Structural, opto-electronic and electrical properties of pure NiO nanostructures and Ga-Li co-doped NiO

Abstract

Nickel oxide (NiO) nanoparticles along with Gallium (Ga) and Lithium (Li) doping of 1% have been synthesized by sol-gel method using nickel nitrate [Ni(NO3)2.6H2O], Gallium nitrate [Ga(NO3)3] and Lithium nitrate [LiNO3] in appropriate proportions. NiO nanostructures have also been synthesized by hydrothermal method using Nickel chloride [NiCl2.6H2O], DI (Deionized) water, ethanol and ammonium hydroxide. The synthesized samples were then subjected to characterizations like XRD, Raman Spectroscopy, UV-VIS Spectroscopy, FESEM, EDX and conductivity studies. Rietveld refinement was done for all the samples and the variation in bond length, bond angle, lattice parameters, crystallite size and lattice strain was calculated. Raman spectroscopy revealed different phonon modes and their frequencies which can be directly correlated with the XRD analysis. As reported in the literature, NiO can be both direct and indirect band gap semiconductor. Direct band gap of about 3.4-3.8 eV and indirect band gap in the range of 2.8-3.3 eV was calculated from UV-Vis data. FESEM and EDX data gave the appropriate particle size and morphology of the samples. Pressure dependent and magnetic field dependent conductivity studies revealed quite astounding results and enhancement in the conductivity with Li and Ga doping in NiO.