## 3 Results  
Figure 2 shows the image of FE-SEM of pristine CNW and MWCNT/CNW. The pristine CNW showed tight cross-sections with typical CNW morphology with various nano-porous surface (Figure 2a). On the other hand, all samples where MWCNT was used as the buffer layer exhibited thick buffer layers compared to the pristine CNW (Figure 2b-d). The thickness of the MWCNT-based buffer layer with 30, 50, 70 \(\upmu\)L was 7.8, 8.3, and 8.7 \(\upmu\)m, respectively. As the concentration increased, the buffer layer tended to become thicker. The height of CNW examined in all samples was 1.8-2.0 \(\upmu\)m. In surface FE-SEM, only the arrangement of nanowalls was different with no-change in shape and density. These no-change of the CNW surface is different from the carbon nanowalls grown on different substrates [8]. Figure 3 shows the Raman spectra results of all samples. In Figure 3a, three peaks that can be commonly found in carbon materials were identified. Three common peaks are D peak (1350 cm\({}^{-1}\)), G peak (1580 cm\({}^{-1}\)), and 2D peak (2700 cm\({}^{-1}\)). The D peak near 1350 cm\({}^{-1}\) can confirm the degree of defects due to the alignment of the carbon crystals. The high D peaks were observed in all samples, and these characteristics can be easily investigated in CNT and CNW. G peaks near 1580 cm\({}^{-1}\) are common in graphite-based carbon materials. The higher the intensity of the G peak, the better the  
Figure 1: Schematic of experiments: (**a**) cleaning of Si wafer substrate; (**b**) synthesis of CNW (carbon nanowall) on MWCNT-based buffer layer; (**c**) measurement of electrical properties of samples. Figure 2: The image of surface (inset) and cross section FE-SEM: (**a**) pristine MWCNT (**b**) CNT (30 \(\upmu\)L)/CNW; (**c**) MWCNT (50 \(\upmu\)L)/CNW; (**d**) MWCNT (70 \(\upmu\)L)/CNW. graphitization and the better the carbon material. Then, the D peak occurred at 1620 cm\({}^{-1}\) was able to be examined only in CNW. This peak is mainly discovered at the edge of graphene. CNW is vertically grown with multiple graphene layer on a substrate, and the top of CNW may be opened to the edge of graphene. In addition, CNW has a large number of carbon branches, and the peak of D peak can be occurred because the end of this branch can have the shape of a graphene edge. On the other hand, in the case of CNT, single or multilayer graphene layers are curled and the edge of the graphene cannot be identified, so D peak does not appear. The 2D peak of 2700 cm\({}^{-1}\) appeared in all samples, and as the I\({}_{\text{2D}}\)/I\({}_{\text{G}}\) ratio of 0.5 or less was confirmed, it may imply that all samples had a multilayer graphene structure. Figure 3b shows the I\({}_{\text{D}}\)/I\({}_{\text{G}}\) ratio of all samples. The I\({}_{\text{D}}\)/I\({}_{\text{G}}\) ratio numerically shows the carbon material defects, and the lower the ratio, the better the quality of the carbon material. All CNW specimens had a higher I\({}_{\text{D}}\)/I\({}_{\text{G}}\) ratio than CNT. With this phenomenon, the mechanism of growth of carbon nanowalls began with a defect by mismatch of carbon onions formed on the amorphous carbon buffer layer [9]. When MWCNT is used as a buffer layer, carbon radicals by CVD can induce C-C bonds with MWCNTs, not substrates, thereby forming graphitic layers more than amorphous carbon. It may be a cause that can lead to improved electrical properties. In addition, carbon nanowalls usually change in structure and properties depending on the substrate [10; 11; 12]. In our research, it is suggested that the structure of all specimens was unchanged because it was a synthesis reaction between the carbon-based substrate and carbon radical, not a reaction to the Si-substrate and the carbon radical, and it caused a non-variation of Raman spectra results. Figure 4 shows the electrical properties of carbon nanowalls grown on MWCNT-based buffer layers. In the Raman spectra, CNW grown on the MWCNT-based buffer layer was not significantly different from normal CNW.