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

Abstract

Three different thicknesses (50, 150 and 500 nm) Zn-doped polyvinyl alcohol (PVA) was deposited on n-4H-SiC wafer as interlayer by electrospinning method and so, Au/(Zn-doped PVA)/n-4H-SiC metal–polymer–semiconductor structures were fabricated. The thickness effect of Zn-doped PVA on the dielectric constant ($\varepsilon ^{\prime }$), dielectric loss ($\varepsilon ^{{\prime }{\prime }}$), loss-tangent (tan $\delta$), real and imaginary parts of electric modulus ($M^{\prime }$ and $M^{{\prime }{\prime }})$ and ac electrical conductivity $(\sigma _{\mathrm{ac}})$ 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 $\varepsilon ^{\prime }$ and $\varepsilon ^{{\prime }{\prime }}$ decrease with increasing frequency almost exponentially, $\sigma _{\mathrm{ac}}$ increases especially, at high frequencies. The $M^{\prime }$ and $M^{{\prime }{\prime }}$ values were obtained from the $\varepsilon ^{\prime }$ and $\varepsilon ^{{\prime }{\prime }}$ data and the $M^{\prime }$ and $M^{{\prime }{\prime }}$ vs. f plots were drawn for these structures. While the values of $\varepsilon ^{\prime }$, $\varepsilon ^{{\prime }{\prime }}$ 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 $\sigma _{\mathrm{ac}}$ 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.