Yazar "Parlak, Mehmet" seçeneğine göre listele

Listeleniyor 1 - 12 / 12
  • [ X ]
    Öğe
    Analysis of current conduction mechanism in CZTSSe/n-Si structure
    (Springer New York LLC, 2018) Terlemezoğlu, Makbule; Bayraklı Sürücü, Özge; Güllü, Hasan Hüseyin; Çolako?lu, Tahir; Yıldız, Dilber Esra; Parlak, Mehmet
    In this study, Cu2ZnSn(S,Se)4 (CZTSSe) thin films were deposited by the single step thermal evaporation process using the sintered powder of CZTSSe on soda lime glass (SLG) and Si wafer substrates. The structural, optical, and electrical properties of deposited films were investigated. Current–voltage (I–V) in the temperature range of 250–350 K, capacitance–voltage(C–V) and conductance–voltage (G/w–V) measurements at room temperature were carried out to determine electrical properties of CZTSSe/n-Si structure. The forward bias I–V analysis based on thermionic emission (TE) showed barrier height inhomogeneity at the interface and thus, the conduction mechanism was modeled under the assumption of Gaussian distribution of barrier height. The mean barrier height (?¯B0) and standard deviation (?0) at zero bias were obtained as 1.27 eV and 0.18 V, respectively. Moreover, Richardson constant was obtained as 120.46 A cm?2 K?2 via modified Richardson plot and the density of interface states (Dit) profile was determined using the data obtained from forward bias I–V measurements. In addition, by the results of frequency dependent C–V measurements, characteristics of the interface state density were calculated applying high-low frequency capacitance (CHF ? CLF) and Hill–Coleman methods.
  • [ X ]
    Öğe
    Analysis of temperature-dependent transmittance spectra of Zn0.5In0.5Se (ZIS) thin films
    (Springer New York LLC, 2019) Işık, Mehmet; Güllü, Hasan Hüseyin; Delice, Serdar; Gasanly, Nizami Mamed; Parlak, Mehmet
    Temperature-dependent transmission experiments of ZnInSe thin films deposited by thermal evaporation method were performed in the spectral range of 550–950 nm and in temperature range of 10–300 K. Transmission spectra shifted towards higher wavelengths (lower energies) with increasing temperature. Transmission data were analyzed using Tauc relation and derivative spectroscopy. Analysis with Tauc relation was resulted in three different energy levels for the room temperature band gap values of material as 1.594, 1.735 and 1.830 eV. The spectrum of first wavelength derivative of transmittance exhibited two maxima positions at 1.632 and 1.814 eV and one minima around 1.741 eV. The determined energies from both methods were in good agreement with each other. The presence of three band gap energy levels were associated to valence band splitting due to crystal-field and spin–orbit splitting. Temperature dependence of the band gap energies were also analyzed using Varshni relation and gap energy value at absolute zero and the rate of change of gap energy with temperature were determined. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
  • [ X ]
    Öğe
    Determination of current transport characteristics in Au-Cu/CuO/n-Si Schottky diodes
    (Elsevier, 2019) Bayraklı Sürücü, Özge; Güllü, Hasan Hüseyin; Terlemezoğlu, Makbule; Yıldız, Dilber Esra; Parlak, Mehmet
    In this study, the material properties of CuO thin films fabricated by sputtering technique and electrical properties of CuO/n-Si structure were reported. Temperature-dependent current-voltage (I-V) measurement was carried out to determine the detail electrical characteristics of this structure. The anomaly in thermionic emission (TE) model related to barrier height inhomogeneity at the interface was obtained from the forward bias I-V analysis. The current transport mechanism at the junction was determined under the assumption of TE with Gaussian distribution of barrier height. In this analysis, standard deviation and mean zero bias barrier height were evaluated as 0.176 and 1.48 eV, respectively. Depending on the change in the diode parameters with temperature, Richardson constant was recalculated as 110.20 Acm(-2)K(-2) with the help of modified Richardson plot. In addition, density of states at the interface were determined by using the forward bias I-V results.
