Sol-gel processing is a very good method for the preparation of silica and other oxide glass planar optical waveguides, including those doped with rare-earth ions like Nd³⁺ or Er³⁺, for applications such as integrated optics lasers and amplifiers. In active integrated optics devices for 1.54 micrometers , involving Er³⁺ doping, a low vibrational energy glass matrix is desirable, in order to increase the quantum efficiency of the Er³⁺ emission; however, this is even more important in the case of Pr³⁺. Here, therefore, the use of a low vibrational energy sulfide glass becomes particularly adequate, although the sol-gel processing of non-oxide glasses is still in its infancy.

Sol-gel is one of the possible production techniques of silica-on-silicon integrated optical devices, combining low cost with a great flexibility. In the frame of a European project, we have investigated the application of the sol-gel technique for the realization of an erbium-doped optical amplifier. In particular we developed GeO₂-SiO₂-Al₂O₃ sol-gel waveguides doped with Er. The material was optimized in terms of heat treatments, Al₂O₃ co- doping content and Er doping level. RBS measurements showed that well densified films could be obtained heating the coatings at 700 degrees C in O₂ flux. Waveguide properties were tested measuring the propagation losses at 840 nm. In the planar waveguide pumped at 980 nm, erbium showed fluorescence around 1530 nm with up to 6.5 ms. In order to achieve lateral confinement, the planar waveguides were co-doped with Na₂O and channel waveguides were fabricated by ion exchange. The feasibility of sodium-silver and sodium-potassium ion exchange was demonstrated. The influence of the process parameters on passive and active optical properties of the films was studied and straight channel waveguides with Gaussian mode profiles were obtained by the sodium-silver route.

In this work we present result on the preparation of planar waveguides based on HfO₂ and HfO₂-SiO$2). Stable sols containing europium and erbium doped HfO₂ nanoparticles have been prepared and characterized. The nanosized sol was either deposited on quartz substrates or embedded in (3-glycidoxipropil)trimethoxisilane used as a hybrid host for posterior deposition. The refractive index dispersion and luminescence characteristics were determined for the resulting HfO₂ films. The optical parameters of the waveguides such as refractive index, thickness and propagation losses were measured for the hybrid composite. The planar waveguides present thickness of a few micra and support well confined propagating modes.

We report here the processing and optical characterization of Nd³⁺-doped SiO₂-TiO₂-Al₂O₃ planar waveguides deposited on SOS substrates by the sol-gel route combined with spin-coating and rapid thermal annealing. The recipes used for preparing the solutions by sol-gel route are in mole ratio of 93SiO₂:20AlO_1.5: x ErO_1.5. In order to verify the residual OH content in the films, FTIR spectra were measured and the morphology of the material by the XRD analysis. Five 2-layer films annealed at a maximum temperature of 500 degrees C, 700 degrees C, 900 degrees, 1000 degrees C, 1100 degrees C respectively were fabricated on silicon. The FTIR and XRD curves show that annealing at 1050 degrees C for 15s effectively removes the OH in the materia and keeps the material amorphous. The propagation loss of the planar waveguides was measured by using the method based on scattering in measurements and the result was obtained to be 1.54dB/cm. The fluorescence spectra were measured with 514nm wavelength of Ar⁺ laser by directly shining the pump beam on the film instead of prism coupling. The results show that the 1 mole Nd³⁺ content recipe has the strongest emission efficiency among the four samples investigated.

Transparent porous matrices made by the sol-gel method are ideal as hosts for active photo active or electro active organic dopants. Sol-gel optics application are related to an adequate and precise control of the compositional and pore surface variations in the cage of trapped molecules, which is necessary to the preparation of novel optical and electro optical gel-glasses. Gel-glass dispersed liquid crystal (GDLC) with electro optical properties shall be presented as an application of the sol-gel process for trapping micro droplets of nematogenic organic compounds. GDLC films may be used as electro optical devices. Upon application of an external electric field, unaltered GDLCs were made to switch from white opaque to colorless transparent states. The different electro optic features of GDLCs, including GDLC performances for color display applications are reviewed.

