Effect of Bi doping on the structural and optical properties of NiO thin films

Nickel Oxide (NiO) based thin films have drawn widespread attention in optoelectronics applications because of their superior optical and electrical properties. Herein, the effect of Bi doping on the microstructure, phase evolution, composition, electrical and optical properties of NiO thin films are reported. Bi-doped NiO (0–7.5 %) thin films were deposited on glass substrates by the cost-effective spin coating technique. The X-ray diffraction studies showed that the undoped and 2.5 % Bi-doped films develop cubic structure and 5.0 % and 7.5 % of Bi doped films formed an amorphous nature. A systematic decrease in the grain size as well as surface roughness with Bi doping was noticed through AFM analysis. The films are highly transparent (80 %) and the optical band gap increases from 3.45 eV for undoped NiO to 3.99 eV for 7.5 % Bi-doped NiO thin film. The nonlinear optical susceptibility values are found to be in the range of 0.034 × 10-11 to 2.72 × 10-11 esu.