Nickel flux induced effects on structural and optical properties of NiO films fabricated by PA-MOCVD

• NiO epilayers were deposited on Si and sapphire substrates by photo-assisted MOCVD.
• The nickel flux is critical to influence the physical properties of the NiO epilayers.
• NiO layers changed from nanorods structure to continuous dense films with nearly free-boundary.

In the present work, we report the growth of NiO films fabricated by Photo-assisted Metal Organic Chemical Vapor Deposition (PA-MOCVD). The growth parameter of nickel flux affects the crystallographic, morphological and optical properties of NiO films, which were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet–visible spectrophotometer (UV). It is found that the NiO grains were increased with increase in nickel flux from an anomalous state to a cubic shape following the NaCl-type structure. The NiO films presented highly c-axis preferred orientation with significant (111) diffraction. The samples marked A-E under the nickel flux of 2, 4, 6, 8 and 10 sccm respectively have optical band gap values of 3.55 eV, 3.71 eV, 3.82 eV, 3.91 eV and 3.95 eV, respectively. Comparatively, the controllable electrical properties of NiO epilayers can be achieved by the variations of crystal quality arise from the nickel flux.