Atmospheric Pressure Chemical Vapour Deposition of thin Films of Nb2O5 on Glass

A novel route involving atmospheric pressure chemical vapour deposition (APCVD) is reported for coating Nb2O5 onto glass substrates via the reaction of NbCl5 and ethyl acetate at 400-660degreesC. Raman spectroscopy is shown to be a simple diagnostic tool for the analysis of these thin films. The contact angle of water on Nb2O5-coated glass drops on UV irradiation from 60degrees to 5-20degrees. XPS Analysis showed that the Nb:O ratio of the film was 1:2.5. Glancing angle X-ray diffraction showed that all films were crystalline, with only a single phase being observed; this has some preferred orientation in the (201) plane of Nb2O5. The niobium(V) oxide materials show minimal photocatalytic ability to degrade organic material.

Atmospheric pressure chemical vapour deposition of titanium dioxide coatings on glass

Atmospheric pressure chemical vapour deposition of titanium dioxide coatings on glass substrates was achieved by the reaction of TiCl4 and a co-oxygen source (MeOH, EtOH, (PrOH)-Pr-i or H2O) at 500-650degreesC. The coatings show excellent uniformity, surface coverage and adherence. Growth rates were of the order of 0.3 mum min(-1) at 500degreesC. All films are crystalline and single phase with XRD showing the anatase TiO2 diffraction pattern; a = 3.78(1), c = 9.51(1) Angstrom. Optically, the films show minimal reflectivity from 300-1600 nm and 50-80% total transmission from 300-800 nm. Contact angles are in the range 20-40degrees for as-prepared films and 1-10degrees after 30 min irradiation at 254 nm. All of the films show significant photocatalyic activity as regards the destruction of an overlayer of stearic acid.

Atmospheric pressure chemical vapour deposition of boron doped titanium dioxide for photocatalytic water reduction and oxidation

Boron-doped titanium dioxide (B-TiO) films were deposited by atmospheric pressure chemical vapour deposition of titanium(iv) chloride, ethyl acetate and tri-isopropyl borate on steel and fluorine-doped-tin oxide substrates at 500, 550 and 600 °C, respectively. The films were characterised using powder X-ray diffraction (PXRD), which showed anatase phase TiO at lower deposition temperatures (500 and 550 °C) and rutile at higher deposition temperatures (600 °C). X-ray photoelectron spectroscopy (XPS) showed a dopant level of 0.9 at% B in an O-substitutional position. The ability of the films to reduce water was tested in a sacrificial system using 365 nm UV light with an irradiance of 2 mW cm. Hydrogen production rates of B-TiO at 24 μL cm h far exceeded undoped TiO at 2.6 μL cm h. The B-TiO samples were also shown to be active for water oxidation in a sacrificial solution. Photocurrent density tests also revealed that B-doped samples performed better, with an earlier onset of photocurrent. © 2013 The Owner Societies.

Dielectric properties of Ca(Zr0.05Ti0.95)O-3 thin films prepared by chemical solution deposition

Ca(Zr0.05Ti0.95)O-3 (CZT) thin films were grown on Pt(1 1 1)/Ti/SiO2/Si(1 0 0) substrates by the soft chemical method. The films were deposited from spin-coating technique and annealed at 928 K for 4 h under oxygen atmosphere. CZT films present orthorhombic structure with a crack free and granular microstructure. Atomic force microscopy and field-emission scanning electron microscopy showed that CZT present grains with about 47 nm and thickness about 450 nm. Dielectric constant and dielectric loss of the films was approximately 210 at 100 kHz and 0.032 at 1 MHz. The Au/CZT/Pt capacitor shows a hysteresis loop with remnant polarization of 2.5 mu C/cm(2), and coercive field of 18 kV/cm, at an applied voltage of 6 V. The leakage current density was about 4.6 x 10(-8) A/cm(2) at 3 V. Dielectric constant-voltage curve is located at zero bias field suggesting the absence of internal electric fields. (c) 2006 Elsevier B.V. All rights reserved.

SrBi2(Ta0.5Nb0.5)(2)O-9 : W thin films obtained by chemical solution deposition: Morphological and ferroelectric characteristics

The effect of tungsten (W6+) ion substituting on dielectric and ferroelectric behavior in SrBi2(Ta0.5Nb0.5)(2)O-9 (SBTN) thin films prepared by polymeric precursor method was investigated at room temperature. The addition of W6+ ion in the SBTN lattice was evaluated by X-ray diffraction (XRD), microstructural and dielectrical properties. An increase in the grain size is evident when tungsten is introduced in the SBTN lattice. Substitution of tungsten until 10% on B site leads to introduce space charge polarization into the system, resulting in an appreciable decrease in both dielectric constant and tangent loss. The morphology of the thin films investigated by atomic force microscopy leads to an increase in the grain size after tungsten addition. Fatigue resistance was noted with increase in tungsten addition. (C) 2007 Elsevier B.V. All rights reserved.

