Eur. Phys. J. Appl. Phys. (2015) 69: 10303
https://doi.org/10.1051/epjap/2014140266

Effect of vacuum annealing on structural, morphological and optical properties of Sn₂Sb₂S₅ thin films with different thicknesses

¹ Laboratoire de Photovoltaque et Matériaux Semi-conducteurs-ENIT, Université de Tunis El Manar, BP 37, le Belvédère 1002 Tunis, Tunisia
² Laboratoire de Photovoltaque, Centre de Recherches et des Technologies de l’Énergie, Technopole de Borj-Cédria BP 95, 2050 Hammam-Lif, Tunisia
³ Laboratoire de Photovoltaques et Matériaux Semi-conducteurs-ENIT-IPEITunis Montfleury-Université de Tunis, Tunisia

^a e-mail: khedmi-nawel@hotmail.com

Received: 27 June 2014
Revised: 26 November 2014
Accepted: 22 December 2014
Published online: 27 January 2015

Abstract

Sn₂Sb₂S₅ thin films in thickness of 100–900 nm were deposited on unheated glass substrates using thermal evaporation method and annealed in vacuum at temperature of 200 °C for 2 h. X-ray diffraction spectra indicated that all the Sn₂Sb₂S₅ samples are polycrystalline in nature having orthorhombic structure. The various structural parameters, such as, crystalline size, dislocation density, strain and texture coefficient were calculated and the surface morphology of the films was also analyzed. The optical constants, i.e., refractive index, absorption coefficient and optical band gap of the as-deposited and post-annealed films have been determined from the analysis of the transmittance and reflectance spectral data over the wavelength range 300–1800 nm. All the Sn₂Sb₂S₅ thin films before and after annealing have relatively high absorption coefficient between 10⁴ and 10⁵ cm⁻¹ in the visible spectral range. The optical band gap was found to decrease, from 1.72 to 1.5 eV for samples before annealing and from 172 to 1.46 eV for samples annealed in vacuum, with increasing films thickness in the 100–900 nm range.