Optical Properties of NiO Columnar Nanostructure Prepared by OAD Technique

NiO columnar nanostructure was prepared using the thermal evaporation technique with oblique angle deposition (OAD). The morphological, structural, and optical properties change with the creation of the substrate inclination. NiO columnar nanostructure was analyzed using X-ray diffraction (XRD) analysis and field emission scanning electron microscope (FESEM). The strain values ε obtained exhibit that the strain becomes tensile (ε>0) for (2 0 0) and (2 2 2) planes. Conversely, the strain returns to a compressive state (ε<0) for (1 1 1) and (2 2 0) planes. The average tensile strain in NiO columnar nanostructure is obtained at 1.4% while the average compressive strain is obtained at 2.04%. The value of the optical bandgap of the NiO columnar nanostructure is obtained at about 4.06 eV. The refractive index showed two absorption bands around the wavelengths of 520 nm and 700 nm with values of 2.19 and 2.22, respectively. Then, the refractive index increased from 2.22 at 700 nm to 2.35 at 920 nm and remained almost constant over 920 nm.