Showing papers in "Thin Solid Films in 1999"

Photocatalytic activity and photoinduced hydrophilicity of titanium dioxide coated glass

Abstract: Antifogging mirror or self-cleaning glass can be realized utilizing photoinduced hydrophilicity of titanium dioxide. Application fields of functional titanium dioxide coating is now expanding rapidly not only in applications for glass but also in applications for polymer, metal and ceramic materials. The high hydrophilic surface of TiO2 is interesting also on the standpoint of the basic photon related surface science of titanium dioxide. In order to understand the photoinduced hydrophilic conversion on titanium dioxide coating in details, it is inevitably necessary to understand the relationship between the photo reaction and the surface crystal structure. In this paper, photoinduced hydrophilic conversion was evaluated on the different crystal faces of rutile single crystal and also polycrystalline anatase titanium dioxide to clarify the dependence of the crystal structure on the photoinduced hydrophilic conversion.

Texture etched ZnO:Al coated glass substrates for silicon based thin film solar cells

Abstract: ZnO:Al films were r.f.- and d.c.-magnetron sputtered on glass substrates from ceramic (ZnO:Al2O3) and metallic (Zn:Al) targets, respectively. The initially smooth films exhibit high transparencies (T≥83% for visible light including all reflection losses) and excellent electrical properties (ρ=2.7–6×10−4 Ω cm). Depending on their structural properties these films develop different surface textures upon post deposition etching in diluted HCl. The light scattering properties of suitable films can be controlled over a wide range simply by varying the etching time. Moreover, the electrical properties are not affected by the etching process. Thus, within certain limits a separate optimization of the electro-optical and light scattering properties is possible. Amorphous silicon (a-Si:H) based solar cells prepared on these new texture etched ZnO-substrates show high quantum efficiencies in the long wavelength range demonstrating an effective light trapping. First a-Si/a-Si stacked solar cells were realized with initial efficiencies exceeding 10%.

Growth, structure and optical characterization of high quality ZnO thin films obtained by spray pyrolysis

Abstract: Zinc oxide thin films were prepared by spray pyrolytic decomposition of zinc acetate onto a glass substrate. Auger spectroscopy showed that the film stoichiometry is close to the ZnO phase with a little excess of oxygen. X-ray diffraction spectra show that the structure belongs to the hexagonal wurtzite crystal type, with a mean crystallite size in the range 20–33 nm. Under optimized deposition conditions films are c -axis oriented, having a full width at half-maximum (FWHM) value of the (002) X-ray diffraction line of 0.23°. Microstructure was analysed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high resolution electron microscopy (HREM). In regard to the crystal growth, a critical temperature was found to be around 600 K. Above this critical temperature the film is c -axis oriented and almost all grains became round shaped. Optical constants, n and k , were determined using only transmittance data and a direct band gap of 3.28 eV was deduced.

Characterization of the PEDOT-PSS system by means of X-ray and ultraviolet photoelectron spectroscopy

Abstract: Thin films of an electrically conducting polymer blend, poly(3,4-ethylenedioxythiophene) oxidized with poly(4-styrenesulfonate), PEDOT-PSS, have been studied using X-ray and ultraviolet photoelectron spectroscopy. Special attention has been paid to thermal effects and the influence of hydrochloric acid on the chemical and electronic structures of the films, since these issues are important in applications of PEDOT-PSS as a hole-injecting electrode in polymer-based light emitting devices. Three chemically different species were identified in pristine PEDOT-PSS, namely poly(4-styrenesulfonic acid), poly(sodium 4-styrenesulfonate) and poly(3,4-ethylenedioxythiophene). The HCl-treatment is shown to lead to the conversion of the sodium salt into the free poly(styrenesulfonic acid). Heating of PEDOT-PSS films resulted in a decomposition of the free sulfonic acid component (presumably through loss of SO 3 ), whereas the sodium salt is thermally stable. It is shown that phase segregation occurs in the PEDOT-PSS system resulting in a surface entirely covered by PSS part of the PEDOT-PSS, as indicated by both XPS and UPS measurements.

