Derivation of Optical Constants of Metals from Thin-Film Measurements at Oblique Incidence

The reflectance R and transmittance T of thin absorbing films deposited on a transparent substrate are calculated for normal and oblique incidence, s and p polarization, and different film thicknesses. The results are presented as contours of constant R and T on the ñ plane, where ñ is the complex refractive index. The conditions for sensitive dependence of measured quantities on ñ are examined. A computer-based method of finding ñ from chosen combinations of measured R or T values is described. Oblique incidence measurements on thin films can give accurate results in some regions where other methods may be less sensitive. Accurate film-thickness values can be obtained from the optical measurements.