Low temperature dielectric study and photoconductive analysis of ZnO/NiO composite material

Abstract

The sol-gel process was used to synthesize a ZnO–NiO composite material in this study. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the material, which confirmed the existence of both ZnO nanoparticles and NiO sheets in the composite. The composite material contained two distinct crystalline phases, the face-centered cubic phase of NiO and the hexagonal phase of ZnO. The composite's average crystallite size was determined to be 19.0 nm. The particle size of the composite material was calculated to be ∼121 nm. The band edge emission at 393 nm (3.15 eV) was measured using photoluminescence (PL) spectroscopy. The PL spectrum revealed other emissions as well. The dielectric properties of the material were studied at low temperatures in the frequency range of 20 Hz to 1 MHz, and it was found to have a low dielectric dissipation at high frequencies, making it suitable for use in high frequency microwave devices. Impedance data was fitted using Z-View software with a fitting error of <5%. Impedance spectroscopy revealed that the composite material had two dielectric relaxation processes related to the bulk and the grain boundary. Analysis of frequency dependent ac conductivity revealed Overlapping large-polaron hopping (OLPH) is responsible conduction mechanism in our case indicated by variation of temperature (200–280 K) dependent parameter “s” with temperature. Photoconductivity studies showed that the composite material had enhanced electrical conductivity and photoconductivity compared to pure ZnO and NiO. This makes it a promising candidate for use in optoelectronic applications such as solar cells, optical switches, and photodetectors. The responsivity of composite (0.86 mA/Watt) is found to be 10 times greater than that of the responsivity of NiO (0.085 mA/Watt).