Tailoring electronics structure, electrical and magnetic properties of synthesized transition metal (Ni)-doped ZnO thin film

Improving Zinc Oxide (ZnO) conductivity is in dire need due to its major shortcoming of high resistivity as a result of low carrier concentration. In this work, ZnO was doped with a transition metal, Nickel (Ni) in different concentrations (1 mol%, 2 mol%, 3 mol%, and 4 mol%) and the influence of Ni concentrations in ZnO thin film in term of electrical, electronic structure as well as magnetic properties were investigated. ZnO thin films with Ni-doping were successfully produced via a sol-gel spin coating method. High-Resolution Transmission Electron Microscopy (HR-TEM) image observed for 3 mol% Ni:ZnO thin film shows clear and coherent lattice fringes in hexagonal shape with the amorphous structure inside. The resistivity of Ni:ZnO films show to decrease with the addition of Ni-doping down to 1.7 x 10(-1) Omega cm, whilst the conductivity and the carrier concentration improved from 0.28 Sm-1 to 5.87 Sm-1 and 2.23 x 10(14) cm(-3) to 485.14 x 10(14) cm(-3) respectively. Thermal dependence activation energy (E-a) of ZnO thin film is found to be 1.3 eV and increases up to 15.1 eV above 373 K. X-ray Photoemission Spectroscopy/Ultraviolet Photoemission Spectroscopy (XPS/UPS) spectra indicate that Ni-doped ZnO induced more surface defects and native defects in the ZnO system. In addition to that, photoluminescence spectra show that V-o and Z(ni) induced shallow donor in the system. Finally, via Vibrating Sample Magnetometery (VSM) measurement, it is revealed that the ferromagnetism of Ni:ZnO might be induced by the co-existence of V-o and Z(ni) defects. These results may open an attractive path to tailor Ni-doping in ZnO system to act as potential candidates for the optoelectronic and spintronic applications. (C) 2018 Elsevier B.V. All rights reserved.