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The aim of this paper is the replacing of the expensive sputtering method with the low cost sol-gel one in TCO applications. To this end two sets of indium tin oxide (ITO) thin films are compared and discussed in this paper: one obtained by r.f. sputtering and one by the sol-gel technique and dip-coating. For each of these sets of samples, a series of deposition parameters have been varied in an effort to obtain the most promising optical and electrical properties. Comparative structural, morphological and opto-electrical characterization of sol-gel and sputtered ITO-based films was performed by X-ray diffraction, Scanning electron microscopy, Atomic force microscopy, Spectroellipsometry, UV-VIS Spectroscopy and Hall Effect measurements in order to establish whether the chemical deposition method could lead to thin films with competitive properties as those obtained through the physical method. Comparable, high transmittance (85-90 %) in the VIS-NIR range (250-1050 nm) and carrier concentration values (10-10 cm) were obtained between sputtered and sol-gel ITO films. The sputtered ITO film in 75 % N, annealed at 500 °C and the sol-gel 0.1 M ITO film with 10 layers deposited on SiO/glass exhibit degenerate semiconductor behavior. [ABSTRACT FROM AUTHOR]

Abstract: N-doping is often used to improve the photocatalytic properties of TiO2 films in order to achieve visible light response. In this work, we study the effect of annealing treatment (temperature and atmosphere) on the structural and optical properties of undoped and N-doped TiO2 films by means of X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Rutherford backscattering (RBS), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE) and UV–VIS optical transmission spectroscopy. Porous five-layer TiO2 films were deposited by sol–gel method on quartz substrate and thermally treated in oxygen or NH3 flow at 500 and 600 °C. Significant doping effect was achieved after annealing at 600 °C in NH3 and a shift in optical bandgap value down to visible range (2.69 eV) was observed. [Copyright &y& Elsevier]

The article presents a study on nanostructured TiO2(Fe) thin films prepared by sol-gel and dipping method on SiO2/glass substrate in the depollution of contaminated water against Escherichia coli using methods such as X-ray diffraction, spectroscopic ellipsometry, and atomic force microscopy. It cites the effect of iron and polyethylene glycol (PEG) on the porosity, amorphous to anaphase transition, and on the antibacterial activity of TiO2. The correlation of the inhibitory effect towards the E. coli with PEG is shown.

The article presents a study which explored the usefulness of thin films in microelectronics, sensing, nano-photonics, optoelectronics and as ionic conductors. In order to secure a precursor for obtaining layers, a systematic study of the sol-gel film preparation using various phosphorous predecessors was undertaken. The test result showed that only in the films obtained with H3PO4 and P could be detected after thermal treatment. This is explained, according to the author, by the fact that the phosphorous easily evaporated.

Abstract: A comparative study of the sol–gel films prepared in the SiO2–P2O5 system starting with triethylphosphate, triethylphosphite and phosphoric acid as P precursors was performed. The work addresses basic aspects of physics, chemistry, and engineering of oxide films for applications in microelectronics, sensing, nano-photonics, and optoelectronics by establishing the influence of different precursors on the composition, structure and optical properties of the obtained films. The influence of the type of substrate (glass and indium tin oxide coated glass) and of the thermal treatment (200 and 500 °C) on their structure and properties was studied. By spectroscopic ellipsometry, X-Ray photoemission spectroscopy and atomic force microscopy measurements the high vaporization of the phosphorous during the densification of the films by thermal treatment was noticed when P-alkoxides were used. The phosphoric acid that forms chemical bond with silica network during the sol–gel process leads to better incorporation of P in the silica network as compared to the P-alkoxides. [Copyright &y& Elsevier]

Abstract: BaTiO3 thin films were deposited on Pt/Ti/SiO2/Si by rf planar-magnetron sputtering. The films thickness increases with the decrease of both deposition pressure and sample-discharge centre distance. The films annealed at 900°C, for 8h, present direct band gap energy ranged between 3.57 and 3.59eV. The dependence of the structure and microstructure (texture, degree of crystallinity), as well as of the optical characteristics on the deposition parameters, was analysed. Using spectroscopic ellipsometry (SE) measurements coupled with the Bruggeman Effective Medium Approximation (B-EMA), the layer structure and the surface roughness, were determined. The root mean square roughness values of the surface layer, estimated by atomic force microscopy (AFM) analyses, are ranged between 10 and 20nm and were in good agreement with SE data. The obtained films have tetragonal unit cell and show densely packed, non-columnar morphology and hexagon-like crystallite shape. [Copyright &y& Elsevier]

