Iodization of antimony thin films: XRD, SEM and optical studies of nanostructured SbI3

Antimony films of thicknesses of 25, 40 and 80 nm deposited using thermal evaporation technique were annealed at 200 °C for 6 h. Programmed iodization was carried out at room temperature for periods ranging from 5 min to 9 h on both as-deposited and annealed films. X-ray diffraction studies on iodized films reveal that antimony tri-iodide nanoparticles grow only on annealed antimony films. Surface morphology as revealed through SEM consists of antimony and antimony tri-iodide nanoparticles are 25 nm and 1 μm, respectively. Optical absorption of Sb and SbI3 nanoparticles carried out at room temperature. As-deposited antimony film of thickness 25 nm exhibits a sharp rise in the absorption near ultraviolet region while post-deposition annealed films were characterized by red shifted absorption. Interestingly 45 nm thick Sb films exhibit a broad volume plasmon resonance peak around 500 nm with a width of 200 nm. Progressive iodization of 25 nm thick film reveals two absorption bands at 381.7 nm (A2) and 458.3 nm (B3) with photon energies 3.25 and 2.70 eV, respectively, due to the development of SbI3 valence band structure. Last members of hydrogen-like series of absorption levels A2 and B3 due to halogen doublet (3/2, 1/2) splitting have been observed at room temperature.