Parametric Optical Property Database for CdSe1−xSx Alloys

A comprehensive database of the optical response in the form of complex dielectric function (e) spectra of magnetron co-sputtered CdSe1−xSx alloy thin films is developed spanning the full 0 ≤ x ≤ 1 range of compositions. A parametric model is presented and used to determine e describing each film while in both as-deposited and thermally annealed states. This model combines a critical point electronic transition lineshape and an Urbach tail in the above- and below-bandgap portions of the measured spectrum, respectively, while maintaining first derivative continuity. Additionally, this hybrid parametric description of e automatically determines the Urbach energy (EU) describing the width of the sub-bandgap absorption tail, thereby providing a relative measure of the defect density of the modeled material. These as-deposited CdSe1−xSx films are generally found to be the most defective at intermediate compositions with some EU reaching energies > 200 meV. Annealing reduces EU in all films to a relatively uniform value