Dissertations / Theses on the topic 'Thin TiO2 film'

TiO2 films as electron collecting interlayers are important in determining the efficiency of organic photovoltaics (OPVs). Various methods of film deposition have been explored, and they revealed the tradeoff between pinhole free coverage (large shunt resistance) and small film thickness (small series resistance). It is hypothesized that atomic layer deposition (ALD) with its self-limiting nature and sub-nanometer level control would be able to circumvent this problem and provide TiO2 films of pinhole free coverage and small thickness. TiO2 films made by chemical vapor deposition (CVD) and ALD were investigated and compared. Conductive atomic force microscopy (CAFM) was used to characterize film morphology and conductivity. X-ray photoelectron spectroscopy (XPS) was utilized to analyze film composition and chemical state. Cyclic voltammetry (CV) was able to reveal the hole blocking capability of films. Finally, organic photovoltaic devices were made with different TiO2 films to reveal the relationship between device property and film characteristic. It is found that both CVD and ALD created TiO2 films with Ti4+ species containing oxygen from hydroxyl groups. They both showed conformal coverage of the electrode via CAFM and CV measurements, and clearly ALD method achieved this with a thinner film and smaller series resistance. This work provided the evidence of effective and surprising capabilities of electron harvesting and hole blocking of ultrathin ALD TiO2 films for OPVs.

För att undersöka skillnad i prestationsförmåga mellan celler sensiterade med växtextraktsbaserad färg, och celler sensiterademed ruteniumkomplex-baserad färg, samt huruvida presskraften påverkar en cells prestationsförmåga, tillverkades icke-slutna fotoelektrokemiska färg-sensiterade solceller med tunnfilmsfotoelektroder av pressad, nanoporös titandioxid.

Cellerna pressades med tre olika presskrafter och sensiterades med växtextraktsfärg från rödkål, rödbeta, viol och henna, samt en ruteniumkomplex-baserad färg som fick utgöra kontrollbetingelse. För varje cell uppmättes IPCE- och iV-värde och motsvarande fyllnadsgrad (fill factor) och dessa jämfördes.

Ingen signifikant skillnad kunde fastställas mellan celler pressade med olika presstryck. Bland cellerna sensiterade med växtextraktbaserad färg presterade rödbeta bäst. Cellen med högst effektivitet hade fyllnadsgraden 70%. Emellertid uppvisade de växtfärgade cellerna genomgående sämre effektivitet än de rutenium-sensiterade och fotoströmmarna var mycket låga. IPCE-värdena var allmännt låga: den bäst presterande cellen hade ett IPCE-värde på något över 0,06 i våglängdsintervallet 440-470 nm. En förklaring till detta är de övriga ämnen som förutom pigment återfinns i de växtbaserade färgerna. Dessa hindrar pigmentmättnad och förhindrar att växtfärgen når ruteniumfärgens intensitet. En annan anledning består i svårigheten att passa ihop energinivåerna i cellens elektrolyt-halvledarsystem med energinivåerna hos pigmentet i växtfärgen.

Non-sealed photoelectrochemical dye sensitised solar cells (DSSC) with pressed nanoporous TiO2 thin film photoelectrodes were manufactured for the purposes of finding out whether plant extractbased dye sensitised cells can perform as well as ruthenium complex-based dye sensitised cells and whether the pressing force affects the cell performance.

The cells were pressed with three different pressing forces and sensitised with plant extracts from red cabbage, beetroot, violet and henna, as well as with a ruthenium complex-based dye for comparison. The IPCE and iV values and the corresponding fill factors of the cells were evaluated and compared.

No significant difference between the cells pressed with different pressing forces could be established. Among the plant extract-based dye sensitised cells the ones sensitised with beetroot extract performed best. The cell that achieved the highest efficiency had a fill factor of 70%. Compared to the ruthenium-sensitised cells the overall performance of the plant dye sensitised cells were very poor and the produced photocurrents very low. The IPCE values were generally low: one of the best-performing cells had an IPCE value of slightly over 0.06 in the 440-470 nm wavelength ranges. One reason for this is that it is difficult to obtain a plant extract dye as intense and deep in colour as ruthenium complex-based dyes, since pigment saturation is obstructed by the presence of other chemical compounds in the plant extracts. Another is that it is a delicate and difficult matter to match the energy levels in the electrolyte-semiconductor system with the energy levels of the pigments in the plant extract dye.

Atomic Layer Deposition (ALD) is a bottom-up process for the manufacturing of inorganic nanostructured thin films, with thickness down to a fraction of a monolayer. Thanks to its unique mechanism of growth, ALD is a powerful technique that has achieved a lot of interest. In this work, a low pressure ALD process was employed to deposit titanium dioxide (TiO2) for biomedical neuro-chips applications based on electrolyte-oxide-semiconductor field-effect transistors (EOSFET). The aim was to optimize a custom-made ALD process for the deposition of high-k dielectric TiO2 starting from titanium tetra-isopropoxide and deionized water. Dense and pinhole-free thin films were deposited by working at controlled temperature (T<300°C) and by varying the process parameters. The structure-properties correlation of the grown thin films was studied by X-Ray Diffraction, Scanning Electron Microscopy, X-Ray Photoelectron Spectroscopy, Secondary Ion Mass Spectrometry and Ellipsometry. To evaluate the functional biomedical applications of TiO2 thin films via ALD, preliminary cellular-neuronal biocompatibility in-vitro tests were explored. Moreover, to study the influence on cell attachment/adhesion and growth, the surface chemical functionality was explored by wettability analyses by using Water Contact Angle (WCA). Next, to avoid a progressive atmospheric contamination, the hydrophilicity was restored exposing the samples by UV radiation and studying the WCA variation at different exposure times. Finally, further work will test neuronal in-vitro bioactivity by neurons deposition for a possible biomedical application, for the purpose of recording electrical activity and stimulating damaged brain areas.

The photosensitive molecule adsorption on titanium dioxide (TiO2) forms the so-called “dye sensitized TiO2” system, a typical organic/oxide heterojunction, which is of great interest in catalysis and energy applications, e.g. dye-sensitized solar cell (DSSC). Traditionally, the transition metal complex dyes are the focus of the study. However, as the fast development of the organic semiconductors and invention of new pure organic dyes, it is necessary to expand the research horizon to cover these molecules and concrete the fundamental understanding of their basic properties, especially during sensitization.In this work, we focus on two different photosensitive molecules: phthalocyanines and triphenylamine-based dyes. Phthalocyanines are organic semiconductors with symmetric macro aromatic molecular structures. They possess good photoelectrical properties and good thermal and chemical stability, which make them widely used in the organic electronic industries. Triphenylamine-based dyes are new types of pure organic dyes which deliver high efficiency and reduce the cost of DSSC. They can be nominated as one of the strong candidates to substitute the ruthenium complex dyes in DSSC. The researches were carried out using classic surface science techniques on single crystal substrates and under ultrahigh vacuum condition. The photosensitive molecules were deposited by organic molecular beam deposition. The substrate reconstruction and ordering were checked by low energy electron diffraction. The molecular electronic, geometric structures and charge transfer properties were characterized by photoelectron spectroscopy, near edge X-ray absorption fine structure spectroscopy and resonant photoelectron spectroscopy (RPES). Scanning tunneling microscopy is used to directly image the molecular adsorption.For phthalocyanines, we select MgPc, ZnPc, FePc and TiOPc, which showed a general charge transfer from molecule to the substrate when adsorbed on rutile TiO2(110) surface with 1×1 and 1×2 reconstructions. This charge transfer can be prevented by modifying the TiO2 surface with pyridine derivatives (4-tert-butyl pyridine (4TBP), 2,2’-bipyridine and 4,4’-bipyridine), and furthermore the energy level alignment at the interface is modified by the surface dipole established by the pyridine molecules. Annealing also plays an important role to control the molecular structure and change the electronic structure together with the charge transfer properties, shown by TiOPc film. Special discussions were done for 4TBP for its ability to shift the substrate band bending by healing the oxygen vacancies, which makes it an important additive in the DSSC electrolyte. For the triphenylamine-based dye (TPAC), the systematic deposition enables the characterization of the coverage dependent changes of molecular electronic and geometric structures. The light polarization dependent charge transfer was revealed by RPES. Furthermore, the iodine doped TPAC on TiO2 were investigated to mimic the electrolyte/dye/TiO2 interface in the real DSSC.The whole work of this thesis aims to provide fundamental understanding of the interaction between photosensitive molecules on TiO2 surfaces at molecular level in the monolayer region, e.g. the formation of interfacial states and the coverage dependent atomic and electronic structures, etc. We explored the potential of the application of new dyes and modified of the existing system by identifying their advantage and disadvantage. The results may benefit the fields of dye syntheses, catalysis researches and designs of organic photovoltaic devices.
QC 20111114

Liquid spray is essential to industries requiring processes such as spray coating, spray drying, spray pyrolysis, or spray cooling. This thesis reports the design, fabrication, and characterization of a thin film deposition system which utilizes a linear multiplexed electrospray (LINES) atomizer. First, a thorough review of the advantages and limitations of prior multiplexed electrospray systems leads to discussion of the design rationale for this work. Next, the line of charge model was extended to prescribe the operating conditions for the experiments and to estimate the spray profile. The spray profile was then simulated using a Lagrangian model and solved using a desktop supercomputer based on Graphics Processing Units (GPUs). The simulation was extended to estimate the droplet number density flux during deposition. Pure ethanol was electrosprayed in the cone-jet mode from a 51-nozzle aluminum LINES atomizer with less than 3% relative standard deviation in the D10 average droplet diameter as characterized using Phase Doppler Interferometry (PDI). Finally a 25-nozzle LINES was integrated into a thin film deposition system with a heated, motion controlled stage, to deposit TiO2 thin films onto silicon wafers from an ethanol based nanoparticle suspension. The resulting deposition pattern was analyzed using SEM, optical profilometry, and macro photography and compared with the numerical simulation results. The LINES tool developed here is a step forward to enabling the power of electrospray for industrial manufacturing applications in clean energy, health care, and electronics.
M.S.M.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering; Miniature Engineering Systems

This work deals with issues of electrochromism and making active electrochromic film of titanium dioxide. By using various precursors consisting titanium element active film was electrodeposited on glass substrates covered with transparent conductive thin-film In2O3:Sn (ITO). Electrochromic characteristics of these substrates that were electrodeposited for different times and with different voltage have been studied. Than there has been studied the impact of various annealing temperatures on electrochromic characteristics.

