# Wettability of CNW/ITO Micro Structure for Modification of Surface Hydrophilicity
## 3 Results and Discussion
On the other hand, the XRD pattern of 45 min offered a relatively improved (400) peak than the (222) peak, which implies that the (222) plane was the preferred orientation. Figure 4b exhibits the Raman spectra of the pristine-CNW and CNW/ITO micro-structure. To the best of our knowledge, D (1350 cm\({}^{-1}\)), G (1580 cm\({}^{-1}\)), and 2D (2700 cm\({}^{-1}\)) are the common band of carbon materials, and a high D band and D\({}^{\prime}\) band (shoulder band) is a unique band that can only be found in defected graphite [18; 19; 20]. In the Raman spectra of the CNW/ITO micro-structure from Figure 4b, it shows a low I\({}_{\text{D}}\)/I\({}_{\text{G}}\) ratio (1.71) with a low D band than pristine-CNW. As the D\({}^{\prime}\) band is revealed at the graphene edge and sp\({}^{3}\)-hybridization, the conspicuous change of D\({}^{\prime}\) band is an interesting phenomenon [21]. This phenomenon may signify that the opened zigzag shaped-graphene edge was transformed to a closed round edge with a stable structure by ITO nano-particles sputtered. The detailed figure of a reduced D\({}^{\prime}\) band is illustrated in Figure 4c. Additionally, we know that two specimens consist of multi-layered graphene through I\({}_{\text{2D}}\)/I\({}_{\text{G}}\) ratio. Figure 3: Cross-sectional FE-SEM image of CNW/ITO micro-structure: (**a**) pristine-CNW; CNW/ITO micro-structure by ITO nano-particles sputtered for (**b**) 15 min; (**c**) 30 min; (**d**) 45 min; (**e**) reference ITO thin film sputtered on Si substrate for 15 min. Although the wettability is affected by the variations of surface area and structure by the modified CNW/ITO micro-structure, components and functional groups on the surface enable it to have an effect on wettability because the fraction contacted with the water droplets in the CNW/ITO micro-structure is the ITO surface. Hence, X-ray photoelectron spectra analysis was operated to observe chemical variations including the components and functional groups on the ITO surface. The variation in chemical components from XPS results is briefly exhibited in Table 1. In the Table 1, the variation of carbon and oxygen were perceptible, and it is noted that the top of the carbon nanowall was scraped off by indium tin oxide nano-particles sputtered. The cause of the reduction in components of In/Sn may be due to the accumulated sputtering time. Generally, if the sputtering time is prolonged, the particles composing a thin film may be thrown out by sputtered particles. In this case, In (450 eV) and Sn (490 eV) having a relatively lower binding energy than oxygen (530 eV) may bounce off. It is assumed that this resulted in a reduction of In/Sn. The functional groups that contributed to wettability are contained in various chemical groups such as epoxy, carbonyl (C=O), hydroxyl (C-OH), and carboxyl (COOH). Especially the hydroxyl groups that constitute hydrogen bonds with strong bonding energy are a highly important key group. Figure 5a shows the chemical composition of ITO sputtered onto pristine CNW as narrow results of O 1s peak by X-ray photoelectron spectroscopy. This result presented various chemical compositions which were deconvoluted into five peaks, corresponding to a metal oxide bond at 530.1-530.2 eV, O-C=O (carboxyl) bond at 531.1 eV, C=O (carbonyl) group at 531.8-531.9 eV, O-C-O (epoxy) group at 532.5 eV, and C-OH (hydroxyl) bond at 533.1-533.7 eV, respectively. In the case of the pristine-CNW, very low peaks were identified, implying surface non-activation without a functional group. It is noted that a few peaks such as C=O bond and O-C=O bond may appear by natural oxidation in the air. In Figure 5a, the specimens sputtered with ITO commonly exhibit a metal oxide peak around 530.1 eV that is derived from metal oxides. The metal oxide peak reveals an increasing tendency with sputtering time, and it may be because oxygen in the air is adsorbed [22]. The various oxygen-related groups dramatically increased compared to pristine-CNW.