Influence of Doping Concentration on the Zinc Doped Nickel Oxide Nanostructures: Morphological, Structural, and Optical Properties

Abstract

The zinc doped nickel oxide (Zn:NiO) nanostructures with 0 at.% (UD), 1 at.% (1ZNO), and 2 at.% (2ZNO) of Zn concentrations were successfully deposited on the NiO seed-coated glass substrates. The films were successfully produced from two synthesis techniques: the sol-gel spin coating for NiO seed-coated and the solution immersion for the Zn:NiO nanostructures. The films were then pre-baked at 150 °C and subsequently annealed at 500 °C. The Zn doping concentrations affecting NiO in terms of morphological, structural, and optical properties were investigated. The surface morphologies and cross-sectional images of the Zn:NiO nanostructures were observed by field emission scanning microscopy. The observation showed that the groups of nanoflower (NF), which were grown above the nanosheet (NS) array were gradually decreased with the increasing percentage of the Zn doping. The thickness of the NS also drastically decreases as the Zn dopant is increased. The thicknesses measured are 910 nm, 410 nm, and 100 nm for UD, 1ZNO, and 2ZNO, respectively. The X-ray diffraction analysis showed the Zn:NiO peak intensities were affected and decreased as the Zn doping is increased. Take into account the significant differences in the (200) plane, the crystal parameters were calculated. The dislocation density, interplanar spacing, lattice parameter, and unit cell volume increased as the Zn doping increased. Meanwhile, the average crystallite size reduces when the percentage of Zn doping is increased. This condition makes the Zn:NiO nanostructures are promising for sensing applications due to enhanced surface area. The strain and stress values of the Zn:NiO showed the tensile strain and compressive stress, respectively. The transmittance spectra showed the transparencies in the visible region within 400 to 800 nm wavelength increases when the percentage of Zn doping is increased. The average transmittance percentages are 32.1 %, 62.8 %, and 67.0 % for UD, 1ZNO, and 2ZNO, respectively. The optical bandgap increases sharply as the Zn doping increased from 3.55 to 4.75 eV.

Long-Lasting Panchromatic Electrochromic Device and Energy-Dense Supercapacitor Based on Zn-Doped NiO Microstars and a Redox-Active Gel

“…Along the three principal planes of (111), (200), and (220), the crystallite sizes are 37, 36, and 28 nm in NiO, and they reduce to 3.6, 4.9, and 3.6 nm in Zn:NiO, respectively. A similar decrease in crystallite size has been observed in an earlier report for Zn-doped NiO . Yet another study showed a crystallite size decrease from ∼22 to ∼20 nm on going from NiO- to Zn-doped NiO .…”

“…A similar decrease in crystallite size has been observed in an earlier report for Zn-doped NiO. 28 Yet another study showed a crystallite size decrease from ∼22 to ∼20 nm on going from NiO-to Zn-doped NiO. 29 The slight mismatch in the ionic radii of Zn 2+ and Ni 2+ ions, 74 and 70 pm, induces some structural distortion, large enough to induce morphological and structural changes, but small enough to prevent structural collapse.…”

“…In an earlier study, from linear I – V plots for NiO and Zn:NiO nanoflakes, resistivities were estimated to be ∼4.1 × 10 7 and ∼10 × 10 7 Ω m, respectively . Surprisingly, while there are many reports which discuss the optical, morphological, and structural modifications induced by Zn-doping in NiO, ,,− there are hardly any which describe the electrical conduction behavior in detail.…”

Hydrothermal synthesis and solar cell application studies of nickel doped zinc oxide nanocomposites

“…Properties of zinc oxide can be enhanced by doping with other transition metal oxides. This is due to the development of new crystallographic phases in the composite [14][15][16]. Doping can be done with nickel oxide, copper oxide, titanium dioxide etc.…”