International Journal of Materials Engineering and Technology
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Abstract: Amorphous chalcogenide
semiconducting films of two different binary compositions, and
have
been prepared by three different deposition techniques, namely, vacuum thermal
evaporation (VTE), plasma-enhanced chemical vapour deposition (PECVD), and spin
coating (SC). Indications of film-thickness irregularities were found in all the
samples studied: VTE and PECVD samples showed wedge-shaped profiles, while the
SClayers presented
notable surface roughness. Refractive-index values of the thin-film samples were
calculated, with accuracy better than 1%, using the envelope method considered
most suitable for each film-thickness profile. Structural information on the
chalcogenide films has been obtained from X-ray diffraction (XRD) measurements,
and has also been inferred from the detailed analysis of the refractive-index
dispersion, on the basis of the Wemple-DiDomenico single-effective-oscillator
model. The Tauc gap of these films has been calculated and their localized-state
tail width has been estimated by analyzing the optical absorption edges;
valuable information about the degree of structural randomness of these
amorphous alloys was obtained from the Tauc slope, and this is in excellent
agreement with the conclusions drawn from the XRD results.