We present results on photochromic properties of hybrid organic-inorganic host matrices in which dithienylethene or azobenzene derivatives are trapped. Materials were prepared by the sol-gel process in the form of thin films. To increase the photochrome content inside the silica-based gel, modified alkoxysilanes were synthesized. The photochromic functionalized monomers were copolymerized with methyltriethoxysilane or tetraethoxysilane. The study of sol-gel films containing dithienylethene both in the colored and discolored state shows that a large refractive index change, as high as 4.10^-2 can be reached. Design of optical components was performed. Furthermore, from the colored state high remnant optical anisotropy can be photo induced by discoloration with linearly polarized visible light. This anisotropy induces a linear dichroism in the visible absorption band and an important birefringence in the near-IR transparency induces a linear dichroism in the visible absorption band and an important birefringence in the near-IR transparency region. Optical data storage is one of the most fascinating potential applications of this effect. Concerning azobenzene containing materials, we took advantage of material deformation, subsequent to the photoisomerization of the photochromes, to design optical components. Thus, stable surface relief gratings having high modulation depth and high diffraction efficiencies were inscribed on hybrid films. Experiments using near-field optical techniques were performed on the two system in order to improve density data storage.

Photosensitive gel films were patterned with a two-beam interference method by use of 325-nm-wavelength He-Cd laser. We fabricated 2D periodic structures on photosensitive ZrO₂ gel films. The ZrO₂ gel films were prepared from Zr(O-n-C₄H₉)₄ chemically modified by benzoyl acetone. For fabrication of 2D pattern, UV-irradiation process was divided into two pats and the substrate was rotated by 90 degrees between the parts. When total irradiation time was equal to the time for grating fabrication, 2D dotted pattern was obtained. A checked pattern was also obtained with irradiation time of 30 min. We also fabricated surface-relief gratings on photosensitive Pb(Zr, Ti)O₃ (PZT) gel films. The PZT gel films were formed by dip coating with sol solution, which was prepared from Zr(O-n-C₄H₉)₄ chemically modified with benzoyl acetone, Ti(O-n-C₄H₉)₄ chemically modified with benzoyl acetone, Pb(CH₃COO)₂, and alcohol. The gel films could be crystallized by annealing at 700 degrees C for 1 hour. The annealed films had a ferro electric phase and a P-E hysteresis loop was obtained. Uniform gratings with a sub-micrometer period were formed on the gel films by two-UV-beams irradiation and etching with butanol. A maximum first-order diffraction efficiency of 28 percent was obtained under a Littrow mounting condition by use of a linear-polarized 633-nm-wavelength light.

We are developing a silicon-based micro-optical table (MOT) on which various passive and active optical elements can be positioned with sufficient accuracy so that no further alignment is necessary. In order to achieve a zero-alignment assembly of micro-optical systems, we take advantage of lithographic patterning. Conventional lithography is used in combination with a deep reactive ion etch (DRIE) process for silicon in order to pattern a silicon substrate that plays the role of a micro-optical table. Lithography is also used to pattern optical and opto-mechanical structures on optical elements. Specifically, the hybrid sol-gel method is employed in the fabrication of optical and opto-mechanical structures into a photosensitive glass materials. High optical quality thick films and structures are fabricated by a one-step spin-coating process followed by direct UV imprinting. We have achieved a material thickness of 27.5 microns and a maximum patterned thickness of 17.4 microns at an aspect ratio of 0.6. The material exhibits a minimum transmittance of 97 percent between 400-1100 nm, an index of refraction of 1.49, and an rms surface of 14.8 roughness of 14.8 nm after development.

The unique ways in which sol-gel derived silicate networks, that contain photosensitive methacrylate substituents, respond to light are described. Visible laser light in a hybrid acrylate-silica glass waveguide leads to photo initiated polymerization of the monomer. Polymerization proceeds with a high degree of spatial localization to create an 'optical fiber on a chip'. Photo transformations in the matrix are monitored by in situ waveguide Raman spectroscopy. Photo-orientation of the acrylate polymerization is controlled by the polarization sates of the guided wave. In this way, birefringence axes are reversibly written in the fiber.

