Examination of dielectric response of Au/HgS-PVA/n-Si (MPS) structure by impedance spectroscopy method

Abstract

HgS-PVA nanoparticles were obtained via a simple ultrasound-assisted method. The structural and morphological characteristics of the products were analyzed by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The optical properties were also analyzed by UV-Vis spectroscopy, and Fourier transform infrared (FTIR). The XRD pattern demonstrated that the samples were high purity and no impurity other peaks were detected. The optical band gap was calculated by Tauc plot measured as 2.4 eV and a blue shift of about 0.3 eV due to the quantum confinement of charge carriers in a small nanostructure was observed. The surface of the samples consisting of nano-sized particles and the energy between the functional group were proved by SEM measurement and FTIR analysis techniques, respectively. Dielectric behavior was examined in the frequency range of 1 kHz-5MHz by using admittance (C-V and G/omega-V) measurements. The effect of surface states (N-ss) and polarization processes are dominant especially at low frequencies which lead to large discrepancies in C and G values. The dielectric constant value epsilon' reduces with the frequency increments, whereas the ac electrical conductivity sigma(ac) increases, depending on the nature of reducing polarization and series resistance (R-s) effect. The epsilon ''-V and tan delta-V plots give a peak in the inversion region and the magnitude of this peak reduces with the frequency increments, shifting towards the accumulation region that can be ascribed to a frequency dependent dielectric relaxation.