## 3 Results and Discussion
This may have an ameliorating effect due to the establishment of a stronger electrical network and the enhancement of optical properties of the films through the removal of TBAOH residues on the surface of the RuO\({}_{2}\) NSs [18, 19, 20]. Figure 2: Characterization of the deposited RuO\({}_{2}\) NS films. (**a**) FE-SEM image of the deposited single-layered RuO\({}_{2}\) NS films. Dark regions are the RuO\({}_{2}\) nanosheets. (**b**) Cross-sectional HR-TEM image of 10-layered RuO\({}_{2}\) NS films. We investigated the \(R_{\rm s}\) and optical transmittance of the conducting films with varying numbers (5-10 times) of LB coatings. Based on the obtained results for the relation between \(R_{\rm s}\), optical transmittance, and UVO treatment time, the optimized UVO exposure time for the RuO\({}_{2}\) NS conducting films was fixed at 30 min. Figure 4a depicts the \(R_{\rm s}\) of the RuO\({}_{2}\) NS films depending on the number of layers with and without UVO exposure. Owing to the UVO treatment, a reduction in the \(R_{\rm s}\) values was observed in all samples. Without the UVO treatment, it was found that the reduction of \(R_{\rm s}\) was saturated after eight layers of deposition, whereas further \(R_{\rm s}\) reduction was expected for the UVO-treated layers even after 10 layers of deposition. Additionally, the reduction ratio increased with the number of NS layers. The inset of Figure 4a depicts the \(R_{\rm s}\) ratio between the films without UVO treatment and that between the films with 30 min of UVO treatment. As shown, \(R_{\rm s}\) increased from 1.1 for the 5-layered films to 1.5 for the 10-layered films. This implies that the electrical connection between the RuO\({}_{2}\) NS layers becomes further improved as the number of layers increases. For example, an \(R_{\rm s}\) of 1000 \(\Omega\)/sq was achieved at 10 layers in the samples without UVO treatment, whereas this value was achieved at only 7 layers in the 30-min UVO-treated samples. This result indicates that  
Figure 3: Electrical and optical properties of the RuO\({}_{2}\) NS films. Dependence of **(a)** sheet resistance and **(b)** optical transmittance on the UVO treatment time (min). UVO exposure is highly efficient for enhancing the electrical percolation between coatings of RuO\({}_{2}\) NSs by removing the residual TBAOH from the NS surfaces. Figure 4b depicts the variation in the optical transmittance of the RuO\({}_{2}\) NS films with the number of layers with and without UVO exposure. Specifically, this exhibits the improved optical transmittance after UVO treatment. However, the improvement becomes marginal as the number of NS layers increases. To confirm the elimination of the residual organic TBAOH by the UVO treatment, the contents of hydrogen atoms in the LB-deposited film were investigated using Rutherford backscattering spectrometry (RBS). As shown in the inset of Figure 4b, the intensity of the hydrogen peak near  
Figure 4: Dependence of (**a**) sheet resistance and (**b**) optical transmittance on the number of NS layers, where the inset of (**a**) exhibits the ratio of sheet resistance. The inset of (**b**) is the Rutherford backscattering spectrometry (RBS) spectrum of the samples with different UVO treatment times (0, 20, and 30 min). 64-65 keV in the 30-min UVO-treated films was slightly lower in comparison with that in the UVO-untreated films, revealing that the residual TBAOH was effectively removed in the UVO-treated sample. In addition, the intensity of the hydrogen peak in the 20-min UVO-treated sample was almost the same as that in the UVO-untreated sample, indicating that the residual TBAOH on the surface of NSs was not sufficiently removed until after 20 min of UVO exposure. These results are consistent with those provided in Figure 3a, i.e., the relation between UVO treatment time and sheet resistance.