Nanocrystalline NiO structure: Preferred oriented growth

Abstract

Nickel oxide (NiO) nanostructures were deposited on Si (100), potassium bromide (KBr), and glass slide substrates at room temperature by the evaporation technique. The prepared samples were annealed at temperatures of 400 °C and 600 °C in air atmosphere. The structure, morphology, crystalline phase, optical properties, and chemical bonding of nanocrystalline nickel oxide were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-visible absorption spectrum, and FT-IR spectroscopy. XRD results and SEM images showed that nickel oxide nanoparticles have preferred orientation with uniform size distribution. The as-deposited films showed preferred orientation (texture) growth. As the films were annealed, the crystallites were agglomerated to form bigger particles. Optical properties were identified by measuring transmittance using a UV-Vis spectrophotometer. Optical constants such as the refractive index n, the extinction coefficient k, and the films' thickness and roughness were calculated from transmittance data using a reverse engineering method. As the sample annealed, the ad-atom surface mobility increased, and smaller crystallites agglomerated to form bigger ones.