Effect of annealing atmosphere on optical, electrical

and structural properties of CuGaS2 thin films

 

F. Smaïli*, M. Kanzari

Laboratoire de Photovoltaïque et Matériaux Semi-conducteurs -ENIT BP 37, Le belvédère 1002-Tunis, Tunisie

* Corresponding author. E-mail: fethi.smaili@voila.fr

Received: 09 July 2008; revised version accepted: 03 October 2009

 

Abstract

     CuGaS2 thin films were deposited by vacuum thermal evaporation on to heated glass substrates at 200°C. The effect of annealing in air and under nitrogen atmospheres at 400°C for 2 hours on structural, electrical and optical properties of these films was investigated. The structure was characterized by XRD and the optical properties were determined from the analysis of the optical spectra (transmittance and reflectance measurements as a function of wavelength). The thickness of the films was found to be approximately 300 nm. It was found that annealing of CuGaS2 films in nitrogen atmosphere leads to an increase of the mean grain size and to an evolution of a (112) preferred film orientation. Annealing in air results in the growth of oxides phases such as CuO and modifies the films structure and orientation. The electrical properties of the films have also been studied and the films have p-type electrical conductivity after annealing in nitrogen atmosphere. Moreover, we found that the as-deposited films and those annealed in air were intrinsic. An optical band-gap of approximately 2.36 eV for the film annealed in nitrogen atmosphere was found with approximate absorption coefficient of 105 cm-1.

 

Keywords: Thin Films; CuGaS2; Structural property; Optical property.

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