57 research outputs found
Optical study of titanium dioxide thin films prepared by R.F. sputtering
Optical response of TiO2 layers, prepared by R.F. sputtering from TiO2 target, was studied as a function of target state, oxygen partial pressure and sputtering power. We have found that TiO2 layers deposited from a used target exhibit a high absorptance which decreases greatly when an oxygen partial pressure is introduced. Whereas an increase of sputtering power leads to an absorbent TiO2 matrix.Optical response of TiO2 layers, prepared by R.F. sputtering from TiO2 target, was studied as a function of target state, oxygen partial pressure and sputtering power. We have found that TiO2 layers deposited from a used target exhibit a high absorptance which decreases greatly when an oxygen partial pressure is introduced. Whereas an increase of sputtering power leads to an absorbent TiO2 matrix
Fluorine-doped ZnO thin films deposited by spray pyrolysis technique
Fluorine doped ZnO thin films (FZO) are prepared onto glass substrates at 350 degrees C by the chemical spray pyrolysis technique. X-ray diffraction spectra show a polycrystalline of ZnO (wurtzite structure) where the amount of fluorine doping affects to preferential orientation (002 plane along c-axis) and does not vary the lattice parameters. Therefore, F introduction in lattice is by the substitution of O(-2) ions by F(-1) ions. Any variation is observed in transmittance and reflectance measurements in 400-2000 nm wavelength range when samples present F dopant; they have transmittance around 80% in the near infrared and visible zones. The FZO films are degenerate and exhibit n-type electrical conductivity. The best resistivity and mobility are 7.6 x 10(-3) Omega cm and 3.77 cm(2) V(-1) s(-1) respectively. The calculated values of the mean free path are very small compared to the grain sizes calculated using XRD measurements. Therefore, we suggest that ionized impurity and/or neutral impurity scattering are the dominant scattering mechanisms in these films
Structural, optical, and electrical properties of Yb-doped ZnO thin films prepared by spray pyrolysis method
Yb-doped ZnO thin films were prepared on glass substrates by spray pyrolysis technique in order to investigate the insertion of Yb ions in the ZnO matrix and the related optical properties of the films. The molar ratio of Yb in the spray solution was varied in the range of 0-5 at. %. X-ray diffraction patterns showed that the undoped and Yb-doped ZnO films exhibit the hexagonal wurtzite crystal structure with a preferential orientation along [002] direction. No secondary phase is observed in Yb-doped ZnO films. All films exhibit a transmittance between 75 and 90% in the visible range with a sharp absorption onset about 375 nm corresponding to the fundamental absorption edge at 3.3 eV. The photoluminescence measurements show a clear luminescence band at 980 nm that is characteristic of Yb(3+) transition between the electronic levels (2)F(5/2) and (2)F(7/2). This is an experimental evidence for an efficient energy transfer from ZnO matrix to Yb(3+). Hall effect measurements showed low resistivities and high carrier mobilities which makes these films of interest to photovoltaic devices.This work is supported by the program interdisciplinaire énergie du CNRS Grant No. PE10-2.1.2-2
Cellule solaire polyacetylene-sulfure de cadmium spray
SIGLECNRS T 55196 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Thin films for CIS solar tells
In this paper, we present our Studies on three materials CuInS2, ZnO and CdS which can be used to elaborate CIS solar cells. For instance, we have used spray pyrolysis and chemical bath deposition to prepare these compounds. Sprayed CuInS2 thin films have exhibited a preferential (112) orientation with chalcopyrite structure and p type conductivity. Their energy gap value was around 1.45 eV, which perfectly matches the solar spectrum. We also studied the Cu:In :S ratio effect on its properties. Sprayed Undoped and indium-doped ZnO films were highly transparent since their energy gap value was 3.2eV. The films were polycrystalline and exhibited an hexagonal wurtzite-type structure. Their orientation was modified by an adequate indium doping which leads to a resistivity value of about 10-3 Wcm. Homogeneous and strongly adherent CdS very thin layers of about 70 