Determination of the optical constants and thickness of a thin film on a substrate - An alternative to the envelope method

The envelope method is a well-known methods of analysis. used for the determination of the optical constants - refractive index and extinction coefficient - and thickness of a thin film on a substrate. from the spectrophotometric traces of transmittance or reflectance of the film-coated substrate against wavelength. However. we have found that simultaneous analysis of the transmittance and reflectance traces against wavelength has often yielded more reliable values for the optical constants and thickness of the film, as compared to the envelope method of analysis. Some of the inherent uncertainties and consequent sources of error involved in the envelope method are avoided in the present approach.