Structural, morphological and spectroscopic ellipsometry studies on sputter deposited Sb₂S₃ thin films

Abstract

In this work we are discussing RF magnetron sputter deposition of Sb₂S₃ thin films, postdeposition thermal processing, and the material characterization. After thermal treatment at 300 °C in N₂/S environment, films were crystallized in orthorhombic structure, which was determined by XRD and Raman spectroscopy. Crystallite size, lattice parameters, strain, texture coefficient and degree of preferred orientation are reported. AFM and SEM images of the annealed films revealed a compact and uniform surface, composed of grains of large-size in the order of micrometers and well-defined rhombic geometry. Elemental analysis by EDXS showed a slight sulfur excess in the films. Optical properties and electronic band to band transitions were determined by spectroscopic ellipsometry. The dielectric function of Sb₂S₃ films was well represented by a Tauc–Lorentz and Lorentz oscillator models collection. Optical constants n and k revealed notable differences caused by thermal treatment, which are consistent with amorphous (as deposited) and polycrystalline (annealed) film properties, such as increase in E _g and lowering of n and k values. The optical band gap of the annealed films from the ellipsometric measurements was in the range of 1.63–1.7 eV with an absorption coefficient larger than 10⁴ cm⁻¹ in the above band gap region. The films showed p-type conductivity and photo-response.