled monolayer of -OH groups that react with a monolayer of trimethylaluminum gas source. Ar ion milling was then used to expose the edge of the Au/dielectric/Au structure for molecular electrode contacts. The junctions are characterized by atomic force microscope and tunnel current properties. The Au/self-assembled monolayer/Al2O3/Au tunnel junction, with a very thin oxide insulator layer (15.4 Å), is stable and has a small tunneling current density of about 0.20 ~ 0.75 A/cm2 at 0.5 V. Organometalic cluster molecules were attached to bridge the electrodes. Through tunnel current modeling, low temperature and photo current measurements, molecular current was found to be consistent with direct tunneling through the organic tethers to available states at the metal center.
This novel electrode was also used to study the efficiency of organic conducting thin films where the photovoltaic efficiency can be improved when the electrode separation distance is below the exciton diffusion length. Copper (II) phthalocyanine (CuPc) was thermally evaporated between the nano-gap electrodes formed by Au/Al2O3/Au tunnel junctions. A large photocurrent enhancement over 50 times that of bulk CuPc film was observed when the electrode gap distance approached 10 nm. CuPc diffusion length is seen to be 10 nm consistent with literature reports. All devices show diode I-V properties due to a large Schottky barrier contact resistance between the small top Au electrode and the CuPc film.
To add another dimension of nm-scale patterning, nanowires can be used as line-of-sight shadowmasks provided that nanowire location and diameter can be controlled. Lateral ZnO nanowires were selectively grown from the edge of a Si/Al2O3/Si multi-layer structure for potential integration into devices utilizing Si processing technology. Microstructural studies demonstrate a 2-step growth process in which the tip region, with a diameter ~ 10 nm, rapidly grew from the Al2O3 surface. Later a base growth with a diameter ~ 22 nm overgrew the existing narrow ZnO nanowire halting further tip growth. Kinetics studies showed surface diffusion on the alumina seed surface determined ZnO nanowire growth rate.
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Lynch, Mark Francis. "Chemical reactions of small molecules on metal surfaces : a density functional theory study." Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314017.
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Li, Chunxia, and 李春霞. "A study on gate dielectrics for Ge MOS devices." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B43703872.
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Li, Chunxia. "A study on gate dielectrics for Ge MOS devices." Click to view the E-thesis via HKUTO, 2010. http://sunzi.lib.hku.hk/hkuto/record/B43703872.
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Lin, Xi 1973. "First-principles density functional theory study of sulfur oxide chemistry on transition metal surfaces." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29642.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2003.Vita.
Includes bibliographical references (p. 297-309).
In this thesis, the chemistry of sulfur oxides on transition metals is studied extensively via first-principles density functional theory (DFT) computations, focusing on the chemical reactivity and selectivity in sulfur poisoning chemical processes that address environmental concerns. The systematic approach we establish can be extended to general computational studies of small gas-phase molecules interacting with extended surfaces or finite-size clusters. The thesis starts with a theoretical presentation of modem quantum many-body theory that brings together mean-field theory, DFT, and Green's function quantum Monte Carlo theory. The essence of chemical reactivity theory in the framework of DFT is emphasized. The thesis continues with an extensive survey of the current status of sulfur oxide chemistry and an overall presentation of our computational approaches towards a detailed understanding of chemical reactivity and selectivity. The basic guidelines in chemical reactivity are systematically constructed by computed comprehensive thermodynamic data of surface S, O, SO, SO2, SO3, and S04 species as a function of coverage at low and intermediate temperatures. Under these basic guidelines, experimentally measured surface spectra are interpreted, contradictory experimental observations are resolved, and applicable experimental measurements are suggested for confirming computational predictions. Moreover, the chemical reactivity study is supplemented by our chemical kinetics study focusing on the catalytic oxidation of SO2 under oxygen rich conditions. This is the key process that hampers the implementation of the next-generation automotive catalytic converter. The revealed Langmuir-Hinshelwood mechanism demonstrates the essential catalytic performance of the Pt(1 11) surface.
(cont.) The thesis closes with a chemical selectivity analysis of the effects of catalyst particle size on chemisorption of gas-phase adatoms. In summary, the presentation of the chemistry of sulfur-containing molecules in this work is aimed at a scientific understanding of the strong poisoning effects in heterogeneous catalysis. However, the chemistry of sulfur-containing molecules has many more fundamental implications, such as in designing novel re-conjugated conducting devices for quantum computers. The underlying hybrid bonding flexibility of sulfur allows it to simultaneously bind to heavy transition metal atoms (such as Pt, Cu, or Au) and first-row atoms (such as oxygen atoms or carbon atoms in organic molecules).
by Xi Lin.
