Uncertainty analysis for the determination of B 4 C optical constants by angle-dependent reflectance measurement for 40 nm to 80 nm wavelength.

The index of refraction and the extinction coefficient for thin films of boron carbide were determined by angle-dependent reflectance measurements in the vacuum-ultraviolet spectral range. The numerical approximation was done using transfer-matrix formalism in combination with particle swarm optimization for the fitting algorithm. By this, not only for the reflectance measurement but also for the numerical approximation, a profound uncertainty budget was developed. This includes possible effects due to contamination and intermediate layers. Thus it was possible to establish a method for determination of n and k with reliable and highly traceable uncertainties, and to significantly improve the consistency of existing data required for current developments in optical technology.