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Öğe Analysis of inhomogeneous barrier and capacitance parameters for Al/rubrene/n-GaAs (100) Schottky diodes(ELSEVIER SCIENCE SA, 2015) Tugluoglu, N.; Caliskan, F.; Yuksel, O. F.In this paper, 5,6,11,12-tetraphenylnaphthacene (rubrene) was prepared on n type GaAs (100) substrate by spin coating. The device parameters of Al/rubrene/n-GaAs (100) Schottky diode have been investigated by means of current-voltage (I-V) characteristics in the temperature range 100-300 K by steps of 50 K and capacitance-voltage (C-V) and conductance-voltage (G-V) characteristics at 1 MHz and 300 K. It was observed that ideality factors increased and barrier heights decreased with the decreasing temperature. The observed anomaly of temperature dependence of Schottky barrier height and ideality factor are explained by Gaussian distribution of Schottky barrier height in the same temperature ranges. Al/rubrene/n-GaAs Schottky barrier diode has been shown to have a Gaussian distribution with mean barrier height ((Phi) over bar (B)) of 1.076 eV and standard deviation (sigma(s)) of 0.119 V. Schottky barrier height (Phi(B)), series resistance (R-s), and the density of interface trap states (N-s s) of the diode were calculated as 1.004 eV, 1.18 k Omega and 2.145 x 10(11) eV(-1) cm(-2) for 1 MHz, respectively. (C) 2014 Elsevier B.V. All rights reserved.Öğe Analysis of temperature dependent electrical properties of Au/perylene-diimide/n-Si Schottky diodes(ELSEVIER SCIENCE SA, 2013) Yuksel, O. F.; Tugluoglu, N.; Safak, H.; Nalcacigil, Z.; Kus, M.; Karadeniz, S.The electrical properties of Au/perylene-diimide/n-Si Schottky diode have been determined by means of current-voltage measurements in the temperature range of 75-300 K. These devices showed good rectifying behavior and the temperature dependence of the current-voltage characteristics could be explained by thermionic emission mechanism. The experimental values of barrier height and ideality factor for device have been calculated as 0.168 eV and 7.63 eV at 75 K and 0.690 eV and 1.57 eV at 300 K, respectively. The fabricated Schottky diode shows non-ideal current-voltage behavior and so it is thought that the device have a metal-interface layer-semiconductor configuration. In addition to current-voltage measurements, the room temperature capacitance-voltage characteristics of Au/perylene-diimide/n-Si devices were also investigated. The barrier height value of 1.051 eV obtained from the capacitance-voltage measurements was found to be higher than that of 0.690 eV obtained from the current-voltage measurements at room temperature. Furthermore, the energy distribution of the interface state density determined from current-voltage characteristics increases exponentially with bias from 8.01 x 10(12) eV(-1) cm(-2) at ( E-c - 0.666) eV to 5.86 x 10(13) eV(-1) cm(-2) at (E-c - 0.575) eV. (C) 2013 Elsevier B. V. All rights reserved.Öğe Electrical Characterization of Au/Fluorene-Carbazole (FC)/p-Si Schottky Barrier Diodes(ELSEVIER SCIENCE BV, 2016) Yildirim, M.; Tugluoglu, N.; Yuksel, O. F.; Erdogan, A.; Kus, M.The Fluorene-Carbazole (FC) was synthesized by Suziki method in this study. The organic semiconductor is prepared on p-type Si substrate by spin coating method. We have produced Au/FC/p-Si Schottky diodes. We have investigated the current-voltage characteristics over temperature range between 200 and 350 K. The measured current-voltage (I-V) characteristics of device have demonstrated a good rectification behaviour at all temperatures. The parameters such as the ideality factor (n), barrier height (Phi(B)) and series resistance (R-S) were determined from the experimental data using standard current-voltage analysis method. At T=200 K, we have found the values of the n and Phi(B) as 2.78 and 0.491 eV respectively. On the other hand, their values were found as n=1.86 and Phi(B)=0.779 eV at T=350 K. The values of R-S are calculated using Cheung and Cheung functions between 200 K and 350 K. The H(I)-I plot of Cheung and Cheung method shows RS of 1823.23 Omega for 200 K and value of 952.6 Omega for 350 K. (C) 2015 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of Conference Committee Members of International Semiconductor Science and Technology Conference 2015 (ISSTC 2015).