OPTICAL CHARACTERIZATION OF WEDGE-SHAPED THIN-FILMS OF AMORPHOUS ARSENIC TRISULFIDE BASED ONLY ON THEIR SHRUNK TRANSMISSION SPECTRA

Inhomogeneities in thin films have a large influence on the optical tr ansmission spectrum. If not corrected for, this may lead to too large calculated values of the absorption coefficient or the apparent presen ce of an absorption band tail as well as serious errors in the values of the refractive index and film thickness. The effect of thickness va riation on the optical transmission spectrum is taken into considerati on in the present case of amorphous arsenic trisulphide thin films pre pared by thermal evaporation. The analytical expressions proposed by S wanepoel, enabling the derivation of the optical constants of a wedge shaped thin film from its shrunk transmission spectrum only, have succ essfully been applied. Finally, the refractive-index dispersion is dis cussed in terms of the single-oscillator Wemple and DiDomenico model.