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

Abstract

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 Ni 2 O 3 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 2.59x10 -3 Ωcm at a Ni doping concentration of 3wt% compared with undoped Al-doped ZnO film (5.58x10 -3 Ωcm). 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.