Tin-doped indium oxide (ITO) thin films have been deposited by sol–gel process using ‘sols’ of indium and tin isopropoxides. The thickness of one deposited ITO layer is approximately 50 nm. The desired thickness was obtained by 1–5 successive depositions. The XTEM cross-sectional view of an ITO sample with five depositions showed a clear delimitation of the layers with an alternating structure dense/porous ITO layers. The void fraction in porous regions varies between 20 and 25%. Cubic bixbyite In2O3 nanocrystals with size of 10–20 nm and no phases separation of tin oxide were observed. The optical properties of the films have been investigated by optical transmission and spectroscopic ellipsometry. Reliable optical constants and porosity are obtained only with the model of internal structure based on XTEM results. [Copyright &y& Elsevier]

TiO2 based nanustructured coatings have been prepared by sol–gel method on glass and SiO2/glass substrates. The films were thermally treated in oxidative and reductive conditions at 500 °C. The influence of the substrate and of the thermal treatment on the optical properties of the films was studied. The samples were characterized by spectroscopic ellipsometry (SE), scanning electron microscopy (SEM), Rutherford backscattering spectroscopy (RBS) and Raman spectroscopy. SE results supported by other optical and structural measurements have proven the transformation of CuO from as-prepared samples into Cu2O in samples heated in oxidative conditions and into metallic Cu in samples heated in reductive conditions as well as the transformation of the amorphous TiO2 in anatase. [Copyright &y& Elsevier]

In this paper we study the changes in the microstructural and optical properties of silicon thin films produced by the variation of the parameters (temperature and pressure) of the low-pressure chemical vapour deposition (LPCVD) process. Silicon thin films prepared by LPCVD on oxidized silicon substrates over a large range of process parameters (Tdep=500–615°C, pdep=20–100 Pa) have been characterized by Raman spectroscopy, spectroscopic ellipsometry (SE), X-ray diffraction (XRD) and atomic force microscopy (AFM) techniques. The phase transition of as-deposited silicon from an amorphous to a crystalline phase via an intermediate mixed phase (few grains in amorphous silicon matrix) can be monitored by the changes in the optical properties and in the Raman spectra. LPCVD parameters, which control the deposition kinetics, are able to influence the optical properties, the structure and/or morphology of the as-deposited LPCVD silicon films. The SE and Raman results prove that it is possible to grow by LPCVD (from pure silane), a silicon film in a (poly)crystalline state at a temperature as low as 500°C. [Copyright &y& Elsevier]

Structures containing silicon nanocrystals (nc-Si) are very promising for Si-based light-emitting devices. Using a technology compatible with that of silicon, a broader wavelength range of the emitted photoluminescence (PL) was obtained with nc-Si/SiO2 multilayer structures. The main characteristic of these structures is that both layers are light emitters. In this study we report results on a series of nc-Si/SiO2 multilayer periods deposited on 200 nm thermal oxide SiO2/Si substrate. Each period contains around 10 nm silicon thin films obtained by low-pressure chemical vapour deposition at T=625°C and 100 nm SiO2 obtained by atmospheric pressure chemical vapour deposition T=400°C. Optical and microstructural properties of the multilayer structures have been studied by spectroscopic ellipsometry (using the Bruggemann effective medium approximation model for multilayer and multicomponent films), FTIR and UV–visible reflectance spectroscopy. IR spectroscopy revealed the presence of SiOx structural entities in each nc-Si/SiO2 interface. Investigation of the PL spectra (using continuous wave-CW 325 nm and pulsed 266 nm laser excitation) has shown several peaks at 1.7, 2, 2.3, 2.7, 3.2 and 3.7 eV, associated with the PL centres in SiO2, nc-Si and Si–SiO2 interface. Their contribution to the PL spectra depends on the number of layers in the stack. [Copyright &y& Elsevier]