Ph.D.
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Kulkarni, Anish S. "Study of Tunable Analog Circuits Using Double Gate Metal Oxide Semiconductor Field Effect Transistors." Ohio University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1234552603.
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Ichikawa, Shin-nosuke. "Study of Transition Metal Vanadium Oxide for Cathode Material of Secondary Lithium-Ion Battery." Kyoto University, 2009. http://hdl.handle.net/2433/123889.
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Kyoto University (京都大学)0048
新制・課程博士
博士(エネルギー科学)
甲第14736号
エネ博第189号
新制||エネ||43(附属図書館)
UT51-2009-D448
京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻
(主査)教授 八尾 健, 教授 尾形 幸生, 教授 萩原 理加
学位規則第4条第1項該当
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Cai, Wei. "Ballistic Electron Emission Microscopy and Internal Photoemission Study on Metal Bi-layer/Oxide/Si, High-k Oxide/Si, and “End-on” Metal Contacts to Vertical Si Nanowires." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1269521615.
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Mueanngern, Yutichai. "Mechanistic Study for Selective Hydrogenation of Crotonaldehyde Using Platinum/Metal-Oxide Catalysts—A Gas-Phased Kinetics Study." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462804731.
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劉志宏 and Zhihong Liu. "A study of thermally nitrided silicon dioxide thin films for metal-oxide-silicon VLSI techology." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1990. http://hub.hku.hk/bib/B31231895.
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Tarkin, Eylem. "Characterization And Study Of Solution Properties Of Poly(propylene Oxide) Synthesized By Metal Xanthate Catalysts." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1086099/index.pdf.
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Zinc xanthates polymerize propylene oxide into high polymer (PPO) with coordination mechanism. In order to identify structure and stereoisomerisms of this polymer, PPO was subjected to thermal and column fractionation. Obtained fractions were characterized by end-group analysis, cryoscopy, viscometry, IR and 13C-NMR spectroscopy, melting temperature. PPO is composed of a high molecular weight, stereoregular, crystallizable polymer (K-polymer) with low molecular weight (=500 g/mol) D-polymer. Presence of double bonds and hydroxyl terminals was interpreted as the product of an anionic mechanism.
K-Polymers can be thermally fractionated on the basis of their melting temperature (Tm) rather than molecular weight (Mwt). It’
s found that higher Tm fractions have lower Mwt, but they precipitate at higher temperatures than higher Mwt but lower Tm fractions. In column fractionation, K-polymers were deposited on glass beads from isooctane solution in a narrow temperature interval. Then the precipitated samples were split into a number of fractions by using again isooctane but at a higher temperature than the precipitation temperature by increasing residence time from 5 minutes to several hours. It&
#8217
s found that rate of solubility is not controlled by molecular weight, but controlled by percentage crystallinity and Tm. Highest Tm polymers, with relatively higher Mwt showed faster rate of solution than that of lower Tm, lower Mwt but higher percent crystalline fractions. This discrepancy was accounted by suggesting a stereo-block structure where tactic blocks are bound each other with non-crystallizable atactic blocks. The mechanism of polymerization was also discussed in some detail.
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Chinchani, Rameshwari. "Strained silicon/silicon-germanium heterostructure complimentary metal oxide semiconductor devices a simulation study of linearity /." Ohio : Ohio University, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1176143999.
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Goh, Inn Swee. "A study of strained SiGe layers using metal oxide semiconductor capacitors and heterostructure bipolar transistors." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318307.
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Chen, Yi-Hsuan, and 陳怡璇. "Solid State Cation Exchange Reaction to Form Multiple Metal Oxide Heterostructure Nanowires." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/27975237450790288633.
