# Structural Modifications in Epitaxial Graphene on SiC Following 10 keV Nitrogen Ion Implantation
## 1 Introduction  
Graphene is well known as a two-dimensional material with several remarkable properties like high electrical conductivity, high flexibility, low electric noise and high mechanical strength [1]. The lack of bandgap limits its application potential. Graphene based digital devices cannot be \"switched-off\" due to a constant flow of electrons. Switching is a necessity in electronic devices such as switches and transistors. Efforts are made to control the bandgap in growth and post processing, but it is a big challenge. Modification of surfaces functionalizes graphene and has demonstrated a band gap [2], which makes possible its usage in digital electronics, nanoelectronics, spintronics, magnetronics and much more. The structural changes also alter its optical, electrical, mechanical and magnetic properties, thus offers its applicability for biosensors, gas sensors, optoelectronic devices, solar cells, detectors, batteries, pressure sensors, etc. The structure of graphene has been altered using various methods such as chemical doping, covalent functionalization and electron/ion beam irradiation [3; 4; 5]. The ion beam technology is a high precision and high reproducibility process. Structural modifications introduced using ion irradiation are much more effective due to the reason that there is an efficient transfer of energy from energetic incident ions to the atoms of graphene. Impurity doping can be done by ion irradiation (both by insertion of atoms from primary ion beam or via backscattered atoms from the substrate) and various atoms, molecules or ions can be explored. This range of options is not offered by any other technology. Both dopant and defects introduction in the material at the same time up to a desired depth can be also tailored. The low energy ion implantation has been shown to modify the different types of graphene, such as produced by mechanical exfoliation, chemical vapor deposition (CVD) and sublimation epitaxy (epitaxial graphene) process. Experimental and theoretical studies showed an array of nanodots and nanowires on graphene on SiO\({}_{2}\) using 30 keV Ga ion irradiation [6]. The structural modification in mechanically exfoliated multilayer graphene on SiO\({}_{2}\) substrate caused an increase in defects with the increase in dwell time of ion irradiation, along with an increase in the compressive strain using focused ion beam (FIB) with Ga ions [7]. It was also shown that multilayered graphene is p-type doped due to defects thereby resulting in increasing the work function [7]. Modified single layer CVD graphene showed metal-insulator transition at larger doses of Ga ion irradiation using FIB [8]. There was a change of work function of graphene with an increase in defect density with increasing Ga irradiation dose [8]. Argon ion irradiation in the energy range of 0-200 eV with time of 0-10 s was applied on few layers of graphene. The study optimized beam energy and irradiation time to remove surface contaminants and to flatten the surface damage [9]. Nanopores were formed (size of two nanometers) following the treatment of exfoliated graphene on SiO\({}_{2}\) with hydrogen plasma etching [10]. Single layers of graphene nanopatterning were obtained by using helium ions and nanostructures and nanoribbons appeared at a dose of \(2.0\times 10^{16}\) ions/cm\({}^{2}\)[11]. Nanopores were also obtained in exfoliated graphene using 35 keV Ga ion irradiation [12]. Different types of ions create different levels of defects. [PERSON] et al. used B, N and F ion irradiation on CVD grown monolayer graphene at 35 eV and 20 eV energy between \(1\times 10^{14}\) ions/cm\({}^{2}\) to \(6\times 10^{15}\) ions/cm\({}^{2}\) fluence [13]. [PERSON] and co-workers observed that 25 eV N ion implantation at \(5\times 10^{14}\) ions/cm\({}^{2}\) fluence resulted in doping of epitaxial graphene (EG) with N concentration of around 1% [14]. Ion implantation on EG with 25 eV B and N ions showed an increase in resistance and a change in magnetoresistance from positive to negative [15].