  • [ X ]
    Öğe
    Electrical characterization of CdZnTe/Si diode structure
    (Springer Heidelberg, 2020) Doğru Balbaşı, Ciğdem; Terlemezoğlu, Makbule; Güllü, Hasan Hüseyin; Yıldız, Dilber Esra; Parlak, Mehmet
    Temperature-dependent current-voltage (I - V), and frequency dependent capacitance-voltage (C - V) and conductance-voltage (G - V) measurements were performed in order to analyze characteristics of CdZnTe/Si structure. Obtained profiles enable us to understand the different characteristics of the diode structure such as the carrier conduction mechanism and the nature of the interfacial layer. Over the temperature range between 220 and 340 K, taking consideration of the disparity in the forward-biased current, the diode parameters such as saturation current (I-0), zero-bias barrier height (Phi(B0)) and ideality factor (n) have been obtained. The barrier height increased (0.53 to 0.80 eV) while the ideality factor decreased (4.63 to 2.79) with increasing temperature from 220 to 340 K, indicating an improvement in the junction characteristics at high temperatures. Due to the inhomogeneity in barrier height, the conduction mechanism was investigated by Gaussian distribution analysis. Hence, the mean zero-bias barrier height ((Phi) over bar (B0)) and zero-bias standard deviation (sigma(0)) were calculated as 1.31 eV and 0.18, respectively. Moreover, for holes in p-type Si, Richardson constant was found to be 32.09 A cm(-2) K-2 via modified Richardson plot. Using the capacitance-voltage (C - V) and conductance-voltage (G - V) characteristics, series resistance (R-s) and density of interfacial traps (D-it) have been also investigated in detail. A decreasing trend for R-s and D-it profiles with increasing frequency was observed due to the impurities at the CdZnTe/Si interface and interfacial layer between the front metal contact and CdZnTe film.
  • [ X ]
    Öğe
    Frequency effect on electrical and dielectric characteristics of HfO2-interlayered Si-based Schottky barrier diode
    (Springer, 2020) Güllü, Hasan Hüseyin; Yıldız, Dilber Esra; Sürücü, Özge; Parlak, Mehmet
    This study reveals the electrical properties of In/HfO2/n-Si structure with atomic layer-deposited interfacial oxide layer, HfO2 thin film between In top metal contact and monocrystalline Si wafer substrate. From the dark current-voltage measurements, the diode structure showed good rectifying behavior and low saturation current of about two order of magnitude and 1.2 x 10(- 9) A, respectively. According to the conventional thermionic emission model, zero-bias barrier height and ideality factor were calculated from the forward bias current-voltage curve at room temperature under dark conditions as 0.79 eV and 4.22 eV, respectively. In order to get detailed information about density of interface states and series resistance of this structure, capacitance-voltage and conductance-voltage measurements in the frequency range of 10-1000 kHz were performed. As a result, a decreasing capacitance profile with increasing frequency was obtained. In addition, peak-like behavior in the capacitance profiles was observed and these were found to be the indication of density of states. Further analysis was performed on the evaluation of density of interface states values and these values were calculated by using two different methods: Hill-Coleman and high-low frequency capacitance. These profiles were also analyzed by eliminating the effect of series resistance values on the measured capacitance and conductance; then the values of corrected capacitance and conductance as a function of applied voltage were discussed. Based on these analyses on the capacitive characteristics of the diode, dielectric constant, dielectric loss, loss tangent, electrical conductivity, and the real and imaginary part of electric modulus were investigated for complete understanding on the diode characteristics.
  • [ X ]
    Öğe
    Frequency effect on electrical and dielectric characteristics of In/Cu 2 ZnSnTe 4 /Si/Ag diode structure
    (Springer New York LLC, 2019) Güllü, Hasan Hüseyin; Bayraklı Sürücü, Özge; Terlemezoğlu, Makbule; Yıldız, Dilber Esra; Parlak, Mehmet
    In/Cu 2 ZnSnTe 4 /Si/Ag diode structure was fabricated by sputtering Cu 2 ZnSnTe 4 (CZTTe) thin film layer on the Si layer with In front contact. The frequency dependent room temperature capacitance and conductance measurements were carried out to obtain detailed information of its electrical characteristics. Admittance spectra of the diode exhibited strong frequency dependence and the obtained values showed decreasing behavior with the increase in the applied frequency. The effect of interfacial film layer with series resistance values and density of interface states were investigated by taking into consideration of non-ideal electrical characteristics of the diode. The distribution profile of the interface states was extracted by Hill-Coleman and high–low frequency capacitance methods. As a function of frequency, they were in proportionality with the inverse of applied frequency. Dielectric constant and dielectric loss parameters were calculated from the maximum value of the diode capacitance at the strong accumulation region. The loss tangent showed a characteristic peak behavior at each frequency. Based on the time-dependent response of the interfacial charges to the applied ac field, the values of ac electrical conductivity and complex electric modulus were calculated and discussed as a function of frequency and bias voltage.