Optical sol-gel materials have been of interest for many years. The reason is that through the preparation of sold with nanoparticulate liquid structures, transparent coatings of many inorganic oxides can be produced. By using oxides for example, with different refractive indices, reflective or antireflective coatings can be fabricated. To obtain stable layers, the gel coating have to be densified at higher temperatures, in general between 400 and 600 degrees C. This may be suitable for glass surfaces, but not for temperature sensitive substrates like plastics. In addition to this, if multilayer coatings have to be produced, between each step a densification process has to be carried out before the net coating step takes place. This leads to an unsatisfying situation if industrial low cost processing is required. In addition to this, the dip coating process is not suitable for high speed or large area coating techniques. This is one of the reasons whey the sol-gel process never has gained a real high significance for industrial coatings on glass and is limited to special products so far.

Optical homogeneity of organic dye-doped sol-gel silica slab has been improved. Single longitudinal mode laser oscillation with 1.58GHz line width at 467 nm wavelength has been achieved. The first operation of a distributed feedback dye-doped sol-gel silica laser, with periodic gain modulation induced by the interference pattern of the pump laser beams, has been demonstrated in the red and the blue optical regions. 20nm wavelength tuning range, 4.5 percent slope efficiency and 60pm laser line width have also been obtained. Based on the quenching of phosphorescence by oxygen, a novel oxygen senor has been developed using erythrosin B doped silica. The oxygen sensing is effective from 0.014 mbar to 600mbar, and the sensitivity improves by a factor of 10 as compared to transition-metal optical fiber oxygen sensors.

Semiconducting ferro electric antimony sulphoiodide (SbSI) microcrystallite doped organically modified TiO₂ thin film and bulk solids are successfully fabricated by the sol- gel process. Ferro electric SbSI crystallites have some attractive properties, including high dielectric permittivity, high electro-optical coefficient and high photoconductivity. SbSI is also an intrinsic semiconductor with a relatively narrow energy gap. If the crystal size is near its Bohr radius and the microcrystallites are dispersed in a suitable matrix, a dramatic improvement of the third order non linearity will be achieved due to the quantum confinement effect. It is clear that the SbSI quantum dot composites are good candidates for electro-optical devices. Glycidoxypropyltrimetroxysilane modified TiO₂ is used as the matrix and SbSI is synthesized in situ by using SbI₃ SC9NH₂)₂ and H₂S gas. The size is controlled by the heat-treatment conditions and is characterized by the XRD and HRTEM measurements. The optical absorption spectrum gives evidence of the quantum confinement effect. The third order susceptibility of the SbSI quantum dot is measured by the degenerate four wave mixing method.

Recently, we have successfully incorporated gold nanoclusters into silica matrix by a sol-gel technique, where the synthesis of gold clusters was conducted in presence of PVP. In this paper, we report linear and nonlinear optical properties of the polymer-blocked gold clusters in silica matrix. The Au/SiO₂ glass were characterized by transverse electron microscopy (TEM), x-ray diffraction (XRD), and Mie-Drude analysis of linear absorption spectra. The hydrophilic polymer, exhibiting the strong metal-polymer interaction which stemmed from the lone pair from the nitrogen with the metal particles, prohibited the flocculation and growth of gold clusters in gel-glass transition. The degenerate four-wave mixing experiment was performed to obtain the nonlinear susceptibility (chi) ⁽³), which was evaluated to be 1.7 X 10^-9 esu, in consistent with a theoretical value expected from hot electron contribution.

