Optical constants with improved accuracy in the regions of L-, M- N- and O-absorption edges and their impact in multilayer modeling
Résumé
We are presenting a new set of measurements and a self-consistent determination of the optical constants (refractive index) of Cr, W and Pt thin films in the EUV/soft x-ray range. We use a combination of photoabsorption and reflectance data in the photon energy range 25 to 800 eV which include the L- and M-shell absorption edges of Cr and the N- and O-shell absorption edges of W and Pt. Our experimental data demonstrate for the first time highly resolved fine structure in the region of the Cr M2,3 and L2,3 edges, the W N4,5 and N2,3 edges and the Pt O2,3, N6,7 and N2,3 edges in both the absorptive and dispersive portions of the refractive index, resulting in differences of up to a factor of 3 compared to optical constant values published earlier, for these materials. The improved accuracy of the new optical constants is validated via the f-sum rule test and by simulating experimental reflectance data of single-layer and multilayer coatings containing these materials [1-3]. The implications of these new results, as well as plans for future work, will also be discussed.