# Facile Synthesis of Highly Conductive Vanadium-Doped NiO Film for Transparent Conductive Oxide
## 3 Results  
### Study of Material Properties  
To study the effect of V doping on NiO, the materials were subjected to analysis using XRD. In our work, both pristine and 3 at.%V:NiO NPs exhibited a very broad XRD pattern (Figure 1a). The diffraction peaks of the prepared powder samples show a cubic face-centered crystal system with four characteristic diffraction peaks at 20 = 36.98\({}^{\circ}\), 43.21\({}^{\circ}\), 62.67\({}^{\circ}\), and 75.34\({}^{\circ}\), which could be assigned to the (111), (200), (220), and (311) planes of NiO, respectively. The synthesized NiO NP formation was confirmed using the Joint Committee on Powder Diffraction Standards (JCPDS) card no. 03-065-2901 with space group Fm3m [29]. Meanwhile, no extra diffraction peaks related to vanadium or vanadium oxide were observed. A similar trend was also observed for the 1.5 at.%V:NiO sample, but an extra diffraction peak of V\({}_{2}\)O\({}_{5}\) was observed at a higher doping percentage (5 at.%V:NiO). This result indicates that a light doping concentration of V hardly changes the phase structure of NiO [2]. Additionally, it could be observed that the 3 at.%V:NiO NP diffraction peak at 43.25\({}^{\circ}\) shows a broadening and slight shifting towards a higher angle (Figure 1b). This result indicates the incorporation of vanadium into the NiO lattice. It is also important to mention that the diffraction peak broadening of the 3 at.%V:NiO sample reveals the reduction of particle size. To further understand the effect of particle size after doping, we calculated the crystalline size of both samples by the Debye-Scherrer formula, \(D_{p}=\frac{0.89}{\cos}\lambda\), where D\({}_{\text{p}}\) is the crystalline size, \(\lambda\) is the X-ray wavelength, \(\beta\) is the full width at half-maximum (FWHM), and \(\theta\) is the diffraction angle of the peak. Interestingly, we observed that the crystalline size of peak (200) significantly decreased after doping from 3.09 nm to 2.82 nm. Hence, the dissociation density (\(\delta\)) and lattice strain (\(\varepsilon\)) were calculated by the equations [30] = \(\frac{1}{D_{p}{}^{2}}\) and = \(\cos\left/4\right.\), and values are tabulated in Table 1. It can be concluded that the NiO crystalline size was decreased by V doping; thereby, the dissociation density and lattice strain were enhanced. Figure 2a shows the FTIR spectra of Ni(ac)\({}_{2}\), V\({}_{2}\)O\({}_{5}\), NiO, and 3 at.%V:NiO for a comparative study of the precursor materials and products. In our case, the characteristic stretching vibration of the Ni-O absorption band was observed at 468 cm\({}^{-1}\), which originated from the Ni(ac)\({}_{2}\) species. The peak at 676 cm\({}^{-1}\) in the doped sample was ascribed to the presence of vanadium. We observed that the Ni-O stretching band in NiO and the V-O-V stretching band in the 3 at.%V:NiO sample were shifted to lower wavenumber regions as compared with the Ni(ac)\({}_{2}\) and V\({}_{2}\)O\({}_{5}\) precursor samples. These red shifts are associated with changes in the surface area and surface defects due to the oleylamine (capping agent) added during the synthesis. The elemental compositions of both the pristine and 3 at.%V:NiO NPs were confirmed by energy-dispersive X-ray spectroscopy (EDAX). Figure 2b shows that the 3 at.%V:NiO powder sample consisted of Ni, V, and O with no impurity elements. The weight and atomic percentage values of the Ni, O, and V elements are given in the inset of Figure 2b. The EDX mapping of elements in Figure 2c revealed the uniform distribution of Ni, V, and O in the sample. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Samples** & **20 (\({}^{\circ}\))** & **hkl** & **FWHM** & **d\({}_{\text{sp}}\) (A\({}^{\circ}\))** & **D\({}_{\text{p}}\) (nm)** & **\(\xi\) (nm\({}^{-1}\))** & \(\varepsilon\times\mathbf{10^{-2}}\) \\ \hline NiO & 43.251 & 200 & 2.94 & 2.095 & 3.04 & 0.1082 & 0.955 \\
3 at.%V:NiO & 43.278 & 200 & 3.17 & 2.094 & 2.82 & 0.1257 & 1.054 \\ \hline \hline \end{tabular}
\end{table}