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    Frequency and voltage dependent profile of dielectric properties, electric modulus and ac electrical conductivity in the PrBaCoO nanofiber capacitors
    (Elsevier Science Bv, 2016) Demirezen, S.; Kaya, A.; Yeriskin, S. A.; Balbasi, M.; Uslu, I.
    In this study, praseodymium barium cobalt oxide nanofiber interfacial layer was sandwiched between Au and n-Si. Frequency and voltage dependence of epsilon', epsilon', tan delta, electric modulus (M' and M '') and sigma(ac) of PrBaCoO nanofiber capacitor have been investigated by using impedance spectroscopy method. The obtained experimental results show that the values of epsilon', epsilon', tand, M', M '' and sigma(ac) of the PrBaCoO nanofiber capacitor are strongly dependent on frequency of applied bias voltage. The values of epsilon', epsilon '' and tand show a steep decrease with increasing frequency for each forward bias voltage, whereas the values of sigma(ac) and the electric modulus increase with increasing frequency. The high dispersion in epsilon' and epsilon '' values at low frequencies may be attributed to the Maxwell-Wagner and space charge polarization. The high values of epsilon' may be due to the interfacial effects within the material, PrBaCoO nanofibers interfacial layer and electron effect. The values of M ' and M '' reach a maximum constant value corresponding to M-infinity approximate to 1/epsilon(infinity) due to the relaxation process at high frequencies, but both the values of M ' and M '' approach almost to zero at low frequencies. The changes in the dielectric and electrical properties with frequency can be also attributed to the existence of N-ss and R-s of the capacitors. As a result, the change in the epsilon', epsilon '', tan delta, M', M '' and ac electric conductivity (sigma(ac)) is a result of restructuring and reordering of charges at the PrBaCoO/n-Si interface under an external electric field or voltage and interface polarization. (C) 2016 The Authors. Published by Elsevier B.V.
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    The investigation of dielectric properties and ac conductivity of Au/GO-doped PrBaCoO nanoceramic/n-Si capacitors using impedance spectroscopy method
    (Elsevier Sci Ltd, 2016) Kaya, A.; Alialy, S.; Demirezen, S.; Balbasi, M.; Yeriskin, S. A.; Aytimur, A.
    Graphene oxide-doped praseodymium barium cobalt oxide (GO-doped PrBaCoO) nanoceramic was used an interfacial layer for the purpose of increasing the capacitance in Au/n-Si metal semiconductor (MS) structures. The frequency and voltage dependence of dielectric constant (epsilon'), dielectric loss (epsilon ''), loss tangent (tan delta), the real and imaginary parts of electric modulus (M' and M '') and ac electrical conductivity (sigma(ac)) of Au/GO-doped PrBaCoO nanoceramic/n-Si capacitors were investigated in detail by impedance spectroscopy method in the wide frequency range of 1 kHz to 1 MHz at room temperature. Experimental results showed that epsilon'-V plot has two distinct peaks that are located at about 0 and 2 V, respectively, at low frequencies, but the first peak disappears at high frequencies. While the value of M' increase with increasing frequency M '' shows a peak and the peak position shifts to higher frequency with increasing applied voltage. Such peak behavior can be attributed to the particular distribution of interface states located between Au and interfacial layer and to the interfacial polarization. It can be concluded that the interfacial polarization and the charges at interface can easily follow ac signal at low frequencies. In addition, the ln(sigma(ac)) vs ln(omega) plot of the capacitor for 3 V has two linear regions (I and II) with different slopes which correspond to low and high frequency ranges, respectively. Such behavior of ln(sigma(ac)) vs ln(omega) plot indicated that there are two different conduction mechanisms in the Au/GO-doped PrBaCoO nanoceramic/n-Si capacitor at room temperature. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.