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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 Capacitance and Conductance-Frequency Characteristics of Au/n-Si Schottky Structure with Perylene-Diimide (PDI) Organic Interlayer(SPRINGER, 2017) Yuksel, O. F.; Kus, M.; Yildirim, M.We report the interface properties of a perylene-diimide thin film between Au and n-Si substrate fabricated by the spin coating method. The relaxation time (tau) and interface trap density (D (it)) characteristics of the fabricated structure were obtained across various voltage ranges (0.0 V-300 mV) and various frequency ranges (1 kHz-1 MHz). We observed a peak in G (it)/omega versus log (f) plots from 0.0 V to 300 mV. This peak shows the presence of the interface state and its relaxation time. We observed a decrease in values at the same time as an increase in N (ss) values with the increasing applied voltage for the sample. The N (ss) and tau values found to be in the ranges 1.50 x 10(12) eV(-1) cm(-2)-2.83 x 10(12) eV(-1) cm(-2) and 2.83 x 10(-6) s-4.82 x 10(-7) s between 0.0 V and 0.3 V, respectively.Öğe A detailed analysis of current-voltage characteristics of Au/perylene-monoimide/n-Si Schottky barrier diodes over a wide temperature range(AMER INST PHYSICS, 2011) Yuksel, O. F.; Kus, M.; Simsir, N.; Safak, H.; Sahin, M.; Yenel, E.The current-voltage characteristics of Au/perylene-monoimide (PMI)/n-Si Schottky device have been investigated at a wide temperature range between 75 and 300 K in detail. The measured current-voltage (I-V) characteristics of the device show a good rectification behavior at all temperatures. The electronic parameters such as the ideality factor and the barrier height are determined from the experimental data using standard current-voltage analysis method and also temperature dependence of these parameters is analyzed. In addition to the standard analysis, using the Cheung and Cheung method, the series resistance and some other electrical properties are calculated for the device, and a good agreement is obtained between relevant diode parameters. It was observed that Au/PMI/n-Si Schottky diodes exhibit space charge limited (SCL) conduction at all temperatures. Therefore, we have analyzed this SCL current mechanism in more detail. From this analysis, several electronic parameters related with the SCL mechanism are determined, and it is found that Poole-Frenkel effect is dominant in reverse bias. (C) 2011 American Institute of Physics. [doi:10.1063/1.3610394]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 A Highly Sensitive Ascorbic Acid Sensor Based on Graphene Oxide/CdTe Quantum Dots-Modified Glassy Carbon Electrode(PLEIADES PUBLISHING INC, 2019) Kucukkolbasi, S.; Erdogan, Z. O.; Baslak, C.; Sogut, D.; Kus, M.Quantum dots (QDs) and graphene oxide (GO) are extremely attractive and important nanomaterials in analytical applications because of their their unusual chemical, physical and electronic properties. In this work, CdTe QDs with the size of about 3 nm were prepared and a novel electrochemical sensing material of ascorbic acid on GO/CdTe QDs/GC electrode was explored. Transmission electron microscopy (TEM) was used to examine the morphological characterization of CdTe QDs and cyclic voltammetry (CV) and electrochemical impedance spectroscopy were used to perform the electrochemical investigations of the GO/CdTe QDs/GC electrode. Because of the synergy between the CdTe QDs and GO, this novel sensing based on CdTe QDs/GO/GC electrode responded even more sensitively and selectively than that based on bare GC electrode. Effects of pH value, buffer concentration, deposition potential and deposition time and electroactive interferents on the response of GO/CdTe QDs/GC electrode for ascorbic acid sensor were discussed. Under optimum working conditions, a linear response of the modified electrode was obtained over the concentration range of 32.3-500.0 mu M with the detection limit of 6.1 mu M for ascorbic acid. Finally, the inexpensive, reliable and sensitive modified electrode based on GO/CdTe QDs/GC was succesfully applied for the determination of ascorbic acid in citrus samples.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 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 Optical properties of perylene-monoimide (PMI) and perylene-diimide (PDI) organic semiconductor thin films(ELSEVIER SCIENCE SA, 2014) Kisnisci, Z.; Yuksel, O. F.; Kus, M.The optical properties of thin films of perylene-monoimide (PMI) and perylene-diimide (PDI), which are well known organic semiconductors, were determined using the spectroscopic measurements. For this purpose, optical measurements such as the absorption and reflection of films were performed in near ultraviolet, visible and near infrared spectral regions. Optical band gap of PMI and PDI were determined by means of absorption measurement. In addition, from the absorption and reflection spectra, the dispersion of several optical parameters of materials such as the absorption coefficient and the refractive index were calculated. Single oscillator dispersion analysis was performed based on the Sellmeier equation and some relevant dispersion parameters obtained. (C) 2014 Elsevier B.V. All rights reserved.Öğe The radioluminescence and optical behaviour of nanocomposites with CdSeS quantum dot(ELSEVIER SCIENCE BV, 2017) Keskin, I. C.; Turemis, M.; Kati, M. I.; Kibar, R.; Sirin, K.; Cipiloglu, M. A.; Kus, M.In this work, highly luminescent alloyed CdSeS QDs are successfully synthesized by two phase route method by using oleic acid (OA) as a surfactant. OA capped CdSeS QDs prepared in two different synthesis duration were compared in terms of luminescence and optical properties. The nanocomposites blended with CdSeS QDs which have highly luminescent efficiency in different ratios by Low Density Polyethylene (LDPE) and these nanocomposites were mainly investigated radioluminescence (RL) and optical properties (UV/VIS absorption). Structural, morphological, thermal properties of the nanocrystal and nanocomposites were examined using; XRD, FT-IR, TEM, SEM, TG-DTA techniques. OA capped CdSeS and also nanocomposites were showed two RL spectrum peaks in green and red region at around 528 nm and 710 nm respectively. Also, it is seen that the radioluminescence intensity changes linearly with the particle size of the QDs and about 12% size change of quantum dot led to a threefold increase in RL intensity. The luminescence glow curves are in compliance with absorption and fluorescence spectra. The absorption bands showed a significant blue shift for the nanocomposites as compare to powder CdSeS. The optical band gap of the OA capped CdSeS calculated as 1.77 eV. It was observed that the optical band gap of LDPE was decreased by the adding ratio of CdSeS from 3.71 eV to 2.25 eV. (C) 2017 Elsevier B.V. All rights reserved.