The temperature and field dependence of the magnetization of epitaxial, undoped anatase TiO2 thin films on SrTiO3 substrates was investigated. Low-energy ion irradiation was used to modify the surface of the films within a few nanometers, yet with high enough energy to produce oxygen and titanium vacancies. The as-prepared thin film shows ferromagnetism which increases after irradiation with low-energy ions. An optimal and clear magnetic anisotropy was observed after the first irradiation, opposite to the expected form anisotropy. Taking into account the experimental parameters, titanium vacancies as di-Frenkel pairs appear to be responsible for the enhanced ferromagnetism and the strong anisotropy observed in our films. The magnetic impurities concentrations was measured by particle-induced X-ray emission with ppm resolution. They are ruled out as a source of the observed ferromagnetism before and after irradiation.

In this work, a series of simple, rapid and effective photoelectrochemical methodologies have been developed and successfully applied to the study of kinetic and thermodynamic characteristics of photocatalytic oxidation processes at TiO2 nanoparticulate films. As an application of the systematic studies of photocatalytic processes by photoelectrochemical techniques, a rapid, direct, absolute, environmental-friendly and accurate COD analysis method was successfully developed. In this work, the TiO2 nanoparticles colloid was prepared by the sol-gel method. The TiO2 nanoparticles were immobilized onto ITO conducting glass slides by dip-coating method. Thermal treatment was carried out to obtain nanoporous TiO2 films of different structures. At low calcination temperature (below 600°C), nanoporous TiO2 films of pure anatase phase were prepared. At high calcination temperature (above 600°C), nanoporous TiO2 films of mixed anatase and rutile phases were obtained. At these film electrodes, the work was carried out. By employing steady state photocurrent method and choosing phthalic acid as the model compound, the photocatalytic activity of the TiO2 nanoporous films calcined at various temperatures and for different lengths of time was evaluated. It was found that the films with mixed anatase and rutile phases calcined at high temperature exhibited high photocatalytic activity. Based on semiconductor band theory, a model was proposed, which explained well this finding. By employing linear sweep voltammetry (under illumination) and choosing glucose (an effective photohole scavenger) as a model compound, the characteristics of the photocatalytic processes at nanoparticulate semiconductor electrodes were investigated. Characteristics of the nanoporous semiconductor electrodes markedly different from bulk semiconductor electrodes were observed. That is, within a large range of electrode potentials above the flat band potential the electrodes behaved as a pure resistance instead of exhibiting variable resistance expected for bulk semiconductor electrodes. The magnitude of the resistance was dependent on the properties of the electrodes and the maximum photocatalytic oxidation rate at TiO2 surface determined by the light intensity and substrate concentration. A model was proposed, which explained well the special characteristics of particulate semiconductor electrodes (nanoporous semiconductor electrodes). This is the first clear description of the overall photocatalytic process at nanoparticulate semiconductor electrodes. The investigation set a theoretical foundation for employing photoelectrochemical techniques to study photocatalytic processes. By using the transient technique (illumination step method analogous to potential step method in conventional electrochemistry), the adsorption of a number of strong adsorbates on both low temperature and high temperature calcined TiO2 nanoporous films was investigated. Similar adsorption characteristics for different adsorbates on different films were observed. In all the cases, three different surface bound complexes were identified, which was attributed to the heterogeneity of TiO2 surface. The photocatalytic degradation kinetics of the pre-adsorbed organic compounds of different chemical nature was also studied by processing the photocurrent-time profiles. Two different photocatalytic processes, exhibiting different rate characteristics, were observed. This was, again, attributed to the heterogeneity of the TiO2 surface corresponding to heterogeneous adsorption characteristics. The catalytic first order rate constants of both fast and slow processes were obtained for different organic compounds. It was found that for different adsorbates of different chemical nature the magnitudes of rate constant for the slow kinetic process were very similar, while the magnitudes of rate constant for the fast process were significantly affected by the photohole demand characteristics of different adsorbates. Photohole demand distribution that depends on the size and structure of the adsorbed molecules was believed to be responsible for the difference. By employing steady state photocurrent method, the photocatalytic degradation kinetic characteristics of both strong adsorbates and weak adsorbates of different chemical structures were compared at pure anatase TiO2 nanoporous TiO2 films as well as at anatase/rutile mixed phase TiO2 nanoporous film electrodes. At the former electrodes for all the different organic compounds studied, the photocatalytic reaction rate increased linearly with concentration at low concentrations. Under such conditions, it was demonstrated that the overall photocatalytic process was controlled by diffusion and was independent of the chemical nature of organic compounds. However, the linear concentration range and the maximum photocatalytic reaction rate at high concentrations were significantly dependent on the chemical nature of the substrates. This was explained by the difference in the interaction of different organic compounds with TiO2 surface, the difference in their photohole demand distributions at the TiO2 surface and the difference in their nature of intermediates formed during their photocatalytic mineralization. In contrast, at the latter electrodes for the photocatalytic oxidation of different organic compounds the linear ranges (diffusion control concentration range) and the maximum reaction rates at high concentration were much larger than at the former electrodes and much less dependent on the chemical nature of the organic compounds. The spatial separation of photoelectrons and photoholes (due to the coexistence of rutile phase and anatase phase) and the increase in the lifetime of photoelectrons and photoholes are responsible for the excellent photocatalytic activity of the electrodes. By employing the thin-layer photoelectrochemical technique (analogous to the thin-layer exhaustive electrolytic technique), the photocatalytic oxidation of different organic compounds at the mixed phase TiO2 nanoporous electrodes were investigated in a thin layer photoelectrochemical cell. It was found that the charge derived from exhaustive oxidation agreed well with theoretical charge expected for the mineralisation of a specific organic compound. This finding was true for all the compounds investigated and was also true for mixtures of different organic compounds. The photocatalytic degradation kinetics of different organic compounds of different chemical identities in the thin layer cell was also investigated by the photoelectrochemical method. Two kinetic processes of different decay time constants were identified, which were attributed to the degradation of preadsorbed compounds and the degradation of compounds in solution. For the degradation of compounds in solution, a change in the overall control step from substrate diffusion to heterogeneous surface reaction was observed. For different organic compounds, the variation of the rate constant was determined by the photohole demand rather than by the chemical identities of substrates. The kinetics of the fast kinetic process, on the other hand, was greatly affected by the adsorption properties of the substrates. For the strong adsorbates, the rate was much larger than for weak adsorbates. However, the rate constant of the process was independent of the chemical identities of the substrates and the variation of the constant was also determined by the photohole demand. Based on the principles of exhaustive photoelectrocatalytic degradation of organic matter in a thin layer cell, a novel, rapid, direct, environmental-friendly and absolute COD analysis method was developed. The method was tested on synthetic samples as well as real wastewater samples from a variety of industries. For synthetic samples with given compositions the COD values measured by my method agree very well with theoretical COD value. For real samples and synthetic samples the COD values measured by my method correlated very well with those measured by standard dichromate COD analysis method.

In this work, a series of simple, rapid and effective photoelectrochemical methodologies have been developed and successfully applied to the study of kinetic and thermodynamic characteristics of photocatalytic oxidation processes at TiO2 nanoparticulate films. As an application of the systematic studies of photocatalytic processes by photoelectrochemical techniques, a rapid, direct, absolute, environmental-friendly and accurate COD analysis method was successfully developed. In this work, the TiO2 nanoparticles colloid was prepared by the sol-gel method. The TiO2 nanoparticles were immobilized onto ITO conducting glass slides by dip-coating method. Thermal treatment was carried out to obtain nanoporous TiO2 films of different structures. At low calcination temperature (below 600°C), nanoporous TiO2 films of pure anatase phase were prepared. At high calcination temperature (above 600°C), nanoporous TiO2 films of mixed anatase and rutile phases were obtained. At these film electrodes, the work was carried out. By employing steady state photocurrent method and choosing phthalic acid as the model compound, the photocatalytic activity of the TiO2 nanoporous films calcined at various temperatures and for different lengths of time was evaluated. It was found that the films with mixed anatase and rutile phases calcined at high temperature exhibited high photocatalytic activity. Based on semiconductor band theory, a model was proposed, which explained well this finding. By employing linear sweep voltammetry (under illumination) and choosing glucose (an effective photohole scavenger) as a model compound, the characteristics of the photocatalytic processes at nanoparticulate semiconductor electrodes were investigated. Characteristics of the nanoporous semiconductor electrodes markedly different from bulk semiconductor electrodes were observed. That is, within a large range of electrode potentials above the flat band potential the electrodes behaved as a pure resistance instead of exhibiting variable resistance expected for bulk semiconductor electrodes. The magnitude of the resistance was dependent on the properties of the electrodes and the maximum photocatalytic oxidation rate at TiO2 surface determined by the light intensity and substrate concentration. A model was proposed, which explained well the special characteristics of particulate semiconductor electrodes (nanoporous semiconductor electrodes). This is the first clear description of the overall photocatalytic process at nanoparticulate semiconductor electrodes. The investigation set a theoretical foundation for employing photoelectrochemical techniques to study photocatalytic processes. By using the transient technique (illumination step method analogous to potential step method in conventional electrochemistry), the adsorption of a number of strong adsorbates on both low temperature and high temperature calcined TiO2 nanoporous films was investigated. Similar adsorption characteristics for different adsorbates on different films were observed. In all the cases, three different surface bound complexes were identified, which was attributed to the heterogeneity of TiO2 surface. The photocatalytic degradation kinetics of the pre-adsorbed organic compounds of different chemical nature was also studied by processing the photocurrent-time profiles. Two different photocatalytic processes, exhibiting different rate characteristics, were observed. This was, again, attributed to the heterogeneity of the TiO2 surface corresponding to heterogeneous adsorption characteristics. The catalytic first order rate constants of both fast and slow processes were obtained for different organic compounds. It was found that for different adsorbates of different chemical nature the magnitudes of rate constant for the slow kinetic process were very similar, while the magnitudes of rate constant for the fast process were significantly affected by the photohole demand characteristics of different adsorbates. Photohole demand distribution that depends on the size and structure of the adsorbed molecules was believed to be responsible for the difference. By employing steady state photocurrent method, the photocatalytic degradation kinetic characteristics of both strong adsorbates and weak adsorbates of different chemical structures were compared at pure anatase TiO2 nanoporous TiO2 films as well as at anatase/rutile mixed phase TiO2 nanoporous film electrodes. At the former electrodes for all the different organic compounds studied, the photocatalytic reaction rate increased linearly with concentration at low concentrations. Under such conditions, it was demonstrated that the overall photocatalytic process was controlled by diffusion and was independent of the chemical nature of organic compounds. However, the linear concentration range and the maximum photocatalytic reaction rate at high concentrations were significantly dependent on the chemical nature of the substrates. This was explained by the difference in the interaction of different organic compounds with TiO2 surface, the difference in their photohole demand distributions at the TiO2 surface and the difference in their nature of intermediates formed during their photocatalytic mineralization. In contrast, at the latter electrodes for the photocatalytic oxidation of different organic compounds the linear ranges (diffusion control concentration range) and the maximum reaction rates at high concentration were much larger than at the former electrodes and much less dependent on the chemical nature of the organic compounds. The spatial separation of photoelectrons and photoholes (due to the coexistence of rutile phase and anatase phase) and the increase in the lifetime of photoelectrons and photoholes are responsible for the excellent photocatalytic activity of the electrodes. By employing the thin-layer photoelectrochemical technique (analogous to the thin-layer exhaustive electrolytic technique), the photocatalytic oxidation of different organic compounds at the mixed phase TiO2 nanoporous electrodes were investigated in a thin layer photoelectrochemical cell. It was found that the charge derived from exhaustive oxidation agreed well with theoretical charge expected for the mineralisation of a specific organic compound. This finding was true for all the compounds investigated and was also true for mixtures of different organic compounds. The photocatalytic degradation kinetics of different organic compounds of different chemical identities in the thin layer cell was also investigated by the photoelectrochemical method. Two kinetic processes of different decay time constants were identified, which were attributed to the degradation of preadsorbed compounds and the degradation of compounds in solution. For the degradation of compounds in solution, a change in the overall control step from substrate diffusion to heterogeneous surface reaction was observed. For different organic compounds, the variation of the rate constant was determined by the photohole demand rather than by the chemical identities of substrates. The kinetics of the fast kinetic process, on the other hand, was greatly affected by the adsorption properties of the substrates. For the strong adsorbates, the rate was much larger than for weak adsorbates. However, the rate constant of the process was independent of the chemical identities of the substrates and the variation of the constant was also determined by the photohole demand. Based on the principles of exhaustive photoelectrocatalytic degradation of organic matter in a thin layer cell, a novel, rapid, direct, environmental-friendly and absolute COD analysis method was developed. The method was tested on synthetic samples as well as real wastewater samples from a variety of industries. For synthetic samples with given compositions the COD values measured by my method agree very well with theoretical COD value. For real samples and synthetic samples the COD values measured by my method correlated very well with those measured by standard dichromate COD analysis method.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environmental and Applied Science
Full Text