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碩士國立交通大學
材料科學與工程學系所
104
Metal oxide nanostructure has been investigated extensively due to its wide range of physical properties; among them, zinc oxide is one of the most promising materials. It exhibits fascinating functional properties and various kinds of morphology. ZnO heterostructure especially has attracted great attention since its performance can be varied readily and further improved by combining with other materials. The mechanism of cation exchange is remains elusive, especially in metal oxide heterostructures; it is unpredictable how the confined interface and the effects of ions diffusion will affect the transformation. In this work, the experiment was carried out in in situ UHV-TEM, which equipped with video recorder; in this way, we could observe the phenomena of the transforming directly. Moreover, we analyze the structure and composition of the epitaxial interface by Cs-corrected STEM equipped with EDS, and simulate the anion sublattice of epitaxial interface by atomic model. In this study, we deposited few nanometer of alumina onto ZnO nanowire by thermal evaporation, and successfully transformed ZnO nanowires into multiple Al2O3/ZnO heterostructure through solid state cation exchange reaction. During heating, alumina ions diffused into ZnO lattice, exchange with zinc ions, and combined with oxygen to form Al2O3 crystals mosaicked into the nanowire. In the process, the anion sublattice remains the basics of the parent crystal; therefore, it is a unique method to form new crystals with desired shape and size in nano-heterostructure. Based on these experiment results, we infer a model of the ion path in cation exchange reactions. Additionally, the defects appeared in cation reaction were investigated, which resulted in the remaining of zinc ions.
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Reed, Zachary David. "Fixed frequency dissociation of metal oxide cations and infrared photodissociation studies of metal carbonyl cation systems." 2009. http://purl.galileo.usg.edu/uga%5Fetd/reed%5Fzachary%5Fd%5F200912%5Fphd.
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Thesis (Ph. D.)--University of Georgia, 2009.Directed by Michael Duncan. For abstract see https://getd.libs.uga.edu/pdfs/reed%5Fzachary%5Fd%5F200912%5Fphd.pdf. Includes bibliographical references.
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Li, Jia-Zhen, and 李佳真. "Study on degradation of ozone over metal oxide." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/8ryupc.
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碩士國立臺灣科技大學
化學工程系
105
In this work, the degradation of gaseous ozone over metal oxide catalyst under ambient condition in a continuous flow reactor was investigated. In first part, the effects of calcination and amount of A-ion on physical properties were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), surface area and porosimstry analyzer (BET), energy dispersive spectrometer (EDS), and scanning electron microscope (SEM), respectively. The excessive amount of A will create the multilayer or bulk A on the surface, resulting in the decrease in active site. The intermediates on catalyst surface and in gas were respectively determined by FTIR, TGA, EA, XRD, and IC. The results showed the presence of nitrogen oxides both on the catalyst surface and in gas phase, the reactivity of catalyst was gradually decreased due to the adsorption of NOx. Moreover, the reaction parameters, such as retention time, relative humidity, temperature, amount of catalyst, and ozone concentration were studied for conduction of reaction kinetics. Langmuir-Hinshelwood and Power law models were successfully applied to estimate the adsorption and rate constants. Finally, in order to further confirm the practicability of this A/B catalyst, the A/B pellet was fabricated to lower pressure drop and avoid dust emission. In the 200h long-term test, the conversion was kept at over 90% for simulated field conditions, 350 ppm of ozone, GHSV=7375h-1, and relative humidity of 60~ 85%. The results indicated the activity of prepared catalyst have matched the practical standards.
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Wang, Tzu-Juei, and 王子睿. "Study of SiGe Heterostructure Metal (Oxide) Semiconductor FETs." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/85419943733667498540.
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碩士國立成功大學
微電子工程研究所碩博士班
92
In this these, two p-type SiGe doped-channel field-effect transistors with different Ge profile were grown by solid-source molecular beam epitaxy (SSMBE). Secondary ion mass spectrum (SIMS) was used to verify the Ge profile in Si1-xGex channel. Then, the SiGe-based MESFETs with a uniform Ge channel and with a Ge graded-channel were successfully fabricated. The graded variation of the Ge fraction in channel induced built-in field can prevent transconductance from shaping down drastically under forward gate bias and increase the carrier confinement for device operation. It is found that by grading Ge fraction in the channel, the devices exhibit the excellent property not only of higher current density (65 mA/mm) but also enhancement in extrinsic transconductance (14.2 mS/mm) and linear operation range over a wider dynamic range than those of devices with uniform Ge profile for the same integrated Ge dose in SiGe conducting well. In addition, MESFETs suffer from a reduced gate voltage swing due to the onset of a significant leakage current across the Schottky gate under forward bias condition. SiGe/Si metal-oxide-semiconductor heterojunction field effect transistors (MOSHFETs) are fabricated with photo-CVD oxide as the insulating layer and compared with SiGe/Si heterostructure MESFETs with similar structure. Photo-CVD oxide is a good candidate for gate dielectrics in SiGe MOSFETs because its low processing temperature can avoid the relaxation of strained SiGe layers and segregation of Ge atoms. From the experimental results, SiGe MOSHFETs with different Ge profile show good FET characteristics.
