# Correlating Disorder Microstructure and Magnetotransport of Carbon Nanowalls
## 3 Results and Discussion  
### Morphological and Microstructural Characteristics  
Figure 2a-d present the SEM image of the CNWs formed with different parameters of synthesis: Ar flux, time and deposition temperature. In the samples synthetized at 60 min, the thickness of the walls (the longitude in the transverse direction to the substrate obtained by a cross-sectional SEM image) decrease from 3.1 to 1.5 \(\upmu\)m, reducing the Ar flux or increasing the temperature, while the lengths of the walls became almost saturated around 1.5 \(\upmu\)m. This suggests that, in contrast to the Ar flux, the temperature re-evaporates the nucleation sites, as is necessary for the growing of the walls. The sample formed in less time deposition, 30 min, only grows to around 0.23 \(\upmu\)m and 0.5 \(\upmu\)m in length and thickness, respectively. Table 1 shows a summary of the values obtained. The interlayer space of the walls varies between 0.33 and 0.35 nm, as observed in the TEM images (Figure 3a). The increase of the defect amount and temperature may break the single wall structure into many graphene nanocrystallites (GNs) (see Figure 3b,c), since each wall is composed of small graphite regions or nanographite domains [29]. The in-plane lattice constant of the GNs (observed as fringes in Figure 3c) is comparable to that of the graphite (2.53 \(\pm\) 0.10 A and 2.46 A [30], respectively). Additionally, it was found that there were nanoparticles with curved layers (see Figure 3d), similar to those obtained by [PERSON] from carbon black [31]. The Raman spectra (see Figure 4a,b) reveal a strong G-peak around 1580 cm\({}^{-1}\), which confirms the apparition of the graphene sheets and assigned to \(E_{\rm 2g}\) phonons from the Brillouin zone [32]. The D-band around 1354 cm\({}^{-1}\) is activated with induced disorder. Another peak appears around 1614, named D\({}^{\prime}\), identified on the edges. The relation between the intensities of the peaks \(I(D)/I(G)\), associated with disorder, is presented in Table 1. An increase of the values is caused by the deposition temperature due to the size reduction of the clusters by re-evaporation that consequently would create defects. Similarly, the application of short time (30 min) leads to high defects (\(I(D)/I(G)=2.4\)) because the radical  
Figure 1: CNWs deposited onto electrode configurations for MR measurements. Figure 2: The SEM images for the CNWs grown at **(a)** 1400 sccm-700 \({}^{\circ}\)C-30 min, **(b)** 1050 sccm-600 \({}^{\circ}\)C-60 min, **(c)** 1400 sccm-600 \({}^{\circ}\)C-60 min and **(d)** 1400 sccm-700 \({}^{\circ}\)C-60 min. formations and nucleation sites are not formed enough. Here, the influence of the Ar flux is weak. Different types of defects can be defined, such as edges, grain boundaries, vacancies, substitutional and implanted atoms, and a change of carbon hybridization (for example, from sp\({}^{2}\) into sp\({}^{3}\)) [33]. The average defect distance between the point defects (\(L_{D}\)) can be related to the invers \(I(D)/I(G)\), using the following equation [34]:  
\[L_{D}^{2}(\text{nm}^{2})=\frac{C_{D}}{E_{L}^{4}}\frac{I(G)}{I(D)} \tag{2}\]  
where \(C_{d}=3600\) and \(E_{L}\) is the excitation laser energy used in the Raman experiment (1.96 eV). Table 1 reveals the values obtained. The nature of the defects can be identified by the \(I(D)/I(D^{\prime})\) relation. According to [PERSON] et al. [35], the \(I(D)/I(D^{\prime})\) around 3.5 is attributed to boundary-like defects in graphite-related materials. As a consequence, the values presented in Table 1 show that the disorder-induced bands would occurs principally  
Figure 4: The RAMAN spectra for the CNWs grown at 30 min with 1400 sccm-700 \({}^{\circ}\)C (purple line) and at 60 min with 1050 sccm-600 \({}^{\circ}\)C (red line), 1050 sccm-700 \({}^{\circ}\)C (black line), 1400 sccm-600 \({}^{\circ}\)C (green line) and 1400 sccm-700 \({}^{\circ}\)C (blue line). The figure includes (**a**) the D and G bands and (**b**) 2D bands. Figure 3: TEM images. (**a**) Interlayer spaces of the walls.