Ellipsometry study of the dielectric function of Ag2Se thin films deposited by electrodeposition

Polycrystalline β-Ag2Se thin films were obtained by electrodeposition. Crystal structure, morphology, and chemical composition properties of the films were analyzed and discussed. In addition, the complex dielectric function < ε > and band gap energy of electrodeposited β-Ag2Se thin films were studied by ellipsometry spectroscopy technique. A dispersion model with three Tauc-Lorentz oscillators was used to fit the ellipsometry angles Ψ and Δ, taking into account a multilayered system consisting of Glass/Fluorine-doped Tin Oxide (FTO)/FTO + β-Ag2Se/β-Ag2Se/roughness. The optical effect contribution of the FTO + β-Ag2Se interlayer in the optical model was also observed by optical transmittance. As a result, the experimental band gap of β-Ag2Se thin films is 0.24 eV.