Analysis of errors in thin-film optical parameters derived from spectrophotometric measurements at normal light incidence

A comparative analysis is made of the errors in deriving the optical parameters (n, refractive index; k, absorption coefficient; d, film thickness) of thin films from spectrophotometric measurements at normal light incidence. The errors in determining n, k, and d by the (TRfRb), (TRfRm), (TRbRm)I (TRf), (TRm), and T(k = 0) methods are compared. It is shown that they are applicable to optical constants of thin films in the n > 1.5, k < 4.5, and d/lambda = (0;02-0.3) range, and their combinations make possible the determination of n and k to an accuracy of better than +/-4%. To derive the optical constants in a wide spectral range with high accuracy and isolate the correct physical solutions reliably, one should apply all methods, using the relevant solutions with the lowest errors, as shown in this research, when determining the optical constants of As2S3 and Sb2Se3 films. (C) 1998 Optical Society of America.