Influence of the deposition technique on the structural and optical properties of amorphous As S films

• Published in: Applied surface science 2005-06, Vol.246 (4), p.348-355
• Main Authors: González-Leal, J.M., Stuchlik, M., Vlcek, M., Jiménez-Garay, R., Márquez, E.
• Format: Article
• Language: English
• Subjects: As [sbnd]S films; PECVD; Spin coating; Thermal evaporation
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2004.11.050

Amorphous chalcogenide films of stoichiometric composition As 40S 60 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 localised-state tail width of these semiconducting films. In addition, information about the degree of structural randomness of these thin-film amorphous alloys was also obtained from this analysis, which is in good agreement with the conclusions derived from the X-ray diffraction results.