Determination of the thickness and optical properties by reflectance method

Abstract

In this study, we propose a method based on the reflection spectrum envelope to calculate the thickness and optical constants of a semi-transparent thin film deposited on a glass substrate. To validate this method, we compare these optical constants with those obtained from the transmission spectrum in two different thickness cases: one involving a film with a thickness of 700 nm and the other with a thin film of 80 nm. Comparative results of the methods, including well-established approaches such as Swanepoel, Chambouleyron, Sellmeier, Lorentz and Forouhi–Bloomer reveal notable accuracy with RMS errors of 0.21, 0.22, 0.31, 0.36 and 0.38% respectively. In contrast, the “Cauchy” method shows lower precision with a higher RMS error at 0.71%. The method proposed in this study, applied to a film with a thickness of 700 nm, demonstrates the lowest RMS error at 0.17%.