Water, together with energy and food, has been addressed as one of the main urgent problem of humanity. The reduction of fresh clean water sources will definitely lead to huge issues in the next future, especially in developing countries. The conventional wastewater treatments suffer some limitations related to the effectiveness in decontamination (mechanical filtration), in the heavy use of chemicals (chlorination), or in elevate operational costs and energy requirements (desalination and reverse osmosis). In this sense, new materials such as nanocomposites may overcome these issues taking advantage of the peculiar properties of materials at nanoscale. Research on novel nanotechnologies must bring advances in order to contrast and prevent water scarcity and pollution. In order to be effective, these nanotechnologies should run at low operational cost, even in places unequipped by strong infrastructures and in concert with conventional cheap methodologies. Among the alternative water purification methods, TiO2-based photocatalysis has attracted great attention due to material stability, abundance, non-toxicity and high decontamination efficiency. In this material, electron-hole pairs, generated by light absorption, separate from each other and migrate to catalytically active sites at the surface of the photocatalyst. Photogenerated carriers are able to induce the water splitting reaction and, consequently, to decompose organic pollutants. The main deficiency of this material, related to its large band gap, is that only the UV fraction of the solar spectrum is effective to this purpose. Several approaches have been proposed to overpass this issue and, among them, the use of metal-TiO2 nanocomposites with proper nanostructurarion seems very promising for water purification strategies. Aim of this work is to investigate the possibility to develop efficient solar-driven TiO2 photocatalyst taking advantage of metallic nanostructures to efficiently couple the incident light to the photoactive semiconductor. Two approaches have been followed: TiO2 nanoparticles obtained via pulsed laser ablation in liquid and optical engineering of multilayered metal-TiO2 thin films. The first approach maximizes the exposed surface, thus enhancing the photocatalytic efficiency. However, in this case nanomaterials is dispersed in the surrounding environment, and in order to avoid this drawback we have investigated, as second approach, the use of metal-TiO2 thin films.

Titanium oxide has been widely studied for its potential application in many scientific and technological fields. In particular, its photoelectrochemical properties are of great interest for possible applications in the conversion of solar energy into electricity, hydrogen production by water photosplitting and photocatalytic degradation of recalcitrant organic and inorganic pollutants (O'Regan and Grätzel 1991; Linsebigler, Lu et al. 1995; Mills and Le Hunte 1997; Grätzel 2001; Carp, Huisman et al. 2004; Mor, Varghese et al. 2006; Aprile, Corma et al. 2008; Varghese, Paulose et al. 2009). During the three years of the Ph.D. School in Molecular Sciences, the experimental work, performed at the Institute for Energetics and Interphases (IENI) of the Italian National Research Council (CNR) of Padua (Italy) (under supervision of Dr Monica Fabrizio), was focused on the study and optimization of vapor deposition techniques, physical vapor deposition (PVD) e chemical vapor deposition (CVD), of titanium oxide-based nanostructured materials for photocatalytic applications and their chemical-physical, morphological and functional characterizations. The PVD magnetron sputtering instrumentation (located at IENI-CNR laboratories) was adapted for ceramic thin film deposition, varying the geometrical and mechanical configuration. Therefore, the optimal synthesis conditions of photocatalytic titanium oxide thin films were identified by tuning the main process parameters: power supply (DC or RF), deposition time, substrate heating and motion, target-substrate distance, total pressure, inlet gas partial pressure. In order to improve the photocatalytic efficiency of titanium oxide thin films, several nitrogen doping attempts were carried out. Such kind of doping, indeed, was reported in literature as the most efficient way to reduce the titanium oxide band gap thus permitting the absorption of a larger solar spectrum fraction maintaining its photochemical stability (Asahi, Morikawa et al. 2001; Kitano, Funatsu et al. 2006; Asahi and Morikawa 2007). A large part of the experimental work was addressed towards the development and setting up of an apparatus for the photoinduced current measurement in titanium oxide electrodes under UV irradiation. The thin film deposition process studies performed on several planar substrates, such as soda-lime glass, ITO or fused quartz, the optimization of the process parameters and the knowledge of the titanium oxide-based system behavior permitted to figure out and develop new materials with improved photocatalytic efficiency. In particular, hybrid nanocomposites employing single wall carbon nanohorns (SWCNHs) as substrate for titanium oxide deposition were developed. In recent years, many published papers aimed to improve the titanium oxide photocatalytic behavior with mesoporous carbon-based hybrid nanocomposites (Orlanducci, Sessa et al. 2006; Liu and Zeng 2008; Wang, Ji et al. 2008; Yu, Quan et al. 2008). As a potential titanium oxide support, SWCNHs are very interesting nanostructures in virtue of their electronic properties, morphological features and high production yield (Kasuya, Yudasaka et al. 2002; Gattia, Vittori Antisari et al. 2007). Part of the great family of carbon nanotubes, they consist of a single layer of a graphene sheet wrapped into an irregular cone-shaped tubule with a variable diameter of generally few nanometers and a length of about ten nanometers (Iijima, Yudasaka et al. 1999; Murata, Kaneko et al. 2000). Depending on synthesis parameters, the SWCNHs assemble together in three types of spherical aggregates with diameters in the order of hundred nanometers (Yudasaka, Iijima et al. 2008). The photocatalytic efficiency improvement of titanium oxide in the hybrid material SWCNHs/TiO2 is due to the mesoporous morphology with high surface area (over than 300 m2g-1) of such carbon nanostructure aggregates and to the formation of the heterojunction with the oxide, which can reduce the electron-hole recombination process and therefore the overall efficiency of photocatalytic process (Cioffi, Campidelli et al. 2007; Petsalakis, Pagona et al. 2007). An important result obtained during the Ph.D. activity was the synthesis, through magnetron sputtering, of a novel nanostructured morphology of titanium oxide named “strelitzia-like titanium oxide” induced by the SWCNHs employed as substrates (Battiston, Bolzan et al. 2009). Therefore, the experimental activity was focused on the comprehension and optimization of nucleation and growth of this novel titanium oxide architecture. Moreover, in collaboration with the Institute of Inorganic Chemistry and Surfaces (ICIS) of the Italian National Research Council (CNR) of Padua (Italy), the TiO2 metal-organic chemical vapor deposition (MOCVD) was performed (Battiston, Bolzan et al. 2009) obtaining the SWCNH coating with different morphologic features with respect to the PVD synthesized morphologies. The characterization the hybrid nanocomposite obtained via MOCVD, that showed a homogeneous covering of SWCNH grains, suggested its employment as substrate for the magnetron sputtering deposition thus maximizing the strelitzia-like titanium oxide structure nucleation on all SWCNH aggregates. The broad nucleation of such novel nanostructures permitted to perform a deeper structural and functional characterization which finally showed that strelitzia-like nanocomposites have higher photocatalytic performances compared to the other kinds of titanium oxide samples investigated. The characterizations of thin films and hybrid nanocomposites were carried out in close cooperation with Padua University (Italy), IENI-CNR, ICIS-CNR, ITC-CNR (Construction Technologies Institute in Milan, Italy), Turin University (Italy) and Piezotech Japan Ltd (spin off of Research Institute for Nanoscience Kyoto, Japan), where a three month stage was performed with a fellowship of Italian Interuniversity Consortium on Materials Science and Technology. The structural, compositional, morphological and functional analyses were performed respectively by XRD, Raman spectroscopy, ICP-MS, SIMS, XPS, Cathodoluminescence, SEM, TEM, AFM, mechanical profiler, photocurrent measurements and photocatalytic degradation of phenol under UV irradiation.
L'ossido di titanio è considerato un eccellente materiale fotocatalizzatore grazie alla sua elevata efficienza, alla stabilità fotochimica, all’atossicità e al basso costo. Grazie a queste proprietà, i materiali nanostrutturati di ossido di titanio sono largamente studiati e impiegati in diversi settori tecnologici quali quelli della fotocatalisi, della degradazione fotocalitica di composti organici ed inorganici, della sensoristica e della conversione dell’energia solare in elettricità (O'Regan and Grätzel 1991; Linsebigler, Lu et al. 1995; Mills and Le Hunte 1997; Grätzel 2001; Carp, Huisman et al. 2004; Mor, Varghese et al. 2006; Aprile, Corma et al. 2008; Varghese, Paulose et al. 2009). Il lavoro svolto nell’arco dei tre anni di attività di ricerca effettuata, nell’ambito della Scuola di Dottorato in Scienze Molecolari, presso i laboratori dell’Istituto per l’Energetica e le Interfasi (IENI) del CNR di Padova (sotto supervisione della Dott.ssa Monica Fabrizio), è stato focalizzato sullo studio e ottimizzazione di tecniche di deposizione da fase vapore, physical vapor deposition (PVD) e chemical vapor deposition (CVD), e caratterizzazione chimico-fisica, morfologica e funzionale di materiali nanostrutturati a base di ossido di titanio per applicazioni fotocatalitiche. La strumentazione PVD magnetron sputtering, presente presso i laboratori IENI, è stata adattata per la deposizione di film di natura ceramica, intervenendo sulla configurazione geometrica e meccanica dell’apparato. In seguito, è stato possibile individuare le condizioni ottimali di sintesi per la deposizione di film sottili di ossido di titanio efficienti dal punto di vista fotocatalitico, studiando ed agendo sui principali parametri di processo: modalità DC o RF, tempo di deposizione, movimentazione e riscaldamento del substrato, distanza target-substrato, pressione totale, pressioni parziali dei gas introdotti in camera e potenza trasferita al plasma. Al fine di incrementare l’efficienza fotocatalitica dei film sottili, sono stati condotti diversi tentativi di sintesi introducendo azoto come drogante dell’ossido di titanio. Tale drogaggio è riportato in letteratura (Asahi, Morikawa et al. 2001; Kitano, Funatsu et al. 2006; Asahi and Morikawa 2007) come il metodo più idoneo per ridurre l’energy gap efficace del materiale, permettendo contemporaneamente l’assorbimento di una frazione più ampia dello spettro solare ed il mantenimento della stabilità fotochimica. Parte consistente del lavoro sperimentale è stata impiegata, inoltre, per intraprendere lo sviluppo e l’allestimento di un sistema per la misura della corrente fotoindotta, in seguito ad irraggiamento di luce UV-VIS, dell’ossido di titanio. Lo studio del processo di deposizione su vari tipi di substrati piani (vetro, ITO, silice pura), l’identificazione dei parametri di processo ottimali e la conoscenza acquisita del comportamento di tali sistemi ha permesso, infine, lo sviluppo e la progettazione di nuovi materiali più efficienti dal punto di vista fotocatalitico. In particolare, sono stati progettati e realizzati nanocompositi ibridi, impiegando Single Wall Carbon Nanohorn (SWCNH) come substrati per le deposizioni di ossido di titanio. Negli ultimi anni, infatti, sono stati pubblicati numerosi articoli sulla sintesi di materiali nanocompositi ibridi che impiegano materiali mesoporosi a base di carbonio, con lo scopo di incrementare le proprietà fotocatalitiche dell’ossido di titanio (Orlanducci, Sessa et al. 2006; Liu and Zeng 2008; Wang, Ji et al. 2008; Yu, Quan et al. 2008). Con questo scopo, i SWCNH rappresentano un buon candidato grazie alle loro proprietà elettroniche, caratteristiche morfologiche e all’alta resa di produzione (Kasuya, Yudasaka et al. 2002; Gattia, Vittori Antisari et al. 2007). Essi sono costituiti da aggregati, a simmetria sferica e delle dimensioni dell’ordine del centinaio di nanometri, di coni irregolari di grafene a parete singola di qualche nanometro di diametro e qualche decina di nanometri di lunghezza (Iijima, Yudasaka et al. 1999; Murata, Kaneko et al. 2000; Yudasaka, Iijima et al. 2008). L’incremento dell’efficienza fotocatalitica dell’ossido di titanio nel materiale ibrido SWCNH/TiO2 è giustificato dalla morfologia mesoporosa ad elevata area superficiale di questi aggregati (superiore a 300 m2 g-1) e dalla formazione dell’eterogiunzione con l’ossido, che può ridurre sensibilmente la ricombinazione elettrone-lacuna e incrementare, perciò, l’efficienza globale del processo fotocatalitico (Cioffi, Campidelli et al. 2007; Petsalakis, Pagona et al. 2007). Un importante risultato conseguito nello svolgimento dell’attività di dottorato riguarda l’ottenimento, grazie all’impiego del magnetron sputtering, di una nuova singolare morfologia nanostrutturata dell’ossido di titanio, chiamata “strelitzia-like titanium oxide”, indotta proprio dalla particolare morfologia dei SWCNH impiegati come substrati (Battiston, Bolzan et al. 2009). La successiva attività sperimentale è stata, quindi, indirizzata alla comprensione e all’ottimizzazione dei meccanismi di nucleazione e crescita di queste innovative strutture nanocomposite ibride SWCNH/TiO2. A questo proposito, in collaborazione con l’Istituto di Chimica Inorganica e delle Superfici (ICIS) del CNR di Padova, è stato eseguito un approfondito studio sull’influenza del metodo di deposizione utilizzato su nucleazione e crescita dell’ossido di titanio sui SWCNH, impiegando anche la tecnica metal-organic chemical vapor deposition (MOCVD) (Battiston, Bolzan et al. 2009), che ha permesso di ottenere morfologie del rivestimento molto differenti da quelle ottenute tramite magnetron sputtering. Lo studio e la caratterizzazione del nuovo materiale nanocomposito, ottenuto via MOCVD, ne ha suggerito l’impiego come substrato per la deposizione via magnetron sputtering permettendo, infine, di giungere all’ottimizzazione della nucleazione delle strelitzie di ossido di titanio, sfruttando ogni singolo aggregato di SWCNH. Tale risultato ha permesso, inoltre, di eseguire una approfondita caratterizzazione di tipo strutturale e funzionale della nuova morfologia dell’ossido di titanio che, infine, ha dimostrato possedere proprietà fotocatalitiche superiori rispetto a tutti i materiali a base di ossido di titanio con cui è stata comparata. Le caratterizzazioni dei film sottili e dei nanocompositi ibridi sono state eseguite in stretta collaborazione con diversi gruppi di ricerca appartenenti, oltre che all’Università di Padova e al CNR IENI, anche al CNR-ICIS, al CNR-ITC (Istituto per le Tecnologie delle Costruzioni), l’Università di Torino e Piezotech Japan Ltd, spinoff del Research Institute for Nanoscience con sede a Kyoto (Giappone), presso cui è stato svolto uno stage della durata di tre mesi nell’ambito della convenzione Italia-Giappone a cui prende parte il Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM). Le analisi effettuate sono state di tipo strutturale (XRD e Spettroscopia Raman), composizionale (ICP-MS, SIMS, XPS, Catodoluminescenza), morfologico (SEM, TEM, AFM e profilometro meccanico) e funzionale (misure di fotocorrente e degradazione fotocatalitica di composti organici).

