Structural refinement, charge density mapping and microstructural analysis of Sb 2 (S,Se) 3 thin films
Noodhana Jeevanantham, Balasundaraprabhu Rangasamy, Sankaran Prasanna, Dhayalan VelauthapillaiAbstract
Present study aims to understand the crystalline nature of Sb 2 (S,Se) 3 thin films sequentially prepared using RF magnetron and subsequent hot wall deposition techniques. Post-deposition annealing was carried out at 250 °C. X-ray diffraction (XRD) and Rietveld refinement confirms the orthorhombic Pnma phase, with anisotropic lattice expansion upon selenium substitution with the lattice parameters a = 11.5 Å, b = 3.9 Å, and c = 11.35 Å. Visualization of Electronic Structure and Analysis (VESTA) analysis was used to construct the crystal structure using the atomic coordinates for Sb, S and Se. Coordination numbers indicate each antimony atom surrounded by six sulfur and selenium atoms, forming Sb–S 6 and Sb–Se 6 octahedra. VESTA simulations from Fourier-transformed structure factors, revealed more directional anisotropy in electronic charge distribution across the (322), (213), and (103) crystallographic planes. The (103) plane exhibits strong charge localization along Sb–Se bonds, while the (322) plane shows smoother electron density with minimal trapping. The mapping revealed a high concentration of charges with the presence of few vacancies at a spatial resolution of 0.5 Å across each lattice planes. TEM confirms the orthorhombic phase formation, fine grains and crystalline periodicity. EDX confirms the uniform Sb, S, and Se distribution attributing to composition of the films.