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李伯紀. "The study of internal cation mobilities in the molten binary metal chloride systems." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/17695963701444695477.
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Huang, Hong-Cheng, and 黃虹彰. "Study of Oxide Traps among Gold Nano-Particles in Metal-Oxide-Semiconductor Device." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/75496997630524976687.
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碩士臺灣大學
電子工程學研究所
98
In this work, Metal-Oxide-Semiconductor structure with Au nanocrystals formed by chemical redundant method for charge storage is fabricated. Scanning Electron Microscope is utilized to calculate the density of nanocrystals. In the characterization of memory performance, we use high frequency capacitance-voltage (C-V) measurement to measure the memory window size for comparing the storage capacity and charging efficiency. On the other hand, through the time dependent variation of device capacitance measured under fixed voltage, the effective charge loss rate can be calculated to compare the retention regarding the stored charge of devices. In the study of device, we compared the impacts between different structural parameters at first, include using gold nanoparticles and silver nanoparticles, and the variance of different diameters of gold nanoparticles, such as 10 nanometer and 20 nanometer. When the density of the gold nanoparticles increased also has influence that charge retention dropping while causing the memory window size increasing. Further, we want to improve the performance of device in addition, using excimer laser annealing to fix the defects in oxide layer, but we find the gold nanoparticles would be melted after heated by laser, and diffused into oxide layer then break down under the bias voltage.
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Wu, Shu-Hua, and 吳杼樺. "Study on Lanthanum Oxide Metal-Insulator-Metal Capacitor for Radio-Frequency/Analog Applications." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/64392587197921354844.
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碩士國立交通大學
電子工程系所
98
In this study, the low-temperature metal-insulator-metal (MIM) capacitor with the high dielectric constant (high-k) lanthanum oxide (La2O3) film deposited by electron beam (e-beam) evaporation was fabricated and characterized for radio frequency (RF) and analog applications. The operational principles and the implementation issues of the high-k La2O3 MIM capacitor are discussed, including leakage current and conduction mechanisms, analog properties and distortion mechanisms, stress behaviors and degradation processes, as well as dielectric breakdown and reliability characteristics. To begin with, we evaluate the conduction mechanisms for high-k La2O3 MIM capacitors. Unlike the conventional SiO2 MIM capacitor where the quantum-mechanical tunneling is pronounced, the trap-related mechanisms are important for high-k MIM capacitors with low temperature fabrication, due to the high trap and interface state density in the high-k dielectric. Secondly, the effects of voltage, temperature, and frequency on the capacitance of high-k La2O3 MIM capacitors are investigated in detail on the basis of fundamental high-k dielectric behaviors: polarization and relaxation. The space charge polarization and relaxation are principally responsible for the positive voltage coefficient of capacitance (VCC). However, the dipolar polarization and relaxation dominate the positive temperature coefficient of capacitance (TCC). Interplay of these two effects on analog characteristics is crucial for developing the precise MIM capacitors with high-k dielectrics. The changes in VCC and TCC caused by the constant voltage stress (CVS) also verify the above inferences. VCC decreases since the space charge mobility reduced by stress induced traps, but TCC increases because the quantity of trap induced dipoles grows during stress. Furthermore, the stress behaviors and the reliability issues of high-k La2O3 MIM capacitors under various CVS conditions are also studied. The wear-out mechanisms of La2O3 MIM capacitors during electrical stress are trap generation and charge trapping. This could be identified by measuring the stress induced leakage current (SILC) at low field and by detecting the capacitance variation under electrical stress, respectively. Moreover, the very distinct two-step time-dependent dielectric breakdown caused by CVS testing could be observed. It is ascribed to firstly the interfacial layer (IL) breakdown leading to the severe charge trapping/detrapping, followed by the breakdown of the bulk high-k layer. Therefore, the high intrinsic defect density in the IL not only affects the leakage current and analog characteristics of MIM capacitors, but also plays an important role on the device failure rate. In summary, a highly stable and reliable 10-nm La2O3 MIM capacitor with low leakage current (9.4 nA/cm2 at �{1 V), high breakdown strength (�� 7 MV/cm at 25 �aC), small VCC (671 ppm/V2 at 100 kHz), low thermal budget (�T 400 �aC), and sufficient high capacitance density (11.4 fF/�慆2) has been successfully demonstrated. The results highlight the promise of the La-based high-k MIM capacitors as the next-generation passive component in RF/analog circuits.
