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 × 10−1 Ω cm, whilst the conductivity and the carrier concentration improved from 0.28 Sm-1 to 5.87 Sm-1 and 2.23 × 1014 cm−3 to 485.14 × 1014 cm−3 respectively. Thermal dependence activation energy (Ea) 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 Vo and Zni 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 Vo and Zni 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.