Structural, morphological and optical properties

of the CuInS2 thin films

 

R. Brini1*, F. Chaffar Akkari1, M. Kanzari1, B. Rezig1, J. Werckmann2

1 Laboratoire de Photovoltaïque et Matériaux  Semiconducteurs, LPMS

Ecole Nationale d’ingénieurs de Tunis (ENIT), BP 37 le Belvédère  1002 Tunis - Tunisie

2 Institut de Physique et Chimie des Matériaux (IPCMS),

23 Rue du Loess B.P 43, CP 67034 Strasbourg, France

* Corresponding author. E-mail: Brini_rawdha@yahoo.fr

Received: 26 June 2008; revised version accepted: 03 October 2008

 

Abstract

     Structural, morphological and optical properties of CuInS2 thin films grown in particular conditions by the single source thermal evaporation have been studied. Firstly, the films were grown onto substrates no submitted to a thermal gradient and the vapour incident angle with respect to the surface normal is q = 0. The films were annealed from 250 to 550 °C in argon atmosphere after evaporation. The surface topography was imaged with scanning electron microscopy (SEM). The maximum grain size of the samples after annealing at 550°C was over 150 nm. The XRD spectra analysis concludes that the polycrystalline CuInS2 thin film after annealing is obtained at 450°C. We obtain CuInS2 layers with high structural and morphological quality when annealing temperature is above 450°C. Secondly, we use the oblique angle deposition technique combined with substrate rotation to grow CuInS2 thin films by vacuum thermal method on to glass substrate. During depositions, the substrate temperature was maintained at 200°C. Due to the shadowing effect, the oblique angle deposition technique can produce nanoroods tilted toward the incident deposition flux. The evaporated atoms arrive at the growing interface at a fixed angle q measured from the substrate normal. The substrate is rotated with rotational speed w fixed at 0.033 rev s-1. We show that the use of this growth technique leads to an improvement in the optical properties of the films. Indeed high absorption coefficient (105-3.105 cm-1) in the visible range and near-IR spectral range are reached. SEM shows that the films had a microstructure with columns that are progressively inclined as the incident angle was increased. The surface morphology show an improvement without presence of secondary phase for the higher incident angles (q> 60°).

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