Growth and characterization of magnetron sputtered ZnO:Nb films

The Nb-doped, ZnO (ZnO:Nb) films were deposited by D. C. magnetron sputtering on glass substrates. The impacts of the growth conditions, including argon pressure, sputtering power, and substrate temperature, on the microstructures and properties of the ZnO:Nb films were evaluated. The films were characterized with X-ray diffraction, scanning electron microscopy, ultraviolet visible transmittance spectroscopy, and conventional probes. The results show that the argon pressure strongly affects the microstructures and properties of the hexagonal-wurtzite phased, polycrystalline ZnO:Nb films with c-axis preferred growth orientation. For instance, as the pressure increased, the films surface became increasingly smooth, uniform and compact. At 10 Pa, its lowest resistivity was found to be 3.52×10-4 Ω&middotcm, with a residue stress of 0.37 GPa. As the pressure increased from 2 to 12 Pa, its optical band-gap widened from 3.29 to 3.43 eV. The averaged transmittance was found to be 87% in the visible light range.