Preparation of micrometer-sized spherical particles containing Rhodamine 6G (R6G) has been investigated for the spherical cavity micro-laser. Using phenyl triethoxy silane (PTES) as a starting material, R6G-doped monodisperse spherical particles were prepared by the vibrating orifice technique. Processing consists of two major processes: (1) Hydrolysis and polymerization of PTES and (2) Droplet formation from PTES oligomers by vibrating orifice technique. A cylindrical liquid jet passing through the orifice of 10 and 20 micrometers in diameter breaks up into equal- sized droplets by mechanical vibration. Alcohol solvent of these droplets was evaporated during flying with carrier gas and subsequently solidified in ammonium water trap. For making smooth surface and god shaped particles, control of molecular weight of PTES oligomer was essential. R6G-doped hybrid spherical particles of 4 to 10 micrometers size of cavity structure were successfully obtained. The spherical particles were pumped by a second harmonic pulse of Q- switched Nd:YAG laser and laser emission peaks were observed at wavelengths which correspond to the resonance modes.

Room temperature persistent spectral hole burning (PSHB) was observed in Sm²⁺ and Eu³⁺-doped Al₂O₃- SiO₂ glasses prepared by a sol-gel method. The glasses were obtained by heating the gels in hydrogen gas and the spectral hole was burned in the excitation spectrum of the ⁷F₀ yields ⁵D₀ transition of the Sm²⁺ and Eu³⁺ ions. The depth of the hole burned at 77 K decreased with increasing the cycling temperature. The decrease in the hole-depth is due to the thermal relaxation of the burnt-state of OH bonds surrounding the rare-earth ions. The depth of hole burned in the Sm²⁺-doped glass heated in 20 percent H₂-80 percent N₂ gas exhibited the PSHB at room temperature. We considered that the electron transfer between the rare-earth ions and the Al-related defect centers acts for hole burning.

Sol-gel matrices have been investigated for some years as potential matrices for rare earth luminescence. The design of sol-gel matrices inside which the hydroxyl content can be minimized and/or inside which the rare earth is protected via complexation or encapsulation is desirable to avoid the RE³⁺ luminescence quenching. We have investigated the Nd³⁺ Sm³⁺, Dy³⁺, Er³⁺ and Tm³⁺ optical properties in siloxane-zirconium hybrid matrices prepared at room temperature. In these hydrophobic matrices, RE³⁺ fluorescence is always observed but lifetimes and quantum yields are strongly dependent on the synthetic procedure. By using the reducing power of the hydridosilanes precursors, it is also possible to prepare hybrid materials with cations in different valence states. The in situ formation of hydrogen, provided by the cleavage of the Si-H bonds during hydrolysis and condensation reactions, reduces the europium and cerium in Eu²⁺ and Ce³⁺ leading to a broad visible emission. In addition to this emission, a blue emission of the sol-gel matrices under UV excitation is also observed.

The sol-gel process was used in the fabrication of new polycrystalline silicate scintillators. Lutetium orthosilicate (LSO) is one of the most promising scintillators discovered in almost five decades, with a unique combination of important properties for X and (gamma) -ray spectroscopy, namely high density, fast decay, and large light yield. However, the practical utilization of LSO as a single crystal is hindered by difficulties related to high temperature crystal growth by the Czochralski method. In the new approach presented here, Ce-doped lutetium silicate crystals are grown from a gel. The processing temperatures are much lower than that of conventional processes. The polycrystalline scintillators are characterized by XRD, TEM, DTA, light decay measurement and gamma-ray spectral response.

The Nd³⁺ ions doped bulk glasses and thin films with the trimethylphosphate (TMP) as the precursor of P₂O₅ were prepared by the sol-gel technique. Their optical properties have been investigated. The Fourier Transform IR (FTIR) of Nd³⁺ doped SiO₂-TiO₂-P₂O₅ films have been measured to study the influence of P₂O₅ content in the removal of hydroxyl group. Fluorescence spectral results show stronger fluorescence intensity along with the narrowing of the emission bands due to the availability of the co-dopant P₂O₅ in the sol-gel glasses compared with those of aluminum co-doped glasses. Our experimental results show that up to 6wt percent of Nd₂O₃ could be incorporated into the P₂O₅-SiO₂ glass matrix without significant fluorescence quenching effect due to the usage of the TMP as a precursor. We have also found that the hydroxyl groups could easily be removed at lower temperatures, as we increase the P₂O₅ content. It indicates that the P₂O₅ co-doping has a great potentiality in reducing the process temperature.

