Structural, optical and electrical properties of Bi2−xMnxTe3 thin films

Undoped and Mn doped Bi2Te3 (x = 0, 0.05 and 0.10 at%) thin films were prepared via thermal evaporation method from their bulk alloys. X-ray diffraction revealed the presence of hexagonal Bi2Te3 crystalline phase only in all undoped and Mn doped films. EDAX quantitative analysis revealed that the effective Mn doping is close to that of the intended. SEM observations revealed uniform spherical grains for all films with more porous and less dense grains at higher Mn content. The increase in Mn doping ratio to x = 0.1 decreases the carrier density and the carrier type changes to the P-type conduction. The transmittance values increased with Mn doping whereas the reflectance decreased. The optical band gap increased from 0.25 to 0.39 eV. Two layer-model was successfully used to simulate the ellipsometry measurements. The main layer was described by a combined contribution of Drude and Lorentz models. The thickness, the optical constants, and the surface roughness of the undoped and Mn doped films were extracted from the ellipsometry measurements. Upon Mn doping, the PL was quenched.