# Structural Modifications in Epitaxial Graphene on SiC Following 10 keV Nitrogen Ion Implantation
## 3 Results
### Raman Spectroscopy
Since the transmitted energy in this study is higher than the threshold energy required for C and Si atom, the displacement of Si and C atoms from its lattice site occurs and which causes breaking of the SiC bonds. This results in a reduction of the intensity of the FTO (2/4) peak along with the LO peak, which can be observed in Figure 3. At the highest fluence (\(1\times 10^{14}\) ions/cm\({}^{2}\)), a shift and narrowing of the FTO (2/4) peak along with the LO peak is observed (Figure 3a). This is in agreement with a previous study, which reported that this could be due to the fact that point defects trap the free carriers. The LO phonon loses the plasmonic coupling as a result of defects causing a shift in the LO peak [43]. Figure 3b illustrates newly formed Raman bands in the range around \(\sim\)500-550 cm\({}^{-1}\) at the highest fluence. This is due to the formation of Si-Si bonds in the samples implanted at a fluence \(1\times 10^{14}\) ions/cm\({}^{2}\)[44]. In addition to that there also occur less intense bands in the region of 650-800 cm\({}^{-1}\) in the Raman spectra of the sample with the highest fluence. This could be due to the formation of a new vibrational modes of Si-C following the ion implantation. [PERSON] and co-workers reported that defects generated in SiC by ion irradiation result in breakdown of Raman selection rules, which leads to generation of Si-Si and C-C and new Si-C vibrational modes [44]. Further, Figure 3b shows a bump in the region 815-950 cm\({}^{-1}\) which is due to the superposition of three transverse optical phonons which are 2 TO (X), 2 TO (W) and 2 TO (L) of silicon [45]. The relative Raman intensity which is denoted as RRI is the ratio between the average intensity of the first order Raman modes in the ion-implanted sample and that of the pristine sample [46]. Figure 4a shows a decrease in RRI from its maximum value of 1 in the non-implanted sample to the value of 0.30 in the sample implanted at fluence of \(1\times 10^{14}\) ions/cm\({}^{2}\). Increased amount of defects with increasing fluence is the reason behind the reduction in the value of RRI, which is in agreement with a previous study [46]. The total disorder, which quantifies the damage of the crystallinity of materials is defined as 1-A\({}_{\text{norm}}\). The A\({}_{\text{norm}}\) is the ratio between the total area under the principal first order Raman band in the implanted material and the area under the principal first order Raman band of the crystalline material [47]. The ranges used for estimating the area under principal first order bands (FTO (2/4) and LO) are -760 cm\({}^{-1}\)-800 cm\({}^{-1}\) and 955 cm\({}^{-1}\)-990 cm\({}^{-1}\). Following ion implantation total area under principal first order bands of implanted sample reduces which results in rise in total disorder in implanted samples. The rise in the value of the total disorder with increasing the fluence signifies the decreased crystallinity of the material with increasing fluence [47]. Figure 4b shows the change in the total disorder at varying fluences following the ion implantation, with increment in the value of the total disorder to 0.73 in the highest fluence implanted sample (\(1\times 10^{14}\) ions/cm\({}^{2}\)). Raman results suggest that one can introduce different levels of defects into both EG and SiC by just tuning the fluence which forms a platform for developing high performance supercapacitors, sensors, etc. as defects in controlled manner enhance storage capacity and sensing capacity of EG/SiC.