Determination of surface roughness and optical constants of inhomogeneous amorphous silicon films

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 for the absorption coefficient or the apparent presence of an absorption band tail as well as serious errors in the values of refractive index and thickness. The effects of thickness variation, surface roughness and variation in refractive index on the transmission spectrum are analysed. Analytical expressions are derived from which all the optical constants of an inhomogeneous film can be calculated from the transmission spectrum.