Annealing effects on structural, optical and electrical properties of e-beam evaporated CuIn0.5Ga0.5Te2 thin films


Yilmaz K., Karaagac H.

APPLIED SURFACE SCIENCE, vol.256, no.21, pp.6454-6458, 2010 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 256 Issue: 21
  • Publication Date: 2010
  • Doi Number: 10.1016/j.apsusc.2010.04.034
  • Journal Name: APPLIED SURFACE SCIENCE
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.6454-6458
  • Istanbul Technical University Affiliated: No

Abstract

CuIn0.5Ga0.5Te2 (CIGT) thin films have been prepared by e-beam evaporation from a single crystal powder synthesized by direct reaction of constituent elements in a stoichiometric proportion. Post-depositional annealing has been carried out at 300 and 350 degrees C. The compositions of the films were determined by energy dispersive X-ray analysis (EDXA) and it was found that there was a remarkable fluctuation in atomic percentage of the constituent elements following to the post-depositional annealing. X-ray diffraction analysis (XRD) has shown that as-grown films were amorphous in nature and turned into polycrystalline structure following to the annealing at 300 degrees C. The main peaks of CuIn0.5Ga0.5Te2 and some minor peaks belonged to a binary phase Cu2Te appeared after annealing at 300 degrees C, whereas for the films annealed at 350 degrees C single phase of the CuIn0.5Ga0.5Te2 chalcopyrite structure was observed with the preferred orientation along the (1 1 2) plane. The effect of annealing on and near surface regions has been studied using X-ray photoelectron spectroscopy (XPS). The results indicated that there was a considerable variation in surface composition following to the annealing process. The transmission and reflection measurements have been carried out in the wavelength range of 200-1100 nm. The absorption coefficients of the films were found to be in the order of 10(4) cm(-1) and optical band gaps were determined as 1.39, 1.43 and 1.47 eV for as-grown and films annealed at 300 and 350 degrees C, respectively. The temperature dependent conductivity and photoconductivity measurements have been performed in the temperature range of -73 to 157 degrees C and the room temperature resistivities were found to be around 3.4x10(7) and 9.6x10(6) (Omega cm) for the as-grown and annealed films at 350 degrees C, respectively. (C) 2010 Elsevier B.V. All rights reserved.