Validation of a correction procedure for removing the optical effects from transmission spectra of thin films on substrates

Abstract

Transmission spectra of thin films on double side polished substrates feature a quasi sinusoidal baseline superimposed onto the true absorption spectra of the thin film. The quasi sinusoidal baseline is due to strong interference from multiple reflections within the film and can directly affect the relative degree of the measured absorption in the film. In a previous article [S. W. King and M. Milosevic, J. Appl. Phys. 111, 073109 (2012)], we described a method for the removal of these optical effects from infrared transmission spectra. This method renormalizes the spectrum and removes modulations imprinted onto the absorption by interference fringes. Here, we use simulated spectra for a model material to explicitly validate that the proposed correction procedure accurately extracts the pure absorption coefficient of the thin film and is not an ad hoc baseline correction procedure.