Influence of substrate temperature on atomic layer growth and properties of HfO2 thin films

Abstract: Atomic layer growth of hafnium dioxide from HfCl4 and H2O has been studied at substrate temperatures ranging from 180–600°C. A quartz crystal microbalance was used for the real-time investigation of deposition kinetics and processes affecting the growth rate. It was shown that the layer-by-layer growth was self-limited at temperatures above 180°C. The data of ex situ measurements revealed that the structure, density and optical properties of the films depended on the growth temperature. The absorption coefficient of amorphous films grown at 225°C was below 40 mm−1 in the spectral range of 260–850 nm. The refractive index of the films grown at 225°C was 2.2 and 2.0 at 260 and 580 nm, respectively. The polycrystalline films with monoclinic structure grown at 500°C had about 5% higher refractive index but more than an order of magnitude higher optical losses caused by light absorption and/or scattering.

Growth mechanism of microcrystalline silicon obtained from reactive plasmas

Abstract: Three models proposed for the growth mechanism of hydrogenated microcrystalline silicon films (μc-Si:H) from reactive (silane and hydrogen mixture) plasmas are reviewed. The `etching model' is discussed using experimentally obtained relationship between radical generation rate in plasmas and growth rate of films. The `chemical annealing model' is investigated through the growth of films using a layer-by-layer method with and without cathode shutter. Substrate-temperature dependence of crystallinity of the resulting films and initial growth behavior of silicon films on atomically flat GaAs substrate clearly support the ‘surface diffusion model’.

SiC MEMS: Opportunities and challenges for applications in harsh environments

Abstract: Many measurement and control applications requiring MEMS technology are in the presence of harsh environments, e.g. high temperatures, intense shock/vibrations, erosive flows, and corrosive media. Unlike Si, SiC as a semiconductor material is exceptionally well suited for addressing such application opportunities. However, many challenges must be met in order to develop a mature SiC MEMS fabrication technology. These challenges are primarily technical in nature and relate to material and processing aspects. This paper presents a review of recent advancements in areas that are critical to the establishment of a SiC MEMS technology.

Low-temperature synthesis of anatase thin films on glass and organic substrates by direct deposition from aqueous solutions

Abstract: Crystalline titania thin films were obtained on glass and various kinds of organic substrates at 40–70°C by deposition from aqueous solutions of titanium tetrafluoride. Transparent films consisting of small anatase particles (∼20 nm) exhibited excellent adhesion to relatively hydrophilic surfaces. Uniform coatings were successfully prepared on substrates with complex shapes such as cotton and felt fiber. Growth rate and particle size were controlled by both the deposition conditions and the addition of an organic surfactant. Organic dyes were incorporated into the anatase films using organic-dye dissolving solutions and a surfactant. The photo-catalytic property of the titania films deposited in the precursor solutions at relatively low temperatures was identified as that of thermally crystallized anatase.

Optical, electrical and structural properties of sol gel ZnO:Al coatings

Abstract: Single and multilayer transparent conducting aluminium doped zinc oxide films have been prepared on DESAG AF45 substrates by the sol gel dip coating process. Zinc acetate solutions of 0.1–0.5 M in isopropanol stabilised by diethanolamine and doped with a concentrated solution of aluminium nitrate in ethanol were used. Each layer was fired at 600°C in a conventional furnace for 15 min. The final coatings were then tempered under a flux of forming gas (N2/H2) at 400°C for 2 h. The coatings have been characterised by surface stylus profiling, optical spectroscopy (UV-NIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and combined Hall and van der Pauw techniques. Single layers with thickness, d, ranging from 25 to 186 nm are polycrystalline with the zincite structure and exhibit a small preferential orientation with the (002) direction perpendicular to the surface (texture coefficient, TC, ranging from 1.8 to 2.8). They consist of almost spherical particles with size ranging from 15 to 25 nm (thin sample) to 40 nm (thick sample) with crystallite sizes ranging from 23 to 40 nm (002), respectively. The film resistivity decreases from 5×10−1 Ω cm (d=25 nm) to 4×10−2 Ω cm (d=186 nm). Multilayer coatings built with about 20 nm thick layers are also slightly textured along the (002) direction (TC ranging from 1.9 to 2.8). A structural evolution in morphology from spherical to columnar growth was observed. The crystallite size calculated from the (002) reflex increases with the number of layers from 23 nm for a single layer to over 100 nm for ten layers. The resistivity decreases from 5×10−1 Ω cm for a single layer to 5×10−3 Ω cm for ten layers (d=174 nm). A model for the growth of the crystallites in sol gel multilayer coatings is presented.

