Specific features of the optical spectra in Tl2In2S3Se layered single crystals by N. M. Gasanly, I. Guler, and K. Goksen

Crystal Research and Technology

Cryst. Res. Technol. 42, 621 (2007) - Abstract -

Specific features of the optical spectra in Tl₂In₂S₃Se layered single crystals

N. M. Gasanly, I. Guler, and K. Goksen

Physics Department, Middle East Technical University, 06531 Ankara, Turkey

Keywords	optical constants, dispersion of refractive index, optical band gap, layered crystals
PACS	78.20.Ci, 78.40.-q, 78.40.Fy, 61.10.Nz
DOI	10.1002/crat.200610874

The optical properties of Tl₂In₂S₃Se layered single crystals have been studied by means of transmission and reflection measurements in the wavelength range of 450-1100 nm. The analysis of the absorption data revealed the presence of both optical indirect and direct transitions with energy band gaps of 2.16 and 2.42 eV, respectively. The observed coexistence of indirect and direct energy band gaps is related to the anisotropy of the Tl-containing layered crystals. The dispersion of the refractive index is discussed in terms of the Wemple-DiDomenico single-effective-oscillator model. The refractive index dispersion parameters: oscillator energy, dispersion energy, oscillator strength and zero-frequency refractive index were found to be 4.78 eV, 43.58 eV, 13.18 x 10¹³ m^-2 and 3.18, respectively. From X-ray powder diffraction study, the parameters of monoclinic unit cell were determined.

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