Optical properties of thermally evaporated Bi2Se3 thin films treated with AgNO3 solution

Bismuth selenide (Bi2Se3) thin films have been prepared onto clean glass substrates by the thermal evaporation technique. The deposited films were then immersed in silver nitrate solution for different periods of time, followed by annealing in Argon atmosphere at 473 K for 1 h, to obtain Ag/Bi2Se3 samples. The prepared films have been examined by X-ray and transmission electron microscopy for structural determination. The optical transmission and reflection spectra of the deposited films have been recorded within the wavelength range 400–2500 nm. The variation of the optical parameters of the prepared films, such as refractive index, n, and the optical band gap, Eg as a function of the immersion duration times has been determined. The refractive index dispersion in the transmission and low absorption region is adequately described by the well-known Sellmeier dispersion relation, whereby the values of the oscillator strength, oscillator position, the high-frequency dielectric constant, ε∞ as well as the carrier concentration to the effective mass ratio, N/m* were calculated as a function of the immersion duration time.