Dependence of the sheet resistance of indium-tin-oxide thin films on grain size and grain orientation determined from X-ray diffraction techniques

Abstract: ITO thin films (100–200 nm) are deposited on glass and plastic (PET and polycarbonate) substrates by r.f. sputtering. Process parameters such as oxygen partial pressure, r.f. power, and post deposition annealing parameters are varied to determine the dependence of the sheet resistance on process parameters. The microstructure of these thin films is determined using an X-ray diffractometer (XRD) and a transmission electron microscope (TEM). The experimentally observed dependence of the sheet resistance on the grain size and grain orientation of these films is correlated to the dependence of the electron mobility on grain boundary scattering. Larger grain sizes (≈25 nm) in ITO films result in lower sheet resistance (250 Ω/□). This type of large grain size microstructure is produced with moderate r.f. power (≈100 W) and low oxygen partial pressure (≈10%). There is a unique correspondence between grain size and grain orientation. ITO films with a strong peak intensity ratio of (400) orientation to all other orientations (≈0.35) have the largest grain size (≈25 nm) resulting in the lowest sheet resistance (250 Ω/□) and high transmission (≈86.7%) at λ=550 nm .

Surface OH group governing adsorption properties of metal oxide films

Abstract: Time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy and contact angle measurements were applied to investigate the relationship between the adsorption of organic substances from the atmosphere and the surface OH group density of metal oxide films deposited onto glass by r.f. reactive magnetron sputtering. The amount of adsorbed carbon substances on the films is dependent on the surface OH group density of the films. This fact indicates that the surface OH group density is a major factor governing the adsorption of organic substances from the atmosphere on the films. It is also found that the surface OH group density is dependent on the film materials. This dependence is explained with respect to the electronegativity of the metal element directly bound to oxygen atoms.

Phase transition and properties of Ti Al N thin films prepared by r.f.-plasma assisted magnetron sputtering

Abstract: Pseudobinary (Ti1−xAlx)N films were synthesized by a new inductively combined rf-plasma assisted planar magnetron sputtering method From X-ray diffraction measurement, the deposited (Ti1−xAlx)N films were identified as having the B1 structure up to 50 mol% Al (x=05) In the range from x=06 to x=07, two phases with the B1 and B4 structures were observed These results suggest that the critical composition for the phase change from B1 to B4 structure is located between 50 mol% Al and 60 mol% Al The critical composition decided experimentally shows a discrepancy with the theoretically predicted value (65 mol% Al), which may arise from a somewhat high substrate temperature (450°C) in this study Oxidation resistance increases with increasing the Al content in the (Ti1−xAlx)N films up to 70 mol% Al, irrespective of coexistence of the B1 and B4 phases in the (Ti1−xAlx)N films with x=06 and x=07, while both the hardness and Young's modulus show a maximum value, respectively Thus, it is indicated that the existence of the (Ti1−xAlx)N films with the B1 structure is quite effective for improving the oxidation resistance, and the appearance of the B4 phase in the pseudobinary nitride films degrades mechanical properties such as the hardness and Young's modulus

