Accurate and facile determination of the index of refraction of organic thin films near the carbon 1s absorption edge
Hongping Yan, Cheng Wang, Allison R. McCarn, and Harald Ade
Accepted
A practical and accurate method to obtain the index of refraction, especially the decrement, d, across the carbon 1s absorption edge is demonstrated. The combination of absorption spectra scaled to the Henke atomic scattering factor database, the use of Doubly Subtractive Kramers-Kronig relations, and high precision specular reflectivity measurements from thin films allowed the notoriously difficult to measure d to be determined with high accuracy. No independent knowledge of the film thickness or density is required. High confidence interpolation between relatively sparse measurements of d across an absorption edge has been achieved. Accurate optical constants determined by this method will greatly improve the simulation and interpretation of resonant soft X-ray scattering and reflectivity data. The method was demonstrated using poly(methyl methacrylate) and should be extendable to all organic materials.