Preparation and investigation of structure, optical, nonlinear optical and thermoelectric properties of Bi 2 Se 3 thin film

Bi2Se3 thin film was prepared using thermal evaporation . Structure and surface topography were investigated using both of Diffraction Electron Microscope (DEM) and Transmission Electron Microscope (TEM). Optical results confirmed that thin film has a direct energy gap. Moreover, the values for all of oscillating energy (Eo), dispersion energy (Ed) and ratio of the free carrier concentration on the effective mass (N/m*) were determined optically. The dielectric constant (ε\) and tangent loss (ε\) were calculated. The density of states (DOS) for both of valence band (Nv) and conduction band (Nc) and also position of Fermi level were determined. The nonlinear optical results such as third-order optical susceptibility (χ(3)), refractive index (n2) and absorption coefficient (βc) were determined. The influence of temperature on IV results was studied; finally the dependence of all of Dispersion factor (D), parallel inductance (Lp) and Seebeck coefficient (S) values on temperature for this film was studied.