  • [ X ]
    Öğe
    Investigation of carrier transport mechanisms in the Cu-Zn-Se based hetero-structure grown by sputtering technique
    (Canadian Science Publishing, 2018) Güllü, Hasan Hüseyin; Terlemezoğlu, Makbule; Bayraklı Sürücü, Özge; Yıldız, Dilber Esra; Parlak, Mehmet
    In this paper, we present results of the electrical characterization of n-Si/p-Cu-Zn-Se hetero-structure. Sputtered film was found in Se-rich behavior with tetragonal polycrystalline nature along with (112) preferred orientation. The band gap energy for direct optical transitions was obtained as 2.65 eV. The results of the conductivity measurements indicated p-type behavior and carrier transport mechanism was modelled according to thermionic emission theory. Detailed electrical characterization of this structure was carried out with the help of temperature-dependent current-voltage measurements in the temperature range of 220-360 K, room temperature, and frequency-dependent capacitance-voltage and conductance-voltage measurements. The anomaly in current-voltage characteristics was related to barrier height inhomogeneity at the interface and modified by the assumption of Gaussian distribution of barrier height, in which mean barrier height and standard deviation at zero bias were found as 2.11 and 0.24 eV, respectively. Moreover, Richardson constant value was determined as 141.95 Acm-2K-2 by means of modified Richardson plot. © 2018 Published by NRC Research Press.
  • [ X ]
    Öğe
    Investigation of electrical characteristics of Ag/ZnO/Si sandwich structure
    (Springer, 2019) Güllü, Hasan Hüseyin; Bayraklı Sürücü, Özge; Terlemezoğlu, Makbule; Yıldız, Dilber Esra; Parlak, Mehmet
    In this study, temperature-dependent current-voltage (I-V), frequency-dependent capacitance-voltage (C-V) and conductance-voltage (G/omega-V) measurements are carried out for the electrical characterization of a zinc oxide (ZnO) thin film-based diode. The sandwich structure in the form of Ag/ZnO/Si/Al is investigated at temperatures between 220 and 360 K and in the frequency region of 1 kHz-1 MHz. ZnO thin film layer is deposited on a p-Si wafer substrate as a transparent conductive oxide layer by taking into consideration possible electronic applications with intrinsic attractive material properties. At each temperature step, the I-V curves showed about two orders of magnitude rectifying behavior and, according to the Schottky diode relation, the saturation current, zero-bias barrier height and ideality factor were extracted as a function of the temperature. In the case of non-ideal diode characteristics due to the inhomogeneties in the diode as observed from the characteristics of the calculated parameters, effective barrier height values are evaluated. In addition, based on the existence of the interface layer, density of interface states in the band gap region and parasitic resistances were determined by the capacitance measurements.
  • [ X ]
    Öğe
    Structural and temperature-dependent optical properties of thermally evaporated CdS thin films
    (Elsevier Ltd, 2019) Işık, Mehmet; Güllü, Hasan Hüseyin; Delice, Serdar; Parlak, Mehmet; Gasanly, Nizami Mamed
    In this work, structural and temperature dependent optical properties of thermally evaporated CdS thin films were investigated. X-ray diffraction, energy dispersive spectroscopy and Raman spectroscopy experiments were carried out to characterize the thin films and obtain information about the crystal structure, atomic composition, surface morphology and vibrational modes. Temperature-dependent transmission measurements were performed in between 10 and 300 K and in the spectral range of 400–1050 nm. The analyses of transmittance spectra were accomplished by two different methods called as the absorption coefficient and the derivative spectrophotometry analyses. All evaluated band gap energy values at each studied temperature were in good agreement with each other depending on the applied analyses techniques. Room temperature gap energy values were found around 2.39 eV and 2.40 eV from absorption coefficient and derivative spectrophotometry analyses, respectively. Band gap energy depending on the sample temperature was studied under the light of two different models to investigate average phonon energy, electron phonon coupling parameter and the rate of change of band gap energy with temperature. © 2019 Elsevier Ltd
  • [ X ]
    Öğe
    Study on the electrical properties of ZnSe/Si heterojunction diode
    (Springer New York LLC, 2017) Güllü, Hasan Hüseyin; Bayraklı Sürücü, Özge; Yıldız, Dilber Esra; Parlak, Mehmet
