• SEMSETTIN ALTINDAL

      Articles written in Bulletin of Materials Science

    • A comparative study on dielectric behaviours of Au/(Zn-doped PVA)/$n$-4H-SiC (MPS) structures with different interlayer thicknesses using impedance spectroscopy methods

      HAVVA ELIF LAPA ALI KÖKCE AHMET FARUK ÖZDEMIR IBRAHIM USLU SEMSETTIN ALTINDAL

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      Three different thicknesses (50, 150 and 500 nm) Zn-doped polyvinyl alcohol (PVA) was deposited on $n$-4HSiC wafer as interlayer by electrospinning method and so, Au/(Zn-doped PVA)/$n$-4H-SiC metal–polymer–semiconductorstructures were fabricated. The thickness effect of Zn-doped PVA on the dielectric constant ($\epsilon^{\prime}$), dielectric loss ($\epsilon^{\prime\prime}$), losstangent ($\tan \delta$), real and imaginary parts of electric modulus ($M^{\prime}$ and $M^{\prime\prime}$) and ac electrical conductivity ($\sigma_{\rm ac}$) of them were analysed and compared using experimental capacitance ($C$) and conductance ($G/\omega$) data in the frequency range of 1–500 kHz at room temperature. According to these results, the values of $\epsilon^{\prime}$ and $\epsilon^{\prime\prime}$ decrease with increasing frequency almost exponentially, σac increases especially, at high frequencies. The $M^{\prime}$ and $M^{\prime\prime}$ values were obtained from the $\epsilon^{\prime}$ and $\epsilon^{\prime\prime}$ data and the $M^{\prime}$ and $M^{\prime\prime}$ vs. $f$ plots were drawn for these structures.While the values of $\epsilon^{\prime}$, $\epsilon^{\prime\prime}$ and $\tan \delta$ increase with increasing interlayer thickness, the values of $M^{\prime}$ and $M^{\prime\prime}$ decrease with increasing interlayer thickness. The double logarithmic $\sigma_{\rm ac}$ vs. $f$plots for each structure have two distinct linear regimes with different slopes, which correspond to low and high frequencies, respectively, and it is prominent that there exist two different conduction mechanisms. Obtained results were found as a strong function of frequency and interlayer thickness.

    • Dielectric properties of Ag/Ru$_{0.03}$–PVA/$n$-Si structures

      YOSEF BADALI SERHAT KOÇYIGIT IBRAHIM USLU SEMSETTIN ALTINDAL

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      Ag/Ru$_{0.03}$−PVA/$n$-Si structures were successfully prepared and their morphological and electrical properties were investigated. The obtained electrical results suggested that the complex dielectric constant ($\epsilon^* = \epsilon^{\prime} − j\epsilon^{\prime\prime}$), complex electric modulus $M^∗ = M^{\prime} + jM^{\prime\prime}$, loss tangent ($\tan \delta$) and alternating current (ac) electrical conductivity ($\sigma_{\rm ac}$) are all a strong function of the frequency ($f$) and applied voltage. The changes in these parameters are the results of the existence of the surface states ($N_{\rm ss}$) or interface traps ($D_{\rm it} = N_{\rm ss}$), interfacial polymer layer, surface and dipole polarizations and hopping mechanisms. The values of $\epsilon^{\prime}$ and $\epsilon^{\prime\prime}$ show a steep decline with increasing frequency and then reach a constant value at high frequency, whereas the increments of $M^{\prime}$ and $M^{\prime\prime}$ with frequency are exponential. The $\tan \delta$ vs. $\log f$ plot has a strong peak behaviour, especially in the accumulation region. These experimental results suggested that the Ru$_{0.03}$−PVA interfacial layer could be used as a high dielectric material instead of conventional materials.

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