Structural and optical properties of sputtered ZnO films

Abstract: ZnO thin films were deposited by r.f. magnetron sputtering from zinc oxide target. The composition (O/Zn atomic ratio) determined by Rutherford backscattering spectrometry depends narrowly on the sputtering parameters. The O/Zn atomic ratio is found to increase with the oxygen partial and the total pressures; however substoichiometric films were obtained at low pressures and high sputtering powers in the non-reactive deposition process. X-ray diffraction measurements show that all the films are crystallized in the wurtzite form and present a preferred orientation along the [002] direction. The crystallinity is found to increase with the kinetic energy of the sputtered particles. The films contain compressive stresses originating mainly from the contribution of the intrinsic component. A post deposition heat treatment is essential to produce relaxation of the stresses. Scanning electron micrographs show that the ZnO deposits have a columnar structure: the compactness of the films is dependent on the sputtering conditions. The EXAFS measurements show that Zn atoms have a tetrahedral environment with a zinc–oxygen distance of 1.95 A. Infrared investigations confirm these findings and show that zinc atoms stay tetrahedrally coordinated even though the O/Zn atomic ratio changes from 0.95 to 1.06. The optical constants (refractive index and absorption coefficient) vary also in a wide range. Their variations were related to the composition and structure evolution.

ITO/Ag/ITO multilayer films for the application of a very low resistance transparent electrode

Abstract: Multilayer transparent electrodes, having a much lower electrical resistance than the widely used transparent conducting oxide electrodes, were prepared by using magnetron sputtering. The multilayer structure consisted of three layers, tin-doped indium oxide (ITO)/Ag/ITO. Because only Ag deposits with a thickness larger than 14 nm form a continuous film, the optimum thickness of Ag thin films was determined to be 14 nm for high optical transmittance and good electrical conductivity. With about 55–60 nm thick ITO films, the multilayer showed a high optical transmittance in the visible range of the spectrum and had color neutrality. The electrical and optical properties of the ITO/Ag/ITO multilayer were changed mainly by Ag film properties, which were affected by the deposition process of the upper layer. A high quality transparent electrode, having a resistance as low as 4 Ω/□ and a high optical transmittance of 90% at 550 nm, was obtained and could be reproduced by controlling the preparation process parameters properly. It could satisfy the requirement for the SVGA mode STN-LCD.

Electrical and optical properties of diamond-like carbon

Abstract: Diamond-like carbon (DLC) films, amorphous hydrogenated or nonhydrogenated forms of carbon, are metastable amorphous materials characterized by a range of attractive mechanical, chemical, tribological, as well as optical and electrical properties. The films can be prepared at low temperatures, from a large variety of precursors, by a diversity of techniques, and their characteristics can be modified by incorporation of different elements such as N, F, Si, or metals. The diversity of methods used for the deposition of DLC films provides the flexibility to tailor their properties according to specific needs and potential applications. The optical gap of these materials is in the range of 1–4 eV and the electrical resistivity spans 14 orders of magnitude. The dielectric constant of DLC films covers the range of 2.5–6. The talk will review the optical and electrical characteristics of DLC and discuss the actual and potential applications based on these properties.

Subwavelength-structured antireflective surfaces on glass

Abstract: The usability of porous sol–gel coatings and periodic or stochastic subwavelength surface-relief structures for low-cost broadband antireflective (AR) surfaces on glass and on plastics was studied experimentally. Porous sol–gel coatings were produced by dip-coating on glass. Large-area periodic subwavelength surface-relief master structures were manufactured by holographic exposure of photoresist and transferred into nickel by electroforming. Stochastic surface-relief master structures were produced by a PVD process. The surface-relief structures were replicated in organically modified sol–gel materials on glass and in acrylic materials by embossing. With porous sol–gel coatings and periodic subwavelength surface-relief master structures, hemispherical reflectance values of

Growth of organic thin films by the matrix assisted pulsed laser evaporation (MAPLE) technique

