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    Effect of an azo dye (DR1) on the dielectric parameters of a nematic liquid crystal system
    (Elsevier, 2007) Ozder, S.; Okutan, M.; Koysal, O.; Goktas, H.; San, S. E.
    The dielectric parameters and relaxation properties of azo dye (DR1) doped E7 and pure E7 liquid crystal (LC) have been investigated in a wide frequency range of 10k-10MHz through the dielectric spectroscopy method at room temperature. Dielectric anisotropy (Delta epsilon) property of the LC changes from the positive type to negative type and dielectric anisotropy values decrease with doping of DR1. The relaxation frequency f(r) of E7 and E7/DR1 LC was calculated by means of Cole-Cole plots. Influence of bias voltage on the dielectric parameters has also been investigated. (c) 2006 Elsevier B.V. All rights reserved.
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    Influence of Annealing Temperature on the Electrical and Optical Properties of CdS Thin Films
    (Polish Acad Sciences Inst Physics, 2012) Elmas, S.; Ozcan, S.; Ozder, S.; Bilgin, V.
    CdS thin films were grown onto glass substrates at the substrate temperature of 573 +/- 5 K by ultrasonic spray pyrolysis technique. The electrical and optical properties of the films were characterized before and after thermal annealing by using electrical resistivity measurements and UV/VIS spectrophotometer, respectively. Thermal annealing of CdS films was carried out in air ambient at various annealing temperatures from 473 to 673 K. The variation in electrical conductivity and optical parameters such as transmittance, absorbance and energy band gap of the films with thermal annealing temperature was investigated.
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    Investigation of optical parameters of Ag-In-Se thin films deposited by e-beam technique
    (Elsevier Science Bv, 2008) Colakoglu, T.; Parlak, M.; Ozder, S.
    The optical properties of the Ag-In-Se (AlS) thin films deposited by e-beam technique were investigated by means of the optical transmittance measurements. The optical absorption coefficients of the films were found to vary from 10(3) to 10(5) cm(-1) over the wavelength range of 300-1100 nm. The real and imaginary parts of the refractive index and dielectric constant for the as-grown and annealed films in between 100 and 400 degrees C were evaluated by means of both envelope method (EM) and continuous wavelet transform (CWT) method and the results were in quite good agreement with each other. The refractive index, n, dispersion over the measured wavelength range was explained by applying single-oscillator model (SOM) and the related parameters were calculated. The optical absorption process for the AIS thin films was characterized by three direct transitions from three closely spaced valence bands to a single conduction band due to the splitting of the valence band under the influence of the tetragonal crystalline field and spin-orbit interaction. The direct optical band gap energy decreases as the annealing temperature increases because of the increase in the width of band tail states near valence-band edge caused by the Se segregation. The two distinct parameters of the quasicubic model; crystal-field splitting Delta(CF), and spin-orbit splitting, Delta(SO), were calculated for as-grown and annealed AlS thin films. (C) 2008 Elsevier B.V. All rights reserved.