Temperature dependence of the structural and optical properties of thermally vacuum evaporated InSbSe3 thin films

The ternary composition InSbSe3 was synthesized by direct fusion of the stoichiometric quantities of two binary components Sb2Se3 and In2Se3 in an evacuated silica tube. The structural properties of InSbSe3 in its powder and thin film forms were investigated by X-ray. Analysis of X-ray diffractograms showed that the fine powder of InSbSe3 as well as thin films annealed at 423 and 473 K for 1 h are all of polycrystalline triclinic structure with unit cell parameters: a = 6.032 Angstrom, b = 7.040 Angstrom, c = 12.186 Angstrom, alpha = 95.783degrees, beta = 51.808degrees, gamma = 95.852degrees and unit cell volume of 402.496 Angstrom(3). The refractive index, n, and the extinction coefficient, k, of the as-deposited thin films before and after annealing were determined for samples of different thicknesses (114-267 nm) in the spectral range 500-2500 nm. The spectral behaviour of n showed anomalous dispersion in the region of the fundamental absorption edge. The value of the high-frequency dielectric constant (a,) was obtained as 8.8 for the as-deposited thin films can be explained on the basis of the single oscillator model. The optical constants and the dielectric constant of the thin films were all affected by annealing temperature. The existing allowed optical transitions in the as-deposited thin films as well as annealed thin films were found to be indirect. The indirect energy gap was decreased from 1.46 eV for as-deposited thin films to 1.29 and 1.16 eV as the films were annealed at 423 and 473 K for 1 h, respectively. (C) 2004 Elsevier B.V. All rights reserved.