Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Subject: search.filters.subject.Absorption spectroscopyWoS Q: search.filters.wosQuartile.Q2

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  • Article
    Citation - WoS: 11
    Citation - Scopus: 11
    The Effects of Native and Light Induced Defects on Optoelectronic Properties of Hydrogenated Amorphous Silicon-Germanium (a-Sige:h) Alloy Thin Films
    (Springer Verlag, 2010) Güneş, Mehmet; Yavaş, Mert; Klomfaß, Josef; Finger, Friedhelm
    Effects of native and light induced defects states in hydrogenated amorphous silicon-germanium alloy thin films with different Ge concentrations have been investigated by using steady-state photoconductivity, dual beam photoconductivity (DBP), transmission spectroscopy and photothermal deflection spectroscopy (PDS) techniques. In the annealed state, sub-bandgap absorption spectra obtained from both PDS and DBP overlap very well at energies above 1.4 eV. However, differences in α (hν) spectrum exist in the lower energy part of absorption spectrum. The α (hν) value measured at 1.0 eV is the lowest for 10% Ge sample and increases gradually as Ge content of the sample increases. In the light soaked state, time dependence of photoconductivity decay obeys to t -x power law, where x changes from 0.30 to 0.60 for samples with low Ge content and 0.05-0.1 for samples with high Ge content. Correspondingly, the increase of the sub-bandgap absorption coefficient at lower energies obeys to t y power law, where y values are lower than the x value of the same sample. It can be inferred that sub-bandgap absorption and photoconductivity measurements are not controlled by the same set of defects created in the bandgap of alloys. © 2009 Springer Science+Business Media, LLC.
  • Article
    Citation - WoS: 13
    Citation - Scopus: 16
    Thermochromism in Oligothiophenes: the Role of the Internal Rotation
    (American Chemical Society, 2002) Elmacı, Nuran; Yurtsever, Ersin
    The relation between thermochromism in polythiophenes and the internal rotation is studied by density-functional theory (DFT). For head-to-tail methyl-substituted thiophenes, rotational potential maps of dimer and trimer are calculated. With time-dependent-DFT methodology the absorption spectra of these oligomers in UV-vis region are calculated as functions of the torsional angles. Theoretical temperature-dependent UV-vis spectra are generated from the distribution of torsional angles. The results show that the internal rotation alone is not sufficient to explain the mechanism of thermochromism.