Evolution of Structural, Thermal, Optical, and Vibrational Properties of Sc₂S₃, ScCuS₂, and BaScCuS₃ Semiconductors

Abstract

In the present work, we report on the synthesis of Sc 2 S 3 , ScCuS 2 and BaScCuS 3 powders using a method based on oxides sulfidation and modification of their properties. The crystal structures and morphology of samples are verified by XRD and SEM techniques. Thermal stability has been studied by DTA which has revealed that Sc 2 S 3 decomposes to ScS through melting at 1877 K. ScCuS 2 and BaScCuS 3 melt incongruently at temperatures of 1618 K and 1535 K, respectively. The electronic structure calculations show that the investigated compounds are semiconductors with indirect band gap (E g ). According to the diffuse reflection spectroscopy, Sc 2 S 3 , ScCuS 2 and BaScCuS 3 are wide-bandgap semiconductors featured the E g values of 2.53 eV, 2.05 eV and 2.06 eV, respectively. The band gap decreases with the introduction of copper (I) and barium cations into the crystal structure of the compounds. Variation of local structure has been verified by Raman and infrared spectroscopy. The calculated vibrational modes of ScCuS 2 correspond to CuS 4 and ScÀ S layer vibrations, even though ScS 6 octahedra-like structural units can be found in the structure.