Öğe Electrical properties of Au/perylene-monoimide/p-Si Schottky diode(ELSEVIER SCIENCE SA, 2013) Yuksel, O. F.; Tugluoglu, N.; Gulveren, B.; Safak, H.; Kus, M.In this work, we have fabricated an Au/perylene-monoimide (PMI)/p-Si Schottky barrier diode. We have investigated how electrical and interface characteristics like current-voltage characteristics (I-V), ideality factor (n), barrier height (Phi(B)) and series resistance (R-s) of diode change with temperature over a wide range of 100-300 K. Detailed analysis on the electrical properties of structure is performed by assuming the standard thermionic emission (TE) model. Possible mechanisms such as image force lowering, generation-recombination processes and interface states which cause deviations of n values from the unity have been discussed. Cheung-Cheung method is also employed to analysis the current-voltage characteristics and a good agreement is observed between the results. It is shown that the electronic properties of Schottky diode are very sensitive to the modification of perylene-monoimide (PMI) interlayer organic material and also to the temperature. The ideality factor was found to decrease and the barrier height to increase with increasing temperature. The temperature dependence of barrier height shows that the Schottky barrier height is inhomogeneous in nature at the interface. Such inhomogeneous behavior was explained on the basis of thermionic emission mechanism by assuming the existence of a Gaussian distribution of barrier heights. (c) 2013 Elsevier B.V. All rights reserved.Öğe Frequency dependent interface state properties of a Schottky device based on perylene-monoimide deposited on n-type silicon by spin coating technique(ELSEVIER SCI LTD, 2013) Tugluoglu, N.; Yuksel, O. F.; Karadeniz, S.; Safak, H.We have reported a detailed investigation of frequency dependent properties of the Au/perylene-monoimide (PMI)/n-Si Schottky diodes in this study. Schottky diodes based on PMI have been fabricated by spin coating method. The capacitance-voltage (C-V) and conductance-voltage (G-V) characteristics have been measured in the frequency range from 30 kHz to 1 MHz at room temperature. The values of measured capacitance C-m and conductance G(m) under both reverse and forward bias have been corrected for the effect of series resistance to obtain the real diode capacitance and the conductance values. The density of interface states (D-it) distribution profiles as a function of frequency has been extracted from the corrected C-V and G-V measurements. Interface trap states of the PMI/n-Si Schottky device have decreased by increasing the applied frequency and were found to be 8.13 x 10(11) and 1.75 x 10(11) eV(-1) cm(-2) for 30 kHz and 1 MHz, respectively. (C) 2013 Elsevier Ltd. All rights reserved.Öğe Investigation of optical and dispersion parameters of electrospinning grown activated carbon nanofiber (ACNF) layer(ELSEVIER SCIENCE SA, 2018) Dincer, K.; Waisi, B.; Onal, G.; Tugluoglu, N.; McCutcheon, J.; Yuksel, O. F.Activated carbon nanofiber (ACNF) layers are prepared by electrospinning method. We have investigated the optical properties of ACNF layer using UV-vis-NIR spectrophotometer. The optical constants such as refractive index, extinction coefficient and dielectric constants were evaluated using reflectance and transmittance spectra for ACNF layer. The optical energy gap of ACNF layer was determined as 1.07 eV. The refractive index dispersion of ACNF layer was analyzed by using the single oscillator model proposed by Wemple and DiDomenico. The dispersion parameters such as oscillator energy and dispersion energy values of ACNF layer were determined. Several dispersion parameters such as optical dielectric constant at higher frequency, lattice dielectric constant, oscillator average wavelength, oscillator average strength and the ratio of carrier concentration to the effective mass were also determined by analysis of refractive index dispersion. Furthermore, the optical conductivity of ACNF layer was evaluated from the analysis of optical dielectric constants.Öğe The modification of Schottky barrier height of Au/p-Si Schottky devices by perylene-diimide(AMER INST PHYSICS, 2013) Yuksel, O. F.; Tugluoglu, N.; Safak, H.; Kus, M.Perylene-diimide (PDI) thin film was fabricated by spin coating method on p-Si single-crystal substrate to prepare Au/PDI/p-Si Schottky device. The electrical properties of the Au/PDI/p-Si Schottky device were investigated by current-voltage (I-V) measurements in the temperature range 80-300K and room temperature capacitance-voltage (C-V) measurement. Results showed a rectification behavior. Junction parameters such as ideality factor (n), barrier height (phi(B0)), series resistance (R-s) interface state density (N-ss), built-in potential (V-bi), carrier concentration (N-A), and the width of the depletion layer (W-D) were obtained from the I-V and C-V measurements. The values of ideality factor (n) and barrier height (BH) for the Au/PDI/p-Si structure from the I-V measurements were obtained as 1.77 and 0.584 eV at 300 