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Öğe Ag-doped HfO2 thin films via sol–gel dip coating method(Springer Nature, 2019-10-01) Pakma, Osman; Kaval, Şehmus; Kari̇per, İshak AfşinIn this study, undoped and Ag-doped HfO2 thin films were deposited on glass substrates by means of sol–gel dip coating method. These films were then thermally annealed at 500 °C for 1 h. The structural and optical properties of undoped and Ag-doped HfO2 thin films were characterized by X-ray diffraction, UV–Vis spectrometry and scanning electron microscope. The results of this analysis were compared and interpreted with the results obtained in literature by various methods of coating with HfO2. The X-ray diffraction peaks of the films paired with monoclinic HfO2 crystalline peaks. The refractive indices of the films decreased with doping Ag, at 500 nm wavelengths. The optical band gap values of Ag-doped HfO2 thin films increased with doping Ag. The porous structures were observed on the surface films, especially with 5% Ag doping.Öğe Analysis of frequency dependent interface state density and series resistance of Al CZTSeS n Si schottky diode(Ulusal Fotovoltaik Teknoloji Platformu, 2016) Yüksel, Ömer Faruk; Tuğluoğlu, Nihat; Pakma, Osman; Özel, FarukÖğe The analysis of the charge transport mechanism of n-Si/MEH-PPV device structure using forward bias I-V-T characteristics(Elsevier, 2010-03-04) Kavasoğlu, Abdülkadir Sertap; Yakuphanoğlu, Fahrettin; Kavasoğlu, Neşe; Pakma, Osman; Birgi, Özcan; Oktik, ŞenerIn this study, temperature dependent current-voltage (I-V) measurements and investigation of the dc current transport mechanism of n-Si/MEH-PPV device have been performed. While the series resistance value displayed strongly temperature dependent behaviour, the ideality factor varied between 3.2 and 1.8 in the temperature range 110-330 K. The temperature dependent ideality factor behaviour at low temperature region (110-220 K) shows that tunnelling enhanced recombination is valid rather than thermionic emission theory and the characteristic tunnelling energy is calculated as 30 meV. There is a slightly linear relationship between the ideality factor and temperature at region II (230-330 K) which is attributed to drift-diffusion current transport in the n-Si/MEH-PPV device as stated already by Osvald.Öğe Batman ilindeki ince film a-Si teknolojili fotovoltaik sistemin performans değerlendirmesi(Balıkesir Üniversitesi, 2018-07-17) Pakma, OsmanBu çalışmada Batman ilinde ince film a-Si teknolojisine sahip 2.16 kWp güce sahip şebeke bağlantılı sistemin bir yıllık elektrik enerjisi üretim verileri alınmış ve modüllerin performansı dış parametrelerde göz önüne alınarak değerlendirilmiştir. Sistem ölçümleri Ocak ayından Aralık ayına kadar tüm 2016 yılını kapsamaktadır. İnce film a-Si PV sistemden 2016 yılı süresince şebekeye 2.631 MWh enerji sağlanmıştır. Sistemin nihai verimi (Yf) 1.13 den 4.89 kWh/KWp/gün’e, performans oranı da (PO) %53 ile %78 arasında değişmektedir. Ortam ve buna bağlı olarak modül sıcaklıklarının sistem performansına etkisinin %6 - %9 arasında olduğu hesaplanmıştır. Ayrıca diğer sistem bölümlerinin de sistem performansı üzerinde değişen oranlarda etkili olduğu belirlenmiştir.Öğe Characterization of Au N Inp photovoltaic structure with organic thin film(Uppsala University, 2012) Güllü, Ömer; Özerden, Enise; Rüzgar, Şerif; Asubay, Sezai; Pakma, Osman; Kılıçoğlu, Tahsin; Türüt, AbdulmecitÖğe Current density-voltage analyses and interface characterization in Ag/DNA/p-InP structures(American Institute of Physics, 2012-02-15) Güllü, Ömer; Pakma, Osman; Türüt, AbdülmecitThe current density-voltage (J-V) characteristics of Ag/DNA/p-InP metal-insulator-semiconductor (MIS) structures have been investigated in room temperature. We have observed that the Ag/DNA/p-InP structure shows an excellent rectifying behavior and that this structure increases the barrier height (φ b0). The main electrical parameters of these structures, such as ideality factor (n), barrier height, and average series resistance values were found to be 1.087, 0.726 eV, and 66.92Ω. This value of n was attributed to the presence of an interfacial insulator layer at the Ag/p-InP interface and the density of interface states (N ss) localized at the InP/DNA interface. The values of N ss localized at the InP/DNA interface were found at 0.675-E v in the 1.38 × 10 12 eV -1 cm -2.