Nous avons comparé trois méthodes différentes de dopage de TiO2 à l'azote par pulvérisation cathodique, et avons exploré les propriétés structurelles, optiques et la photo-activité de ces matériaux. Tout d'abord, des films minces successifs de TiO2 et TiN ont été créés par pulvérisation d'une cible de titane et en alternant les gaz réactifs d'oxygène et d'azote dans l'enceinte de dépôt. L'épaisseur totale de chaque multicouche a été maintenue constante tandis que nous avons fait varier la composition globale des films (rapport TiN/TiO2) entre 5% et 30% et le nombre de des couches TiN/TiO2 entre 9 à 45. Deuxièmement, nous avons préparé des couches homogènes de N-TiO2 par l'introduction simultanée des gaz réactifs d'oxygène et d'azote au cours du dépôt. Nous avons systématiquement fait varier le rapport azote/oxygène afin de modifier d'une façon contrôlée la concentration de l'azote incorporé dans les films de 0% et 6%. Enfin, nous avons préparé des couches minces de TiN et les ont fait subir l'oxydation à des températures différentes pendant plusieurs intervalles de temps. Les mesures d'XPS ont montré que l'azote a été dopé avec succès, dans tous les films de TiO2, dans les sites substitutionnels et/ou interstitiels en fonction des conditions de dépôt. La variance de la concentration et la position du dopage à l'azote avait une influence significative sur les propriétés optiques, structurelles et photo-actives des trois types des films de TiO2 dopés. Les paramètres de dépôt par pulvérisation ont été optimisés grâce à des diagnostics du plasma et à un Plan d'Expériences. Cette étude a montré que nous pouvons modifier d'une façon contrôlée et à souhait plusieurs caractéristiques physiques et chimiques importantes des couches de N-TiO2, qui pourront avoir un grand potentiel pour de nombreuses applications

博士
國立中山大學
材料與光電科學學系研究所
100
Ti thin films were deposited by a radio frequency ion-beam sputtering system. Deposition resulted from sputtering a Ti target (99.995%) with an Ar ion beam. Epitaxial TiO thin films with different orientations, which came from oxidizing Ti thin films, were prepared on single-crystal NaCl substrate. The formation of epitaxial TiO2 thin films (anatase or rutile phase) by oxidation of epitaxial TiO thin films was investigated. The composition, microstructure, and orientation relationships between interfaces were analyzed by TEM and Fourier transformation in the present report. Epitaxial TiO thin films with different orientations were prepared on single-crystal NaCl substrate in the present study. The formation of epitaxial TiO2 thin films (anatase or rutile) by oxidation of epitaxial TiO thin films, which were first grown on different NaCl surfaces, was investigated. The composition, microstructure, and orientation relationships between interfaces were analyzed by TEM and Fourier transformation in this report. The TiO to anatase phase transformation has been studied by transmission electron microscopy in this Article. It is shown that prior formation of TiO from Ti film can induce the formation of anatase by thermal oxidation in air, otherwise only rutile is formed. Ti film deposited on the NaCl (001) surface is induced to form epitaxial TiO film by thermal oxidation in air. Further thermal oxidation in air partially transformed TiO into anatase (A) with a parallel orientation relationship of {200}A // {200}TiO. Detailed analysis of the lattice fringes image of the specimen reveals the presence of very high density of misfit dislocations. The TiO to anatase transformation is reversible as further annealing in a vacuum can turn the anatase back into TiO and eliminates the misfit dislocations. The transformation is analyzed in terms of the crystal structure, orientation relationship, and the dislocation distribution, which show that the TiO to anatase transformation is due to the close similarity between their structures. (Chapter 1) The anatase TiO2 (001) surface was shown to have superior photoreactivity. Epitaxial anatase (001) films used to be grown on single-crystal SrTiO3 and LaAlO3 substrates. It is shown in this report that these films can be grown also on the NaCl substrate, which is much cheaper and easily prepared. Epitaxial TiO (001) films were first grown on the NaCl (001) substrate. By testing the TiO-to-anatase transformation over temperature and time ranges, an epitaxial anatase (001) film was prepared by simple thermal oxidation in air. The formation of a single-variant anatase (001) film instead of a multiple-variant film is discussed in this report. (Chapter 2) An epitaxial rutile (100) thin film has been grown on NaCl substrate instead of other more expensive substrates. An epitaxial TiO (111) thin film with minor Ti phase was first deposited on the NaCl (111) surface by thermal evaporation. It was then transformed into the epitaxial rutile (100) thin film by subsequent thermal oxidation in air. TEM was used to analyze the phases and the orientation relationship. Our previous result showed that an epitaxial anatase (001) film was formed on the NaCl (001) surface in a similar process. The substrate-dependent formation of different TiO2 phase is also discussed in terms of the mismatch of the interfaces. (Chapter 3)

碩士
逢甲大學
光電物理研究所
92
TiO2 thin film has many applications in high technology, such as anti-reflecting coating, self-cleaning and photo catalyst ect. This thesis concentrates on the properties of thin film, which grew by RF-magnetron sputtering system and Pulse Laser Alberation system. By adjusting the partial pressure of oxygen、coating period、and different substrate, such as (111)Si, (100)SiO2, MgO, (100)SrTiO3 and (100)LAO, we investigate the thin film property of different kind of situations, which is measured by XRD, Raman spectrum, SEM and contact angle. Moreover, R. Swanepoel method was applied to determine the thickness and refraction index of the thin film.