K, 7.78 and 0.176 eV at 80 K, respectively. It was seen that the BH value of 0.584 eV calculated for the Au/PDI/p-Si structure was significantly larger than the value of 0.34 eV of conventional Au/p-Si Schottky diodes at room temperature. Thus, modification of the interfacial potential barrier for Au/p-Si diodes has been achieved using a thin interlayer of the peryleen-diimide organic semiconductor; this has been ascribed to the fact that the peryleen-diimide interlayer increases the effective barrier height because of the interface dipole induced by passivation of the organic layer. Furthermore, the energy distribution of the interface state density determined from I-V characteristics increases exponentially with bias from 1.11 x 10(12) eV(-1) cm(-2) at (0: 556 - E-v) eV to 11.01 x 10(13) eV(-1) cm(-2) at (0:449 - E-v) eV. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4789021]Öğe Optical characterization of Cu2ZnSnS4 nanocrystals thin film(SPRINGER, 2016) Kisnisci, Z.; Ozel, F.; Yuksel, O. F.; Tugluoglu, N.Synthesis of nanostructured powders of tetragonal Cu2ZnSnS4 (CZTS) nanocrystals was carried out based on the hot-injection process. High-quality CZTS thin films were prepared by spin coating method onto the Corning 1737 glass substrates. CZTS nanoparticles were characterized using X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and high resolution TEM. It is observed that a good quality CZTS film can be obtained by spin deposition at room temperature. The optical properties of the film were studied using UV-visible spectra between 300 and 1000 nm wavelength range. The direct optical band gap of the film evolved as 1.49 eV. This value is close to the ideal band gap for highest theoretical conversion efficiency of solar cell. The optical absorption coefficients of the film between 300 and 1000 nm are found to be about 2 and 7.6 x 10(4) cm(-1), respectively. The optical dispersion parameters of the film were also determined by Wemple-DiDomenico single oscillator model.Öğe Optical characterization of Cu2ZnSnSe4-xSx nanocrystals thin film(ELSEVIER SCIENCE SA, 2016) Yildirim, M.; Ozel, F.; Tugluoglu, N.; Yuksel, O. F.; Kus, M.Cu2ZnSnSe4-xSx (CZTSeS) nanocrystals have been shown to be a potential application for sustainable thin-film solar cell devices. In this paper, we have presented the growth of nanocrystals CZTSeS and their thin films applications successfully prepared on soda-lime glass substrates by using spin coating techniques. The CZTSeS nanocrystals have been synthesized by hot-injection method. In-depth characterization has indicated that pure stoichiometric CZTSeS nanocrystals with an average particle size mostly distributed between 15 and 20 nm have been formed. We have analyzed the optical transmission and reflection spectra of nanocrystal CZTSeS thin film. Optical band gap E-g and absorption coefficient (a) of thin film have been determined by standard optical analysis and also several optical parameters such as refractive index (n), extinction coefficient (k), the Urbach energy (E-U) and real and imaginary parts of dielectric constant (epsilon) have been calculated. Detailed characterization data including X-ray diffraction, surface morphology, cross section analysis, optical transmittance and reflectance spectroscopy have been presented in order to use in the performance of single-junction solar devices. Optical measurements have showed a band gap of 1.51 eV, which is optimal for a single-junction solar device. (C) 2016 Elsevier B.V. All rights reserved.Öğe Temperature dependence of current-voltage characteristics of Al/rubrene/n-GaAs (100) Schottky barrier diodes(ELSEVIER SCIENCE BV, 2016) Yuksel, O. F.; Tugluoglu, N.; Caliskan, F.; Yildirim, M.5,6,11,12-tetraphenylnaphthacene (rubrene) is fabricated by spin coating technique on n type GaAs (100) substrate. The current-voltage (I-V) characteristics of Al/rubrene/n-GaAs (100) Schottky diode have been measured in the temperature range of 100-300 K. The experimental values of saturation current (I-0), ideality factor (n) and barrier height (Phi(B)) are calculated as 2.749 pA, 6.051 and 0.297 eV at 100 K and 57.54 pA, 1.918 and 0.870 eV at 300 K, respectively. The values of series resistance (R-S) are calculated using Cheung functions at all temperatures. The R-S values are found as 1276.4 Omega and 119.7 Omega for 100 K and 300 K, respectively. It is found that barrier heights increased while ideality factors and series resistances decrease with the increasing temperature. (C) 2015 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of Conference Committee Members of International Semiconductor Science and Technology Conference 2015 (ISSTC 2015).