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Lin, Chieh-En, and 林傑恩. "A study of poly lactic acid/metal oxide nanocomposites." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/35406470488905705308.
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碩士國立勤益科技大學
化工與材料工程系
97
In this studies are divided into PLA/SiO2、PLA/Al2O3、 PLA/SiO2/Al2O3, respectively. Study on the properties from different contents of metal alkoxide. Organic/inorganic Poly(lactic acid)(PLA) metal alkoxide hybrid films are prepared using the sol-gel method. These hybrid films are subjected to thermal stability, mechanical properties, optical properties, surface morphology and structures properties analyses. Also, dynamic mechanical analysis (DMA) and thermo-mechanical analysis (TMA) are used to assess the material dimensional stability and haze meter and ultraviolet and visible spectroscopy (UV-Vis) for optical properties and thermo gravimetric analyzer are used to material degradation temperature and Scanning Electron Microscope (SEM) are used to surface morphology stability and X-ray photoelectron spectrometer (XPS) are used to surface composition and element contents. The results show that the mechanical and thermal properties of PLA can be enhanced effectively using the sol-gel method; in particular, the enhancement of mechanical properties is the most conspicuous. The rigidity is significantly enhanced and the coefficient of thermal expansion is also significantly reduced.
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Cherng, Shih Yi, and 施宜成. "Study of Novel Lithium-Intercalated Mixed Metal Oxide Electrodes." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/99737731384158894998.
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碩士國立中央大學
化學工程研究所
82
This study is concerned with synthesis of Li-Fe-Co-O ternary compounds using solid state reaction and coprecipitation method, and characteristic test of battery using these compounds. To gain the best matreial, this study uses different reaction temperatures and times for sythesis. The result reveals that the
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Petrov, Kostadin Veselinov. "Modified Cation Exchange Membrane for Phosphate Recovery - a Comparative Study." Master's thesis, 2018. http://hdl.handle.net/10362/51206.
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林震宇. "The study of metal oxide nanowires prepared by reactive evaporation." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/37112822707857804885.
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Lin, Kung-An, and 林恭安. "Study of Si-based Metal-Oxide-Semiconductor Light Emitting diodes." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/26633036026955022357.
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碩士國立臺灣大學
光電工程學研究所
94
Using silicon as the light emitting material, it can be easily integrated with the ultra large-scale integrated (ULSI) circuit .As the dimension of devices in the silicon ULSI is scaled down, it also brings up the problem of the time delay among components. Therefore, silicon light emitting sources provide an effective solution for data transmission. This thesis is devoted to the study of metal-oxide-silicon light emitting diodes (LEDs). First of all, SiO2 nano-particles as the oxide layer are spun upon the silicon substrate. The roughness between silicon and oxide layer results in nano-scale carrier confinement. Because of nano-scale carrier confinement, light efficiency is raised. It is a simple fabrication method. The components have good light emission efficiency. Then, comparison of the difference between FZ wafers and CZ wafers gives us the new point that CZ wafers can also be a material for light emitting component. Although FZ wafers have high quality, they still cost higher in price than CZ wafers. Because the quality of CZ wafers is improved in the past years, there is a tendency of replacing FZ wafers with CZ as a light emitting component. In the experiments, we observe optical power saturation phenomenon in high injection currents. In order to understand the reason why the phenomenon happens, we use a theoretical model to simulate and analyze the measurements. According to the theoretical investigation, the cause of the phenomenon is that lattice temperature is raised as the injection current increases. Because near lasing actions from Si-based light sources were observed in 2000 and 2004, we tried to fabricate Farby-Perot cavities for Si lasers similar to III-V-based laser diodes in our Lab .The fabrication conditions are experimentally studied. The difficulty in the cavity fabrication is addressed. Finally some possible improvements are proposed in the hope that Si-lasers can be realized and lead to a great impact on the industry of USLI in the future.
