Microstructural, optical, and electrical properties of Ni–Al co-doped ZnO films prepared by DC magnetron sputtering

•Ni–Al co-doped ZnO (NiAl:ZnO) composite thin films were deposited by DC magnetron sputtering at room temperature.•All films showed a highly preferential (002) c-axis orientation.•XPS revealed the presence of metallic Ni, NiO, and Ni2O3 states, and Ni atoms were successfully doped in the NiAl:ZnO films.•NiAl:ZnO (3wt% Ni) film showed the lowest electrical resistivity of 2.59×10−3Ωcm.•Band gap widening (4.18eV) was observed in the NiAl:ZnO films with 5wt% Ni. Ni–Al co-doped ZnO (NiAl:ZnO) films with fixed Al content at 2wt% and different Ni contents (2.5, 3, and 5wt%) were deposited by DC magnetron sputtering in an argon atmosphere at room temperature. X-ray diffraction revealed that all films showed a highly preferential (002) c-axis orientation. XPS revealed the presence of metallic Ni, NiO, and Ni2O3 states, and Ni atoms were successfully doped in NiAl:ZnO films, which did not result in a change in ZnO crystal structure and orientation. The electrical resistivity of NiAl:ZnO film was decreased to 2.59×10−3Ωcm at a Ni doping concentration of 3wt% compared with undoped Al-doped ZnO film (5.58×10−3Ωcm). The mean optical transmittance in the visible range was greater than 80% for all films. Band gap widening (4.18eV) was observed in the NiAl:ZnO films with 5wt% Ni, attributed to the Burstein–Moss shift due to the increase of carrier concentration.