碩士
明志科技大學
材料工程研究所
99
Titanium dioxide in high-power process has a wide process window and better structural properties. The low-power process will not be able to get titanium dioxide structured. If the structural propertied of titanium dioxide was not good, then in this case will have a greater leakage current with this devise. The bandgap of Cu2O and Cu4O3 is about 2.25 eV and 1.7 eV in this experiment. Copper oxide and titanium dioxide will be produced diodes in a variety of conditions, the results show high-power process of titanium dioxide with Cu4O3 have best rectifying characteristics and photovoltaic effect. High-power process titanium dioxide film with Cu4O3 diode for the different test, the test results of photovoltaic efficiency show this result is about 0.15%, the conversion efficiency loss is because the low parallel resistance, and also because the relationship between the parallel resistance is too low lead sin-wave testing can’t be negative half-wave-type filter for full-wave rectifier test. At ESD test, the devise can live at 8kV electrostatic bombardment, but cause leak current lead the trigger voltage and clamping voltage properties not well.

碩士
國立聯合大學
電子工程學系碩士班
102
Room-temperature sputtered TiO2 on bottom electrode of Pt/p-Si and patterned by evaporated Ag as top electrode, memory device in the structure of Ag/TiO2/Pt was investigated on its bipolar resistive switching properties. The forming voltage and switching voltage VSET were found to rise with the deposition time 2 to 5 hrs, which are ascribed to the increasing thickness. The thicker film would require higher voltage to induce the field strength for the path formation, and also gives rise to a more resistive interior and therefore a lower off-state current IOFF. The on-state current ION shows no obvious variation with thickness. The film resistance could be extracted from the low-frequency intercept of the complex impedance plot. While the low-freq intercept increased with deposition time, the high-freq intercept remained nearly constant. Both agree with previous results. Compared with those by 2-4 hrs, device of 5 h exhibits properties of resistance ratio 245, endurance 1E4, retention over 1E4 s, but larger distribution of switching voltages VSET/VRESET, switching current IRESET, and on-state current ION. This larger parametric distribution could be reduced via rapid thermal annealing under atmosphere air, Ar, and O2, and the O2 treatment presents the best improvement. The XPS analysis reveals stronger atomic bondage and the reuse of path formation/rupture is then reached for O2 case. Subsequent temperature of 400/500/600 C under O2 is conducted, and the device at 500 C shows the best performance of VSET/VRESET/IRESET /ION distribution down to 0.1V/0V/1.95mA/0.75mA. Poly-crystallization is observed at 600 C and larger parametric distribution. The filament size varies with the current compliance of 5-20 mA, and results into the increasing bi-stable currents and switching voltage/current. The off-state current IOFF rises with electrode area, which indicates a lower film resistance over larger area. The on-state conduction is dominated by filament path, and therefore shows no electrode area dependence.

碩士
國立東華大學
物理學系
99
In this work, we studied the photocatalytic decomposition and modification of octadecyltrichlorosilane (OTS) self-assembled monolayers by using TiO2 thin film in air. The TiO2 thin films were deposited on Atomic Force Microscopy (AFM) probes or silicon substrates by plasma sputtering and had anatase phase. The wavelength of UV light for photocatalytic excitation was 365 nm. We observed the local decomposition and modification of OTS SAMs by AFM and Lateral Force Microscopy (LFM). Large area photocatalytic reaction on OTS SAMs was measured by the contact angle of water on sample surface. 　　We found that at low humidity, the photocatalytic efficiency was not obviously related to the light intensity, because the efficiency was limited by the supply of water molecules in air. As the humidity increased, the efficiency also increased. We also found that applying a negative bias on TiO2 thin film could obviously increase the efficiency, and a positive bias could slightly decrease the efficiency. We deduced that not only H2O molecules but also O2 molecules are the major reactants. Under the electric field associated to the applying bias, the generated O2－ could be driven to the OTS surface and increase the efficiency. At low humidity (40% RH), the contribution of O2－ to the photocatalytic reaction was estimated to be about 86%. At high humidity (80% RH), the contribution became about 24%.

碩士
華梵大學
電子工程學系碩士班
94
Abstract The purpose of thesis is to study the nonlinear optical characteristics of thermally poled TiO2 thin film and SiO2-TiO2 stacked film. In this thesis, we used electron-beam and thermal evaporations to deposit TiO2 thin film and SiO2-TiO2 stacked film on the fused quartz plate. We changed different thermal poling parameters (temperature, time and voltage) to induce second-order nonlinearities of our samples and then used Maker fringe technique to measure their nonlinear optical coefficients and depths. Our final goal is to find out the optimal poling parameters. We monitored the decay behavior of nonlinear optical intensity of our samples. We also compared the nonlinear optical intensity of poled thin film and fused quartz plate before and after etching. We found that nonlinear optical coefficient seems not to exist within the film.

碩士
國立臺灣大學
化學工程學研究所
91
Titania solutions were prepared by thermal hydrolysis, sol-gel method, and obtained from P25-suspension, Hombikat XXS100 and Hombikat UV100WP TiO2 solution (Sachtleben Chemie GmbH Com., Germany). The TiO2 films were coated on glass plates and optical fibers by the dip-coating method. The thickness of films ranged from 60~600 nm after calcinations at 500°C. Process parameters for coating TiO2, such as the concentration of TiO2 solution, the rate of dipping and the times of coating were studies. The films became thicker, and the crystal size increased by increasing the concentration of TiO2 solution, the dipping rate and the numbers of coating. However, films were found crack or aggregate when the film thickness was thick. From SEM micrographs, AFM surface profiles and the ASTM adhesion tests, the films coated by thermal hydrolysis and Hombikat XXS100 solution were among the best, following by the films coated by sol-gel, P25-suspension, and Hombikat UV100WP solution. From the result of XRD, the anatase phase was found for all films. Furthermore, the wavelength of absorption was under 400nm from the UV-Vis spectra. For TiO2 superhydrophilicity property, it was found that the contact angle of water decreased to near zero under UV-light irradiation, and recovered to the initial contact angle in darkness. An optical-fiber reactor (OFR) with TiO2-coated fibers was designed and assembled to transport UV light to fiber-supported TiO2 and conducted a photocatalytic reaction. Gas-phase ammonia was decomposed in the OFR under UV-light irradiation showing a good photocatalytic reactivity of TiO2-coated fibers.

碩士
國立高雄第一科技大學
環境與安全衛生工程研究所
102
Photocatalytic oxidation processes are often applied to control volatile organic compounds (VOCs), which use semiconductor oxides as photocatalysts to yield electron-hole pairs on their surfaces while irradiated with suitable light energy. Producing highly reactive species, such as, hydroxyl and superoxide radicals is considered as key mechanisms for fast degradation of hazardous air pollutants (HAPs). But, due to the fast recombination of the electron-hole pairs, the degradation rates of many VOCs are not high enough and have low quantum efficiencies. Accordingly, this study aimed to develop a gas-phase photoelectrocatalytic reaction process by providing additional biases to photocatalytic oxidation processes for achieving low recombination rates of electron-hole pairs and high degradation rates of VOCs. Other than preparing various kinds of photocatalysts with different characteristics, several affecting factors including reaction temperature, water vapor content, applied biases were also evaluated in this study. Methyl tert-butyl ether (MtBE) was tested as a target compound in this research. The experimental results demonstrated a higher MtBE degradation rate achieved in external bias assisted photocatalytic reactions than in no bias assisted ones. The degradation of MtBE in these reactions followed a pseudo first-order reaction kinetic. For the effects of operation conditions, the MtBE degradation rate increased with reaction temperature and humidity initially, but it declined for further increasing temperature and humidity. Similar reaction patterns were also observed for the effects of the external bias on the degradation rate of MtBE. All of these results indicated the adsorption phenomena dominantly affect the photocatalytic degradation rate of MtBE. Both increase in temperature and humidity can enhance surface reaction rate of MtBE on TiO2, but reduce the adsorption of MtBE by TiO2. As a result, while temperature and humidity changing, peak reaction rates for MtBE were detected due to the compromised results of enhanced surface reaction rate but reduced adsorption rate for MtBE. Two kinds of thin-film photocatalysts, pure TiO2 and CuO-composited TiO2, were prepared in this study. The later one kept high activities while using visible light as light sources, but the former one had higher photocatalytic activities than the later one wile irradiated with near-UV light. In addition, due to more photo-generated electrons transported away from catalysts and their electron-hole recombination rates were reduced, higher MtBE degradation rates were achieved when the catalysts embedded with less narrow spacing of comb-shape circuits.