    ZnSe thin film is e-beam evaporated on monocrystalline p-Si to fabricate n-ZnSe/p-Si heterojunction. The electrical properties were investigated by current–voltage (I–V), capacitance–voltage (C–V) and conductance–voltage (G/w–V) measurements. The forward bias I–V characteristics were analyzed in the temperature range of 220–360 K. The fabricated diode structure exhibited rectifying characteristics with a two order rectification ratio. The current transport in the junction was modeled by the modification of thermionic emission (TE) in which the observed anomaly was related to the interfacial disorder at the junction. From this analysis, the zero-bias barrier height and ideality factor at room temperature condition were determined as 0.775 and 3.195 eV, respectively. The TE anomaly was also evaluated by considering the fluctuations due to the barrier inhomogeneity and the assumption of Gaussian distribution in barrier height. Therefore, the forward bias I–V results were used to determine the density of interface states. The frequency dependence of C–V and G/w–V characteristics of the n-ZnSe/p-Si heterostructure were studied by taking into account of the effect of the series resistance and interface states at room temperature. According to the high-low frequency capacitance and Hill-Coleman methods, density of interface states was calculated and these experimental values were found in decreasing behavior with increasing frequency. The voltage and frequency dependence of series resistance values obtained from C–V and G/w–V measurements were also related to the insulator layer and the distribution density of interface states. © 2017, Springer Science+Business Media, LLC.
  • [ X ]
    Öğe
    Temperature dependence of band gaps in sputtered SnSe thin films
    (Elsevier Ltd, 2019) Delice, Serdar; Işık, Mehmet; Güllü, Hasan Hüseyin; Terlemezoğlu, Makbule; Bayraklı Sürücü, Özge; Parlak, Mehmet; Gasanly, Nizami Mamed
    Temperature-dependent transmission experiments were performed for tin selenide (SnSe) thin films deposited by rf magnetron sputtering method in between 10 and 300 K and in the wavelength region of 400–1000 nm. Transmission spectra exhibited sharp decrease near the absorption edge around 900 nm. The transmittance spectra were analyzed using Tauc relation and first derivative spectroscopy techniques to get band gap energy of the SnSe thin films. Both of the applied methods resulted in existence of two band gaps with energies around 1.34 and 1.56 eV. The origin of these band gaps was investigated and it was assigned to the splitting of valence band into two bands due to spin-orbit interaction. Alteration of these band gap values due to varying sample temperature of the thin films were also explored in the study. It was seen that the gap energy values increased almost linearly with decreasing temperature as expected according to theoretical knowledge. © 2019 Elsevier Ltd
  • [ X ]
    Öğe
    Temperature dependence of electrical properties in In/Cu 2 ZnSnTe 4 /Si/Ag diodes
    (Indian Academy of Sciences, 2019) Güllü, Hasan Hüseyin; Yıldız, Dilber Esra; Bayraklı Sürücü, Özge; Terlemezoğlu, Makbule; Parlak, Mehmet
    Cu2ZnSnTe4 (CZTTe) thin films with In metal contact were deposited by thermal evaporation on monocrystalline n-type Si wafers with Ag ohmic contact to investigate the device characteristics of an In/CZTTe/Si/Ag diode. The variation in electrical characteristics of the diode was analysed by carrying out current–voltage (I–V) measurements in the temperature range of 220–360 K. The forward bias I–V behaviour was modelled according to the thermionic emission (TE) theory to obtain main diode parameters. In addition, the experimental data were detailed by taking into account the presence of an interfacial layer and possible dominant current transport mechanisms were studied under analysis of ideality factor, n. Strong effects of temperature were observed on zero-bias barrier height (?B0) and n values due to barrier height inhomogeneity at the interface. The anomaly observed in the analysis of TE was modelled by Gaussian distribution (GD) of barrier heights with 0.844 eV mean barrier height and 0.132 V standard deviation. According to the Tung’s theoretical approach, a linear correlation between ?B0 and n cannot be satisfied, and thus the modified Richardson plot was used to determine Richardson constant (A?). As a result, A? was calculated approximately as 120.6 A cm?2 K?2 very close to the theoretical value for n-Si. In addition, the effects of series resistance (Rs) by estimating from Cheng’s function and density of surface states (Nss) by taking the bias dependence of effective barrier height, were discussed.