Optical constants of thin films by an optimized reflection ratio method

Abstract

A new method for determining optical constants n and k, for thin absorbing films supported by a dielectric substrate, has been devised. Measurement of the ratio of two reflection coefficients R_parallel/R_{perpendicular} is made at two angles of incidence, and the film thickness d is determined independently. Optimum angles of incidence for experimental measurement have been determined for 10less-than-or-eq, slantnless-than-or-eq, slant40 and 10less-than-or-eq, slantkless-than-or-eq, slant40 for many optical film thicknesses d/λ in the range 001less-than-or-eq, slantd/λless-than-or-eq, slant025. The method, when used at these optimum angles, yields n and k accurate to ±005 for values of d/λgt-or-equal, slanted005, providing angles are measured to better than ±01°, reflection ratios are measured to better than ±001 and values of d/λ are measured to better than ±0005.