Comparative study of structural and morphological properties of nanostructured CuIn_2n+1S_3n+2 (n = 0, 1 and 2) thin films produced by oblique angle deposition

¹ Laboratoire de Photovoltaïque et Matériaux Semiconducteurs - ENIT - Université Tunis ElManar, BP 37, Le belvédère 1002 Tunis, Tunisia
² Institut des NanoSciences de Paris-CNRS-Université Pierre et Marie Curie, 140 rue de Lourmel, 75015 Paris, France

^a e-mail: azzasinaoui@yahoo.fr

Received: 3 August 2013
Accepted: 30 September 2013
Published online: 8 November 2013

Abstract

CuInS₂, CuIn₃S₅ and CuIn₅S₈ films were grown by thermal evaporation using oblique angle deposition technique. During the deposition, the substrate temperature was maintained at T_s = 150 °C and the deposition angle was fixed at α = 0° and 85°. The powders and thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). From the XRD data of powders, we calculated the lattice parameters of the structure for the different compounds. XRD patterns of thin films revealed that all samples deposited at α = 0° were polycrystalline. Indeed, CuInS₂ and CuIn₃S₅ films had a chalcopyrite structure with preferred orientation along (1 1 2) while CuIn₅S₈ films exhibit a spinel structure with preferred orientation along (3 1 1). However, CuIn_2n+1S_3n+2 with n = 0, 1 and 2 films deposited at α = 85° were amorphous in nature. The surface and cross-section of the films were observed by AFM and SEM. The oblique angle deposition films showed an inclined columnar structure, with columns tilting in the direction of the incident flux. The surface roughness of the different films deposited, respectively, at α = 0° and 85° was determined by two methods (AFM and spectrophotometric analysis). The obtained values show an increase of the surface roughness by increasing the deposition angle α.