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  • Küçük Resim
    Öğe
    Effects of polymerization medium on electrical conductivity and optical properties of organic semiconductor-based polypyrrole
    (Wiley, 2007) Yakuphanoǧlu, Fahrettin; Aydın, Mehmet Enver
    The effects of tetrabutylammonium tetrafluoroborate (TBAFB), tetrabutylammonium hexafluorophosphate (TBAPF(6)), and paratoluene sulfonoicacid (PTSA) polymerization mediums on the electrical conductivity and optical properties of the polypyrrole (PPy) have been investigated. The electrical conductivity and optical properties of the samples polymerized in presence of TBAFB, TBAPF6, and PTSA organic salts change with medium of prepared polymer. The electrical conductivity of the TBAFB, PTSA, and TBAPF6 samples at 27 degrees C were found to be 3.43 x 10(-1), 4.48 x 10(-2), and 1.60 x 10(-4) (S/cm), respectively. The lowest optical band gap of the polymer was found to be 2.23 eV. The refractive index dispersion of the samples obeys single oscillator model. The obtained results suggest that polymerization medium changes electrical conductivity and optical properties of the PPy.
  • Küçük Resim
    Öğe
    Electrical characterization of Al/MEH-PPV/p-Si Schottky diode by current-voltage and capacitance-voltage methods
    (2007) Aydın, Mehmet Enver; Yakuphanoǧlu, Fahrettin; Eom, Jae-Hoon; Hwang, Do-Hoon
    The electrical characterization of the Al/poly[2-methoxy-5-(2?-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)/p-Si structure has been investigated by current-voltage and capacitance-voltage methods. The Al/MEH-PPV/p-Si Schottky diode with the ideality factor value of 1.88 obeys a metal-interfacial layer-semiconductor (MIS) configuration rather than an ideal Schottky diode due to the existence of an insulating layer on the organic semiconductor. The barrier height (?b, o = 0.80 eV) obtained from the I-V characteristic is lower than the barrier height (?b, o = 1.19 eV) obtained from the C-V characteristic. The discrepancy between ?b, o (I - V) and ?b, o (C - V) can be due to the existence of the interfacial native oxide and the organic MEH-PPV layers between the semiconductor and Schottky contact metal. The barrier height value for the Al/MEH-PPV film/p-Si/Al contact obtained at the room temperature that is significantly larger than that for the conventional Al/p-Si Schottky diode. The density distribution curves of the interface states is in the range (0.32-Ev) to (0.68-Ev)eV. The interface state density Nss ranges from 3.84×1014 cm-2 eV-1 in (0.32-Ev)eV to 1×1014 cm-2 eV-1 in (0.68-Ev)eV, of the Al/MEH-PPV/p-Si. The interface state density has an exponential rise with bias from the midgap towards the top of the valence band of the p-Si.
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    Öğe
    Investigation of ZnO nanostructures: Effect of metal and spinning speed on the physical properties
    (Inderscience Publishers, 2013) Benhaliliba, Mostefa; Benouis, Chahinez E.; Aida, M. S.; Ocak, Yusuf Selim; Yakuphanoǧlu, Fahrettin
    In this current work, we report on the surface morphology of pure (ZnO) and metal doped (MZO, M = Cu, Fe and Cd) zinc oxide nanostructures grown by sol-gel spin coating route onto a glass substrate at room temperature and speed of 1,000 rpm. We also investigate the effect of spinning speed on the physical and surface properties of coated ZnO films. The doping ratios Cu/Zn, Fe/Zn, Cd/Zn were kept at 2% in the solution. Atomic force microscope (AFM) revealed that nano-grains change in shape and growth orientation as a result of metal content. Average of grains sizes were found to be 87, 122, 174 and 260 nm respectively for pure, Cu, Fe and Cd doped ZnO. Based on the histogram profile, the shape looks like Gaussian curve for the pure ZnO, and it changes considerably for the M-doped ZnO films. Parameters of surface are investigated such as distribution of heights, power spectrum density (Psd), Fourier transform (Ft) of the picture and surface roughness (Rms). Spinning speed influences the surface and physical properties of coated ZnO films. The optimum results, high transparency (?72%) and low resistivity (9 k?cm), have been obtained with an increase in speed.