Browsing by Author "Monchev B."

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    Compositional dependence of the optical properties of silver containing As2Se3 thin films
    (2012-01-01) Ilcheva V.; Petkov P.; Petkova T.; Boev V.; Monchev B.
    We obtained amorphous thin films by evaporation and condensation in three-component systems based on As, Se and Ag. The aim was to investigate the influence of the third component on the thin film structure and optical properties. The refractive index and the film thickness were determined from the upper and lower envelopes of the optical transmission spectra measured in the spectral range 400 - 2500 nm. The absorption coefficient (α) was determined after extrapolating the values of n in the region of strong absorption (where α ≥ 104 cm-1); its spectral distribution is discussed. The dispersion of the refractive index was analyzed in terms of the single-oscillator Wemple-DiDomenico model. The shift of the optical absorption edge was described using the non-direct transition model proposed by Tauc. The optical band gap was calculated from the Tauc plot ahv B(Egopt - hv)2; the compositional dependence of the optical gap is also discussed. © Published under licence by IOP Publishing Ltd.
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    Optical behavior of (GeS1.5)1-x(AgI)x glasses
    (2013-01-01) Monchev B.; Petkova T.; Petkov P.; Ilcheva V.
    In this research we report deposition of thin films from the already synthesized chalcohalide (GeS1.5)1-x(AgI)x glasses, where x=5, 10, 20 mol.%. The bulk samples used and the corresponding layers are checked by XRD analysis which reveals only a diluted halo on the respective diffractograms. Some basic optical parameters of the investigated Ge-SAgI thin films are estimated and their relation with materials' composition is determined. The influence of the third component on the optical absorption is discussed. The optical energy gap (Eg) is determined from the Tauc plot h =B(EgTauc - h )2 and Eg 04 is found from the relationship a=f(hv ). The Eg values calculated by both methods reveal slight increase with silver iodide addition probably due to structural changes.© 2013 The Authors. Published by Elsevier B.V.