Further studies of the sensitivities attainable in using three optical functions to calculate n, k and thickness for thin films

All 56 combinations of three optical functions chosen from R_s, R_p, T_s, T_p, Φ_rs, Φ_rp, Φ_ts and Φ_tp have been investigated to discover their regions of sensitivity in n, k and d/λ coordinate space. When the arrays of error parallelepipeds were plotted, single quadrant patterns of high sensitivity were generated by 21 of these combinations, these being the ones containing one photometric and two polarimetric functions; the best combination was R_pΦ_rpΦ_tp which was viable at all angles of incidence and all thicknesses up to d/λ = 0.08. The remaining 35 combinations produced two-lobe patterns which were insensitive at small angles of incidence but improved as the angle of incidence increased and were best at 60°.