A series of sol-gel based photopolymerizable silica glass for holographic storage have been synthesized via a facile chemical design in an effort to overcome the cracking problem incurred during the irradiation stage. The holographic composite material includes a low molecular weight polydimethylsiloxane (PDMS) with end-capped hydroxyl groups, an epoxide-containing coupling agent, a photopolymerizable acrylate monomer, and the sol-gel-derived silica matrix. Inclusion of PDMS provides improved compression stress and strain and toughness over the original unmodified samples, without deterioration on the diffraction efficiency (£b). A plateau value of £b ~ 40 % can be found under a beam power of 5.02 mW. Correlation between the molecular weight of acrylate polymer and £b of the holographic composite material is described and the discrepancies analyzed. The premature saturation of polymerization in the holographic system is attributed to the retarded free radical polymerization within the silica matrix. Minor variation of £b with photoinitiator concentration is observed, indicating that only moderate molecular weight is required for a reasonably high £b. The crack-free mechanism is based on the chemical and physical interactions within the material system. We also investigated the pore size and volume effect for optical properties, especially in studies of diffraction efficiency. With mixing rubber additives, the pore characteristics change via measurement of BET technique. The results indicated that moderate pore size made high diffraction efficiency for porous matrix and some characterizations also were presented. On the other hand, the optical application of this recording medium was described via 3D projected fringes profilometry (PFP) measurement. We recorded coded pattern on medium by employing fiber devices as light source. Using endoscope as image-derived tool, we get double-projected fringe images on tiny object. By PFP technique, a performed retrieved image can be achieved.

A series of photopolymerizable silica for optical storage has been prepared using sol-gel process in this study. The inorganic-organic hybrid materials were based on methacroloxy-propyl-trimethoxysilane (MPTS) and tetraethylorthosilicate (TEOS). Thin films of the hybrids were prepared using spin coating, knife coating, and the closed-mold methods, while the knife coating showing better film flatness and controlled film thickness. Results indicate crack-free polymerizable silica can be obtained using a recipe with 1 wt% photoinitiator. Samples after irradiation shows increased transmittance, suggesting that photopolymerization did take place with the aid of photoinitiators. Spectroscopic study from FTIR indicates C=C conversion in the acrylic part of MPTS reaches 57.51%. The grating period is observed by the optical microscopy. The maximum diffraction efficiency is 48.21%, as obtained from the sample of pure MPTS. From BET measurements, the pore size of the polymerizable silica increases with the increasing amount of MPTS, consistent with the results from measurements of apparent density. Factors affecting the diffraction efficiency are analyzed; these include sample flatness, sample thickness, the conversion of monomer, and concentration of the photoinitiator. Formation mechanism of the periodic grating is proposed based on this study. Addition of MPTS can greatly alleviate problem of phase separation; yet, movement acrylic segment in MPTS is severely limited. On the other hand, samples with more TEOS tend to be densified more with decreased diffraction efficiency

The thesis discusses how to utilize Sol-gel method to prepare nano-sized TiO2 films of photoelectrodes and the their use in Dye-Sensitized Solar Cells. The main goal is the study on the production of TiO2 photoelectrodes. When making nano-sized TiO2 films of photoelectrodes, we have to first produce TiO2 sol via the Sol-gel method optical thin films are then made by spin coating. After its spin coating, we study the crystalline phase and morphology of nano-sized TiO2 films of photoelectrodes in terms of two ways: Supercritical drying and oven drying. Among the Dye-Sensitized Solar Cells that are made with different drying methods, owing to higher porosity and surface area, the nano-sized TiO2 films of photoelectrodes made by supercritical drying adsorb more dye molecules and are thus more efficient.

