Structural, energy gap tuning, photoluminescence and magnetic properties of Sn-doped Zn0.96Ni0.04O nanostructures

Abstract

Ni (4%) doped ZnO and Ni, Sn (Ni = 4% and Sn = 1 and 2%) dual doped ZnO nanostructures have been synthesized by sol-gel route. The hexagonal ZnO structure of Ni/Sn doped ZnO was not disturbed by Sn addition and no secondary or impurity phases of Ni/Sn were identified in the XRD pattern. The continuous suppression of nucleation and hence the growth rate by Sn doping reduce the grain size and the replacement of Sn4+ ions with lower ionic radius instead of Zn2+ in Zn–Ni–O lattice is also accelerate the size decrement. Hexagonal wurtzite structure was not affected by Sn substitution. The reduced size and higher transmittance at Zn0.94Ni0.04Sn0.02O is recommended for the industrial application like transparent electrode. The continuous blue shift of energy gap from 3.53 eV (Sn = 0%) to 3.75 eV (Sn = 2%) is clarified by Burstein-Moss (BM) band filling effect with the help of energy level diagram. The existence of Zn–O–Ni/Sn bonding is verified by Fourier transform infra-red examination. The improved visible PL emissions like near violet, blue and green emissions by Sn doping is due to the existence of higher oxygen vacancies and oxygen related defects in Zn–Ni–Sn–O lattice. The room temperature ferromagnetism (RTFM) with elevated saturation magnetization by Ni/Sn doping in ZnO is stimulated by the intrinsic exchange interaction between Zn/Ni/Sn ions through the defects induced by Sn.