Influence of the concentration of Sb2O3 and the viscosity of the precursor solution on the electrical and optical properties of SnO2 thin films produced by the Pechini method

SnO2:Sb multi-layer coatings were prepared by the Pechini method. An investigation was made of the influence of the concentration of Sb2O3 and the viscosity of the precursor solution on the electrical and optical properties of SnO2 thin films. The use of a multi-layer system as an alternative form of increasing the packing and. thus. decreasing porosity proved to be efficient, decreasing the system's resistivity without altering its optical properties. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Surface protection of fluoroindate glasses by sol-gel dip-coated SnO2 thin layers

SnO2 coatings were deposited by a sol-gel dip-coating process to shield fluoroindate glasses (40In-F-3:16BaF(2):20SrF(2):20ZnF(2):2NaF:2GaF(3)) against corrosion in aqueous environments. The effect of the number of coating applications and of the withdrawal speed on the thickness, density and roughness of tin oxide films was investigated by X-ray reflectivity. Film thickness increases both with the number of coating applications and the withdrawal speed. The aqueous leaching of uncoated and SnO2-coated fluoroindate glasses was studied by scanning electron microscopy (SEM) and infrared spectroscopy (FTIR), showing that the glass surface was protected against hydrolytic attack. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Numerical simulation of the liquid phase in SnO2 thin film deposition by sol-gel-dip-coating

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Characterization of metallic electrical contacts to SnO2 thin films lightly doped with Eu3+ ions, and photo-induced resistivity

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Rare earth centers properties and electron trapping in SnO2 thin films produced by sol-gel route

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influence of pH of Colloidal Suspension on the Electrical Conductivity of SnO2 thin Films Deposited Via Sol-Gel-Dip-Coating

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of pH of colloidal suspension on crystallization and activation energy of deep levels in SnO2 thin films obtained via sol-gel

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evaluation of Bulk and Surfaces Absorption Edge Energy of Sol-Gel-Dip-Coating SnO2 Thin Films

The absorption edge and the bandgap transition of sol-gel-dip-coating SnO2 thin films, deposited on quartz substrates, are evaluated from optical absorption data and temperature dependent photoconductivity spectra. Structural properties of these films help the interpretation of bandgap transition nature, since the obtained nanosized dimensions of crystallites are determinant on dominant growth direction and, thus, absorption energy. Electronic properties of the bulk and (110) and (101) surfaces are also presented, calculated by means of density functional theory applied to periodic calculations at B3LYP hybrid functional level. Experimentally obtained absorption edge is compared to the calculated energy band diagrams of bulk and (110) and (101) surfaces. The overall calculated electronic properties in conjunction with structural and electro-optical experimental data suggest that the nature of the bandgap transition is related to a combined effect of bulk and (101) surface, which presents direct bandgap transition.

Schottky emission in nanoscopically crystallized Ce-doped SnO2 thin films deposited by sol-gel-dip-coating

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Visible emission from Er-doped SnO2 thin films deposited by sol-gel

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

Grain size effect on the electrical response of SnO2 thin and thick film gas sensors

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

Structural characterization of undoped and Sb-doped SnO2 thin films fired at different temperatures

SnO2 thin films were obtained by the sol-gel method starting from inorganic precursor solutions. In this work, we compare the structure of undoped and Sb-doped SnO2 films prepared by dip-coating. The films were deposited on quartz substrates and then fired at different temperatures ranging from 383 up to 1173 K. The density and the thickness of the films were determined by X-ray reflectivity (XRR) and their porous nanostructure was characterized by grazing-incidence small angle X-ray scattering (GISAXS). XRR results corresponding to undoped and Sb-doped samples indicate a monotonous decrease in film thickness when they are fired at increasing temperatures. At same time, the apparent density of undoped samples exhibits a progressive increase while for Sb-doped films it remains invariant up to 973 K and then increases for T = 1173 K. Anisotropic GISAXS patterns of both films, Sb-doped and undoped, fired above 573 K indicate the presence of elongated pores with their major axis perpendicular to the film surface. For all firing temperatures the nanopores in doped samples are larger than in undoped ones. This suggests that Sb-doping favours the pore growth hindering the film densification. At the highest firing temperature (1173 K) this effect is reversed.

Electro-optical properties of Er-doped SnO2 thin films

Photoconductivity of SnO2 sol-gel films is excited, at low temperature, by using a 266 nm line-fourth harmonic-of a Nd:YAG laser. This line has above bandgap energy and promotes generation of electron-hole pairs, which recombines with oxygen adsorbed at grain boundary. The conductivity increases up to 40 times. After removing the illumination on an undoped SnO2 film, the conductivity remains unchanged, as long as the temperature is kept constant. Adsorbed oxygen ions recombine with photogenerated holes and are continuously evacuated from the system, leaving a net concentration of free electrons into the material, responsible for the increase in the conductivity. For Er doped SnO2, the excitation of conductivity by the laser line has similar behavior, however after removing illumination, the conductivity decreases with exponential-like decay. (C) 2003 Elsevier Ltd. All rights reserved.

Enhanced electrical property of nanostructured Sb-doped SnO2 thin film processed by soft chemical method

The effect of the Sb addition on the microstructural and electrical conductivity of the SnO2 thin film was studied in this work. Experimental results show that the Sb addition allowed to control the grain size and electrical conductivity of the SnO2 thin film, resulting in a nanostructured material. The nanostructured Sb-doped SnO2 thin films present high electrical conductivity, even in the presence of high porosity, supporting the hypothesis that nanostructured material must possess strong electrical conductivity. This work involves important aspects that can be applied to the development of high performance transparent conducting thin film. (C) 2003 Elsevier B.V. All rights reserved.

Drude's model calculation rule on electrical transport in Sb-doped SnO2 thin films, deposited via sol-gel

The evaluation of free carrier concentration based on Drude's theory can be performed by the use of optical transmittance in the range 800-2000 nm (near infrared) for Sb-doped SnO2 thin films. In this article, we estimate the free carrier concentration for these films, which are deposited via sol-gel dip-coating. At approximately 900 mn, there is a separation among transmittance curves of doped and undoped samples. The plasma resonance phenomena approach leads to free carrier concentration of about 5 x 1020 cm(-3). The increase in the Sb concentration increases the film conductivity; however, the magnitude of measured resistivity is still very high. The only way to combine such a high free carrier concentration with a rather low conductivity is to have a very low mobility. It becomes possible when the crystallite dimensions are taken into account. We obtain grains with 5 nm of average size by estimating the grain size from X-ray diffraction data, and by using line broadening in the diffraction pattern. The low conductivity is due to very intense scattering at the grain boundary, which is created by the presence of a large amount of nanoscopic crystallites. Such a result is in accordance with X-ray photoemission spectroscopy data that pointed to Sb incorporation proportional to the free electron concentration, evaluated according to Drude's model. (c) 2006 Elsevier Ltd. All rights reserved.