Amorphous chalcogenide films of stoichiometric composition As40S60 have been prepared by three different deposition
techniques, namely, vacuum thermal evaporation, plasma-enhanced chemical vapour deposition (PECVD) and spin coating.
Indications of film-thickness inhomogeneities were found in all samples. Thermally evaporated and chemically deposited
samples showed wedge-shaped surface profiles, while significant surface roughness was evidenced in the spin-coated ones.
Refractive-index values of the film samples were obtained, with accuracy better than 1%, by using the envelope method most
suitable for each particular film surface profile. Structural information of the samples has been gained from X-ray diffraction
experiments, and also inferred from the analysis of the dispersion of the refractive index, on the basis of a single-oscillator
model. Analysis of the optical absorption spectra allowed both calculating the optical band gaps and estimating the localisedstate
tail width of these semiconducting films. In addition, information about the degree of structural randomness of these thinfilm
amorphous alloys was also obtained from this analysis, which is in good agreement with the conclusions derived from the Xray
As–S films , Thermal evaporation , Spin coating , PECVD