When entrapping indicators in sol-gel materials for optical sensing purposes, one should be careful to take into account that changes in the cage properties, caused by variations in the synthetic procedures, might affect the performance of the dopant. We show - for SiO₂ sol-gel entrapped pH and polarity indicators - that such variations are brought about by changing the water-silane r-ratio preparation conditions and by changing the environmental humidity to which the material is exposed. The observations are interpreted in terms of changes in the acidity and polarity of the cage surface.

Research in recent years has demonstrated that biological molecules such as enzymes, immunoglobulins, and other proteins can be immobilized in sol-gel derived matrices and retain their biological function. Development of glasses with encapsulated biomolecules has opened the possibility of solid-state optical biosensors for the detection and measurement of desired analytes. In this work, we report the successful use of sol-gel silica glasses with encapsulated antibodies for the detection of trinitrotoluene (TNT). Results show that both competitive immunoassay and displacement immunoassay are feasible using antibody-doped glasses, and these materials can detect TNT at < 1 ppm. Moreover, the sol-gel immobilized antibodies retained the ability to discriminate between TNT and an analog, trinitrobenzene. Finally, enhanced stability was observed in the sol-gel immobilized as compared to surface immobilized antibodies.

Tremendous progress has been made in recent years in understanding some of the fundamental aspects of chemical and biological sensing/ Most research and commercialization efforts have been focused upon fabricating individual senors for specific and usually narrow applications and application environments. Inasmuch as most commercially available chemical and biological senors were developed independently of one another, trying to integrate them into one device would be extremely difficult and costly. The challenge of integration rests primarily on developing a multi-functional 'platform' sensing technology that can allow the high volume, low cost fabrication of large numbers of individual sensor on a single array. Just as an image on a view screen is composed of a large number of light generating pixels, a sensor array would also be composed of a large number of 'sensels', individual sensor elements to generate an 'image' or map of an unknown substance, be it liquid or vapor, being examined. Emphasis needs to be given to the types of platform approaches that have the greatest likelihood of supporting broad based sensing capabilities. This paper is intended as an overview of some of the sensing platform. Also disclosed is our new sensor array technology. Through the merging of technologies and resources, highly sophisticated, commercially viable sensor systems could be practical within only a few years.

Photoupconverted emission and wavelength-dependent optical limiting and non linearity have been reported in fullerene C₆₀ and its complex C₆₀[W(CO)₃diphos] toluene solutions and sol gel films. Up converted emission indicates the absorption and emission from upper-lying excited states. Significant improvement of optical limiting performance in C₆₀[W(CO)₃diphos] compared to C₆₀ has been achieved in a wide spectral range. Optical non linearity increases with the increment of wavelength.

Coumarin molecules are widely used as laser dyes and their luminescence properties show a large potential for their use as light emitters in organic light emitting devices. These molecules however are lacking of photo, chemical and thermal stability. At the outset, the fact that when the coumarin or other organic active molecules are covalently bonded to a metal oxide host, the stability properties can be improved. In this paper we outline the synthesis of several different coumarin-3-carboxylic acids by using a one-pot synthesis from dipotassium o-methoxybenzylidenemalonates. We also outline a preparative route for the synthesis of corresponding coumarin-3-carboxylic amides with a side chain containing terminal trimethyoxysilane functionality, which allows the creation of a covalent bond between the molecule and a silicon oxide host matrix. These silylated coumarins are then covalently bonded through a sol-gel method to a developing siloxane host matrix. The silicon matrix materials have been synthesized through hydrolysis and simultaneous condensation of metalalkoxides such as phenylmethyltrimethoxysilane. Coumarin dyes are bonded in- situ to the developing matrix during the preparation of the matrix. The excitation and emission spectra of these molecules are examined in liquid phase to evaluate the effect of varying substitution pattern on luminescence characteristics. The photo luminescence characteristics are also measured from a solid thin film to explore the effect of the matrix on emission wavelengths. These materials show potentiality for their applications in thin film electro luminescence devices whose fabrication and properties are finally discussed.