Abstract: High spectral (1.5 cm−1) and spatial (~1000 nm lateral and vertical) resolution Raman spectra taken at room temperature in the depth of a thin (350 nm) YBCO film with good superconducting properties are presented and discussed. The differences between Raman spectra corresponding to different depths in the film are interpreted as depth-dependant changes in the film''s structure, degree of oxygenation, and superconducting properties. These changes are in agreement to what we expect from a film obtained by pulsed laser deposition technique. The resonance of the most significant Raman shift (500 cm− 1), monitoring the oxygen content of YBCO films, for 488 nm excitation light, was used to overcome the relatively small penetration depth of visible light in YBCO (~200 nm). We found the range of parameters for the depth profiling Raman system such as to obtain the maximum signal intensity and a reasonable number of distinctive Raman spectra corresponding to different depths of the YBCO film. [Copyright &y& Elsevier]

Abstract: This work describes the preparation of HfO2 thin films by the sol–gel method, starting with different precursors such as hafnium ethoxide, hafnium 2,4-pentadionate and hafnium chloride. From the solution prepared as mentioned above, thin films on silicon wafer substrates have been realized by ‘dip-coating’ with a pulling out speed of 5cmmin−1. The films densification was achieved by thermal treatment for 10min at 100°C and 30min at 450°C or 600°C, with a heating rate of 1°Cmin−1. The structural and optical properties of the films are determined employing spectroellipsometric (SE) measurements in the visible range (0.4–0.7μm), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The main objective of this paper was to establish a correlation between the method of preparation (precursor, annealing temperature) and the properties of the obtained films. The samples prepared from pentadionate and ethoxide precursors are homogenous and uniform in thickness. The samples prepared starting from chloride precursor are thicker and proved to be less uniform in thickness. Higher non-uniformity develops in multi-deposition films or in crystallized films. A nano-porosity is present in the quasi-amorphous films as well in the crystallized one. For the samples deposited on silicon wafer, the thermal treatment induced the formation of a SiO2 layer at the coating–substrate interface. [Copyright &y& Elsevier]

Abstract: We report spectroscopic characterization of epitaxial YBCO thin films grown on LaAlO3 by pulsed laser deposition. Raman spectroscopy and spectroscopic ellipsometry were used for film characterization and the results were correlated with X-ray diffraction measurements. The mentioned techniques allowed us to analyze crystallographic, micro-structural, and morphological properties of YBCO thin films. We also demonstrated that relatively low resolution Raman spectroscopy and spectroscopic ellipsometry are reliable techniques for a rapid and non-destructive characterization of epitaxial YBCO thin films. [Copyright &y& Elsevier]

Quasi-amorphous titanium oxynitride (TiON) films were obtained by annealing sol–gel anatase TiO 2 films in NH 3 atmosphere at 600 °C. These films were irradiated with 50 laser pulses using the fourth harmonic (266 nm) radiation of the Nd-YAG laser, with an average fluence of 20 mJ/cm 2 . HRTEM observations of the pulsed laser irradiated films evidenced the rutile TiO 2 nanocrystallites formation. The rutile structure was not present either in the TiON films before the laser irradiation, or in the initial sol–gel anatase TiO 2 films. During the laser irradiation, the film structure remains in the solid state phase, as it results from the temperature estimation and microscopic observations. For the rutile nanocrystals formation, the atomic diffusion length of the oxygen and titanium atoms should be in the nanometric range during the laser pulse action, which implies a diffusivity close to the values observed in the liquid phase. We consider that the rutile phase formation is a proof of the fast atomic diffusion in the solid amorphous matrix, during the laser irradiation. [ABSTRACT FROM AUTHOR]