博士
國立交通大學
環境工程系所
92
The interest in heterogeneous photocatalysis to remove trace organic compounds present in air exhaust streams and in indoor environments is intense and increasing. The attractive advantages of this technology are: (i) photocatalytic oxidation can proceed at ambient temperature and pressure; (ii) the excitation source can be sunlight or low-cost fluorescent light sources; (iii) photocatalysts are generally nontoxic, inexpensive, and chemically and physically stable; and (iv) final oxidation products are usually innocuous. However, it must be consider the conversion of pollutants, the toxicity of intermediates when the pollutant is not completely mineralized, as well as the reduction of reaction rate when the catalyst is deactivated. In the study, we chose five oxygenates (1-propanol, 2-propanol, propionaldehyde, acetone and N, N-dimethylformamide) which are commonly used in industries, laboratories and household. The effect of operating factor, the production of intermediates and the deactivation of catalyst on the photooxidation of oxygenates on TiO2 surface was investigated. The photocatalytic decomposition reaction of oxygenates obeyed the first-order equation. The higher initial oxygenates concentration, the faster the reaction rate. The initial rate of oxygenates degradation can be well described by the Langmuir-Hinshelwood rate form. The specific reaction rate constant and the equilibrium adsorption can be found from Langmuir-Hinshelwood rate form. The decomposition rate increased with increasing the oxygen content. The rate of oxygenates oxidation increased with increasing the concentration of water vapor, but decreased at high water vapor concentrations. The rate of oxygenates decomposition increased with increasing the temperature, but reduced at temperatures higher than 100oC. There were gaseous intermediates during photocatalytic oxidation of 2-propanol, 1-propanol and propionaldehyde. Acetone was the reaction intermediate of 2-propanol. Both of propionaldehyde and acetaldehyde were the reaction intermediates of 1-propanol. Acetaldehyde was the propionaldehyde intermediate. The kinetic model of 2-propanol photooxidation was successfully developed by the competitive Langmuir-Hinshelwood rate form, incorporating the inhibition effect coming from the formation of acetone. The difference between observed and estimated half-lives became larger when the initial concentration of acetone was increased. It is assumed that the intermediates competed with parent compound so that delayed the half-life. The detection of CO2 production can support this assumption. Catalyst deactivation during photocatalytic oxidation of 2–propanol and acetone was not found but photocatalytic deactivation was observed in oxidation of 1–propanol, propionaldehyde and DMF. The Levenspiel deactivation kinetic model and exponentially decaying model were used to describe the decay of catalyst activity. Fourier transform infrared (FTIR) was used to characterize the surface and the deactivation mechanism of the photocatalyst. Results revealed that carbonylic acids, aldehydes, amines, carbonate and nitrate were adsorbed on the TiO2 surface during the photocatalytic reaction of DMF. The ions, NH4+ and NO3-, causing the deactivation of catalysts were detected on the TiO2 surface. Several treatment processes were applied to find a suitable procedure for the regeneration of catalytic activity. Among these procedures, the best one was found to be the H2O2/UV process. Summary, it is feasible to remove the gaseous oxygenates by photocatalysis. The best operating condition was low inlet concentration of reactant, low flow rate, moderate concentration of water vapor, temperature at 100oC and oxygen content more than 20%. The suitable process of regeneration was H2O2/UV process; the activity of catalyst was almost recovered.

碩士
南台科技大學
奈米科技研究所
96
This research studied the titanium dioxide (TiO2) thin film, at thickness of 500nm, on ITO glass substrate, prepared by radio frequency magnetron sputtering from TiO2 target and analyzes the optical characteristics and surface morphology. The thin films were prepared at different temperatures and at two kinds of heat treatment process: (1) deposited in vacuum condition with substrate heating at temperature ranging from 100 to 400oC, (2) deposited in vacuum condition at RT and then post annealed at 100oC to 400oC in atmospheric furnace. The crystallization state of films was studied by X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). The surface morphology was evaluated with Atomic Force Microscopy (AFM), and the optical characteristics were analyzed by UV-VIS spectrometer and contact angle measurement. Analysis of the temperature and crystallization of different films were summarized as following: (1) at substrate heating below 150oC or post annealed below 250oC were amorphous. (2) at substrate heating at 150 to 300oC or post annealed at 250oC to 400oC were anatase crystalline. (3) at substrate heating from 350 to 400oC was at transitional state from anatase to rutile, above 400oC was rutile crystalline. According to the results of the SEM and XRD, the largest grain size in the film was observed on substrate heating condition at 300oC, grain size decreased above 300oC due to the transformation of crystal phase. According to the results of the AFM, the surface roughness increases with prepared temperature. In the two heat treatment process, the roughest surface occurred on thin films in anatase crystalline at 300oC. From 350 to 400oC, the roughness of films prepared by post annealing did not change too much, however for those prepared by substrate heating, the roughness decreases because of crystalline transformation. The absorptive performance was related with crystalline phase and grain size. As prepared temperature increases, the grain size increases and the band gap decreases that causes the films to absorb smaller frequency light. In the other words, the absorptive ability is red shifted to larger light wavelength. Besides, rutile phase has smaller band gap the anatase phase that resulted in red shift of absorption too. All these trends were confirmed by examining the transparency and absorptive performance of thin films between 200 nm ~600 nm on UV-VIS spectrometer. All films have good transparency about 70% above 400 nm. The hydrauphilic ability was related with crystalline phase and roughness. Better hydrauphilic ability was observed on anatase surface, however at the same temperature of different heat treatment process, the rougher surface possessed the poor hydrauphilic ability.

碩士
國立虎尾科技大學
光電與材料科技研究所
100
In this study, Plasma-enhanced chemical vapor system (PECVD) along with using argon gas (Ar) heated TTIP vapor as the carrier gas transmission, coupled to the oxygen RF plasma excitation gas was used to prepare the thin film of Titanium dioxide (TiO2). TTIP flow rate, O2 flow and RF power of the PECVD process along with annealing temperature was adjusted and optimized. Through the measurement of film characteristics by using X-ray Diffraction (XRD), the analysis by using Field Emission Scanning Electron Microscope (FE-SEM), using UV visible to measure the degradation rate of the Methylene blue(MB) solution, using Contact Angle(CA) to measure titanium dioxide thin film adsorption of methylene blue solution absorption rate, and analyzing titanium dioxide thin film, the process parameters was optimized to establish this film. These results show that plasma enhanced chemical vapor deposition system, the annealing time and titanium dioxide films have intimate relationship. Moreover, when TTIP carrier gas flow of 80 sccm along with O2 flow of 15 sccm, pressure of 200 mtorr, RF power 300W, annealing temperature of 500 ℃ in 30 minutes, the best anatase (Anatase) peak as well as the grain size at 18 to 35nm range can be obtained by using the Scherrer equation. After optimizing the parameters of the titanium dioxide film that placed at distance of 2.5cm to the UV LED Chip (395nm 72W) with the irradiation light intensity of 250mW/cm2, the degradation rate was up to 56% in the 60 minutes.

碩士
國立虎尾科技大學
光電與材料科技研究所
98
TiO2 films were deposited on ST-cut quartz by radio frequency magnetron sputtering. The crystalline structure, surface morphology and luminescent characteristics of films were examined by X-ray diffraction, scanning electron microscopy, and photoluminescence spectrometer. The dense and uniform TiO2 thin film was applied to the surface acoustic wave device. The electromechanical coupling coefficient, temperature coefficient of frequency and liquid sensitivity of TiO2 / quartz surface acoustic wave device were investigated. This study also investigated the effect of the interaction between the resistance and the ultraviolet light in the TiO2 thin film on different sputtering parameters.

碩士
國立臺北科技大學
光電工程系研究所
98
In this study, we fabricated anisotropic thin film of titanium dioxide by bideposition technique. In order to control the column angle, we used the asymmetric deposition angle and the pitch of thicknesses. In optical properties, it can enhance the birefringence and broaden angular spectrum of over 80% polarization conversion. In the experiment, we used electron beam evaporation to fabricate anisotropic thin film of titanium dioxide which is combined with different type of deposition angles and the major indices are measured by polarization conversion. We found that asymmetric deposition angle changed from large to small at the same pitch of thicknesses, it caused the column angle changed from large to small and the property of birefringence enhanced from large to small. On the other hand, the different pitch of thicknesses changed from small to large and the property of birefringence enhanced from small to large at the same asymmetric deposition angle. Using this database, it will be designed and applied for the optical element on the wide angle polarization conversion in the future.

碩士
大同大學
材料工程學系(所)
98
This research is to make titanium dioxide and silicon dioxide particle by sol—gel method when the thin film obtain proper roughness . After that time , we use low—surface energy materials on glass substrate by dip-coating . The morphology of the thin films was analyzed by Field - Emission Scanning Electron Microscope, UV/Visible Spectrophotometer, and Water Contact Angle Meter . Experimental results show that transparent ratio in the range of visible light of the thin films was influenced by concentration and heat treatment tempture .

碩士
國立成功大學
材料科學及工程學系碩博士班
96
In this study, we use the photocatalyst of TiO2 to reduce metallic ion and grow metallic nanowire by thermal reduction. We coat TiO2 thin film on silicon wafer by chemical vapor deposition and electron beam evaporator deposition. Then the thin film sample were annealed at different temperatures to modify their properties, thus we can observe what characters affect the growth of metallic nanowires. We find the crystallinity and morphology of thin film affect the growth of nanowires. The phtocatalytic capability of the CVD TiO2 thin film is better than that of E-Beam, which also results in more metallic nanowires. It is also found that CVD TiO2 film is p-type semiconductor. The AgNO3 in used as precursor to grow silver nanowires. The optimized thermal treatment parameters to grow silver nanowires were studied. And a growth by this mechanism was proposed as “Thermal-assisted photoreduction of metallic nanowires”. And gold and copper nanowires can also been grown by this method, however, the platinum was failed. We find that the valence of ion show significant effect upon the growth of metallic nanowires.

碩士
國立臺灣師範大學
機電工程學系
103
In this study, sol-gel method was used to fabricate Peroxotitanic-acid (PTA) based Titania (TiO2) material. A two-step process was employed to deploy PTA with different concentrations, which were then deposited on a test glass by using spin-coating. After high-temperature sintering, a TiO2 thin film was then formed. Through tuning the parameters of proportions of the concentration, times of the spin-coating, and the changes of sintered temperature, the effect of experimental parameters on the TiO2 thin film structures and characteristics were investigated. XRD, FESEM, UV/VIS/NIR spectrometers, and other sophisticated instruments were utilized for measurement and analysis of the relationship between process parameters and film characteristics. Preferred experimental parameters were then selected for further study of photocatalytic characteristics. The screened results were employed for photocatalytic water contact angle and Methylene Blue (MB) experiments; with the use of spectrometer for quantitative analysis of the sample, the optical, hydrophobic/philic, and photocatalytic degradation pollutants characteristics were investigated. Experimental results showed that the photocatalytic TiO2 thin film of anatase was successfully fabricated with smooth, no cracks, and great crystallinity properties. Furthermore, as the number of coating and sintering temperature increased, the crystal grains became larger and more condensed. The thin film displayed optical characteristics of lower transmittance and higher reflectance comparing to un-coated glass; furthermore, its lowest relative transmittance in UV range was 0.35, and its average reflectance was more than 20%. All these verified its availability for energy saving glass applications. Finally, this study confirmed that TiO2 thin film has a hydrophilic characteristic and a characteristic of photocatalytic degradation of pollutants, where the best contact angle is up to 18.48°, and the best degradation of MB is 25.2%. In the future, the optimum parameters of this material are expected to be used for high-level-related products including energy saving glass or solar cell.