Optical homogeneity of organic dye-doped sol-gel silica slab has been improved. Single longitudinal mode laser oscillation with 1.58GHz linewidth at 467nm wavelength has been achieved. The first operation of a distributed feedback dye-doped sol-gel silica laser, with periodic gain modulation induced by the interference pattern of the pump laser beams, has been demonstrated in the red and the blue optical regions. 2Onm wavelength tuning range, 4.5%slope efficiency and 6Opm laser linewidth have also been obtained. Based on the quenching ofphosphorescence by oxygen, a novel oxygen sensor has been developed using erythrosin B doped sol-gel silica. The oxygen sensing is effective from O.Ol4mbar to 600mbar, and the sensitivity improves by a factor of 10 as compared to transition-metal optical fiber oxygen sensors.

Structural changes during thermally induced polymerization of the dipped thin films prepared from TMSPM, zirconium n- tetrapropoxide and methacrylate acid were investigated using near- and mid-IR spectroscopy. In the mid-IR spectra, the intensity of the band due to C equals C was decreased by the heat-treatment at 160 degrees C. The intensity of the band due to C equals O in the polymerized methacrylate, was increased. In the near-IR spectra, the intensities of a band due to the first overtone of fundamental (nu) _as(CH₂equals) and a combination changes show that heat-treatment of the films at 160 degrees C leads to depletion of C equals C bonds, indicating that polymerization has occurred of TMSPM and methacrylic acid. However, in the mid-IR spectra, the intensity of the band at around 3500 cm^-1, due to O- H bonds, increased with the progress of polymerization of vinyl groups. Near-IR spectra of the dipped thin films showed that this increase in intensity of the O-H band is due to the increase of monomeric water molecules hydrogen bonded to silanols. This indicates that polymerized samples are more hydrophilic than unpolymerized ones. The refractive index of the dipped films, measured with a prism coupling method, increased from 1.508 to 1.516 with the polymerization for composition Zr/(Zr + Si) of 0.2.

A transparent organic/inorganic hybrid, which is simple to prepare by the sol-gel process, is poly(ethylene oxide) (PEO)/silica. The reason for its simplicity is that PEO is soluble in water and mixes easily with bonds with silanols. Hybrids of PEO/silica were prepared with PEO molecular weights 200, 1000, 2000, 3400, and 8000. Raman microscopy was used look at environmental effects of the polymer in the silica spectra. Both the hydrogen-bonding between the organic and inorganic components and the steric effects of the organic component resulted in changes in the Raman spectra. With low molecular weight PEO, the spectra showed large shifts in CH bands. For high molecular weight PEO, the spectra showed broadening, indicative of more fluid behavior of the PEO. The interaction between the ether oxygens and the silica network varied with molecular weight and the ratio of PEO to silica.

The influence of aluminum ions on the UV optical absorption of germano-silicate sol-gel glass system is studied through investigating the variation of structure and photochemical transformation of germanium-related oxygen deficient centers (GODCs). The absorption spectra studies reveal that co- doping by aluminum and subsequent UV radiation effect the transformation of the GODCs from germanium lone pair center to neutral oxygen mono-vacancy in germano-silicate xerogel specimen. Possible mechanism of such an effect is discussed.

In this contribution we provide evidence for thermochromic color changes unique to silica based materials formed at low temperatures by the sol-gel process. The materials formed have potential application as temperature sensitive light filters, visual temperature indicators, self-diagnostic labels for electronic devices and IR recording media. The dopants, diamine complexes of copper(II)/nickel(II) chloride, change from purple to green following heating to 100 degrees C and revert to purple on cooling in the atmosphere. This color change has been explained by the substitution of water molecules by chloride ions in the first coordination sphere of the metal ions. When the same compounds are incorporated into a silica sol-gel matrix under acidic conditions the gel-glasses may be pale green, dark green, yellow, olive-yellow, blue or brown depending on the metal ion chosen and the extent of thermal treatment. Studies on the complexes themselves and on granular silicas doped with some of the complexes are assisting us in understanding the molecular mechanisms that give rise to these color changes.