Abstract: A novel variation of conventional pulsed laser evaporation, known as matrix assisted pulsed laser evaporation, or MAPLE, has been successfully used to deposit highly uniform thin films of a variety of organic materials including a number of polymers. The MAPLE technique is carried out in a vacuum chamber and involves directing a pulsed laser beam (λ=193 or 248 nm; fluence=0.01 to 0.5 J/cm2) onto a frozen target (100–200 K) consisting of a solute polymeric or organic compound dissolved in a solvent matrix. The laser beam evaporates the surface layers of the target, with both solvent and solute molecules being released into the chamber. The volatile solvent is pumped away, whereas the polymer/organic molecules coat the substrate. Thin uniform films ( nm) of various materials, such as functionalized polysiloxanes and carbohydrates, have been deposited on Si(111) and NaCl substrates. The films prepared using this method have been examined by optical microscopy, scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy and electrospray mass spectrometry. Careful control of the processing conditions allowed the complex polymer/organic molecules to be transferred to the substrate as uniform films without any significant chemical modification. Using MAPLE, large or small regions within a substrate can be discretely coated with submonolayer thickness control. The use of MAPLE films for chemical sensor applications has been investigated and the potential of this technique for producing high quality thin films of other organic compounds will be discussed.

Wet chemical deposition of ATO and ITO coatings using crystalline nanoparticles redispersable in solutions

Abstract: The deposition of SnO2:Sb (ATO) and In2O3:Sn (ITO) transparent conducting coatings on glass substrate has been demonstrated by many techniques such as CVD, sputtering, vacuum deposition and sol-gel process. This paper presents an alternative process for the deposition of such coatings at room temperature by spin, dip and spray coating techniques using solutions prepared with crystalline nanoparticles fully redispersed in water (for ATO, ITO) or alcohol (for ITO) with solid contents up to 10‐15 Vol.%, respectively. The deposited green coatings have been sintered at temperature as high as 9008C. In2O3:Sn coatings have a resistivity of 1.5 £ 10 22 V cm as sintered and 3.4 £ 10 23 V cm after annealing in nitrogen atmosphere. The resistivity of ATO single coatings shows a minimum ra 1:7 £ 10 22 V cm after annealing at 5508C. SnO2:Sb coatings present long term stability but the resistivity of annealed ITO coatings steadily increases with time to a value three times higher. All coatings have a high optical quality with transmission in the visible range larger than 90%. q 1999 Elsevier Science S.A. All rights reserved.

W- and F-doped VO2 films studied by photoelectron spectrometry

Abstract: Thermochromic tungsten- and fluorine-doped vanadium dioxide films, which are in discussion as intelligent window coatings, were deposited by reactive sputtering. Results of optical measurements and photoelectron spectrometry (XPS, UPS) at low doping levels (≤2.6%) are presented, and together with structural properties they can be well correlated. By applying antireflective coatings the transmittance of films in the visible spectral range may be enhanced to more than 60% with fairly good switching characteristics at room temperature in the case of tungsten doping.

Optical and electronic properties of transparent conducting ZnO and ZnO:Al films prepared by evaporating method

Abstract: Undoped and Aluminium-doped Zinc oxide films have been prepared by thermal evaporation of zinc acetate (Zn(CH3COO)2·2H2O] and aluminium chloride (AlCl3) onto a heated glass substrate. The structural, optical and electrical properties of the films have been studied. The effects of heat treatment for the as-deposited films in air and vacuum are investigated. Over 80% transmittance films with conductivity as low as 2×10 −3 Ω cm can be produced by controlling the deposition parameters. The electron carrier densities are in the range 0.2–7×10 19 cm−3 with mobilities of 22–58 cm2/Vs.

Transparent conductive ITO thin films through the sol-gel process using metal salts

Abstract: The electrical and optical properties, structure and morphology of ITO thin films were investigated. Ten percent by weight Sn-doped indium oxide (ITO) films were prepared on soda-lime-silicate glass substrate by the sol-gel spin coating method using inorganic metal salts. All layers studied with a thickness range of 50–350 nm were polycrystalline with grain sizes in the range 20–30 nm depending on the annealing conditions. SnO or SnO 2 phase was not detected in terms of XRD, TEM analysis techniques and the resultant phase was only In 2 O 3 cubic bixbyite. The sheet resistance of 250 nm thin films annealed at 400°C was 6.18×10 3 Ω/□ in air, 1.09×10 3 Ω/□ in nitrogen, 15.21×10 3 Ω/□ in oxygen, respectively. Four-hundred degree centigrade-annealed 150 nm films showed more than 85% of the average visible transmittance, regardless of annealing atmospheres. According to AFM analysis RMS roughness was 18 A for a 50 nm film and 25 A for a 350 nm film, respectively. XPS results revealed that Sn was incorporated into In 2 O 3 structure substitutionally.

