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En l'actualitat s'està donant un canvi de mentalitat, tant social com polític o econòmic, per a la millora dels aspectes mediambientals. Així aquest canvi es pot començar a veure en diferents aspectes socials com són les formacions de les plataformes Agenda 21, en aspectes polítics com pot ser la participació en el Fòrum de les Cultures 2004 o en àmbits empresarials amb la creació de normatives ISO en temes de gestió mediambiental, com és la norma 14001.És per aquest motiu que les aplicacions científic-tecnològiques en aspectes de neteja, depuració d'aigües o obtenció d'energies més netes, estan tenint un increment molt important. De totes elles la fotocatàlisi heterogènia sembla que és la que té un futur més prometedor. Aquesta tecnologia es fonamenta en l'aprofitament de la llum solar per a produir reaccions d'oxidació i reducció. Les reaccions d'oxidació són aprofitades per a degradar contaminants orgànics i les de reducció són aprofitades per a la reducció de protons a hidrogen. El problema que presenta aquesta tecnologia és que es fonamenta en l'aprofitament de la llum UV, que representa només el 8% de la llum solar total. Aquest percentatge no permet una aplicació industrial prou rendible.En aquest treball s'ha realitzat una recerca de materials idonis per a la fotocatàlisi, trobant que el material amb les característiques fotocatalítiques més idònies és el TiO2 en la seva forma cristal·lina anatasa. Encara que aquest material es prepara majoritàriament en forma de pols, presenta un problema a posteriori dels processos de catàlisi, que és la seva recuperació. Per a aquest motiu s'han sintetitzat capes primes de TiO2 sobre substrats de vidre i quars mitjançant la tècnica MOCVD. En aquest treball s'han trobat les millors condicions de preparació per tal d'obtenir una resposta fotocatalitica major.Paral·lelament a l'optimització de les condicions de síntesis s'han realitzat estudis teòrics per comprovar els efectes del dopatge en el TiO2. La creació de vacants d'oxigen en l'estructura cristal·lina aconsegueix la formació d'una semibanda semiocupada propera a la banda de conducció. Això permet la promoció d'electrons d'aquesta semibanda a altres amb una energia menor que la del gap, permetent l'excitació a longituds d'ona dins de la regió del visible.Els experiments realitzats amb aquest tipus de material dipositat sobre vidre i quars per MOCVD, demostren aquesta absorció dins de la regió del visible. Aquestes dades d'absorció són confirmades amb les obtingudes amb la tècnica de fotoconductivitat. Les aplicacions industrials que pot presentar aquest material, sota radiació visible, són nombroses. En aquest cas s'ha provat la fotodegradació de nonilfenols i dioxines. Aquestes dues substàncies estan catalogades per les autoritats nord-americanes i europees com dues de les substàncies més tòxiques presents en el mediambient. Per al cas de la fotodegradació de nonilfenols s'ha aconseguit una degradació del 98% d'aquest en 30 minuts En ambdós casos, la fotodegradació de nonilfenols i dioxines, s'ha demostrat que aquesta s'aconsegueix sense la formació d'intermitjos de major toxicitat. Les proves de fotodegradació amb catalitzador de TiO2 estequiomètric sota radiació visible ha demostrat una nul·la activitat. / En la actualidad se está dando un cambio de mentalidad, tanto en lo social como en lo político y en lo económico, para la mejora de aspectos medioambientales. Esto se traduce en la formación de Agendas 21 locales, participación política, como en el Forum 2004 de Barcelona o la creación de normas ISO medioambientales por parte del empresariado. Por este motivo las aplicaciones científico tecnológicas, en aspectos como limpiezas, depuración u obtención de energías más limpias, están teniendo un incremento más que destacable. De todas ellas la fotocatálisis heterogenia parece tener un futuro más prometedor. Esta tecnología se fundamenta en el aprovechamiento de la luz solar para producir reacciones redox. Las reacciones de oxidación son aprovechadas para degradar contaminantes orgánicos y las de reducción para la obtención de hidrogeno a partir de los protones. El problema que presenta esta tecnología es que se fundamenta en el aprovechamiento de la radiación UV, que representa sólo el 8% de la luz solar total. Este porcentaje no permite una aplicación industrial rentable.En este trabajo se ha realizado una búsqueda de materiales idóneos para la fotocatálisis, encontrando que el material que presenta las mejores características es el TiO2 en su forma cristalina anatasa. Aunque este material se prepara, en su gran mayoría, en forma de polvo, presenta un problema a posteriori a los procesos de catálisis, que es su recuperación. Por este motivo se han sintetizado capas delgadas de TiO2 sobre sustratos de vidrio y cuarzo mediante la técnica MOCVD. En este trabajo se han encontrado las mejores condiciones de preparación para obtener la mejor respuesta fotocatalítica. Paralelamente a la optimización de las condiciones de síntesis se han realizado estudios teóricos para comprobar los efectos del dopaje en el TiO2. La creación de vacantes de oxigeno en la estructura cristalina consigue la formación de una semibanda semiocupada cercana a la banda de conducción. Esto permite la promoción de electrones de esta semibanda a otras con una energía menor a la del gap, permitiendo la excitación a longitudes de onda dentro de la región del visible.Los experimentos con este tipo de material demuestran una absorción óptica en la región del visible. Estos datos vienen confirmados por los obtenidos por fotoconductividad.Las aplicaciones industriales que presenta este material bajo radiación visible son numerosas. En este caso se ha probado la fotodegradación de nonilfenol y dioxinas. / Nowadays, new environment requirements have produced a change in people social, political and economical mentality. Those changes are visible and reflected in social activities like local forum discussions organization such as Agenda 21, or the Forum Barcelona 2004, but also economical like the ISO14001 implementation.These are one of the reasons why, new scientific and technological efforts in waste water treatments or less contaminant energies processes are growing up. From all of them, one of the most promising processes is the heterogeneous photocatalysis because it can be use as degradation process but also to produce hydrogen which is the most promising energetic vector. This technology is based on the use of the light to produce redox reactions. Oxidation reactions are useful to degrade organic compounds and reduction reactions are able to obtain hydrogen from protons. The most important limitation of the photocatalysis is that standard catalysers require UV light as energy source. This kind of radiation represents only the 8% of the total energy from the sun. This low reaction yield makes this technique un-attractive to the industry.In the present work, TiO2, in its anatase form has been prepared as thin film by the MOCVD technique and its degradation properties have been characterised. In parallel to this work, theoretical studies have confirmed the effects of TiO2 auto-doping on the energy band-gap variation. Oxygen vacancies in the crystal structure have been found to produce the formation of a semi-occupied band next to the conduction band. This phenomenon permits electrons excitations by applying a radiation in the visible range.Optical measurements have confirmed the absorption in the visible range (about 500 nm) for understoichiometric TiO2-x thin films due to electron transitions from the new band. These values are confirmed by photoconductivity measurements.The film growth parameters have been studied in order to optimize the thickness, roughness, and composition to obtain the highest degradation activity in the visible range, obtaining an increase of 10% in the photodegradation rate. AFM studies have allowed to know how affect the growth to the surface and photodegradation rate. Photodegradation of nonylphenols and dioxins, which are classified as one of the most hazardous substances present in the environment for US and European authorities, have been tested using visible light. TiO2 films with no oxygen understoichiometry did no show photodegradation in the visible range.In the case of nonylphenol, the photodegradation reaction shows a 98% yield after 30 minutes. For dioxins, in the same time, was obtained a 40% yield of degradation. In both cases, no hazardous by-products were formed after catalytical degradation.

