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Abstract: Fluorine doped SnO2 thin films were spray deposited using three tin precursors, tin tetrachloride, dibutyl-tin-diacetate and butyl-tin-trichloride, adding small amounts of hydrogen peroxide (H2O2) to the source solutions. The molar ratio range [H2O2]/[Sn]=0 to 0.8 with respect to the tin precursor was investigated. At a given deposition temperature T d, a net optimum was found close to [H2O2]/[Sn]=0.5 for the deposition rate, the electrical properties and the crystalline quality. The effect of H2O2 addition was found to increase the growth rate, even at a temperature as low as 340 °C. The higher was the deposition temperature T d, the larger was the increase. The deposition process of FTO films was optimized at T d =420 °C. At this temperature, the most significant result with respect to solar cell applications was obtained with butyl-tin-trichloride as tin precursor and [H2O2]/[Sn]=0.6; carrier concentration : 4.5×1020 cm−3; mobility : 34 cm2 V−1 s−1; resistivity: 4.1×10−4 Ω cm. It is concluded that the main effect of addition of hydrogen peroxide is to improve the film crystallization at a lower T d than in the absence of H2O2, increasing the carrier mobility significantly and keeping a high deposition rate. [Copyright &y& Elsevier]

Abstract: This work presents the effect of postdeposition annealing on the structural, electrical and optical properties of undoped ZnO (zinc oxide) thin films, prepared by radio-frequency sputtering method. Two samples, 0.17 and 0.32 µm-thick, were annealed in vacuum from room temperature to 350 °C while another 0.32 µm-thick sample was annealed in air at 300 °C for 1 h. X-ray diffraction analysis revealed that all the films had a c-axis orientation of the wurtzite structure normal to the substrate. Electrical measurements showed that the resistivity of samples annealed in vacuum decreased gradually with the increase of annealing temperature. For the 0.32 µm-thick sample, the gradual decrease of the resistivity was essentially due to a gradual increase in the mobility. On the other hand, the resistivity of the sample annealed in air increased strongly. The average transmission within the visible wavelength region for all films was higher than 80%. The band gap of samples annealed in vacuum increased whereas the band gap of the one annealed in air decreased. The main changes observed in all samples of this study were explained in terms of the effect of oxygen chemisorption and microstructural properties. [Copyright &y& Elsevier]