Performances presented by zinc oxide thin films deposited by spray pyrolysis

Abstract: The effect of doping and annealing atmosphere on the performances of zinc oxide thin films prepared by spray pyrolysis have been studied. The results show that the way doping influences the electrical and structural properties depends also on the characteristics of the doping element. Annealing the as-deposited films in an inert atmosphere leads to a substantial reduction in the resistivity of the films deposited and to an increase on the degree of film’s crystallinity.

Chemical bath deposition of indium sulphide thin films: preparation and characterization

Abstract: Indium sulphide (In2S3) thin films have been successfully deposited on different substrates under varying deposition conditions using chemical bath deposition technique. The deposition mechanism of In2S3 thin films from thioacetamide deposition bath has been proposed. Films have been characterized with respect to their crystalline structure, composition, optical and electrical properties by means of X-ray diffraction, TEM, EDAX, optical absorption, TRMC (time resolved microwave conductivity) and RBS. Films on glass substrates were amorphous and on FTO (flourine doped tin oxide coated) glass substrates were polycrystalline (∈ phase). The optical band gap of In2S3 thin film was estimated to be 2.75 eV. The as-deposited films were photoactive as evidenced by TRMC studies. The presence of oxygen in the film was detected by RBS analysis.

Tribological performance and tribochemistry of nanocrystalline WC/amorphous diamond-like carbon composites

Abstract: The tribological performance and tribochemistry of vacuum deposited nanocrystalline WC/amorphous diamond-like carbon (DLC) composite coatings were investigated. Coating chemistry was varied by regulation of carbon content between 30 and 90 at.%. Deposition temperature was used to adjust the degree of β-WC crystallinity from near amorphous with 1–3 nm sized grains to nanocrystalline with 5–10 nm sized grains, which were embedded in unhydrogenated DLC matrix. The microstructure critically influenced both the hardness and tribological properties of WC/DLC composites. Coatings with poorly crystallized WC were softer (15 GPa) and exhibited lower friction and higher wear rates in comparison to harder (26 GPa) composites with larger WC nanocrystals. The hardness of WC/DLC composites was at least twice as high as the hardness of metal doped DLC coatings reported in the literature. Micro Raman and X-ray photoelectron analysis was performed on transfer films formed on the surface of steel balls in sliding against WC/DLC composites in humid air and dry nitrogen, which found both oxides and graphite carbon, providing self-lubrication. The high hardness and self-lubricating properties of WC composites resulted in low wear rates and friction coefficients of about 0.2. Relationships among coating chemistry, structure, hardness, friction, wear rates, as well as, tribofilm composition and structure are discussed.

Transparent and conductive aluminum doped zinc oxide films prepared by mid-frequency reactive magnetron sputtering

Abstract: In this study, aluminum doped zinc oxide films were prepared by reactive mid-frequency (MF) magnetron sputtering (Leybold TwinMagTM) at deposition rate of approx. 9 nm/s and substrate temperature of 100 to 300°C. Process stabilization in the metallic mode was performed by the control of plasma impedance due to adjustment of oxygen flow. Metallic Zn:Al targets with different aluminum content were used. ZnO:Al films prepared by this technique exhibit resistivity of 3.0×10−4 Ω cm at 200°C substrate temperature and 4.8×10−4 Ω cm at 100°C, respectively, for films of approx. 500 nm thickness. The optical, electrical and structural properties of these films were investigated by means of optical spectroscopy (UV-VIS-NIR), X-ray diffraction, atomic force microscopy, Hall mobility and conductivity measurements. Electron probe micro analysis and secondary ion mass spectroscopy were used for chemical characterization.

