Incorporation of Co ions on the physical properties of NiO nanoparticles and fabrication of superior photo-response p-Co-doped NiO/n-Si heterostructure-based diodes

Abstract

In this work, we have effectively synthesized pure NiO and Co-doped NiO nanoparticles (NPs) for different doping levels like 3, 6, and 9 wt% of Co by a simple co-precipitation method. The synthesized NPs were characterized systematically by advanced instruments. The XRD profile confirms the cubic crystal structure of the prepared Co-doped NiO NPs. The calculated average crystallite size was found to increase with doping concentration from 20 to 29 nm. The FESEM micrograph revealed the spherical NPs in pure and sponge-like surface morphology in doped NiO samples. TEM/HRTEM and SAED analysis was also performed for 9 wt% Co-doped NiO samples and confirms the formation of spherical cubic phase NPs. The presence of elements such as Co, Ni, and O was confirmed by the EDX spectrum. The X-ray photoelectron spectroscopic measurements also confirm Co²⁺ ionic state in NiO NPs. By incorporating Co ions into the NiO system, the optical bandgap energy of the NiO NPs is reduced from 3.48 to 3.33 eV. The functional group and vibration modes of the prepared samples were examined using the FTIR spectrum. A strong emission band at 485 nm was obtained in the PL emission spectrum. All prepared samples were used to fabricate a p-Co-doped NiO/n-Si junction diode. The calculated ideality factor was found to be n = 5.22 for pure NiO NPs under dark conditions and n = 1.91 for the 9 wt% of Co-doped NiO NPs under illumination. The highest doping of 9 wt% of p-Co doped NiO/n-Si junction-diode showed maximum photosensitivity of 434.96. Furthermore, the calculated quantum efficiency of the diode with a Co doping level is found to increase from 167 to 2433.4 %. The fabricated p-Co-doped NiO/n-Si diodes are highly appropriate for photo-detection applications.