Influence of Ru-dopant on the structural, morphological, optical and electrical properties of NiO films

Authors: Yeasir Ahmed, Md Rasadujjaman*, Md Rezaul Karim, Md Sahab Uddin,
Md Anwar Hossain*

Abstract: In this study, the influence of ruthenium (Ru) doping on nickel oxide (NiO) films were investigated to achieve suitable optoelectronic properties. NiO films with different Ru doping concentrations (1.5, 2.5, and 3.5 wt%) were coated onto a cleaned hot (80 °C) glass substrate using a low-cost, home-made spin coater. The films were then pre-annealed at 80 °C and further annealed at 400 °C for crystallization. The formation of pure NiO films exhibiting a cubic polycrystalline structure with favorable growth orientation towards the (200) plane was confirmed. Ru doping at 1.5 and 2.5 wt% suppressed the growth of NiO films, and further incorporation of Ru (3.5 wt%) returns the preferred orientation in the (200) plane. Ru doping into NiO films generated defects such as void structures on the surface and shown a uniform distribution of Ru dopant across the films and confirmed the formation of NiO–RuO₂ composite. The band gap was reduced from 3.68 to 3.48 eV until the Ru doping concentration reached 2.5 wt%, which may be due to the generation of additional energy levels near the valence band, resulting in reduced transmission. The estimated resistivity decreased from 76.03 to 10.04 Ω–cm due to Ru doping, indicating an increase in film conductivity. Therefore, the introduction of Ru resulted in a reduced resistivity with preferential band gap, indicating a positive influence on the properties of NiO films.

Paper Link: https://www.sciencedirect.com/science/article/pii/S0925838824046735?dgcid=author