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Huang, Zhangyan, and 黃章彥. "Study on the low electrical resistivity metal oxide thin films." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/r779v7.
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碩士中國文化大學
化學工程與材料工程學系奈米材料碩士班
100
We use the AlFeCoNi、CrFeCoNi、TiCo1.5Ni1.5 alloy target deposited the thin films in this paper. Then, some of the thin films were vacuum annealed at high temperature for investigating the effects of annealing conditions on their electrical resistivity. The annealing temperatures were from 500℃ to 1000℃. The microstructure of the thin films were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy；their resistivities were measured by four-point probe. The results indicated that the as-deposited thin film had an amorphous structure. All of these films would transform to FCC structure after vacuum annealed at high temperatures. Results indicated the lowest resistivity of the alloy oxide thin film was the AlFeCoNi oxide thin film, and its resistivity was 15μΩ-cm after annealed at 800°C for 30min. This value is not only lower than ITO (150μΩ-cm) and RuO2 single crystal (35μΩ-cm), but also lower than our previous studies on the TixFeCoNi oxide thin films. Moreover, AlFeCoNi oxide films had good thermal stability, because its resistivity did not change significantly after annealed for 4 hours.
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Sheu, Cheng-Wei, and 徐政維. "Study of metal electrode contacts to Zinc Oxide thin films." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/9qnww4.
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碩士國立虎尾科技大學
光電與材料科技研究所
96
To accomplish high-performance ZnO-based optoelectronic devices, the formation of high quality metal electrode contacts is essential. A superior rectifying junction with metals and low-resistance ohmic contacts onto the ZnO surface was the best mechanism that promoted their use in diode, UV detector, gas sensor, piezoelectric transducer, and optical applications . There were many reports addressing the mechanisms for the difficulties in the formation of ZnO-based Schottky diodes, including surface morphology, environment activity and subsurface defects . A variety of ZnO surface treatment methods, such as chemical preparation with acid, plasma or irradiation treatments, and surface passivation via a chemical solution were demonstrated to removal the interfacial states of the metal Schottky contact to ZnO. To date, magnetron sputtering is a commonly used system for deposition crystalline ZnO films in application on the optoelectronic devices. However, there were very limited reports on Schottky contacts of ZnO, especially for that of sputtered-ZnO thin films. In this study, the 2 μm-thick undoped-ZnO film was deposited onto silicon substrate using rf magnetron sputtering system and then annealed at 700oC for 30 min under oxygen ambient to achieve a superior c-axis orientation with oxygen-terminated crystalline structure. The films were undoped but show n-type conduction (~ 3.83 ? 1011 cm-3). Ni/Au and Al were respectively, employed to form Schottky and ohmic contact on the ZnO-based structures. These contact metals patterned directly by lift-off of evaporated films onto the ZnO film was denoted as the conventional Schottky diode (sample A), whereas that of the Schottky contact surface processed with an additive oxygen plasma treatment at 270 W for 10 min prior to metal deposition was classified as sample B. In addition to the conventional Schottky diode structure, another set of multilayer Schottky diode structure (sample C) with a homogeneity ITO-ZnO cosputtered layer (~ 250 nm) deposited onto the undoped-ZnO film also prepared to improve the ohmic contact performance. The ITO-ZnO cosputtered film at an atomic ratio of 90% [Zn / (Zn + In) at.%] was annealed at 300oC for 30 min under oxygen ambient and possessed an electron carrier concentration of 7.01 ? 1018 cm-3 . Detail structures of the conventional and multilayer Schottky diodes structures are illustrated in Fig. Carrier concentration and hall mobility of the deposited films were measured by the van der Pauw method. The crystalline structures and surface morphologies were examined by XRD and AFM measurements. Current-voltage properties of these Schottky diode structures were characterized using semiconductor parameter analyzer (HP4156C). A comparison for the I-V characteristic of Ni/Au Schottky contacts to the undoped-ZnO surface with and without oxygen plasma process is shown. Both the reverse and forward currents of the conventional Schottky diode were markedly reduced after processing with an additive oxygen plasma treatment. In addition, the ratios of the forward to leakage current measured at -2 and 2 V were also increased from 4.78 (sample A) to 14.25 (sample B), indicating a better rectifying behavior. The convention Schottky diode had a high ideality factor (n) of 2.47, meaning that the existence of multiple current pathways other than thermionic emission. In contrast, the ideality factor and barrier height (ΦB) were evaluated to be 1.92 and 0.82 eV, respectively. The reduction in the ideality factor as well as the increase in the barrier height performances was consisted with the report that addressed to be the donor-like defect passivation of the oxygen radical in the plasma diffused into the host lattice in the ZnO films surface . Although the rectifying behavior had been significant improved through the oxygen plasma treatment on the Schottky contact surface, the forward current was too small due to the poor ohmic contact behavior. The specific contact resistance was greatly decreased to 1.44 ? 10-3 ? cm2 with a homogeneity ITO-ZnO cosputtered film deposited onto the undoped-ZnO film. Elimination of surface carbon- and hydrogen-related contaminations as well as the compensation of the oxygen-related vacancies reduced not only the defect-assisted tunneling of electron but also the net carrier concentration at the Ni/ZnO surface leading to the better Schottky diodes performance.