The length of ZnO nanotip can be controlled by the deposition time, and the crystal of ZnO nanotip can be enhanced by a thermal annealing at 300oC in this study.The thickness of TiO2 on ITO/glass also can be controlled by the deposition time in this investigate. There are three major parts in this study : 1. (1). The control of thickness of TiO2 film and length of ZnO nanotip and (2). the difference of their photocatalytic activities are two major parts. 2. The relationship between the surface area and the photocatalytic activities of TiO2 powder (P25) and film. 3. The improvement of photocatalytic activity was utilized by the hetrojunction of ZnO nanotip/TiO2 and TiO2/ZnO nanotip, and the P25 is used as a reference for all measurements.

In my study, I attempted to use the high electrical conductivity of graphite modified TiO2 nanoparticles to study the effect of graphite modification to the performance of dye-sensitized solar cell. Graphite oxide (GO) was successfully prepared by the improved Hummer¡¦s method. Graphenes that from the as-prepared GO reduced with hydrazine hydrate and sodium borohydride were characterized by Fourier transform infrared spectroscopy (FT-IR) and UV-visible spectroscopy. The performance of TiO2 based DSSC revealed a short-circuit photocurrent density of 11.24 mA/cm2, an open-circuit voltage of 0.66 V, and a fill factor of 0.48, yielding an overall conversion efficiency of 4.50%. The TiO2 / r-GO composite based DSSC showed higher efficiency than those standard DSSC, revealed a short-circuit photocurrent density of 18.48 mA/cm2, an open-circuit voltage of 0.68 V, and a fill factor of 0.51, yielding an overall conversion efficiency of 7.83%. On the other hand, we found the DSSC that treated with small amount of alcohol in making the TiO2 paste showed superior performance to that with untreated photoanode, the ratio of energy conversion efficiency being 7.11% to 4.50%.