Öğe Current mechanism in HfO 2-gated metal-oxide-semiconductor devices(Hindawi, 2012-06-19) Pakma, OsmanThe present study aimed to examine the current density-voltage (J-V) characteristics of Al/HfO2/p-Si (MOS) structure at temperatures ranging between 100 and 320 K and to determine the structure’s current transport mechanism. The HfO2 film was coated on a single side of the p-Si (111) crystal using the spin coating method. The J-V measurements of the obtained structure at the temperatures between 100 and 320 K revealed that the current transport mechanism in the structure was compatible with the Schottky emission theory. The Schottky emission theory was also used to calculate the structure’s Schottky barrier heights (φB), dielectric constants (εr) and refractive index values of the thin films at each temperature value. The dielectric constant and refractive index values were observed to decrease at decreasing temperatures. The capacitance-voltage (C-V) and conductancevoltage (G/ω-V) characteristics of Al/HfO2/p-Si (MOS) structure was measured in the temperature range of 100–320 K. The values of measured C and G/ω decrease in accumulation and depletion regions with decreasing temperature due to localized Nss at Si/HfO2 interface.Öğe Current transport mechanism of Cu In1 x Gax S1 y sey 2 based heterojunction solar cells(İstanbul University, 2015) Pakma, Osman; Eriş, FerhatIn this study; temperature-dependent current-voltage measurements are used to determine the dominant currenttransport mechanism of ZnO/CdS/Cu(In,Ga)(S,Se)2 heterojunction solar cells. The dominant current-transport mechanism is mainly driven by changes in the Cu and S-stoichiometry. Whereas Cu and S rich devices are dominated by recombination at the CdS/absorber interface, bulk recombination in Cu and S poor devices irrespective of the band gab energy of the absorber.Öğe Design of PV energy system in Batman Turkey(AIP Conf.Proc., 2017) Pakma, Nilay; Pakma, Osman; Güllü, ÖmerÖğe Determination of main parameters of Au/n-Si diodes with and without nitropyridine conjugated anthracene (NAMA) layer from current-voltage characteristics(Selçuk Üniversitesi, 2017) Ongun, Onur; Eymur, Serkan; Pakma, Osman; Yüksel, Ömer Faruk; Sayın, Serkan; Tezcan, Ali Osman; Börekçi, Nazmiye; Tuğluoğlu, NihatÖğe The effects of high-energy electron irradiation on the electrical characteristics of a lead/rhodamine-101/p-Si diode(Çukurova Üniversitesi, 2017) Güllü, Ömer; Pakma, OsmanHigh-energy radiation penetrates the metal-semiconductor (MS) interface and causes damage deep below the interface. Low-energy radiation causes severe lattice damage in the form of vacancies, interstitials and defect complexes at the near interface of the device. The one kind of the radiation is electron beam which is accelerated. Mills was the first to recognize that electrons with energy of 1 MeV would possess enough energy to displace an atom from its lattice position. This observation has led to the increased use of electron accelerators in radiation damage studies. This use has been motivated by two important facts. First, electron bombardment experiments permit the determination of the energy required to remove an atom from its initial position. This is done by increasing the energy of the electrons until an observable change in a radiation-sensitive property is seen. The second important basis for the use electrons lie in the fact that as long as the energy of the electrons is close to the displacement threshold, it is presumed, that only single Frenkel pairs are formed. Thus, many radiation-induced phenomena can be analyzed in terms of a single vacancy and/or interstitial atom, and one avoids the complication