Synthesis of nanodimensional ZnO and Ni-doped ZnO thin films by atom beam sputtering and study of their physical properties

We report the preparation of pure zinc oxide (ZnO) and nickel-doped zinc oxide thin films (∼100 nm) by fast atom beam (FAB) sputtering technique and their characterisation in the perspective of transparent conducting oxide (TCO). Grazing angle X-ray diffraction (GAXRD) reveals that the films are polycrystalline, which has been further confirmed by selected area diffraction (SAD) studies. The nanogranular nature of the films is examined by transmission electron microscopy (TEM). A high optical transmittance (>87%) across UV-vis range and quite low electrical resistivity (∼1×10−3 Ω cm) have been observed in the undoped ZnO films. In Ni-doped ZnO (ZnO:Ni) films the optical transmittance decreases and resistivity increases, which subsequently further affected by an increase in Ni content. Charge carrier concentration, which is the highest in undoped film, reduces after Ni doping. The X-ray photoelectron spectroscopy (XPS) results show that zinc and nickel are in 2+ state. High electrical conductivity of undoped film is explained on the basis of presence of oxygen vacancies deduced from O1s spectra of the films. Decrease of electrical conductivity due to nickel doping is explained on the basis of compensation of oxygen vacancies.