A processing route for development of hydroxyapatite (Ca10(PO4)6(OH)2 or HAp)-titania (TiO2) hybrid coatings on titanium alloy (Ti6Al4V) has been established. HAp powders of different size and morphology were synthesized by aqueous precipitation techniques using different precursor couples and XRD, SEM and FTIR were performed for complete characterization. Hybrid coatings were then prepared via sol-gel by incorporating presynthesized HAp powders into a titanium-alkoxide dip coating solution. Titania network is formed by hydrolysis and condensation of Ti-isopropoxide (Ti[OCH(CH3)2]4) based sols. The effect of titania sol formulation, specifically the effect of organic solvents on the microstructure of the dip coated films calcined at 500 &ordm / C has been investigated. The coatings exhibit higher tendency for cracking when a high vapor pressure solvent, such as ethanol (C2H5OH) is used causing development of higher macroscopic stresses during evaporation of the sol. Titania sol formulations replacing the solvent with n-propanol (CH3(CH2)2OH) and acetly-acetone (C5H8O) combinations enhanced the microstructural integrity of the coating during evaporation and calcination treatments. Sol-gel processing parameters such as multilayer coating application and withdrawal rate can be employed to change the titania thickness in the range of 0.120 - 1.1 microns and to control the microstructure of HAp-titania hybrid coatings. Slower withdraw rates and multi-layer dip coating lead to coatings more vulnerable to cracking. A high calcination temperature in the range of 400 &ordm / C-600 &ordm / C lead to more cracking due to combined effect of densification originated stresses and thermal stresses upon cooling.

The microstructural, electrochemical and optical properties of sol-gel derived tungsten oxide electrochromic coatings have been investigated. Coatings were formed by spinning of tungsten metal based aqueous sol on glass with native ITO layer. Three sol formulations / acetylated peroxotungstic acid (APTA), peroxotungstic acid (PTA) and titanium-doped peroxotungstic acid (Ti-PTA) were employed to obtain 200-300 nm thick multi-layered coatings. Material and electrochromic characterization of the coatings have been performed by DSC, XRD, SEM, cyclic voltammetry and UV-Vis spectroscopy. The electrochromic performance of the WO3 coatings was influenced by calcination temperature, by sol chemistry and by the adsorbed water content. For all sol formulations the coatings calcined at 250 &deg / C were amorphous and have shown better performance compared to crystalline counterparts calcined at 400 &deg / C. High calcination temperature also leads to formation of WO3 nanocrystals for APTA and PTA derived coatings, titanium doping retards crystallization. Presence of acetic acid as in APTA sol improved the electrochromic and electrochemical performance. This was related to removal of organics- acetic acid and peroxo ligands- during calcination, which results in an open W-O network providing more ion insertion sites. The water adsorption affected the electrochromic performance in different ways for the coatings calcined at 250 &deg / C and 400 &ordm / C. The amorphous coatings with limited structural water removal and excessive hydroxyl groups tend to crystallize by condensation of W-OH groups upon storage in open atmosphere, therefore exhibiting degrading electrochromic activity with aging. Conversely, hydroxyl groups enhanced Li+ ion insertion for the stable crystalline coatings calcined at 400 &deg / C.

