Investigation on the Structural and Optical Properties of NiO Nanoflakes. Chemical Bath Deposition of Ni(OH)2 Thin Films

Abstract

Porous nickel oxide (NiO) nanoflakes are grown by the chemical bath deposition. The thin films are produced on an ITO/glass substrate and annealed at a variable temperature in a furnace. The structural and optical properties and the surface morphology of the thin films are studied and analyzed. FESEM results display the presence of nanoflakes with the structure of NiO/Ni(OH)2 in thin films that appear to increase in size with the annealing temperature. The sample grown at 300 ∘ C is observed to have the highest surface area dimension. The EDX result reveals that the atomic ratio and weight of the treated sample has a non-stoichiometric value, which results in the-type behavior of the NiO thin film. The result obtained by AFM indicates the highest roughness value (47.9 nm) for a sample grown at 300 ∘ C. The analysis on XRD shows that the NiO nanoflakes possess a cubic structure with the orientation peaks of (111), (200), and (220). This appears with a stronger intensity at 300 ∘ C. Likewise, XRD result approves the absence of the Ni(OH)2 peak at the annealing. For the optical band gap, the UV-Vis measurements give a lower value of 3.80 eV for 300 ∘ C due to the highest crystallinity. The optimum temperature to synthesize high-quality NiO nanoflakes is 300 ∘ C, which can be an important factor for good sensing devices. K e y w o r d s: annealing temperature, nanoflakes, thin film, chemical bath deposition, nickel oxide.