Investigation of dielectric relaxation and ac conductivity in Au/(carbon nanosheet-PVP composite)/n-Si capacitors using impedance measurements

Abstract

The frequency and voltage dependence of complex dielectric constant $\left({\epsilon }^{*}\right)$, electric modulus ${(M}^{*})$, tangent loss $\left(\text{t}\text{a}\text{n}\delta \right)$, ac electrical conductivity $\left({\sigma }_{ac}\right)$, and impedance $\left({Z}^{*}\right)$ of the Au/(Carbon Nanosheet-PVP composite)/n-Si capacitors was investigated using the impedance spectroscopy (IS) method in wide frequency range (1 kHz–5 MHz). ${\epsilon }^{{\prime }}-V$ plot yielded two distinct peaks located at 1.0 and 2.5 V in the low-frequency region. As the value of ${M}^{{\prime }}$ increases with increasing frequency, ${M}^{{\prime }{\prime }}$ shows a peak whose position shifts toward positive voltages with increasing frequency. Such response of these parameters to frequency can be attributed to the interfacial polarization and a special distribution of interface states at Au/interlayer interface since the dipoles and interface states both have enough time to follow the ac signal easily, thus the dipoles rotate around themselves and align with the field. The plot of $\text{ln}\left({\sigma }_{ac}\right)-\text{l}\text{n}\left(\omega \right)$ has three linear regions corresponding to low, intermediate, and high frequencies, each yielding a different slope value thus indicating a different conduction mechanism for each frequency range. It was found that the obtained value of ${\epsilon }^{{\prime }}$ is approximately five times higher than the bulk SiO₂ at 1 kHz. The dielectric characterization reveals that the presence of the (Carbon Nanosheet-PVP composite) interlayer affects the electrophysical features of the fabricated device. In other words, the utilization of the abovementioned interlayer is showing a considerable improvement in the performance of the MS structure with respect to high-energy storage capacity. The use of the Carbon Nanosheet-PVP composite as an interfacial layer instead of conventional insulators has improved device performance over a wide range of frequencies and voltages.