Abstract
Bi2Te3 films were prepared by thermal evaporation technique. X-ray diffraction analysis for as-deposited and annealed films in vacuum at 150°C were polycrystalline with rhombohedral structure. The crystallite size is found to increase as the film thickness increases and has values in the range 67–162nm. The optical constants (the refractive index, n, and absorption index, k) were determined using transmittance and reflectance data in the spectral range 2.5–10μm for Bi2Te3 films with different thicknesses (25–99.5nm). Both n and k are independent on the film thickness in the investigated range. It was also found that Bi2Te3 is a high refractive index material (n has values of 4.7–8.8 in the wavelength range 2.5–10μm). The allowed optical transitions were found to be direct optical transitions with energy gap Egd=0.21eV. The optical conductivities σ1=ƒ(hν) and σ2=f(hν) show distinct peaks at about 0.13 and 0.3eV, respectively. These two peaks can be attributed to optical interband transitions.
Published Version
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