Preparation and Characterizations of Monocrystalline Na Doped NiO Thin Films

Abstract

In the present work, the effect of Na doping on optical, structural and electrical properties of Na doped NiO thin films were studied. The spray pneumatic method was used to deposit the Na doped NiO thin films in the range 0 to 5 wt.%, it are investigated at a substrate temperature of 420 °C with NiO solution 0.1 M. Firstly in the XRD specra, as found that a only (111) peak was observed for Na doped NiO thin film indicate that the Na doped NiO thin films a monocrystalline in nature with cubic structure. The maximum crystallite size of Na doped NiO thin films was 18.90 nm at 3 wt.%. Secondary, the optical transmissions spectra Na doped NiO thin films having a high transparency with comparing to undoped film in visible region. The band gap energy was decreased after doping by Na and reaching a minimum value is 3.53 eV at 2 wt.%. The minimum value of Urbach energy was 0.312 eV, it is obtained at 3 wt.%. In the end, the minimum electrical resistance of the Na doped NiO films was located at 5 wt.%. The optimum Na doping amount is achieved at 3 at %.

Synthesis and Characterization of Physical Properties of the NiO Thin Films by Various Concentrations

“…The calculation of the optical band gap energy is a major factor in determining the electrical conductivity of the thin films, which based on optical transmission. It was calculated from the classical method by the extrapolation of the curve at A = 0 [18], which represented to the drawn of the (Aℎʋ) 2 as a function of hʋ (see Figure 4a) using the following equations [2,5]: where A is the absorbance, d is the film thickness; T is the transmission spectra of thin films; α is the absorption coefficient values; C is a constant, hʋ is the photon energy and Eg the band gap energy of NiO thin films (see Table 2). On the other hand, the disorder in the NiO thin films was characterized by the Urbach energy (Eu) has been calculated by the following expression [19]:…”

The Deposition Temperature Dependence on the Crystallite Size of NiO Thin Films

“…Table 1 presents that the NiO thin films were nanocrystalline and had a cubic structure with (111) crystal plane at the higher intensity, which has preferential a-axis orientation along with (111) crystal plane. The Miller indices (hkl) were obtained from the Bragg equation [6]:…”

“…The differences a − a 0 of (111) crystal plane are given by the following relation [6]: where a 0 is the standard lattice parameter of NiO (standard a 0 = 0.4176 nm). The crystallite size of (111) crystal plane for the fabricated NiO thin films was calculated from the Scherer's formula [7]:…”

The film thickness effect on the physical properties of NiO thin films elaborated by Sol-gel method

“…The graph in Fig. 3 was plotted according to the following equation [14]: (3) where A is the absorbance, d is the film thickness; T is the transmission spectra of thin films; α is the absorption coefficient values; C is a constant, hv is the photon energy, and Eg is the band gap energy of the semiconductor.…”