Structural, morphological, and optical characterization of indium selenide (In₂Se₃) obtained by mechanical alloying

Abstract The optical, electrical, and thermal properties of indium selenides are strongly influenced by their crystal structure. At room temperature (RT), the indium selenide with the stoichiometry In₂Se₂ exhibits two coexisting crystalline phases namely α and β, both can crystallize in two different crystal structures, hexagonal (2H) and rhombohedral (3 R). In polycrystalline In₂Se₃ powders, the presence of both phases has been observed. In this study, the rhombohedral β (3 R) phase of In₂Se₃ was synthesized by prior mechanical pulverization of powders of selenium and beads of indium, followed by mechanical alloying, achieved after 30 h of milling, and identified by x-ray diffraction (XRD). Scanning electron microscopy (SEM) revealed a morphological evolution with a predominance of agglomerates smaller than 500 nm. Photoluminescence (PL) spectra show an emission of around 1.26 eV, lower than that reported in the literature, and the optic band gap energy E_g, determined by transmission spectra and the Tauc method, was 1.23 eV, a value not previously reported for this phase.