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WEI, TA-CHENG, and 魏大程. "Study of Synthesis and Photodegradation Properties of Metal Oxide Nanostructures." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/yvj4h9.
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碩士國立暨南國際大學
應用材料及光電工程學系
106
This study investigated the synthesis of a metal-oxide nanostructures and explored their photodegradation characteristics. The simple and reliable micelle-mediated hydrothermal method was employed to create the porous cadmium-doped titanium dioxide photocatalysts. Subsequently, through cadmium doping, the titanium dioxide nanoparticles possessed a high specific surface area and the band-gap energy of the overall nanostructures was reduced. Therefore, the possibility of recombination was reduced duo to efficient electron–hole pair separation. Additionally, we took advantage of the characteristics of high specific-surface area and reduced band-gap energy to initiate the generation of hydroxyl radicals and superoxide via light excitations, thereby resulting in the superior photodegradation characteristics. We found that the doping of titanium dioxide with 5% of cadmium possessed superior characteristics— large specific surface area (389.05 m2/g) and wideband light-absorption capability, which extended the light absorption range from ultraviolet regions to visible regions. Moreover, this study used two nonbiological degradable azo dyes, including Remazol Black 5 (RB-5) and Remazol Brilliant Orange 3R (RBO-3R), as organic targets in the photocatalytic experiments. This study further investigated the dynamic model and proved that the involcing photodegradation reaction was in accordance with the characteristics of second-order kinetic model. Furthermore, the photo-degradation capability of titanium dioxide nanoparticles doping with 5% cadmium could result in 80% degradation of both RB5 and 3R dyes. Compared with the undoped titanium dioxide nanoparticles, with the improved photodegradation activity of 55% higher than that of undoped titanium dioxide nanoparticles under the irradiation of the visible light. In addition, a crystal seed-assisted hydrothermal method was used to prepare zinc oxide nanorod arrays. Subsequently, a vulcanization process was adopted to prepare a zinc oxide/zinc sulfide core-shell structure, which was then doped with the divalent copper ions to create a copper-doped core-shell nanostructures. A simple hydrothermal method was used to induce a vulcanization process to facilitate surface passivation in the zinc oxide/zinc sulfide core-shell structure and altered the surface of zinc-oxide nanorods from being hydrophilic (due to adsorbing the environmental moisture or hydroxyl groups) to hydrophobic. In addition, by introducing the heterogeneous interfaces in the core-shell structures, light-absorption range was extended to visible wavelengths and electron–hole pairs were effectively separated, enhancing their photocatalytic properties. It was found that the introduction of copper ion doping could reduce the resistance of nanostructures and decreased the oxygen defects in zinc-oxide nanorods, and further facilitated the separation of electron–hole pairs and lower their possibility of carrier recombination. In photocatalytic tests, the efficiency of photodegradation for degrading the methylene blue dyes was found to be effectively increased based on the Cu-doped ZnO/ZnS core-shell structures under the illuminations of ultraviolet lights and visible lights, which demonstrated the broadband and superior photodegradation capabilities.
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Yang, Chin-Yau, and 楊欽堯. "A Study of Metal-Oxide Indiffused Waveguides in Lithium Niobate." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/89151008726975663187.