Indium tin oxide (ITO) thin films were formed on glass substrates by sol-gel method. Coating sols were prepared using indium chloride tetrahydrate (InCl3&bull / 4H2O) and tin-chloride pentahydrate (SnCl4&bull / 5H2O) stabilized in organic solvents (acetylacetone and ethanol). First attempt was to synthesize ITO thin films using standard/unmodified coating sols. The effect of calcination treatment in air (300 &ndash / 600 &deg / C) and number of coating layer(s) (1, 4, 7 or 10) on optoelectronic properties (electrical conductivity and optical transparency), crystal structure and microstructure of ITO thin films were investigated. In addition, single-layer ITO thin films with optoelectronic properties comparable to multi-layered films were prepared by employing organically modified coating sols. Oxalic acid dihydrate (OAD) &ndash / a drying/microstructure control agent&ndash / addition to standard sol formulation was achieved. The rationale was to improve the optoelectronic properties of ITO films through enhancement in microstructure and chemical characteristics upon OAD addition. The effects of OAD content in the sol formulation and post-coating calcination treatment on electrical/optical properties of ITO films have been reported. Finally, the effects of post coating drying temperature (100 &ndash / 200 &deg / C) and time (10 &ndash / 60 min) on optoelectronic and microstructural properties of OAD-modified ITO thin films were discussed. Thin films have been characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD),x-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-Vis) spectroscopy, fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM) and four-point probe measurement techniques. It was shown that film formation efficiency, surface coverage and homogeneity were all enhanced with OAD addition. OAD modification also leads to a significant improvement in electrical conductivity without affecting the film thickness (45&plusmn / 3 nm). Highly transparent (98 % transmittance in visible region) ITO thin films with a sheet resistance as low as 3.8&plusmn / 0.4 k&Omega / /sqr have been obtained by employing coating sols with optimized OAD amount (0.75 M). The optimum post-coating drying temperature (100 &deg / C) and drying time (10 min) was also determined for 0.75 M OAD-modified ITO thin films.

The pyroelectric ceramic thin films and detectors based on PbTiO3 that exhibits a low dielectric constant and a high pyroelectric coefficient were fabricated by a sol-gel method in this thesis. The lanthanum (La) and calcium (Ca) were adopted as dopants. The PLT and PCT thin films were deposited on Pt/SiO2/Si substrates by spin coating. 1,3 propanediol was used as solvent to minimize the number of cycles of spin coating and drying processes to obtain the desired thickness of thin film. By changing the dopant content and the heating temperature, the effects of various processing parameters on the thin films growth are studied. The effects of various dopant contents on the response of pyroelectric detectors are also discussed. Experimental results reveal that the dopant contents will influence strongly on the characteristics of thin films such as microstructure, dielectricity, ferroelectricity and pyroelectricity. With the increase of dopant content, the grain size, the coercive field (Ec) and the remanent polarization (Pr) of thin films decrease. The relative dielectric constant (£`r) and the pyroelectric coefficient (g) of thin films increase with increasing the dopant content. In addition, the results also show that the PLT(10) and the PCT(25) thin films exhibit large figures of merit Fv for voltage responsivity (Rv) and Fm for specific detectivity (D*) at the heating temperature of 700¢J. In the pyroelectric properties of thin film detectors, Rv and D* increased with an increase of dopant content. However, Rv and D* decreased when La and Ca content exceeded 10 mol% and 25 mol%, respectively. The PLT(10) and the PCT(25) pyroelectric thin film detectors exist both the maximums of Rv and D*. The results are consistent with the evaluations of Fv and Fm of thin films.

The pyroelectric ceramic thin films and detectors based on PbTiO3[abbreviated to PT] that exhibit a low dielectric constant and a high pyroelectric coefficient, which were fabricated by a sol-gel method in this thesis. The (PVDF/PT) pyroelectric bilayer thin films with low leakage current were deposited on PbTiO3/Pt/SiO2/Si substrates by the spin coating. 1,3 propanediol was used as solvent to minimize the number of cycles of the spin coating and drying processes to obtain the desired thickness of PbTiO3 thin film. By changing the concentrations of PVDF solutions (0.6M~1.0M) and thickness of PVDF thin films (50nm~580nm), the effects of various processing parameters on the bilayer thin films growth and the response of pyroelectric infrared detector device are studied. Experimental results reveal that the thickness of PVDF thin films will influence strongly on dielectricity, ferroelectricity, leakage current and pyroelectricity of (PVDF/PT) bilayer thin films. With the increase of the thickness of PVDF thin films, the relative dielectric constant of (PVDF/PT) bilayer thin films decrease from 63 to 20. The tan£_ increases from 0.00152 to 0.0024, leakage current decreases from 1.54x10-6 A/cm2 to 3.86x10-7 A/cm2, Ec decreases from 70.7 KV/cm to 35 KV/cm, Pr decreases from 6.29 £gC/cm2 to 1.14 £gC/cm2, and £^ decreases from 22.5x10-9 C/cm2K to 6.8 x10-9 C/cm2K with an increase of the thickness of PVDF thin film. In addition, the results also show that the largest figure of merit Fv is 1.31x10-10 Ccm/J as the thickness of PVDF thin film is 80nm. With the increase of the thickness of PVDF thin film, the figure of merit Fm decreases from 2.26x10-8 Ccm/J to 1.07x10-8 Ccm/J. The voltage responsivities (Rv) measured at 20 Hz decrease from 1383 V/W to 804 V/W and the specific detectivities (D*) measured at 100Hz decrease from 2.72x107 cmHz1/2/W to 1.71x107 cmHz1/2/W. From the result of D*/J, the result shows the device possesses the best property as the thickness of the PVDF thin film is 165nm. Therefore, the (PVDF/PT) bilayer thin film with the thickness 165nm of PVDF thin film is the most suitable for the applications of pyroelectric thin film IR detectors.

