Thickness homogeneity of GexSb40-xS60 chalcogenide thin films

The thickness homogeneity of thin chalcogenide GexSb40-xS60 films evaporated on glass substrates is investigated. The problem has been tackled by studying the transmission having in mind that inhomogeneities in thin films have a large influence on the optical transmission spectrum. The effects of thickness variation and surface roughness on the transmission spectrum have been considered. It has been found that the film thickness is rather homogeneous over the film area. The inconsistency of the experimental and theoretical oscillations in the transmission spectra indicated inhomogeneities due to surface roughness. An atomic force microscopy study has shown a roughness below 50 nm over an area of 10x10 mu m. Second harmonic generation scanning has also revealed rather good homogeneity over the film area.