碩士
國立高雄第一科技大學
環境與安全衛生工程系碩士班
106
In this study, the TiO2-PVDF photocatalyst thin films made from compositing both titanium dioxide (TiO2-PVDF) and polyvinylidene difluoride (PVDF) together by an immersion-precipitation method were applied as photocatalysts for water purification. PVDF has many superior characteristics including high plasticity, low mechanical resistance, good chemical resistance, high flexibility, and various thicknesses of thin films available for various applications. PCDF can be cut into various sizes and shapes. PVDF also has the advantages of high temperature resistance, oxidation resistance, weather resistance, and radiation resistance. Thus, The TiO2-PVDF composit thin film photocatalysts were prepared and applied in this study. Accordingly, this study aimed to prepare TiO2-PVDF composite thin-film photocatalysts, co-doped by carbon nanotubes (CNTs) or graphene (GR), for sulfadiazine (SDZ) removal. SZD is widely used an antibiotic for treating diseases due to the infections of bacteria and protozoa. But SDZ has been also classified as an emerging pollutant that can be potentially harmful to environmental ecology and human health. Thus, the experiments for the photocatalysis of SDZ was conducted in a batch reactor under near ultraviolet (UV, λ = 365 nm) or visible blue light (LED, λ = 470 nm). The experimental results demonstrated that the prepared porous TiO2-PVDF, TP-G and TP-C composite thin-film photocatalysts had good photocatalytic capabilityies for SDZ removal. The photocatalysis of SDZ follows the first-order reaction kinetics. The titanium dioxide photocatalyst doped with 2.0% graphene has the highest photocatalytic activity (kUV = 0.354 hr-1, kLED = 0.042 hr-1), followed by a catalyst that is doped with 2.0% carbon nanotubes (kUV = 0.348 hr-1, kLED = 0.040 hr-1), and the slowest SDZ dehrdation rate is by TiO2-PVDF (kUV = 0.018 hr-1, kLED = 0.024 hr-1). In general, SDZ degraded fast in acidic conditions. The doping of nanomaterials not only can increase the activity of TiO2 under near-UV light, but also promote its photocatalytic activity while using LED blue ligh as a ligh source.

碩士
輔仁大學
物理學系
97
Abstract The thickness of optical thin film has significant influence to the optical properties. Uniformity of thickness is an important factor in large-area coating process. In this research we use a spectroscope and virtual instruments program－LabVIEW to judge the thickness of the film and a movable shutter to control thickness. Then、use this system in RF magnetron sputtering process to get a uniform large-area TiO2 thin film.

碩士
華梵大學
電子工程學系碩士班
97
In this thesis, sputter technology was used to deposit titanium oxide (TiO2) membrane on Indium tin oxide (ITO/glass) substrate to fabricate pH sensors and Potentiometric potassium sensors. The sensitivity was between 42.51 and 52.5 mV/pH when the buffer solution was between pH2 and pH12, providing good linearity and sensitivity. The potentiometric potassium sensors on TiO2/ITO were fabricated by Poly (vinyl chloride) carboxylated (PVC-COOH), plasticizer Bis (2-ethylhexyl) sebacate (DOS), Potassium Ionophore Valinomycin and K-TpClPB. After six repeated measurements, detection limit was 1×10-6M ,the sensitivity is about 49.76mV/decade for the potassium solutions ranging from 1M to 1×10-6M. The advantage of arrayed-sensors is to enhance signal to noise ratio (S/N) and have high accuracy because of eliminating unreasonable values with read-out circuit. In this study 1×4 linear arrays was prepared to detect potassium using parallel-measurement, the corresponding sensitivity is between 50 and 51.8mV/decade. The Hysteresis and drift of arrayed-sensor were better than that of single-sensor. Otherwise the 1×4 arrayed-sensor used parallel measurement comparing with 1×4 arrayed-sensor used average measurement have more stable output voltage and promote hysteresis.

碩士
大同大學
材料工程學系(所)
96
Titanium dioxide photocatalyst is well developed and wildly used due to its safety, highly catalytic activity, and self-cleaning properties. However, recycling of TiO2 powder is difficult. This motivates the development of TiO2 thin-films processes to extend its application. In this study, Mesoporous TiO2 thin films on stainless steel substrate were prepared by hydrothermal – oxidation of titanium metal thin films which were obtained by DC magnetron sputter technique. Gold nanoparticals prepared by reduction of HAuCl4 were embedded into the holes of the mesoporous TiO2 films by capillary method. The size of hole of TiO2 films is about 100nm and that of Au nanoparticales is 20nm in average. The morphology of the films was analyzed by Field-Emission Scanning Electron Microscope and Scanning Probe Microscopes. The contact angle of the water drop on the thin films was measured. The photocatalystic effect was investigated by the degradation of methylene blue solution. Experimental results show that the deposited films with Anatase structure exhibit the higher photocatalytic efficiency. Photocatalytic efficiency increases with the fraction of anatase phase in TiO2 films. Crystallinity of TiO2 films is affected by annealing temperature, so that higher photocatalysis efficiency is obtained.

碩士
逢甲大學
工業工程與系統管理學研究所
95
The objective of this paper is to obtain the thin filmed process parameters to maximize the refraction rate. The plating material is TiO2 and using electron beam evaporation associated with ion-beam assisted deposition to experiment. The experiment factors are working pressure, substrate temperature and deposition rate. The design of experiment is 23 full factorial design with 3 replications. The analysis of variance indicate that the main effect of working pressure, substrate temperature, deposition rate and three-factor interaction are significance and obtain the optimal thin filmed process parameters that are working pressure 1.0×10-3pa, substrate temperature 300℃ and deposition rate 4Å/sec. The result of confirmation experiment makes sure the optimal thin filmed process parameters.

碩士
國立高雄第一科技大學
機械與自動化工程所
94
ABSTRACT In the paper, we purposed the Intelligent Algorithm which is combined Taguchi Method, Neural Network and Genetic Algorithms, is applied to optimum process parameter to manufacture Titanium Dioxide (TiO2) thin film on PVD system. In proof the method, used the unbalance magnetic sputtering system to manufacture TiO2 on HSS sample. We set the 6 parameter which is subtract bias and clean time on plasma clean procedure and target current, oxygen flow, subtract bias and coating time on coating procedure. The outcome is measured the water contact angle which is photocatalysis effect. First, we used Taguchi Method planed the process experiment. Taguchi Method which can used the minimum experiment times and the orthogonal array which can cover all parameter on quality character effect, is neural network learning sample. Second, we modeled the experiment data in neural network. Finally, used the Genetic Algorithm searched the optimum process parameter for the neural network. After the Intelligent Algorithm calculated We get the optimum process parameter which guess the water contact angle about 4°. We used the parameter on experiment II and measured water contact angle is 3.93°. The error data between Intelligent Algorithm calculated and measure is 1.78%. We proof the Intelligent Algorithm is correct and useful method.

碩士
南台科技大學
機械工程系
97
This study reports the fabrication of titanium dioxide (TiO2) thin films by radio frequency magnetron sputtering. The objective is to analyze the surface morphology and photoelectric characteristics of the thin films with different thickness or on different substrates. The mainly studied items are: （I）the affection to the morphology of TiO2 by the target-to-substrate-distance and the rotation-of-substrate, （II）measurement and analysis the surface morphology and photoelectric characteristics by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM), and the UV-VIS Spectrometer,（III）analysis the photoelectric conversion efficiency of the solar cell made from the TiO2 thin films at different temperatures, or with different thickness. From literature report, TiO2 is a good photo catalytic material under the irradiation by ultraviolet light. In its three crystallization states, Anatase shows the best photo catalyst effect. According to that, efforts were made to search appropriate parameters to obtain films with Anatase crystal. This study experimentally investigated the affection to the morphology of TiO2 thin films by the target-to-substrate-distance, the rotation-of-substrate, the thickness, and different substrates. The results showed that: (1) The Anatase crystalline can be obtained under low temperature(40℃), at target-to-substrate-distance of 5 cm, with no rotation of substrate holder, (2) films with the most obvious Anatase crystalline was found for the thickness of 500 nm on Corning glass substrate and have the highest roughness, (3) With the increase of film thickness, the crystal sizes become smaller, the band gap of TiO2 reduces, the light absorption is red shifted, (4) the photoelectric conversion efficiency can be measured on the organic / inorganic solar cells, consisted the amporphous TiO2 thin films, with thickness of 50 nm.

碩士
國立成功大學
物理學系碩博士班
95
In the study, we use the Ion Beam Sputter(IBS) to deposit TiO2 thin films, and try to understand the possible origin of room-temperature ferromagnetism(RTFM) in the TiO2 system. First, we successfully deposit the TiO2 films with RTFM by doping Fe in TiO2 films. But we also observe the RTFM behavior in the undoped TiO2 films. Therefore, we focus on the undoped TiO2 system. We deposit films under different oxygen flow conditions, and anneal the samples. And according to the analysis of the X-ray diffraction, sheet resistance, and absorption spectrum, the results suggest that the structure does not obviously vary. The ferromagnetism,however,changes with the concentration of oxygen vacancy. We conclude that the FM is correlated to the oxygen vacancy variation in the undoped TiO2 thin films system.

碩士
國立虎尾科技大學
光電與材料科技研究所
99
In this study, titanium dioxide film and the scattering layer in the flexible plastic substrate were prepared by electrophoretic deposition, and the additional embossing process was used to produce titanium dioxide used in dye-sensitized photovoltaic solar polar cell. Flexible plastic substrates can not withstand temperatures above 150 ℃ higher than the manufacturing process, we use low temperature electrophoretic deposition process to produce titanium dioxide photodiode. Many studies have pointed out that the scattering layer can increase the particle and particle collisions and walk the path of light to enhance light efficiency and thus to enhance the dye-sensitized solar cells, found by the FE-SEM processing by the compression process between particles and the particles closer , the original small particles of titanium dioxide particles include large particles of titanium dioxide particles, in which the particles of titanium dioxide particle size of about 145nm ~ 345nm. UV-Visible scattering layer that adds structure in the visible range of 425nm ~ 700nm absorption was significantly stronger than the scattering layer without adding significantly enhanced compared. The efficiency of dye-sensitized solar cell structure does not add bulk range of 1.74% efficiency, adding the most efficient scattering layer of 1.84%.