In this study, the thin titanium oxide (TiO2) film deposited on InP substrate was prepared by atomic layer deposition (ALD), which was used as gate oxide of InP Schottky barrier MOSFET. First, aluminum oxide (Al2O3) by ALD can be used as improvement in oxide of TiO2. Al2O3 of ALD has self-cleaning which can improve interface between oxide and substrate, the leakage current densities can reach 3.1 ¡Ñ 10-9 and 3.3 ¡Ñ 10-7 A/cm2. The Schottky barrier height(£XBp) of Al/InP with (NH4)2S treatment is 0.968 eV, which is higher than that of Al/InP without (NH4)2S treatment (0.806eV). The (NH4)2S solution is a moderate etchant to reduce surface oxides on InP. Therefore, Schottky barrier will not be influenced by Fermi level pinning. The electrical characteristics of Schottky barrier MOSFET with TiO2 as gate oxide were measured in this report. The drain current is 1.73£gA. The drain current increases rapidly when drain voltage is over 1V, it indicates that breakdown field of TiO2 thin film is not high enough. Due to advantages of ALD-Al2O3, such as self-cleaning ability and high breakdown field, the TiO2/Al2O3 prepared by ALD structure was used to improve the problem mentioned above. The electrical characteristics are much improved compared with a single TiO2 film, and drain current can reach 1.37 £gA. The rapid increase of drain current with the increased drain voltage is not observed. The transconductance and mobility are 4.45 ¡Ñ 10-7 S/£gm and 202.3 mm2/V-s, respectively, and a good sub-threshold behavior is obtained. Compared with other researches, we can find that Schottky barrier in on-state is higher than that of silicide sample. It indicates the InP Schottky barrier MOSFET characteristics are limited by high Schottky barrier.

This thesis mainly studying the impact of TiO2 and K2O these two compounds in the Chromium-doped glasses and glass-ceramics. Due to the method of Modified Chemical Vapor Deposition (MCVD) of Chromium-doped fiber preform production process, the Ti and K elements have some difficulties; thus, we discuss the influences of these two elements. We hope to improve the composition after knowing these two elements, in order to make the Chromium-doped fiber preform well. We change the weight percent of TiO2 and K2O in the glass composition, in order to observe the influences. Then, we measure their optical and material properties. The results of experiments show that the well-known nucleation agent: TiO2, have no effect of the crystalline phase. However, its function is to help the formation of crystals. We can conclude by the results of X-ray Diffraction (XRD). K2O plays an important role of the Mg2SiO4 phase. To add K2O or not, is the most important reason to affect the Mg2SiO4 phase formation. We will discuss in detail in this thesis about the phase difference for the fluorescence characteristics of Chromium-doped glass and glass-ceramics. What¡¦s more, we use the previously developed two times laser heat-treatment, hoping to successfully apply for Chromium-doped fiber drawing in the future. The laser heat-treatment of CO2-laser can induce the crystal in the glasses. However, this method only needs just a few seconds, which can reduce the cost of heat-treatment. In addition, we can reduce the crystalline size by using the method of two times laser heat-treatment, which can decrease the scattering loss. Also, we will discuss the impact of laser heat-treatment after changing the composition.

