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Keywords:

  • 68.37.Hk;
  • 68.55.Jk;
  • 78.66.Hf;
  • 81.15.Cd;
  • 84.37.+q;
  • 84.60.Jt

Abstract

Aluminum doped Zinc Oxide (ZnO:Al) films were deposited by rf magnetron sputtering from a ZnO target mixed with Al2O3 of 2.5 % on to glass substrates maintained at different temperatures ranging from 300 to 673 K. Argon gas pressure during the deposition was in the range 0.3–10 mTorr. Structural, optical and electrical properties of the prepared films have been characterized. As the argon gas pressure was increased, the deposition rate was found to decrease and the surface roughness was increased. Furthermore, the carrier concentration and the Hall mobility were decreased and thus the electrical resistivity increased. Depending on their structural properties, these films develop different surface structures upon post deposition etching in diluted HCl (0.5%). The light scattering properties of suitable film can be controlled over a wide range simply by varying the etching time, substrate temperature and argon pressure. The X-Ray diffraction (XRD) studies showed that the films are highly oriented with their crystallographic c-axis perpendicular to the substrate and almost independent of argon pressure and also an improvement in crystallinity for the films deposited at higher temperature was observed. Measurements of transmission spectra reveal that ZnO:Al films have an average transmission of over 85 % in the wavelength range of 400–800 nm. Also the films showed an excellent electrical resistivity of 1.9 x 10–4 Ω-cm, a value comparable to that for indium tin oxide film presently used as a transparent electrode. Finally, the texture-etched films were successfully applied on substrates for silicon thin film solar cells. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)