Optical dielectric functions for amorphous Al2O3 and γ-Al2O3

Abstract

Using the classical oscillator model, the optical dielectric functions for amorphous alumina (a‐Al₂O₃) and gamma alumina (γ‐Al₂O₃) thin films prepared by ion implantation and subsequent annealing of sapphire (α‐Al₂O₃) substrates were determined for the first time from analysis of infrared reflection spectra. Two transverse optical modes at 422 and 721 cm⁻¹ were obtained for the a‐Al₂O₃ film while four modes at 357, 536, 744, and 807 cm⁻¹ were identified for the γ‐Al₂O₃ film. Also, the problems involving the analysis of modes with large damping are discussed.