In this study, nanosized TiO2-containing organic wastewater was treated with a simultaneous electrocoagulation/electrofiltration (EC/EF) process using either a recirculation mode or a flow-through mode. In the EC/EF treatment module, iron and stainless steel (SS 304) were respectively selected as the anode and cathode, and polyvinylidene fluoride (PVDF) with a nominal pore size of 0.1 £gm was used in this work. Applied electric field strength (EFS), transmembrane pressure (TMP), and crossflow velocity (CFV) were selected as the operating parameters for studying their effects on permeate qualities and other performance criteria. In the recirculation mode, the residual chemical oxygen demand (COD) was found to decrease with increasing EFS up to the critical EFS (i.e., 166.7 V/cm) and leveled off. The optimal operating conditions were determined to be an EFS of 166.7 V/cm, a TMP of 1 kgf/cm2, and a CFV of 0.22 cm/s. Under the optimal operating conditions, the removal efficiencies for turbidity, conductivity, total dissolved solids (TSD), and titanium were determined to be 98.7%, 95.1%, 95.8%, and 99.9%, respectively. By using the same operating conditions except in the flow-through mode, the corresponding removal efficiencies were found to be 98.1%, 92.3%, 93.1%, and 99.9%, respectively. Experimental results also showed that the flow-through mode yielded a higher filtration rate than that of the recirculation mode (namely, 5.05 mL/min versus 4.75 mL/min). This is an indication of a lower extent of membrane fouling for the flow-through mode. This was also evidenced by the scanning electron microscope (SEM) micrographs of the post-treatment membranes. In the recirculation mode, a proper practice of backflushing (e.g., a period of 60 min and a duration of 0.5 min) was found to extend the service life of the membrane and to enhance the permeate flux. I so doing, a minimum treatment rate of 90L/hr with a treatment cost of NT$68.10 per cubic meters would be resulted. Permeate obtained was found to meet the criteria of make-up water for cooling towers. Overall speaking, the simultaneous EC/EF treatment module employed in this work is capable of treating nanosized TiO2-containing organic wastewater for the purpose of reclamation.

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Due to the fast expansion and development in the optical communication industry, the demand for the film quality has correspondingly increased. Ion beam sputter deposition (IBSD) achieves the lowest loss, but low throughput. In our Lab., E-beam system was used for CaO, MgO and Cr2O3 evaporation on the circumference of the Cr:YAG crystal fiber. Although the substrate was heated to around 275oC, the thin film didn¡¦t achieve low loss and high laser-induced damage threshold film. Adding ion-beam assisted deposition (IAD) system to enhance the thin film energy and packing density is the main theme of this thesis. The thesis mainly focuses on the characteristics of TiO2 and SiO2 thin film based on E-beam with IAD system. Spectrometer analyzer and Macleod software were used to calculate the refractive index and extinction coefficient. ESCA (electron spectroscopy for chemical analyzer) was adopt to measure the thin film composition of Ti, Si, O. SEM (scanning electron microscope) was used to observe the thin film quality. Low loss and high laser-induced damage threshold thin film are the goal of the present research. With optimized parameters, the refractive index of TiO2 film was achieved to be 2.51 at 500 nm, and the extinction coefficient was less than 2x10-4. The refractive index of SiO2 film can be achieved to be 1.466 at 500 nm, and the extinction coefficient was less than 1x10-4. An HR (R>99.83%) coating at 1233 nm was successfully demonstrated by the IAD deposition system.

ABSTRACT In recent years, there has been increasing demands for high dielectric materials to replace SiO2 for high-density dynamic random access memories with ultra large scale integration (ULSI). As the dimensions of the charge storage node decrease in high-density dynamic random access memories (DRAMs), TiO2 and BaTiO3 are very promising candidates for applications with exhibiting higher dielectric constant, high refractive index and high chemical stability. The physical and chemical properties of LPD thin film by means of several measuring instruments, including Fourier Transform Infrared Spectrometer (FTIR), Auger Electron Spectroscopy (AES), Secondary Ion Spectrometer (SIMS), and X-Ray Diffractometer (XRD). As for the category in the electrical properties, such as C-V curve and I-V curve, of LPD-BTO thin film is comprehended in the most important part of this chapter. Further, we try to improve these electrical properties of LPD-TiO2 and LPD-BTO thin film by post-annealing in oxygen atmosphere at several high temperatures. From leakage current density-electric field intensity voltage (J-E) and capacitance-voltage (C-V) measurements, the leakage current densities are about (LPD-TiO2: 1 ¡Ñ 10-5 A/cm2 and LPD-BTO: 5 ¡Ñ 10-9 A/cm2). And the individual dielectric constants of both films (TiO2 and BTO) are calculated about 40 and 60. This value is larger than thermal oxide, PECVD oxide, and LPD-SiO2. We also can obtain the flat band voltage shifts of LPD-TiO2 and LPD-BTO films which are about ¡V0.5V and 0V; the effective oxide charges which are calculated about ¡V4.52¡Ñ1011 cm-2 and ¡V2.27¡Ñ1012 cm-2 The future goals: (1) Raising the atomic concentration of oxygen within both films and of barium within LPD-BTO film. (2) Shortening the process in preparation of both deposition solutions. (3) Re-checking both models.