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Öğe Determining electrical and dielectric parameters of Al/ZnS-PVA/p-Si (MPS) structures in wide range of temperature and voltage(Springer, 2018) Baraz, Nalan; Yücedağ, İbrahim; Kalandaragh, Yashar Azizian; Altındal, ŞemsettinIn this study zinc sulphide (ZnS) nanostructures have been prepared by microwave-assisted method in presence of polyvinyl alcohol (PVA) as a capping agent. The structural and morphological properties of prepared sample have been investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). These analyses confirm that the sample has nano structure. They have been used this sample to fabrication of Al/ZnS-PVA/p-Si structure. The effect of temperature and voltage on the electrical and dielectric parameters of the Al/ZnS-PVA/p-Si (MPS) structures has been investigated in the wide range of temperature (140-340 K) and voltage (- 2 V to + 4 V) using capacitance/conductance-voltage (C/G-V) measurements at 500 kHz. Experimental measurements revealed that the values of C/G-V increase with increasing temperature but the values of series resistance (R (s) ) increase with decreasing temperature. As well as the dielectric parameters such as the values of real and imaginary parts of the dielectric constants (epsilon' and epsilon aEuro(3)) and electric modules (M' and MaEuro(3)), loss tangent (tan delta), and ac electrical conductivity (sigma (ac) ) were obtained using C and G/omega data. These parameters are found out as strong functions of temperature and voltage. While the values of epsilon', epsilon aEuro(3) and tan delta increase with increasing temperature, the values of sigma (ac) , M' and MaEuro(3) decrease. The Arrhenius plot (ln(sigma(ac)) vs q/kT) shows two distinct linear ranges with different slopes or activation energies (E (a) ) at low (140-230 K) and high (260-340 K) temperatures. Both values of R (s) and (ZnS-PVA) interfacial layers are also very effective parameters on the electric and dielectric properties.Öğe Determining electrical and dielectric parameters of dependence as function of frequencies in Al/ZnS-PVA/p-Si (MPS) structures(Springer, 2017) Baraz, Nalan; Yücedağ, İbrahim; Kalandaragh, Yashar Azizian; Altındal, ŞemsettinWe have studied electrical and dielectric parameters of the Al/ZnS-PVA/p-Si structures using admittance measurements. For this aim, capacitance/conductance-voltage (C/G-V) measurements were performed in the frequency range of 10 kHz-5 MHz and voltages (+/- 4 V) by 50 mV steps at 300 K. Experimental results confirmed that both electric and dielectric parameters are strong function of frequency and voltage and they are especially influenced from series resistance (R-s), surface states (N-ss) and polarization processes. The values of R-s and N-ss which are obtained from the Nicollian and Brews and Hill-Coleman method, respectively, and they are decrease with increasing frequency almost as exponentially. In addition, the values of real and imaginary part of the dielectric constants (epsilon' and epsilon '') and electric modules (M' and M ''), loss tangent (tan delta), and ac electrical conductivity (sigma(ac)) were obtained using C and G/omega data as function of applied bias voltage and they are found to a strong functions of frequency. While the values of epsilon', epsilon '', and tand increase with increasing frequency, M' and rac decrease. Moreover, the epsilon', epsilon '', tand, and rac increase with applied bias voltage, whereas the M' decreases with increasing applied bias voltage. The M '' versus V plot shows a peak and its position shifts to the right with increasing bias voltage and it disappears at high frequencies. As a result, the change in the epsilon', epsilon '', tan delta, M', M '' and rac is a result of restructuring and reordering of charges at the (ZnS-PVA)/p-Si interface under an external electric field or voltage and interface polarization.Öğe Electric and Dielectric Properties of Au/ZnS-PVA/n-Si (MPS) Structures in the Frequency Range of 10-200 kHz(Springer, 2017) Baraz, Nalan; Yücedağ, İbrahim; Kalandaragh, Yashar Azizian; Demir, Gülçin Ersöz; Orak, İkram; Altındal, Şemsettin; Akbari, HosseinPure polyvinyl alcohol (PVA) capped ZnS semiconductor nanocrystals were prepared by microwave-assisted method, and the optical and structural properties of the as-prepared materials were characterized by x-ray diffraction (XRD) and Ultraviolet-visible (UV-Vis) techniques. The XRD pattern shows the formation of ZnS nanocrystals, and the UV-Vis spectroscopy results show a blue shift of about 1.2 eV in its band gap due to the confinement of very small nanostructures. The concentration of donor atoms (N (D)), diffusion potential (V (D)), Fermi energy level (E (F)), and barrier height (I broken vertical bar(B) (C-V)) values were obtained from the reverse bias C (-2)-V plots for each frequency. The voltage dependent profile of series resistance (R (s)) and surface states (N (ss)) were also obtained using admittance and low-high frequency methods, respectively. R (s)-V and N (ss)-V plots both have distinctive peaks in the depletion region due to the spatial distribution charge at the surface states. The effect of R (s) and interfacial layer on the C-V and G/omega-V characteristics was found remarkable at high frequencies. Therefore, the high frequency C-V and G/omega-V plots were corrected to eliminate the effect of R (s). The real and imaginary parts of dielectric constant (epsilon' and epsilon aEuro(3)) and electric modulus (M' and MaEuro(3)), loss tangent (tan delta), and ac electrical conductivity (sigma (ac)) were also obtained using C and G/omega data and it was found that these parameters are indeed strong functions of frequency and applied bias voltage. Experimental results confirmed that the N (ss), R (s) , and interfacial layer of the MPS structure are important parameters that strongly influence both the electrical and dielectric properties. The low values of N (ss) (similar to 10(9) eV(-1) cm(-2)) and the value of dielectric constant (epsilon' = 1.3) of ZnS-PVA interfacial layer even at 10 kHz are very suitable for electronic devices when compared with the SiO2. These results confirmed that the ZnS-PVA considerably improves the performance of Au/n-Si (MS) structure and also allow it to work as a capacitor, which stores electric charges or energy.Öğe Investigation of Electrical Characteristics in Al/CdS-PVA/p-Si (MPS) Structures Using Impedance Spectroscopy Method(Ieee-Inst Electrical Electronics Engineers Inc, 2016) Demir, Gülçin Ersöz; Yücedağ, İbrahim; Kalandaragh, Yashar Azizian; Orak, İkram; Altındal, ŞemsettinThe cadmium sulfide (CdS) nanopowders have been prepared by ball-milling method, and CdS-polyvinyl alcohol (PVA) nanocompound in the form of film has been deposited on a p-Si wafer as an interfacial layer by spin-coating method. The impedance characteristics of the fabricated Al/CdS-PVA/p-Si (metal-polymer-semiconductor)-type structures were studied in the frequency and voltage range of 5 kHz-5 MHz and +/-1 V, respectively, by considering interface states (D-it), series resistance (R-s), and interfacial layer effects at 300 K. While the voltage and frequency dependence profiles of D-it were evaluated from the low-high frequency capacitance (C-LF-C-HF) and Hill-Coleman methods, R-s profiles were evaluated from the Nicollian and Brews method. Doping concentration atoms (N-A) and barrier height [Phi (B)(capacitance-voltage (C-V))] values were also obtained from the reverse bias C-2 versus V plots for each frequency. While D-it and R-s values decrease with increasing frequency almost exponentially, Phi (B)(C-V) increases linearly. Therefore, both the measured capacitance (C-m) and conductance (G(m)/omega) values were corrected to eliminate the R-s effect. The experimental results show that R-s value is more effective on the impedance measurements at high frequencies in the accumulation region, but D-it is effective at low frequencies in the depletion region.Öğe Temperature and Interfacial Layer Effects on the Electrical and Dielectric Properties of Al/(CdS-PVA)/p-Si (MPS) Structures(Springer, 2018) Demir, Gülçin Ersöz; Yücedağ, İbrahim; Kalandaragh, Yashar Azizian; Altındal, ŞemsettinIn the present study, cadmium sulphide (CdS) nanopowders were prepared by using a simple physical ball milling technique, and their x-ray diffraction (XRD) analysis confirmed the formation of hexagonal wurtzite structure of CdS. The morphology of CdS nanopowders was characterized by scanning electron microscope (SEM). Dielectric and electrical properties of the manufactured Al/(CdS-PVA)/p-Si (MPS) type structures were investigated by capacitance-voltage (C-V) and conductance-voltage (G/-V) measurements as functions of temperature and applied bias voltage at 500kHz. Some main parameters of the structure such as real and imaginary parts of complex dielectric constants, epsilon(=epsilon-j epsilon), loss tangent (tan), a.c. electrical conductivity (sigma(ac)), and real and imaginary parts of complex electric modulus, M*(=M+jM) of the structure were investigated in the temperature range between 230K and 340K. Ln(sigma(ac))-q/kT curve showed a linear behavior. The value of activation energy (E-a) was obtained as 0.0601eV at 5.0V from the slope of this curve. Moreover, argand diagrams of complex modulus were studied to determine relaxation process of these structures.