ICT2014 Abstracts

The optical constants of Se and Fe doped bismuth telluride (Bi₂Te₃) films were determined, using transmittance and reflectance data, in the spectral range of 400–1000nm, for thicknesses ranging from 500–1500Å. Bi₂Te_3-xSe_x (0≤x≤0.3) and Bi_2-yFe_yTe₃ (0≤y≤0.3) films were deposited by e-beam deposition technique. X-ray diffraction analyses show that the films are polycrystalline with rhombohedral structure. The crystallite size is found to increase as the film thickness increases and has values in the range of 76 – 350nm. Allowed optical transition was found to be direct throughout the wavelength range and the variation in the bandgap (E_g) is reported for different doping concentrations of Se and Fe. The optical constants, refractive index (n), and absorption coefficient (k), were calculated and found to be independent of the film thickness. Further, the variations in the optical conductivities, with energy, were attributed to inter-band transitions.