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碩士南台科技大學
光電工程系
95
In this study, the guiding characteristics of metal-oxide (In2O3, In2O3/ZnO, and ZnO) indiffused waveguides depending on the diffusion time, temperature, and ambient have been experimentally studied in an x-cut lithium niobate for the first time. In the experiments of an In2O3 thermal indiffusion process, the atomic percentages and depth profiles of the doped Indium atoms were analyzed by using EDS and SIMS techniques. The results show that the diffusion depths and doped concentrations are dependent on the process parameters of diffusion time, temperature, and pressure. It was found that the proposed In2O3 indiffusion process is not easy to make an optical waveguide on the substrate. Thus, an In2O3/ZnO co-diffusion method was proposed to make the successful channel waveguides. Moreover, the measured near-field profiles indicate that the waveguide modes changed between a single and a multi mode under a highly irradiated power due to the photorefractive effects. In comparison with the input TM polarization, the guided modes are easy to oscillate temporally for the TE polarization, and the mode profiles changed obviously as well as an increase of input powers. Besides, the similar results were also observed in the ZnO indiffused waveguides. However, the power variations seem smaller than that of the In2O3/ZnO co-diffused ones.
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Parmar, Mitesh Ramanbhai. "Development And Performance Study Of Nanostructured Metal Oxide Gas Sensor." Thesis, 2011. http://etd.iisc.ernet.in/handle/2005/2425.
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The basic necessities to sustain life are – air, water and food. Although the harmful effects due to contaminated food or water are dangerous to life, these can be reduced/avoided by controlling the intake. Whereas, in case of air, the same amount of control cannot be exercised as there is very little, one can do in case of inhalation. Maximum damage to life is due to air contamination which can be detected and prevented by using gas sensors. The proper use of these sensors not only save lives, but also minimizes social and financial loss.
The objective of this thesis work is to study and explore the use of p-type semiconducting material such as CuO, as a promising gas sensing material for organic compounds (VOCs), compatible with existing silicon fabrication technology. The Thesis consist of 7 chapters:
Chapter 1 covers the general introduction about gas sensors, sensor parameters, criteria for the selection of sensing material, suitability of CuO as sensing material and a brief literature survey.
The second chapter includes the selection of substrate, cleaning procedures and suitable deposition method. The deposition method used in the present thesis work is DC/RF magnetron sputtering. The reactive magnetron sputtering is employed during the deposition of CuO sensing films. It also includes basic introduction about some of the common material characterization techniques.
This is followed by Chapter 3 which includes the optimization of sputtering process parameters such as applied power, working pressure, Ar-O2 ratio and substrate temperature for CuO sensing film and the effect of these on surface morphology. Information on the optimized sputtering parameters for electrode film (silver and gold) deposition has also been included in this chapter.
In order to study the sensing behavior of the sensor, suitable testing set-up is necessary. This leads us to Chapter 4 that discusses the development of an in-house built sensor testing setup and its automization using MATLAB. The automated testing set-up facilitates off-time data plotting as well as real-time data plotting during the sensing process. To demonstrate the working of the set-up, some initial results obtained are also included in this chapter.
After ascertaining the functioning of the automated gas sensor testing set-up, detailed study on the sensing behavior of nanostructured CuO films was performed. This information along with the necessary details is included in Chapter 5. The sensing response of nanostructured CuO films has been studied for different VOCs such as alcohol, toluene and benzene. The study carried out on the effect of different surface additives like multi-walled carbon nanotubes (MWNTs), gold or platinum on ethanol sensing has also been included in this chapter.
During the use of MWNTs as surface additives, different concentrations of MWNTs
– 0.01 mg, 0.05 mg and 0.1 mg have been dispersed on the CuO sensing film. The sample with lowest concentration of MWNTs exhibited highest sensitivity and lower response time. It is due to the fact that, higher concentrations of MWNTs do not result into uniform dispersion over the CuO films and cover the sensing film almost completely.
Operating temperature is the most important factor affecting the performance of a gas sensor. In order to maintain the operating temperature for the portable sensor, the sensor is usually integrated with a heater. The chapter 6 deals with heater optimization including design, simulation and fabrication. In this chapter, microheater as well as macro-heaters were simulated and fabricated. The fabricated macro-heater is bonded with the sensor by eutectic bonding. One of the bonded samples was studied for its sensing response.
The final chapter of the thesis deals with the conclusion of present research work and the possible further work on CuO gas sensor.
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潘文玉. "Raman spectroscopic study on surface structures of mixed metal oxide catalyst." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/96448450424862459473.
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