attendant upon the generation of complex damage regions presumed to occur in heavy-charged particle irradiation. In the present paper, a lead/rhodamine-101(Rh101)/p-Si metal/organic interlayer/ semi-conductor diode was fabricated and the effect of 6 MeV-electron irradiation on the electrical characteristics of the diode structure was investigated. It was seen that after electron irradiation the barrier height values, the series resistance values and ideality factors increased. Furthermore, it was seen that the capacitance values increased after electron irradiation. This was attributed to the change in dielectric constant at the interface and/or to decrease in the net ionized dopant concentration and the interface states. The degradation of the diode properties may be due to the introduction of electron irradiationinduced interfacial defects via displacement damage.Öğe Electrical and photoresponse characteristics of Al/CZTSeS/n-Si schottky photodiode(Selçuk Üniversitesi, 2017) Yüksel, Ömer Faruk; Tuğluoğlu, Nihat; Pakma, Osman; Özel, FarukÖğe Electrical characteristics of the Al/Congo Red (CR)/p-Si semiconductor diodes(Dumlupınar Üniversitesi, 2015-05) Güllü, Ömer; Pakma, Osman; Turut, Abdulmecit; Arsel, İsmailIn this work, we have studied the electrical characteristics of the Al/CR/p-Si MIS Schottky structures formed by coating of the organic material directly on p-Si substrate. It has been seen that the CR thin film on the p-Si substrate has indicated a good rectifying behavior. The barrier height and the ideality factor of the device have been calculated from the I-V characteristic. We have also studied the suitability and possibility of the MIS diodes for use in barrier modification of Si MS diodes. In addition, we have compared the parameters of the Al/CR/p-Si MIS Schottky diodes with those of conventional Al/p-Si MS diodes. We have observed that the b value of 0.77 eV obtained for the Al/CR/p-Si device was significantly larger than BH value of the conventional Al/p-Si MS contact. Thus, the modification of the interfacial potential barrier for metal/Si diodes has been achieved by using the CR organic interlayer. This was attributed to the fact that the CR interlayer increased the effective b by influencing the space charge region of Si. The interface-state density of the MIS diode was found to vary from 1.24×1013 eV-1 cm-2 to 2.44×1012 eV-1 cm-2.Öğe Electrical parameters of safranine T N silicon contacts(İstanbul University, 2015) Güllü, Ömer; Arsel, İsmail; Özkan, Samet; Özaydın, Cihat; Pakma, Osman; Turut, AbdülmecitIn this work, it has been investigated current-voltage (I-V) andcapacitance-voltage-frequency (C-V-f) characteristics of the Al/SafranineT(ST)/n-Si structure. The values of the ideality factor, series resistance and barrier height calculated by using different methods were compared. It was seen that there was an agreement with each other. Also, it was seen that the barrier height value for our device was higher than one value of 0.50 eV of conventional Al/n-Si Schottky contact. The change in the barrier height value of the device was ascribed to ST thin layer modifying the effective barrier height by influencing the space charge region of the Si inorganic semiconductor. The downward concave curvature of the forward bias current-voltage characteristics at sufficiently large voltages have been attributed to the effect of series resistance. Thus, the concavity of the forward bias current-voltage characteristics increases with increasing series resistance value. It has been seen that the values of capacitance are almost independent to a certain value of frequency, after this value, the capacitance decreases with increasing frequency. The higher values of capacitance at low frequencies have been attributed to the excess capacitance resulting from the interface states in equilibrium with the n-Silicon that could follow the alternating current signal.