Ellipsometric characterization of optical, magneto-optical and magnetic recording media.

Abstract

This dissertation presents nondestructive optical characterization methods developed for thin films and bulk materials. These methods can be used to accurately measure polarization rotation and ellipticity, the reflection and transmission coefficients, the wavelength dependence of birefringence, Kerr rotation and ellipticity; the dielectric tensor of magneto-optical (MO) media, as well as the optical constants and thickness of thin film stacks. A series of optical, magneto-optical and magnetic recording media have been studied. A variable angle, multi-wavelength ellipsometer, and a MO Kerr spectrometer were used for these measurements. A general-purpose computer program has been used to analyze the experimental data. The in-plane and vertical birefringence of polycarbonate plastic substrates of optical disks have been measured for wavelengths between 360 nm and 860 nm, which covers the full range of interest for blue as well as for the current red and infrared recording. A dielectric tensor database for MO thin film materials of (BiDy)₃(FeGa)₅O₁₂ garnet, MnBi, multilayered Co/Pt, amorphous TbFeCoTa, fcc cobalt, and Heusler alloy PtMnSb has been established in the wavelength range of 400-780 nm. These materials are then evaluated based on the intrinsic MO figure of merit. In the area of hard disk magnetic recording, the optical constants of nickel phosphorous (NiP) coated substrate, CoNi/NiP magnetic film on NiP coated substrate, and the carbon overcoating layer have been obtained at several wavelengths. The excellent agreement between theory and experiment has shown that this nondestructive method is a sensitive tool for the characterization of optical thin film stacks.