Yazar "Şafak, H." seçeneğine göre listele

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    Investigation of Current-Voltage and Capacitance-Voltage Characteristics of Ag/Perylene-Monoimide/n-gaas Schottky Diode
    (Elsevier, 2012) Şimşir, N.; Şafak, H.; Yüksel, Ö. F.; Kuş, M.
    Ag/perylene-monoimide(PMI)/n-GaAs Schottky diode was fabricated and the current-voltage (I-V) characteristics at a wide temperature range between 75 and 350 K and also the capacitance-voltage (C-V) characteristics at room temperature for 1 MHz have been analyzed in detail. The measured I-V characteristics exhibit a good rectification behavior at all temperature values. By using standard analysis methods, the ideality factor and the barrier height are deduced from the experimental data and also the variations of these parameters with the temperature are analyzed. In addition, by means of the Cheung and Cheung method, the series resistance and some other electrical properties are calculated for the diode. Finally, capacitance-voltage characteristics of device have been analyzed at the room temperature. From analyzing the capacitance measurements, Schottky barrier height is determined and then compared with the value which calculated from the I-V measurements at room temperature. Also, the concentration of ionized donors, built-in potential and some other parameters of diode are found using C-V characteristics. (C) 2012 Elsevier B.V. All rights reserved.
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    Optical Characterisation of CuInSe2 Thin Films Prepared by Two-Stage Process
    (SPRINGER-VERLAG, 2001) Yüksel, Ö. F.; Başol, B. M.; Şafak, H.; Karabıyık, H.
    Optical absorption spectra of CuInSe2 chalcopyrite semiconductor films prepared using a two-stage technique were investigated. In addition to absorption measurements, energy-dispersive analysis of X-rays (EDAX) and X-ray diffraction measurements (XRD) were also performed. Direct bandgap energy values for the CuInSe2 films were derived from the variation of (alphah upsilon)(2) with energy. All the measurements were performed on samples with various Cu/In ratios. It was determined from the absorption measurements that the materials have strong absorption at the fundamental band edge. The E-g values showed an increasing trend with decreasing Cu/In ratios.
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    Optical Constants of Thin Film Prepared by the Cd(OH)(2) Nanowires Synthesized Using the Arc Discharge Method
    (AMER SCIENTIFIC PUBLISHERS, 2014) Akın, Ümmühan; Şafak, H.; Eskizeybek, Volkan; Avcı, Ahmet; Yüksel, Ömer Faruk
    The optical constants of thin film prepared by cadmium hydroxide nanoparticles spray coated on the glass substrate held about at 100 degrees C temperature have been investigated using the optical transmission and reflection spectra. The transmission spectrum exhibits that the film has a high transparency (similar to 80%) at the infrared region. From standard optical analysis, direct band gap energy of Cd(OH)(2) was found as 3.13 eV, and also, it was seen that the calculated refractive index varies between 1.65 and 2.15 throughout the spectral region considered. The dispersion parameters such as oscillator energy, dispersion energy, and static and high frequency refractive index were determined in regard to the Wemple DiDomenico single oscillator model. Finally, some dielectric parameters of material such as relaxation time, dissipation (loss) factor, volume and surface energy loss functions and optical conductivity were calculated.