Effect of Fe doping on the structural, electrical and optical properties of Bi2Te3 thin films

In this work, the structural, morphological, electrical and optical properties of Bi2-xTe3Fex (x = 0, 0.3 and 0.5 at%) thin films were investigated. X-ray diffraction investigations revealed the formation of hexagonal Bi2Te3 structure for undoped and Fe-doped films. Scanning electron microscopy observations revealed an increase in the average grain size from 20.4 to 43.5 nm with increasing Fe doping ratio from 0 to 0.5 at%. A transition from N-type conduction to P-type conduction with a decrease in carrier concentration was observed after Fe doping with 0.3 at%. Energy-dispersive X-ray spectroscopy spectra confirmed the presence of Fe in the doped films. The optical absorbance (Abs), transmittance (T%) and reflectance (R%) spectra of Bi2-xTe3Fex films were measured in the spectral range from 200 to 2500 nm. Both T% and R% were strongly affected by Fe doping. The optical bandgap decreased from 0.26 to 0.17 eV with increasing Fe ratio from 0 to 0.5 at%. Over most of the studied wavelength range, the refractive index values increased with increasing Fe doping ratio. The optical conductivity values were mainly increased with Fe doping. The examined optical and electrical properties of Bi2-xTe3Fex (x = 0, 0.3 and 0.5 at%) thin films may enable rapid material selection for designing certain applications such as optical coatings.