The transparent conductive oxide films with controlled type of conduction are of great importance and their preparation is intensively studied. In our work, the preparation of such films based on doped ZnO was realized in order to achieve controlled type of conduction and high concentration of the charge carriers. Sol–gel method was used for films preparation and several dopants were tested (Sn, Li, Ni). Multilayer deposition was performed on several substrates: SiO 2 /Si wafers, silica-soda-lime and/or silica glasses. The structural and morphological characterization of the obtained films were done by scanning electron microscopy, X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy and atomic force microscopy respectively, while spectroscopic ellipsometry and transmittance measurements were done for determination of optical properties. The selected samples with the best structural, morphological and optical properties were subjected to electrical measurement (Hall and Seebeck effect). In all studied cases, samples with good adherence and homogeneous morphology as well as monophasic wurtzite type structure were obtained. The optical constants (refractive index and extinction coefficient) were calculated from spectroscopic ellipsometry data using Cauchy model. Films with n- or p-type conduction were obtained depending on the composition, number of deposition and thermal treatment temperature. [ABSTRACT FROM AUTHOR]

Abstract: Hydroxyapatite (HA) biocoatings were obtained using two different deposition methods: sol–gel and sputtering. A direct comparison of films obtained using different techniques is necessary because of possible formation of multi-phases and components in HA films. HA films were investigated using spectroscopic ellipsometry (SE) as a powerful method to evaluate composition and structural properties of the films. For both types of films, sputtering and sol–gel, a weak dispersion of the refractive index within the wavelength range 0.4–0.7 µm was found. This corresponds to a high energy bandgap and a high optical transparency in the UV–VIS range. The internal porosity varying in a wide range in the sol–gel films was evaluated using a modeling of SE data. Additionally to SE studies, structural, chemical and optical characterizations of the films were performed using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Two absorption bands observed in the wavelength ranges 550–600 cm− 1 and 1000–1200 cm− 1 can be attributed to the major absorption modes associated with HA in agreement with published data. From XPS analysis, the atom ratio Ca/P was found for sol–gel films close to the stoichiometric value 1.67. For sputtering films, a higher Ca/P ratio of about 2.1 was estimated. However, similar FTIR spectra have been recorded for both sputtering and sol–gel films. XRD studies show also similar crystallization conditions by annealing at temperatures higher than 500 °C. [Copyright &y& Elsevier]

Abstract: One of the most interesting category of multifunctional systems is the magnetoelectrics (ME), i.e., materials having simultaneous magnetic and ferroelectric activity. The present paper describes a simple low-temperature synthesis method of preparing bismuth ferrite thin films by a wet chemical route, using bismuth and iron nitrates and two chelating agents (citric acid and polyvinyl alcohol). The films were layer by layer deposited on substrate (silica glass) using the dip-coating technique. The thickness of the layers were controlled by viscosity of the solutions and withdrawing speed parameters. After specific annealing, in air, the samples were characterized by scanning electron microscopy SEM, spectroelipsometry SE, X-ray photoelectron spectroscopy XPS, Raman spectroscopy. A more thoroughly control of the processing parameters seems to be essential in obtaining BiFeO3 thin films. Solution chemistry variations (differences in precursor type) can have a significant impact on the film properties. [Copyright &y& Elsevier]

The alkoxidic route and the spinning deposition were used to prepare monolayer sol–gel indium tin oxide (ITO) films. The morphology and crystalline structure were investigated by cross-section transmission electron microscopy (XTEM) and atomic force microscopy (AFM). The ITO sol–gel mono-layer contains three regions of different porosities. The basic crystalline structure is that of the In2O3 lattice. The optical properties have been studied by optical transmission and spectroscopic ellipsometry. [Copyright &y& Elsevier]

AlN thin films were grown at 200–450 °C on Si substrates by laser ablation of Al targets in nitrogen-reactive atmosphere using a robust and simple experimental set-up based on a Nd–YAG laser. Infrared spectroscopy results indicate the presence of two broad peaks around 679 and 644 cm−1, typical of AlN compound. Spectroellipsometric spectra were recorded in the range 400–700 nm: the refractive index values were found to be close to those previously reported (less than 9% variation). The cross-plane thermal conductivity of an AlN film was measured in the 80–380 K temperature range by the 3ω method. The values are strongly reduced compared to those of the bulk and the temperature dependence behaviour is glass-like. [Copyright &y& Elsevier]