Optical characterization of wedge-shaped thin films of amorphous arsenic trisulphide based only on their shrunk transmission spectra

Abstract

Inhomogeneities in thin films have a large influence on the optical transmission spectrum. If not corrected for, this may lead to too large calculated values of the absorption coefficient or the apparent presence of an absorption band tail as well as serious errors in the values of the refractive index and film thickness. The effect of thickness variation on the optical transmission spectrum is taken into consideration in the present case of amorphous arsenic trisulphide thin films prepared by thermal evaporation. The analytical expressions proposed by Swanepoel, enabling the derivation of the optical constants of a wedge-shaped thin film from its shrunk transmission spectrum only, have successfully been applied. Finally, the refractive-index dispersion is discussed in terms of the single-oscillator Wemple and DiDomenico model.