Abstract This study focused on the structure of the particles developed in the PMMA matrix as a function of (a) coupling agent (£^-MPS) and (b) TEOS content. We investigated the difference of using TEOS monomer directly added to silica particles. The polymer precursors are catalyzed using acidic catalysts and undergo the sol-gel reaction to form a hybrid sol-gel material. This composite shows that highly optical transparency and microphase separation at the molecular level. The characteristics and properties of the polymer precursors and their hybrid materials were characterized by Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimogravimetic analysis (TGA). As for the influence of chemistry structure on morphology and thermal properties, experimental evidence form observations by scanning electron microscopy (SEM), mulitpoints analysis, and transmission electron microscopy (TEM). TEM was used to study the phase separation as well as the fractal structure of these particles present in the system. According to some result, it was found the compatibility between PMMA and silica mainly comes form incorporating the polymer with silica chemical bonding. This chemical bonding not only restrains silyl ester groups form hydrolyzing but also reduces silanol aggregation. Moreover, the thermal properties of the organic¡Vinorganic hybrid are improved as silica content increases.

Hydrogen ion-sensitive field effect transistor with sol-gel-derived La-modified lead titanate gate Department of Electrical Engineering, National Sun Yat-Sen University *Jen-Fu Su **Ying-Chung Chen Abstract In this thesis the amorphous lead lanthanum titanate (Pb1-xLaxTi1-x/4O3, PLT) membrane has been prepared by sol-gel method as a novel pH-sensitive layer. The lead lanthanum titanate membrane was directly deposited on the SiO2(1000Å)/p-Si substrate by spin-on coating to form the PLT/SiO2/Si EIS structure. The C-V measurement was used for examining the fabrication parameters and sensing properties. Moreover, the PLT membrane was grown onto the SiO2 gate ISFET as the PLT/SiO2 gate ISFET. The electrical properties with the different parameter conditions can be obtained by the I-V measurement. Experimental results show that the fabrication parameters and characteristics of the PLT membrane are determined at the La-modified content about 3 mol% and the firing temperature of 400¢J via the EIS structure. There exhibits the pH response of about 44-52 mV/pH in the range of pH 2-12. Furthermore, the nonideal factors, such as drift of 0.1-0.3 mV/h, hysteresis of 2-13 mV and lifetime decay of about 72 mV/pH-day, can be also obtained via the I-V properties of the ISFET. Finally, the hardware architecture of pH measuring system has been built up. The system makes use of constant current and voltage bias technique to ensure that the variations of the output voltage can give directly the variations of pH value. For the purpose of achieving the function of data calibration and driving the liquid crystal display (LCD), the 8051 microprocessor is employed. Keywords: ISFET, Sol-gel, Lead lanthanum titanate, Drift, Hysteresis, pH meter * Student ** Advisor