Photoluminescence at room temperature in amorphous SrTiO3 thin films obtained by chemical solution deposition

Intense photoluminescence in highly disordered strontium titanate amorphous thin films prepared by the polymeric precursor method was observed at room temperature (300 K). The luminescence spectra of SrTiO3 amorphous thin films at room temperature revealed an intense single-emission band in the visible region. X-ray absorption near edge structure was used to probe the local atomic structure of SrTiO3 amorphous and crystalline thin films. Photoluminescence intensity in the 535 nm range was found to be correlated with the presence of non-bridging oxygen defects. A discussion is presented of the nature of this photoluminescence, which may be related to the disordered structure in SrTiO3 amorphous thin films. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Microstructural and transport properties of LaNiO3-delta films grown on Si(111) by chemical solution deposition

Electrically conductive LaNiO3-delta (LNO) thin films with typical thickness of 200 nm were deposited on Si (111) substrates by a chemical solution deposition method and heat-treated in air at 700 degreesC. Structural, morphological, and electrical properties of the LNO thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), field-emission scanning electron microscopy (FEG-SEM), and electrical resistivity rho(T). The thin films have a very flat surface and no droplet was found on their surfaces. The average grain size observed by AFM and FEG-SEM was approximately 100 nm in excellent agreement with XRD data. The rho(T) data showed that these thin films display a good metallic character in a large range of temperature. These results suggest the use of this conductive layer as electrode in the integration of microelectronic devices. (C) 2003 Elsevier B.V. All rights reserved.

Ferroelectric characteristics of BiFeO3 thin films prepared via a simple chemical solution deposition

BiFeO3 (BFO) thin films were fabricated on Pt(111)/Ti/SiO2/Si substrates by using a polymeric precursor solution under appropriate crystallization conditions. The capacitance dependence on voltage is strongly nonlinear, confirming the ferroelectric properties of the films resulting from the domain switching. The leakage current density increases with annealing temperature. The polarization electric field curves could be obtained in BFO films annealed at 500 degrees C, free of secondary phases. X-ray photoelectron spectroscopy spectra of films annealed at 500 degrees C indicated that the oxidation state of Fe was purely 3+, demonstrating that our films possess stable chemical configurations. (c) 2007 American Institute of Physics.

A Novel Plasma Technique for Surface Treatment: The Plasma Expander

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Developments in hot-filament metal oxide deposition (HFMOD)

Hot-filament metal oxide deposition (HFMOD) is a variant of conventional hot-filament chemical vapor deposition (HFCVD) recently developed in our laboratory and successfully used to obtain high-quality, uniform films of MOx WOx and VOx. The method employs the controlled oxidation of a filament of a transition metal heated to 1000 degrees C or more in a rarefied oxygen atmosphere (typically, of about 1 Pa). Metal oxide vapor formed on the surface of the filament is transported a few centimetres to deposit on a suitable substrate. Key system parameters include the choice of filament material and diameter, the applied current and the partial pressures of oxygen in the chamber. Relatively high film deposition rates, such as 31 nm min(-1) for MoOx, are obtained. The film stoichiometry depends on the exact deposition conditions. MoOx films, for example, present a mixture of MoO2 and MoO3 phases, as revealed by XPS. As determined by Li+ intercalation using an electrochemical cell, these films also show a colouration efficiency of 19.5 cm(2) C-1 at a wavelength of 700 nm. MOx and WOx films are promising in applications involving electrochromism and characteristics of their colouring/bleaching cycles are presented. The chemical composition and structure of VOx films examined using IRRAS (infrared reflection-absorption spectroscopy), RBS (Rutherford backscattering spectrometry) and XPS (X-ray photoelectron spectrometry) are also presented. (c) 2007 Elsevier B.V. All rights reserved.

Properties of BaBi2Ta2O9 thin films prepared by chemical solution deposition technique for dynamic random-access memory applications

We report on the properties of BaBi2Ta2O9 (BBT) thin films for dynamic random-access memory (DRAM) and integrated capacitor applications. Crystalline BBT thin films were successfully fabricated by the chemical solution deposition technique on Pt-coated Si substrates at a low annealing temperature of 650°C. The films were characterized in terms of structural, dielectric, and insulating properties. The electrical measurements were conducted on Pt/BBT/Pt capacitors. The typical measured small signal dielectric constant and dissipation factor, at 100 kHz, were 282 and 0.023, respectively, for films annealed at 700°C for 60 min. The leakage current density of the films was lower than 10-9 A/cm2 at an applied electric field of 300 kV/cm. A large storage density of 38.4 fC/μm2 was obtained at an applied electric field of 200 kV/cm. The high dielectric constant, low dielectric loss and low leakage current density suggest the suitability of BBT thin films as dielectric layer for DRAM and integrated capacitor applications.

Plasma-deposition of Ag-containing polyethyleneoxide-like coatings

Ag-containing polyethyleneoxide (FEO)-like thin films have been deposited in Radio Frequency Glow Discharges fed with vapors of diethyleneglycol-dimethyl-ether and argon. Proper experimental conditions have been utilized in order to fragment the monomer in the glow and, at the same time, sputter Ag from the silver RF cathode of the reactor, in a way that polyethyleneoxide(PEO)-like coatings with embedded Ag clusters have been deposited at the ground electrode. The composition of the coatings has been investigated by means of different techniques; the plasma process has been investigated by means of Actinometric Optical Emission Spectroscopy. A correlation has been found between the amount of silver embedded in the coatings and that sputtered in the discharge, monitored by actinometry, that could eventually be utilized to control in situ the deposition process.

Morphology changes induced by laser irradiation on disperse red 13 films prepared by physical vapor deposition

Surface morphology changes induced by argon laser irradiation (514 nm) on disperse red 13 (DR13) films prepared by physical vapor deposition (PVD) were investigated. Atomic force microscopy was used to characterize the irradiated sample for different periods of irradiation. Needle-shape structures are observed which are attributed to the symmetry of DR13 molecules. The film becomes increasingly closely packed with the irradiation, with lower root mean square roughness for long exposure times. This is due to photoisomerization of DR13 molecules and probably heating of the sample, which can provide the required mobility for the molecular rearrangement. The rearrangement is such that voids in the film are filled in upon irradiating the sample, thus decreasing the film roughness and increasing the packing.