Physics / Fizik

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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: 266
    Citation - Scopus: 292
    High Quality Ito Thin Films Grown by Dc and Rf Sputtering Without Oxygen
    (IOP Publishing Ltd., 2010) Tuna, Öcal; Selamet, Yusuf; Aygün, Gülnur; Özyüzer, Lütfi
    High quality indium tin oxide (ITO) thin films were grown without oxygen by both dc and RF magnetron sputtering techniques on glass substrates. The effects of substrate temperature, film thickness and sputtering method on the structural, electrical and optical properties of the as-grown films were investigated. The results showed that the substrate temperature had substantial effects on the film properties, in particular on the crystallization and resistivity. When the substrate temperature was increased to 150 °C, crystallization in the (2 2 2) plane started appearing for both dc and RF sputtered films. We additionally found that with further increments of substrate temperature, the preferred crystallization orientation changed differently for dc and RF sputtered films. Optical transmission in the visible region for a film thickness of 70 nm was found to be above 85%. The bandgap was calculated to be about 3.64 eV for the substrate temperature of 150 °C for a 70 nm thick film. The value of the bandgap increased with respect to the increment in film thickness as well as substrate temperature. We also measured the temperature dependence of the resistivity and Hall coefficient of the films, and calculated the carrier concentration and Hall mobility. Very low room temperature resistivities for dc and RF magnetron sputtered grown films of about 1.28 × 10-4 Ω cm and 1.29 × 10-4 Ω cm, respectively, were obtained. © 2010 IOP Publishing Ltd.