Optical properties of Zn(O,S) thin films deposited by RF sputtering, atomic layer deposition, and chemical bath deposition

Zn(O,S) thin films 27 - 100 nm thick were deposited on glass or Cu(In_xGa_1-x)Se₂/Molybdenum/glass with RF sputtering, atomic layer deposition, and chemical bath deposition. The complex dielectric functions ε of these films were extracted by spectroscopic ellipsometry and transmission analyses. It is found that ε varies on a large scale, indicative of significant variations in the films´ chemical and physical properties, with the growth methods and deposition parameters. By fitting the ε spectra based on the parabolic band approximation, the E₀ critical point energies and broadening parameters were quantified to provide insights on the band gap, defect density, and phase segregation.