博士
國立東華大學
材料科學與工程學系
107
Positions of the energy bands of TiO2 on the electrochemical potential scale are very favorable for photocatalytic degradation of organic pollutants and for splitting water for producing hydrogen fuel that is a promising source of green energy. However, since TiO2 is a wide- bandgap semiconductor, the reactions can be initiated on the surface of TiO2 only by ultraviolet light. There are a lot of routes to increase the optical absorbance of TiO2 in the visible region. New black titania of hydrogenated TiO2 nanoparticles exhibiting exceptional photocatalytic properties under solar light was recently reported. It is known that hydrogenation drastically improves optical, photocatalytic and other properties of the material. However, it is still not known if all the material is affected or only the top layer because the properties of the defective shell itself have not been studied separately or independently from the core yet; next, if black titania is an ensemble, what is the thickness of the top layer affected? Moreover, there is still a controversy regarding the structure and composition of black titania in the literature. In addition, the influence of other factors like OH affinity or the role of hydrogen has not been undoubtly confirmed. Furthermore, it is not clear now what factors are the most crucial in the photocatalytic properties of black titania. In this thesis, structural and photocatalytic aspects of black TiO2 are explored in attempt to get closer to understanding of the mechanisms that define unique properties of the material. In the PhD project, monolithic hydrogenated titania layers resembling the shell of the black TiO2 is pursued. Different approaches were tried out including oxygen flow rate variations, layered approach in which layers of Ti and TiO2 are mixed to achieve desired reduced phases and hydrogen approach in which TiO2 target is being sputtered in H2-containing plasma. Synchrotron radiation was used for identifying the phases present in the samples. Anatase- defective rutile transformation, with further amorphization and transformation into intermediate Ti oxides were observed. Samples became black and conductive at the stage of transformation into defective rutile already and the amorphous sample showed flat absorbance in the visible region. The amount of OH groups on the surface reaches 80% with increasing hydrogen in the plasma. Nevertheless, the black samples are inferior photocatalytically to transparent titania. Moreover, thin film black titania samples were reproduced and characterized in an attempt to get closer to understanding of the mechanisms defining the exceptional photocatalytic properties. Thin film black H-TiO2-x sample with the enhanced photocatalytic performance was successfully prepared by hydrogen plasma treatment in an MPCVD system. The photocurrent and the methylene blue (MB) photodegradation rate of the black titania increased drastically compared to pure anatase sample. A major difference between pristine and black titania films in photocatalytic deactivation by MB and regeneration with a light treatment was found. Surface properties of the black titania film were analyzed with XPS and SIMS. The products of MB degradation are being chemically bonded to the surface of the black samples, but not pristine TiO2 during the photocatalytic reaction due to the presence of OH groups on the surface of the black photocatalyst and a unique gradiently-doped structure of black titania. The black sample was successfully regenerated with a light treatment that consists of exposure of the deactivated sample to UV-VIS light in DI-water. The differences in the properties of different black titania materials prepared by different researches are discussed and a generalizations deduced from the literature, as well as from the experimental results is made. This allowed to provide a new description of black titania and challenge/strengthen some black TiO2 hypotheses in the literature.

碩士
國立中央大學
化學工程與材料工程學系
101
At present titania-silica (TiO2-SiO2) has received a great interest as a novel class of materials. This study aims to investigate the synthesis of SiO2/TiO2 neutral sol at various SiO2/TiO2 weight ratios of 3/1 and 5/1 (denoted as ST(3) and ST(5), respectively) by peroxo sol-gel method, and also study on the photocatalytic degradation of methylene blue in water of ST films prepared by dip-coating technique. It was found that the transmittance increased along with the presence of silicon dioxide and could enhance the light transmittance up to 4% in case of ST(5) film when compared to the bare glass substrate, whereas the TiO2 film decreased at least 5% of transmittance. Prior to study the effect of the SiO2 migration barrier on sodium migration from substrate into the film layer, the films were treated at 500 oC for 1 hour. The multilayer coating of SiO2 and TiO2 (S/T) was also prepared for comparison. It could observe that ST(5) film could be detected a small amount of 0.04 At.% sodium content at the surface, whereas the multilayer coating showed the content of sodium up to 6.57 At.% but less than the bare TiO2. For the photocatalytic degradation of methylene blue aqueous solution, based on the same amount of Ti species, the presence of SiO2 in the film could enhance the phtocatalytic activity exhibiting the rate constant of 3×10-3 min-1 and 1.518×10-3 min-1 under UVC (254 nm) for calcined and uncalcined ST(5) films. In addition, the photocatalytic reaction of ST(5) film was also active under UVA illumination (365 nm). Thus, this method can be the alternative way to produce the film coating on substrate which possesses high light transmittance and also preserves high photocatalytic activity simultaneously.

碩士
明道大學
材料科學與工程學系碩士班
97
Abstract The super-hydrophilicity and self-cleaning surface of TiO2 thin film which is studied extensively establish new research area of photocatalytic thin film materials.Nano-TiO2 thin film coated on glass is effective in anti-fogging. In this study, we discuss how to improve surface hydrophilicity of TiO2 film. A synthesized nanocrystalline anatase TiO2 by microwave-hydrothermal method was applied. The main advantages of microwave-hydrothermal processing of TiO2 are (a) rapid heating to temperature and (b) extremely rapid kinetics of crystallization. The deposition of the anti-fogging film was performed with a dip-coating method, where the substrate was dipped in a solution of titanium dioxide. This study was to obtain TiO2 thin films by dip-coating in TiO2 aqueous. Films have been deposited on a glass substrates and were found to be homogeneous, and about 100-nm. The obtained thin films were characterized by X-ray diffraction, contacting angle, scanning electron microscopy, UV/VIS spectophotometer, and HAZE computer.

碩士
國立中興大學
材料科學與工程學系
96
The preparation of TiO2 thin film on platinum was carried out for anodes in thin film lithium batteries. In order to optimize the best electrochemical performance, the specimens were deposited for 5, 10 and 20 min and further annealed at 350 and 500℃. The surface morphology of film deposited for 5 minutes was more uniform than the others. The TiO2 coating film consists of nano-sized particles observed by EF-SEM were 10-20 nm, consistent with XRD analyses. Cyclic voltammetry (CV) measurements show oxidation and reduction peaks at 2.20 and 1.61 V, respectively. The discharge and charge plateus were found at 1.75 and 1.98 V vs. Li+/Li by charge/discharge tests. When increasing current density, the specific capacity was dramatically decreased. It was suggested that the diffusion flux of Li+ insertion/extraction into/from TiO2 controlled the reaction rate at higher current density. Finally, the capacity was proportional to the diffusion length. Although the capacity of various prepared films in thickness were approaching one another after 50 cycles due to diffusion along crack surfaces, the more uniform EDT350-1T specimen in the thickness of 0.3 μm was better than the others when it was applied in thin film lithium ion batteries.

碩士
南台科技大學
電機工程系
95
The purpose of this research is to investigate the application of large area TiO2 thin film electrode on dye-sensitized solar cell. The larger area of the TiO2 thin film electrode, the more the dyne can be absorbed. This helps to improve the efficiency of the cell by more electron carriers from the dyne. In our experiment, the TiO2 electrode was grown by using RF sputter. From the thickness-meter we know that the thickness of TiO2 film can grow up to 150nm in 3 hours under 200W sputtering. After that we anneal it around 450 ℃ to obtain the Anatase crystal phase of TiO2 thin film electrode. Then we use the yellow light etching to develop the regular array of the electrodes, and finally we immerse the electrodes into the dyne to widen the light absorption area and put the platinum contact. We then inject the electrolyte in between the electrodes to complete the production of the dye-sensitized solar cell. Our method provides the guide and the variation scheme for the various parameters in making the solar cell, also we have some breakthrough about the size of the cell.

碩士
國立聯合大學
電機工程學系碩士班
96
The ZrO2-TiO2 (ZrTiO4) thin films were deposited on ITO/Glass substrates by using sol-gel technology. The effects of various thermal treatments on the physical properties and electric properties of ZrO2-TiO2 thin film also have been studied with various heat-treated temperatures, heat-treated times, and annealed temperatures. Besides, the ZrO2-TiO2 thin film were investigated by resistance switch effect and expected to applied in resistive random-access memory (RRAM). The ZrTiO4 thin film in this study were polycrystalline when annealed temperature of 700oC for 1hr. When the annealed temperature increased, the grain size more large, and the grain size of non-heated treated thin film were large than heated treated thin films. The surface roughness of thin film was reduced by heated treated temperature and annealed temperature obtained from AFM images. The leakage current mechanism of thin film in high annealed temperature was observed as Schottky Emission, and there were always be Pool-Frenkel mechanism in low annealed temperature. The optimum conditions for the leakage current of ZrTiO4 thin film in this study were heat-treated temperature of 450oC for 30 min and annealed temperature of 800oC for 1hr. It could be arrived 1.04×10-6 (A/cm2) when the electric field on 10 (kV/cm). In the RRAM characteristic, all of the thin films have slightly resistance switching effect in annealed 600oC and 700oC for 1hr. The best of the resistance switching in this study were non-heated treated temperature and annealed temperature 600oC for 1 hr could be arrived 102. The result show that ZrTiO4 thin film were a candidate for applied in RRAM.

碩士
國立成功大學
地球科學系碩博士班
101
TiO2/Fe2O3 and Fe2O3/TiO2 thin films are fabricated by using r.f. magnetron sputtering system. They can be applied within the Vis-light range and enhanced their photocatalytic efficiency. We will investigate photocatalytic properties and mechanism between the TiO2/Fe2O3 (Fe2O3/TiO2) film and Fe2TiO5 film. TiO2 films possess a polycrystalline anatase phase by XRD examination. The film thickness and grain size of TiO2 films increase with the increasing sputtering time, which have a pure composition of Ti and O elements. The surface roughness of TiO2 films becomes larger with the increasing film thickness. The band gap and photocatalytic efficiency are related to the ratio of Ti3+/Ti4+ in the TiO2 films. From the XRD result, Fe2O3 films are the pure hemanite phase. The film thickness of Fe2O3 films increases with time observed by FE-SEM, and they only have the elements of Fe and O atoms by EDS analyses. The roughness and band gap of these films are irregular due to the posting annealing. The photocatalytic activity of Fe2O3 films increases with the increasing film thickness. The composite films of TiO2(90 min)/Fe2O3(20 min) and Fe2O3(20 min)/TiO2(90 min) are individually pure anatase and hematite phase. The band gap of TiO2(90 min)/Fe2O3(20 min) is within the UV-light wavelength, while that of Fe2O3(20 min)/TiO2(90 min) is in the Vis-light range. The two composite films have a similar photocatalytic ability, which is better than that of single TiO2 and Fe2O3 films. This may be resulted from electrons or holes can be hopped between valence band and conduction band to reduce the recovery of electrons and holes. Consequently, the photocatalytic ability is enhanced. Fe2TiO5 film is polycrystalline orthorhombic phase from XRD investigation. The band gap of Fe2TiO5 films is in the Vis-light region. The photocatalytic efficiency is very good and similar with that of the composite film. The photocatalytic mechanism is related to the ratio of Fe2//Fe3+ and Ti3+/Ti4+ in the Fe2TiO5 film. It is because the charge transfer between the element with different chemical states, and thus it can effectively separate the electron and hole pairs to promote the photocatalytic activity.