The STARDUST Mission, which launched in February of 1999, plans to fly through the coma of Comet 81P/Wild2, capture some of the material ejected by the comet, and return the samples to Earth in 2006. The capture media for the encounter is silica aerogel. In the course of the capture media development the aerogel evolved from single density, to discontinuous density changes, to a continuous density change. Since various physical properties such as the index of refraction, the porosity, the dielectric constant, etc., are directly related to the density of these materials, they too vary in a gradient manner. Employing the method developed for the production of the STARDUST media, samples have been produced which exhibit order of magnitude density changes and refractive index gradients of up to 0.1. Other samples have been made which include compositional gradients such as varying dopant/s concentration and oxide composition. The method has been sued to form samples that display liner, planar, and cylindrical gradients. Sol-gel materials have been produced of not only gradient aerogel, but also gradient xerogel, as well as, gradient hybrid aerogel/xerogel materials.

Organic polythiophene polymers are known to be good electrical conductors, however they are lacking of chemical and mechanical stability. In this paper we describe a synthesis of polyethylene dioxythiophene-polystyrene sulfonate (PEDT-PSS) doped sol-gel polyceram material to improve chemical and mechanical properties of PEDT-PSS thin films. Thin films are fabricated by spin and spray coating methods from polymer-sol-gel solutions on sodalime glass, polyurethane, polycarbonate (PC) and polymethyl methacrylate (PMMA) substrates. The effects of different kinds of silicon dioxide network forming sol-gel precursors are investigated in terms of the electrical conductivity and the stability of the electrical conducting properties against various atmospheres and chemicals. Optical transmittances at the visible wavelength region and refractive indices are also determined. Results indicate that a type and an amount of the sol-gel silane precursor have an effect on the electrical, optical and chemical properties of these films. The most conductive and stable coatings are formed when glycidyloxypropyltrimethoxysilane is used as a sol-gel precursor. The maximum conductivity obtained for 150 nm thick film is 17 S/cm. Finally some of the applications, such as antistatic protection coatings on plastics and optical thin film devices of these polycerams are described.

Thin films of indium tin oxide (ITO) are of interest because of their high transparency and low electrical resistivity. Applications include use as electrodes for liquid crystal display and as heat mirrors for solar energy devices. We have developed totally aqueous routes to indium oxide (IO) and ITO materials because, (1) the particulate sols afford a longer shelf life than for alkoxyide derived materials, (2) organics do not have to be removed from the films by baking, and (3) the starting materials are cheaper than the corresponding alkoxides. Indium and mixed indium/tin sols have been prepared form inorganic solutions and treated with alkali to produce white thixotropic sols ca. 0.64 in M^z+ ions. This films were prepared by spinning on low iron or pure silica slides previously cleaned with DECON and washed with distilled water. Films were subsequently heated at 773K in air, or 1173K in air or nitrogen. The film with the lowest resistivity contained ca. 5 percent Sn and had an average optical transmittance between 400 and 600nm of 95 percent. The film was non-porous, smooth in texture, approximately 300nm thick and had a band gap energy of 3.22eV.

Spin coating can often be used to create highly uniform coating son flat substrates using sol-gels and other precursor solutions. Typically, fluid flow considerations dominate the early part of spinning while solvent evaporation controls the behavior at later stages. However, even though evaporation does not control the early stage, it is still occurring throughout the entire process and evaporation-related issues can arise during the flow- dominated stage that may ultimately become coating thickness non-uniformities in the final product. Striation defect formation is a good example of this. During the spin coating process the evaporation of solvent takes place at the top surface of the flowing fluid, thus a concentration profile for the solute specs will exist within the flowing solution. Since the solute species in sol-gel solutions are often prone to condensation or cross-linking reactions, it is possible for this top surface to experience a rapid increase in viscosity and potentially to act as a barrier to further evaporation. This top layer could be equivalent to the skin layer on drying paint.

