Tailoring the physical and optical properties of Sn-doped In2S3 thin films obtained using VTE technique

Abstract

In this study, indium sulfide (In2S3) thin films doped with tin (Sn) were prepared and deposited using the Vacuum Thermal Evaporation (VTE) method with different proportions of Sn (0, 2, 4 and 6%). 0.2 g of In2S3 powder was evaporated in vacuum onto a glass substrate (2,5 cm × 1 cm) under 1.7 × 10−5 mbar. Structural, morphological, optical, and elemental composition properties of obtained thin films have been investigated. X-ray diffraction analysis shows well-crystallized films according to the cubic β-In2S3 phase. The films become almost amorphous when tin exceeds 4% (also confirmed by the FTIR results). Raman Spectroscopy shows the main mode at 326 cm−1. Both the SEM and the AFM photographs exhibit that all films are covered without cracks and pinholes. XPS results verifies the diffusion of dopant into the In2S3 thin films and shows two principal peaks of the binding energies of In and S located at 448 eV and 456 eV respectively. Optical analysis revealed that the transmission is achieved 75–80% in visible and 85–95% in the near-IR region. The optical band gap varied from 2.84 eV to 2.62 eV with adding tin until 6%. The optical parameters, single oscillator energy (E0), dispersion energy (Ed), and high-frequency dielectric constant (ε∞) are also determined via the Wemple-DiDomenico Model. This study reflects the prospect of tailoring the properties and integrating Sn-doped In2S3 nanocomposites as thin-film layers in future solar cells.