Öğe Fabrication and electrical characterization of ZnO SiO2 p Si structure with outsized diode factor(European Union, 2010) Kavasoğlu, Neşe; Kavasoğlu, Abdülkadir Sertap; Pakma, Osman; Kabakçı, Murat; Birgi, Özcan; Oktik, ŞenerÖğe Frequency dependent interface state properties of a schottky device based on coronene deposited on n-type silicon by spin coating technique(Ulusal Fotovoltaik Teknoloji Platformu, 2016) Yüksel, Ömer Faruk; Pakma, Osman; Tuğluoğlu, NihatÖğe Frequency dependent of capacitance-voltage and conductance-voltage characteristics of Au/9-[(5-Nitropyridin-2-aminoethyl) iminiomethyl]-anthracene (NAMA)/n-Si diode(Selçuk Üniversitesi, 2017) Ongun, Onur; Eymur, Serkan; Pakma, Osman; Yüksel, Ömer Faruk; Sayın, Serkan; Tezcan, Ali Osman; Börekçi, Nazmiye; Tuğluoğlu, NihatÖğe I V and C V F characteristics of aniline green N type silicon diode(İstanbul University, 2015) Özkan, Samet; Güllü, Ömer; Arsel, İsmail; Özaydın, Cihat; Pakma, Osman; Turut, AbdülmecitWe have studied the I-V, C-V and C-f characteristics of the Aniline Green (AG)/n-type Si structure. In organic/inorganic semiconductor contact applications, in order to keep the technological difficulties and unknowns to a minimum, silicon is generally chosen as the substrate semiconducting material. In this structure, deposition of organic materials on the inorganic semiconductor can generate large number of interface states at the semiconductor surface that strongly influence the electrical properties of the AG/n-Si structure. The values of the ideality factor, series resistance and barrier height obtained from two methods were compared, and it was seen that there was an agreement with each other. The downward concave curvature of the forward bias current-voltage characteristics at sufficiently large voltages is caused by the presence of the effect of series resistance. Thus, the concavity of the forward bias current-voltage characteristics increases with the increasing series resistance value. The high resistance values have given the high ideality factors. Also, the higher values of capacitance at low frequencies were attributed to the excess capacitance resulting from the interface states in equilibrium with the nSi that can follow the ac signal.Öğe I V characteristics of the orange G P type silicon contacts(Dumlupınar Üniversitesi, 2015) Güllü, Ömer; Arsel, İsmail; Pakma, Osman; Özaydın, Cihat; Turut, AbdülmecitÖğe I-V-T analysing an inhomogeneous Au/Poly(4-vinyl phenol)/p-Si structure with a double gaussian distribution of barrier heights(Springer Nature, 2010-12-29) Pakma, Osman; Tozlu, Cem; Kavasoğlu, Neşe; Kavasoğlu, Abdülkadir Sertap; Özden, ŞadanIn this study, the current-voltage (I-V) characteristics of Au/Poly(4-vinyl phenol)/p-Si structures have been measured over a wide temperature range (100-300 K). These structures have been analyzed according to thermionic emission (TE) theory, as a result of which an abnormal decrease occurred in the zero-bias barrier height (φb0) and an increase in the ideality factor (n) was observed with temperature decrease and nonlinearity in the activation energy plot. By assuming a Gaussian distribution (GD) of barrier heights of the Au/Poly(4-vinyl phenol)/p-Si structures, barrier inhomogeneities are believed to responsible for this behavior. Evidence is given for the existence of a double GD with mean barrier heights (φ̄b0) of 1.042 and 0.623 eV, standard deviations of 0.138 and 0.081 V, and ideality factors 2.76 and 7.26, which remain effective in the temperature ranges of 180-300 and 100-160 K, respectively. As a result, without using the temperature coefficient of the barrier height, the modified ln(Io/T 2)-q2σo 2/2(kT)2 vs. q/kT plot gives φ̄b0 values and Richardson constants (A *) as 1.036 and 0.623 eV, and 36.20 and 19.99 A/cm2 K2, respectively. The effective Richardson constant value of 36.20 A/cm2 K2 is very similar to the theoretical value of 32 A/cm2K2 for p-Si. Consequently, the temperature dependence of the forward bias I-V characteristics of Au/Poly(4-vinyl phenol)//p-Si (MIS) structure could be attributed to the thermionic emission (TE) mechanism with double GD of the barrier heights.