nm were prepared by CBD Process. The obtained films have showed preferential orientation which changes from (002) to (101) with growth temperature and annealing treatment. CdS was very resistive with an energy gap around 2.37eV.In this paper, we present our Studies on three materials CuInS2, ZnO and CdS which can be used to elaborate CIS solar cells. For instance, we have used spray pyrolysis and chemical bath deposition to prepare these compounds. Sprayed CuInS2 thin films have exhibited a preferential (112) orientation with chalcopyrite structure and p type conductivity. Their energy gap value was around 1.45 eV, which perfectly matches the solar spectrum. We also studied the Cu:In :S ratio effect on its properties. Sprayed Undoped and indium-doped ZnO films were highly transparent since their energy gap value was 3.2eV. The films were polycrystalline and exhibited an hexagonal wurtzite-type structure. Their orientation was modified by an adequate indium doping which leads to a resistivity value of about 10-3 Wcm. Homogeneous and strongly adherent CdS very thin layers of about 70 nm were prepared by CBD Process. The obtained films have showed preferential orientation which changes from (002) to (101) with growth temperature and annealing treatment. CdS was very resistive with an energy gap around 2.37eV
ZnO layers prepared by spray pyrolysis
Highly transparent undoped and indium doped ZnO thin films have been grown
on glass substrates by using the spray pyrolysis process. Conditions of preparation have
been optimized to get good quality and reproducible films with required properties.
Polycrystalline films with an hexagonal Wurtzite-type structure were easily
obtained under the optimum spraying conditions. Both of samples have shown high
transmission coefficient in the visible and infrared wavelength range with sharp
absorption edge around 380 nm which closely corresponds to the intrinsic band-gap of
ZnO (3.2 eV).
Orientation and crystallites size were remarkably modified by deposition
temperature and indium doping
Optical study of Ag-TiO
The optical properties of Ag-TiO2 nanocermet thin films are studied with the aim of
optical filtering applications. Beyond the classical properties of cermets with noble metal
inclusions predicted by the effective medium theories, the optical properties of Ag-TiO2
nanocermets deposited by R.F. co-sputtering are governed by their columnar morphology and
the under-stoichiometry of the TiO2 matrix. A careful experimental analysis of the different
parameters and effects involved in the optical response of these nanocermets is performed
both on TiO2 and Ag-TiO2: film thickness, silver volume fraction, thermal treatments,
oxidation. The influence of these parameters on the surface plasmon resonance and the
infrared transmission of the nanocermet thin films is optimized
Preparation and characterization of sprayed FTO thin films
Fluorine doped tin oxide (FTO) thin films have been prepared by spray
pyrolysis technique with no further annealing. Films with 2.5% of fluorine grown at 400 °C present a single phase and exhibit a tetragonal structure with lattice parameters a = 4.687 Å and c = 3.160 Å. Scanning electron micrographs showed homogeneous surfaces with average grain size around 190 nm.
The films are transparent in the visible zone and exhibit a high reflectance in the near infrared region. The best electrical resistivity was 6.3 × 10-4 Ω cm for FTO with 2.5% of fluorine. The ratio of transmittance in the visible to the sheet resistance are in the 0.57 × 10-2–1.96 × 10-2 Ω-1 range
Structural, Optical and Electrical Properties of Transparent Conducting Oxide Based on Al Doped ZnO Prepared by Spray Pyrolysis
Aluminum doped zinc oxide (AZO) thin films were deposited on glass substrates at 350 °C by spray pyrolysis technique. X-ray diffraction patterns show that the undoped and AZO films exhibit the hexagonal wűrtzite crystal structure with a preferential orientation along 2 direction. AFM images showed that AZO film with 3 % of Al has a uniform grain sizes with a surface roughness of about 24 nm. All films present a high transmittance in the visible range. Both undoped and AZO films were n-type degenerate semiconductor and the best electrical resistivity value was around 8.0 ´ 10- 2 W.cm obtained for 3 % Al content
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