The purpose of this work is to compare thin films of vanadium dioxide (VO₂) produced via a sol-gel process and a reactive sputtering technique. The sol-gel process used was based on vanadium oxide triisopropoxide precursor. This was converted to soli n dried ethanol by adding water, and the substrates were then dip coated with a controlled draw method in an inert atmosphere. After drying this was followed by a final reduction stage in a low oxygen partial pressure atmosphere. The reactive sputtering technique used carefully controlled deposition rates from a vanadium metal target in argon/oxygen atmosphere to ensure correct stoichiometry. The films were deposited on silicon substrates and were tested optically and electrically above the below the transition temperature. Results of transmission and reflectivity in the IR region of the spectrum, and electrical conductivity are presented. The results show that the sol-gel technique provides a viable alternative method to sputtering for the production of thin films of vanadium dioxide.

In the paper, appearance and composition of an optical interference multi-layer coatings derived by sol-gel process were introduced. In particular, it is given that the distribution function of micro particles diameter size and the variety situation of porousness and graininess, as well as the influence of heat-treated temperature on optical quality of coatings. A lot of measurement result is supported by ESCA, AES, SEM and AFM and so on.

A second-order nonlinear optical polymer was synthesized with bis-phenol-A as the polymer backbone, p-nitroaniline as the chromophore and cinnamyl group as the photo-sensitizer. The polymer films were obtained by spin-coating and poling by three methods respectively. These methods of poling include needle electrode corona poling, parallel wire electrode corona poling and contact poling, which were used to obtain the molecular orientation. The uniformity of the side-chain polymer films have been studied by external electro-optic measurement. The spatial resolution of system is 3 micrometers . Experimental results demonstrated that parallel wire electrode corona poling is easier to obtained large poled area with good uniformity than that of other methods.

Thin films of CeO₂-TiO₂-ZrO₂ with 23 percent mol of Ce, 45 percent mol of Ti and 32 percent mol of Zr have been prepared by the sol-gel method. The precursor sol was synthesized from a mixture of Ce(NH₄)₂ (NO₃)₆, Ti(OPⁱ)₄ and Zr(OPⁱ)₄ solubilized in isopropanol and then sonicated. Xerogels were characterized by thermal analysis and x-ray diffraction. The films were deposited by dip-coating technique on ITO-Asahi glass and tread at 80 degrees C during 15 min and 450 degrees C during 15 min in oxygen atmosphere. Through the addition of lithium salt to the precursor solution films with different electrochemical performance are obtained. Their possible use as ion storage in electro chromic devices was analyzed by spectroelectrochemical measurements using cyclic voltammetry and chronoamperometry coupled to spectrometric measurement.

A novel optical coating devoted to reduction of CRT panel specular reflection has been developed using the sol-gel route. The sol-gel antireflective (AR) coating is made from tantalum and silicon oxide-based solutions. First layer is an hybrid material based on polymeric mixture of tantalum with silicon oxide. Second and third layers are respective containing tantalum oxide and silica polymeric matrix, since they correspond to the high and low index thin film in the optical stack. Sol-gel synthesis has been carried out starting from cheap precursors in order to produce metallic alkoxide-based solution, each one suitable for liquid- deposition technique use such as dip or spin-coating. After layer deposition, a curing step is required. Both thermal and UV-curing could include layer densification and generate final coating properties. UV-curing is performed using short wavelength irradiation and thermal baking step does not exceed 150 degrees C temperature. CRT front panel prototypes have been produced with sol-gel AR-coat for test measurements. The process time including deposition by dip- coating and curing, is about one hour. This three-layer antireflective coating has been optimized to offer scratch- resistance, easy-clean and broadband antireflection properties on CRT panels.