Self-shadowing and surface diffusion effects in obliquely deposited thin films

Abstract: The production of highly porous films by oblique deposition has attracted recent attention because of the possible applications of such films. The morphology of obliquely evaporated films is thought to be determined mainly by the mechanisms of self-shadowing and surface diffusion. The thin film process simulator GROFILMS has been used to verify the importance of these effects, and clarify some aspects of how they interact to determine the final film morphology. Good agreement between simulations and actual films has been achieved. Temperature control of the film during deposition is shown to be an important consideration for the production of structurally engineered films.

Applicability of Raman scattering for the characterization of nanocrystalline silicon

Abstract: It is shown that Raman scattering alone cannot provide unambiguous information regarding the crystallite size, its distribution and crystalline fraction in nc-/a-Si films unless additional data regarding the structure of the films are obtained by other techniques.

UV curable hard coatings on plastics

Abstract: A photochemically curable transparent hard coating material has been developed to improve the wear resistance of organic polymers. Methacrylate functionalized silanes and nanoscaled boehmite particles were used for the preparation of the UV curable hard coatings by the sol–gel technique. The inorganic network is formed as a result of the controlled hydrolysis and condensation of the methacryloxysilanes in the presence of nanoparticles (particle size: 15 nm). The hydrolysis and condensation of the methacryloxy silane, for two hours in presence of boehmite nanoparticles (43 wt.%), at 100°C leads to a degree of condensation of 80% of the inorganic network, as determined by 29Si-NMR spectroscopy. The organic network is formed by photoinitiated polymerisation of the methacrylic-functions in only a few minutes, using UV light from a Hg high pressure lamp. Transparent coatings on plastic substrates (PC, PMMA) were produced by spray coating with good optical quality and thicknesses of several micrometers. The transparent coatings show excellent adhesion on PMMA and PC (GT/TT=0/0, DIN 53151), even without using primers, and also good abrasion resistance after the Taber abraser test with haze values of 10% after 1000 cycles (CS 10F rolls, 5,4 N, DIN 52347). The water exposition test (65°C, deionized water) and the Suntest, without using filters, did not result in any crack formation, loss of adhesion or yellowing within the test period of two weeks.

Comparison of spray pyrolyzed FTO, ATO and ITO coatings for flat and bent glass substrates

Abstract: Transparent conductive FTO, ATO and ITO films were synthesized by spray pyrolysis technique on flat 12×12 cm borosilicate glass substrates at 500–550°C and investigated with respect to their electrical and optical properties. The resistivity of sprayed ITO films decreases with the thickness down to 3.0×10−4 Ω cm (300 nm). The optical transmission in the visible range is 80% and the near IR reflection up to 96% for thicknesses larger than 300 nm. A reducing treatment at 400°C in forming gas still decreases the resistivity by a factor of two. Bending of the coated glasses in air at 650°C for 1.5 h increases the resistivity of the coatings on the tensile side of the substrate by a factor of 3–4 and by a factor 2 on the compressed side. A subsequent reducing treatment in forming gas at 400°C leads to a drastic decrease of resistivity in both cases by a factor of 5–7 with resulting value ρ=2–3×10−4 Ω cm. ATO layers have lower visible transmission (70–75%) due to stronger absorption and a higher resistivity (ρ=1×10−3 Ω cm). Spray pyrolyzed FTO coatings have a resistivity ρ=5×10−3 Ω cm for film thicknesses >350 nm.

Phase separation on solid surfaces: nucleation, coarsening and coalescence kinetics

Abstract: Fundamental issues of the kinetics of phase separations on surfaces are reviewed with an emphasis on developments during the period from 1990 to present. Issues covered include: (i) the stability of thin films toward clustering, (ii) non-uniform film formation during deposition and (iii) non-uniform film evolution in the post-deposition phase.